Gabriel G. Katul

Journal Article Journal of Geophysical Research: Atmospheres · October 16, 2024 The relaxed eddy accumulation (REA) method is a widely-known technique that measures turbulent fluxes of scalar quantities. The REA technique has been used to measure turbulent fluxes of various compounds, such as methane, ethene, propene, butene, isoprene ... Full text Cite

Multiple time scale optimization explains functional trait responses to leaf water potential.

Journal Article The New phytologist · October 2024 Plant response to water stress involves multiple timescales. In the short term, stomatal adjustments optimize some fitness function commonly related to carbon uptake, while in the long term, traits including xylem resilience are adjusted. These optimizatio ... Full text Cite

Estimating scalar turbulent fluxes with slow-response sensors in the stable atmospheric boundary layer

Journal Article Atmospheric Chemistry and Physics · August 30, 2024 Conventional and recently developed approaches for estimating turbulent scalar fluxes under stable atmospheric conditions are evaluated, with a focus on gases for which fast sensors are not readily available. First, the relaxed eddy accumulation (REA) clas ... Full text Cite

Solar-induced chlorophyll fluorescence sheds light on global evapotranspiration

Journal Article Remote Sensing of Environment · May 1, 2024 The significance of large-scale evapotranspiration (ET) to climate science, water resources management, flood routing, irreversible desertification, and crop yield is not in dispute. Current large-scale ET models combine empirical formulations with a suite ... Full text Cite

The advancing wave front on a sloping channel covered by a rod canopy following an instantaneous dam break

Journal Article Physics of Fluids · May 1, 2024 The drag coefficient Cd for a rigid and uniformly distributed rod canopy covering a sloping channel following the instantaneous collapse of a dam was examined using flume experiments. The measurements included space x and time t high resolution images of t ... Full text Cite

Persistent urban heat.

Journal Article Science advances · April 2024 Urban surface and near-surface air temperatures are known to be often higher than their rural counterparts, a phenomenon now labeled as the urban heat island effect. However, whether the elevated urban temperatures are more persistent than rural temperatur ... Full text Cite

Ecosystem Water-Saving Timescale Varies Spatially With Typical Drydown Length

Journal Article AGU Advances · April 1, 2024 Stomatal optimization theory is a commonly used framework for modeling how plants regulate transpiration in response to the environment. Most stomatal optimization models assume that plants instantaneously optimize a reward function such as carbon gain. Ho ... Full text Cite

A Century of Reforestation Reduced Anthropogenic Warming in the Eastern United States

Journal Article Earth's Future · February 1, 2024 Restoring and preserving the world's forests are promising natural pathways to mitigate some aspects of climate change. In addition to regulating atmospheric carbon dioxide concentrations, forests modify surface and near-surface air temperatures through bi ... Full text Cite

Scalar Flux Profiles in the Unstable Atmospheric Surface Layer Under the Influence of Large Eddies: Implications for Eddy Covariance Flux Measurements and the Non-Closure Problem

Journal Article Geophysical Research Letters · January 16, 2024 How convective boundary-layer (CBL) processes modify fluxes of sensible (SH) and latent (LH) heat and CO2 (Fc) in the atmospheric surface layer (ASL) remains a recalcitrant problem. Here, large eddy simulations for the CBL show that while SH in the ASL dec ... Full text Cite

Linking the Water and Carbon Economies of Plants in a Drying and Warming Climate

Journal Article Current Forestry Reports · December 1, 2023 Purpose of Review : Harsher abiotic conditions are projected for many woodland areas, especially in already arid and semi-arid climates such as the Southwestern USA. Stomatal regulation of their aperture is one of the ways plants cope with drought. Interes ... Full text Cite

Reduced Sediment Settling in Turbulent Flows Due To Basset History and Virtual Mass Effects

Journal Article Geophysical Research Letters · November 28, 2023 The behavior of suspended particles in turbulent flows is a recalcitrant problem spanning wide-ranging fields including geomorphology, hydrology, and dispersion of particulate matter in the atmosphere. One key mechanism underlying particle suspension is th ... Full text Cite

Merging flux-variance with surface renewal methods in the roughness sublayer and the atmospheric surface layer

Journal Article Agricultural and Forest Meteorology · November 15, 2023 Two micrometeorological methods utilizing high-frequency sampled air temperature were tested against eddy covariance (EC) sensible heat flux (H) measurements at three sites representing agricultural, agro-forestry, and forestry systems. The two methods cov ... Full text Cite

Photosynthetic capacity, canopy size and rooting depth mediate response to heat and water stress of annual and perennial grain crops

Journal Article Agricultural and Forest Meteorology · October 15, 2023 Perennial grain crops are promoted as an alternative to annual staple crops to reduce negative environmental effects of agriculture and support a variety of ecosystem services. While perennial grains have undergone extensive testing, their vulnerability to ... Full text Cite

Bridging structural and functional hydrological connectivity in dryland ecosystems

Journal Article Catena · October 1, 2023 On dryland hillslopes, vegetation water availability is often subsidized by the redistribution of rainfall runoff from bare soil (sources) to vegetation patches (sinks). In regions where rainfall volumes are too low to support spatially continuous plant gr ... Full text Cite

Logarithmic scaling of higher-order temperature moments in the atmospheric surface layer

Journal Article International Journal of Heat and Fluid Flow · August 1, 2023 A generalized logarithmic law for high-order moments of homogeneous passive scalars is proposed for turbulent boundary layers. This law is analogous to the generalized log law that has been proposed for high-order moments of the turbulent longitudinal velo ... Full text Cite

Multiscale Temporal Variability of the Global Air-Sea CO2 Flux Anomaly

Journal Article Journal of Geophysical Research: Biogeosciences · June 1, 2023 The global air-sea CO2 flux (F) impacts and is impacted by a plethora of climate-related processes operating at multiple time scales. In bulk mass transfer formulations, F is driven by physico- and bio-chemical factors such as the air-sea partial pressure ... Full text Cite

Sucrose transport inside the phloem: Bridging hydrodynamics and geometric characteristics

Journal Article Physics of Fluids · June 1, 2023 In plants, the delivery of the products of photosynthesis is achieved through a hydraulic system labeled as phloem. This semi-permeable plant tissue consists of living cells that contract and expand in response to fluid pressure and flow velocity fluctuati ... Full text Cite

Hydrologic Connectivity and Patch-To-Hillslope Scale Relations in Dryland Ecosystems

Journal Article Geophysical Research Letters · May 28, 2023 In drylands, runoff during storms redistributes water and nutrients from bare soil areas to vegetated patches, subsidizing vegetation with additional resources. The extent of this redistribution depends on the interplay between surface roughness and permea ... Full text Cite

Fog Intermittency and Critical Behavior

Journal Article Atmosphere · May 1, 2023 The intermittency of fog occurrence (the switching between fog and no-fog) is a key stochastic feature that plays a role in its duration and the amount of moisture available. Here, fog intermittency is studied by using the visibility time series collected ... Full text Cite

Agrivoltaics in Color: Going From Light Spectra to Biomass

Journal Article Earth's Future · May 1, 2023 Agrivoltaics (AV), conceived in the early 1980s, promise to ameliorate competition between solar energy generation and crop production for arable land. The premise behind AV is that excess light not used in photosynthesis can be used for energy production. ... Full text Cite

Estimating source-sink distributions and fluxes of reactive nitrogen and sulfur within a mixed forest canopy

Journal Article Agricultural and Forest Meteorology · April 15, 2023 The vertical source-sink distribution of air pollutants within and above forested canopies is necessary for describing the biological, physical, and chemical processes influencing the soil-vegetation-atmosphere exchange. This study implemented inverse mode ... Full text Cite

Turbulence Organization and Mean Profile Shapes in the Stably Stratified Boundary Layer: Zones of Uniform Momentum and Air Temperature

Journal Article Boundary-Layer Meteorology · March 1, 2023 A persistent spatial organization of eddies is identified in the lowest portion of the stably stratified planetary boundary layer. The analysis uses flow realizations from published large-eddy simulations (Sullivan et al. in J Atmos Sci 73(4):1815–1840, 20 ... Full text Cite

Toward a Realistic Representation of Sucrose Transport in the Phloem of Plants

Journal Article Journal of Geophysical Research: Biogeosciences · March 1, 2023 The significance of phloem hydrodynamics to plant mortality and survival, which impacts ecosystem-scale carbon and water cycling, is not in dispute. The phloem provides the conduits for products of photosynthesis to be transported to different parts of the ... Full text Cite

Correction for Marani et al., Intensity and frequency of extreme novel epidemics.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · March 2023 Full text Cite

Adjustments to the law of the wall above an Amazon forest explained by a spectral link

Journal Article Physics of Fluids · February 1, 2023 Modification to the law of the wall represented by a dimensionless correction function φ RSL (z / h) is derived using atmospheric turbulence measurements collected at two sites in the Amazon in near-neutral stratification, where z is the distance from the ... Full text Cite

Boundary-Layer Processes Hindering Contemporary Numerical Weather Prediction Models

Journal Article Boundary-Layer Meteorology · January 1, 2023 Time integration of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations is the principal approach used in numerical weather prediction. This approach represents a balanced compromise between accuracy and computational cost. The URANS equations r ... Full text Cite

Inferring surface energy fluxes using drone data assimilation in large eddy simulations

Journal Article Atmospheric Measurement Techniques · December 20, 2022 Spatially representative estimates of surface energy exchange from field measurements are required for improving and validating Earth system models and satellite remote sensing algorithms. The scarcity of flux measurements can limit understanding of ecohyd ... Full text Cite

The effect of rainfall amount and timing on annual transpiration in a grazed savanna grassland

Journal Article Hydrology and Earth System Sciences · November 16, 2022 The role of precipitation (P) variability with respect to evapotranspiration (ET) and its two components, transpiration (T) and evaporation (E), from savannas continues to draw significant research interest given its relevance to a number of ecohydrologica ... Full text Cite

The role of geographical spreaders in infectious pattern formation and front propagation speeds

Journal Article Physica D: Nonlinear Phenomena · November 15, 2022 The pattern formation and spatial spread of infectious populations are investigated using a kernel-based Susceptible–Infectious–Recovered (SIR) model applicable across a wide range of basic reproduction numbers Ro. The goal is to examine the role of geogra ... Full text Cite

Instantaneous stomatal optimization results in suboptimal carbon gain due to legacy effects.

Journal Article Plant, cell & environment · November 2022 Full text Cite

Turbulence Structures in the Very Stable Boundary Layer Under the Influence of Wind Profile Distortion

Journal Article Journal of Geophysical Research: Atmospheres · October 27, 2022 In very stable boundary layers (VSBL), a “cocktail” of submeso motions routinely result in elevated mean wind speed maxima above the ground, acting as a new source of turbulence generation. This new source of turbulent kinetic energy enhances turbulent mix ... Full text Cite

Bridging the Urban Canopy Sublayer to Aerodynamic Parameters of the Atmospheric Surface Layer

Journal Article Boundary-Layer Meteorology · October 1, 2022 Within the roughness sublayer (RSL) of dense urban canopies composed of uniformly distributed cuboids, the time and planar-averaged mean velocity profile exhibits an approximate exponential shape characterized by a depth-independent attenuation coefficient ... Full text Cite

Probing eddy size and its effective mixing length in stably stratified roughness sublayer flows

Journal Article Quarterly Journal of the Royal Meteorological Society · October 1, 2022 Stably stratified roughness sublayer flows are ubiquitous yet remain difficult to represent in models and to interpret using field experiments. Here, continuous high-frequency potential temperature profiles from the forest floor up to 6.5 times the canopy ... Full text Cite

Consistent responses of vegetation gas exchange to elevated atmospheric CO2 emerge from heuristic and optimization models

Journal Article Biogeosciences · September 14, 2022 Elevated atmospheric CO2 concentration is expected to increase leaf CO2 assimilation rates, thus promoting plant growth and increasing leaf area. It also decreases stomatal conductance, allowing water savings, which have been hypothesized to drive large-sc ... Full text Cite

Catastrophic hydraulic failure and tipping points in plants.

Journal Article Plant, cell & environment · August 2022 Water inside plants forms a continuous chain from water in soils to the water evaporating from leaf surfaces. Failures in this chain result in reduced transpiration and photosynthesis and are caused by soil drying and/or cavitation-induced xylem embolism. ... Full text Cite

Radial-axial transport coordination enhances sugar translocation in the phloem vasculature of plants.

Journal Article Plant physiology · August 2022 Understanding mass transport of photosynthates in the phloem of plants is necessary for predicting plant carbon allocation, productivity, and responses to water and thermal stress. Several hypotheses about optimization of phloem structure and function and ... Full text Cite

Self-similar geometries within the inertial subrange of scales in boundary layer turbulence

Journal Article Journal of Fluid Mechanics · July 10, 2022 The inertial subrange of turbulent scales is commonly reflected by a power law signature in ensemble statistics such as the energy spectrum and structure functions - both in theory and from observations. Despite promising findings on the topic of fractal g ... Full text Cite

The root-zone soil moisture spectrum in a mediterranean ecosystem

Journal Article Journal of Hydrology · June 1, 2022 Storage of water within soil pores of the root zone introduce memory effects in the dynamics of soil moisture that are considerably longer than the integral timescale of many atmospheric processes. Thus, hydro-climatic states can be “sustained” through lan ... Full text Cite

Does growing atmospheric CO₂ explain increasing carbon sink in a boreal coniferous forest?

Journal Article Global change biology · May 2022 The terrestrial net ecosystem productivity (NEP) has increased during the past three decades, but the mechanisms responsible are still unclear. We analyzed 17 years (2001-2017) of eddy-covariance measurements of NEP, evapotranspiration (ET) and light and w ... Full text Cite

Examining Parameterizations of Potential Temperature Variance Across Varied Landscapes for Use in Earth System Models

Journal Article Journal of Geophysical Research: Atmospheres · April 27, 2022 Earth system models (ESMs) and mesoscale models have come to employ increasingly complex parameterization schemes for the atmospheric boundary layer, requiring surface boundary conditions for numerous higher order turbulence statistics. Of particular inter ... Full text Cite

Examining Parameterizations of Potential Temperature Variance Across Varied Landscapes for use in Earth System Models

Preprint · April 5, 2022 Full text Cite

The Detection, Genesis, and Modeling of Turbulence Intermittency in the Stable Atmospheric Surface Layer

Journal Article Journal of the Atmospheric Sciences · April 1, 2022 Intermittent transitions between turbulent and nonturbulent states are ubiquitous in the stable atmospheric surface layer (ASL). Data from two field experiments in Utqiagvik, · Alaska, and from direct numerical simulations are used to probe these state tra ... Full text Cite

Profiles of high-order moments of longitudinal velocity explained by the random sweeping decorrelation hypothesis

Journal Article Physical Review Fluids · April 1, 2022 Under the assumptions that the random sweeping decorrelation hypothesis applies and that the velocity statistics are near Gaussian, the logarithmic variation of high-order moments of longitudinal velocity with distance from a boundary in the inertial regio ... Full text Cite

Direct partitioning of eddy-covariance water and carbon dioxide fluxes into ground and plant components

Journal Article Agricultural and Forest Meteorology · March 15, 2022 The partitioning of evapotranspiration (ET) into surface evaporation (E) and stomatal-based transpiration (T) is essential for analyzing the water cycle and earth surface energy budget. Similarly, the partitioning of net ecosystem exchange (NEE) of carbon ... Full text Cite

Reduced ecosystem resilience quantifies fine-scale heterogeneity in tropical forest mortality responses to drought.

Journal Article Global change biology · March 2022 Sensitivity of forest mortality to drought in carbon-dense tropical forests remains fraught with uncertainty, while extreme droughts are predicted to be more frequent and intense. Here, the potential of temporal autocorrelation of high-frequency variabilit ... Full text Cite

A Co-Spectral Budget Model Links Turbulent Eddies to Suspended Sediment Concentration in Channel Flows

Journal Article Water Resources Research · March 1, 2022 The vertical distribution of suspended sediment concentration remains a subject of active research given its relevance to a plethora of problems in hydraulics, hydrology, ecology, and water quality control. Many of the classical theories developed over the ... Full text Cite

LOGARITHMIC SCALING OF HIGHER-ORDER TEMPERATURE MOMENTS IN THE ATMOSPHERIC SURFACE LAYER

Conference 12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022 · January 1, 2022 A generalized logarithmic law for high-order moments of passive scalars is proposed. This law is analogous to the generalized log law that has been proposed for high-order moments of the turbulent longitudinal velocity and is derived by combining the rando ... Cite

Examining Parameterizations of Potential Temperature Variance Across Varied Landscapes for use in Earth System Models

Preprint · December 7, 2021 Full text Cite

Laboratory study on behavioral responses of hybrid sturgeon, Acipenseridae, to wake flows induced by cylindrical bluff bodies.

Journal Article The Science of the total environment · December 2021 Interaction between flow and cylindrical-shaped structures generates coherent and periodic turbulent flow that is frequently experienced by fish in natural environments, influencing fish maneuvering and swimming stability. The current study evaluated the b ... Full text Cite

Detecting forest response to droughts with global observations of vegetation water content.

Journal Article Global change biology · December 2021 Droughts in a warming climate have become more common and more extreme, making understanding forest responses to water stress increasingly pressing. Analysis of water stress in trees has long focused on water potential in xylem and leaves, which influences ... Full text Cite

Sweeping Effects Modify Taylor’s Frozen Turbulence Hypothesis for Scalars in the Roughness Sublayer

Journal Article Geophysical Research Letters · November 28, 2021 Taylor’s frozen turbulence hypothesis (FTH) is investigated in the roughness sublayer of a sloped vineyard canopy using a spatial array of fine-wire thermocouples and ultrasonic anemometers. The Ellipse Approximation (EA) method is applied to the measured ... Full text Cite

Roughness-induced critical phenomenon analogy for turbulent friction factor explained by a co-spectral budget model

Journal Article Physics of Fluids · October 1, 2021 Drawing on an analogy to critical phenomena, it was shown that the Nikuradse turbulent friction factor (ft) measurements in pipes of radius R and wall roughness r can be collapsed onto a one-dimensional curve expressed as a conveyance law ft Re1/4 = go (χ) ... Full text Cite

Population agglomeration is a harbinger of the spatial complexity of COVID-19.

Journal Article Chemical engineering journal (Lausanne, Switzerland : 1996) · September 2021 The spatial template over which COVID-19 infections operate is a result of nested societal decisions involving complex political and epidemiological processes at a broad range of spatial scales. It is characterized by 'hotspots' of high infections interspe ... Full text Cite

Velocity and Temperature Dissimilarity in the Surface Layer Uncovered by the Telegraph Approximation

Journal Article Boundary-Layer Meteorology · September 1, 2021 The physicist and mathematician Shang-Keng Ma once commented that “the simplest possible variable is one that can have two values. If there is only one value, no variation is possible." Guided by this dictum, the telegraphic approximation (TA) is applied t ... Full text Cite

Intermittent Surface Renewals and Methane Hotspots in Natural Peatlands

Journal Article Boundary-Layer Meteorology · September 1, 2021 Peatlands account for a large fraction of global methane (CH 4) emissions. These environments exchange CH 4 with the atmosphere via three main mechanisms: diffusion through the peat and water, plant-mediated diffusion, and sporadic release of CH 4 bubbles. ... Full text Cite

A Multiscale Approach to Timescale Analysis: Isolating Diel Signals from Solute Concentration Time Series.

Journal Article Environmental science & technology · September 2021 Solute concentration time series reflect hydrological and biological drivers through various frequencies, phases, and amplitudes of change. Untangling these signals facilitates the understanding of dynamic ecosystem conditions and transient water quality i ... Full text Cite

Intensity and frequency of extreme novel epidemics.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · August 2021 Observational knowledge of the epidemic intensity, defined as the number of deaths divided by global population and epidemic duration, and of the rate of emergence of infectious disease outbreaks is necessary to test theory and models and to inform public ... Full text Cite

Probability law of turbulent kinetic energy in the atmospheric surface layer

Journal Article Physical Review Fluids · July 1, 2021 The probability density function p(k) of the turbulent kinetic energy k is investigated for diabatic atmospheric surface layer (ASL) flows. When the velocity components are near-Gaussian and their squared amplitudes are nearly independent, the resulting p( ... Full text Cite

Flow dynamics and sediment transport in vegetated rivers: A review

Journal Article Journal of Hydrodynamics · June 1, 2021 The significance of riparian vegetation on river flow and material transport is not in dispute. Conveyance laws, sediment erosion and deposition, and element cycling must all be adjusted from their canonical rough-wall boundary layer to accommodate the pre ... Full text Cite

Eddies in motion: Visualizing boundary-layer turbulence above an open boreal peatland using UAS thermal videos

Journal Article Atmospheric Measurement Techniques · May 18, 2021 High-resolution thermal infrared (TIR) imaging is opening up new vistas in biosphere-atmosphere heat exchange studies. The rapidly developing unmanned aerial systems (UASs) and specially designed cameras offer opportunities for TIR survey with increasingly ... Full text Cite

A kernel-modulated SIR model for Covid-19 contagious spread from county to continent.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · May 2021 The tempo-spatial patterns of Covid-19 infections are a result of nested personal, societal, and political decisions that involve complicated epidemiological dynamics across overlapping spatial scales. High infection "hotspots" interspersed within regions ... Full text Cite

Universal Return to Isotropy of Inhomogeneous Atmospheric Boundary Layer Turbulence.

Journal Article Physical review letters · May 2021 A recalcitrant problem in the physics of turbulence is the representation of the tendency of large-scale anisotropic eddies to redistribute their energy content with decreasing scales, a phenomenon referred to as return to isotropy. An unprecedented datase ... Full text Cite

Relation between the spectral properties of wall turbulence and the scaling of the Darcy-Weisbach friction factor

Journal Article Physical Review Fluids · May 1, 2021 Empirical formulas describing the Darcy-Weisbach friction factor remain indispensable for applications in sciences and engineering dealing with turbulent flows. Despite their practical significance, these formulas have remained without theoretical interpre ... Full text Cite

Spectral Signature of Landscape Channelization

Journal Article Geophysical Research Letters · April 28, 2021 Channel networks increase in complexity as the importance of erosion grows compared to diffusion by soil creep, giving rise to a channelization cascade. Simulations, laboratory experiments, and data from a natural landscape are used to uncover the signatur ... Full text Cite

Non-Closure of Surface Energy Balance Linked to Asymmetric Turbulent Transport of Scalars by Large Eddies

Journal Article Journal of Geophysical Research: Atmospheres · April 16, 2021 How large turbulent eddies influence non-closure of the surface energy balance is an active research topic that cannot be uncovered by the mean continuity equation in isolation. It is demonstrated here that asymmetric turbulent flux transport of heat and w ... Full text Cite

Mesoscale temporal wind variability biases global air-sea gas transfer velocity of CO2 and other slightly soluble gases

Journal Article Remote Sensing · April 1, 2021 The significance of the water-side gas transfer velocity for air-sea CO2 gas exchange (k) and its non-linear dependence on wind speed (U) is well accepted. What remains a subject of inquiry are biases associated with the form of the non-linear relation lin ... Full text Cite

The Intensifying Role of High Wind Speeds on Air-Sea Carbon Dioxide Exchange

Journal Article Geophysical Research Letters · March 16, 2021 While it has been known that wave breaking and bubble generation at high wind speeds enhance air-sea carbon dioxide (CO2) exchange rates (F), quantification of their contribution at the global scale remains a formidable challenge. There is urgency to make ... Full text Cite

Differential response of rice evapotranspiration to varying patterns of warming

Journal Article Agricultural and Forest Meteorology · March 15, 2021 Rice is a staple food crop that provides more calories to the global population than any other crop. Rice production is also a major consumer of fresh-water resources. Hence, changes in rice evapotranspiration (ETc) due to projected warming patterns is bec ... Full text Cite

Leaf temperature and its dependence on atmospheric CO2 and leaf size

Journal Article Geological Journal · February 1, 2021 There is general concern that the rapid increase in atmospheric CO2 concentration will lead to reduced stomatal conductance and subsequent increases in leaf temperature. Such an increase in leaf temperature is expected to adversely impact a plethora of pro ... Full text Cite

Multiscale Legacy Responses of Soil Gas Concentrations to Soil Moisture and Temperature Fluctuations

Journal Article Journal of Geophysical Research: Biogeosciences · February 1, 2021 The sensitivity of soil carbon dynamics to climate change is a major uncertainty in carbon cycle models. Of particular interest is the response of soil biogeochemical cycles to variability in hydroclimatic states and the related quantification of soil memo ... Full text Cite

Micro-climatic and crop responses to micro-sprinkler irrigation

Journal Article Agricultural Water Management · January 1, 2021 The frequency and severity of droughts and heat stresses are becoming a threat to crop production and food security in arid and semi-arid regions worldwide. To ameliorate both stresses simultaneously, micro-sprinkler systems are being proposed and their pe ... Full text Cite

Taylor dispersion in osmotically driven laminar flows in phloem

Journal Article Journal of Fluid Mechanics · January 1, 2021 Sucrose is among the main products of photosynthesis that are deemed necessary for plant growth and survival. It is produced in the mesophyll cells of leaves and translocated to different parts of the plant through the phloem. Progress in understanding thi ... Full text Open Access Cite

Scaling Laws for the Length Scale of Energy-Containing Eddies in a Sheared and Thermally Stratified Atmospheric Surface Layer

Journal Article Geophysical Research Letters · December 16, 2020 In the atmospheric surface layer (ASL), a characteristic wavelength marking the limit between energy-containing and inertial subrange scales can be defined from the vertical velocity spectrum. This wavelength is related to the integral length scale of turb ... Full text Cite

A network model for stemflow solute transport

Journal Article Applied Mathematical Modelling · December 1, 2020 While the role of stemflow in directing and concentrating water and nutrients at the tree base is rarely in dispute, its mathematical representation remains a subject of inquiry and research. A network model that seeks to estimate stemflow solute concentra ... Full text Cite

The Persistent Challenge of Surface Heterogeneity in Boundary-Layer Meteorology: A Review

Journal Article Boundary-Layer Meteorology · December 1, 2020 Atmospheric boundary-layer dynamics over heterogeneous surfaces is significant to a wide array of geophysical and engineering applications. Yet, despite over five decades of intense efforts by the research community, numerous open research questions remain ... Full text Cite

Boundary-Layer Flow Over Complex Topography

Journal Article Boundary-Layer Meteorology · December 1, 2020 We review developments in the field of boundary-layer flow over complex topography, focussing on the period from 1970 to the present day. The review follows two parallel strands: the impact of hills on flow in the atmospheric boundary layer and gravity-dri ... Full text Cite

Assessing decoupling of above and below canopy air masses at a Norway spruce stand in complex terrain

Journal Article Agricultural and Forest Meteorology · November 15, 2020 Concurrent below and above canopy sonic anemometer vertical velocity (w) measurements reveal frequent decoupling events between the air masses below and above the canopy at a dense spruce forest stand in mountainous terrain. Decoupling events occurred pred ... Full text Cite

Fluctuation theorem and extended thermodynamics of turbulence.

Journal Article Proceedings. Mathematical, physical, and engineering sciences · November 2020 Turbulent flows are out-of-equilibrium because the energy supply at large scales and its dissipation by viscosity at small scales create a net transfer of energy among all scales. This energy cascade is modelled by approximating the spectral energy balance ... Full text Cite

The Effects of Canopy Morphology on Flow Over a Two-Dimensional Isolated Ridge

Journal Article Journal of Geophysical Research: Atmospheres · October 16, 2020 Momentum and mass exchanges between the atmosphere and forests situated on complex terrain continue to draw significant research attention primarily because of their significance to a plethora of applications. In this paper, we investigated flows behavior ... Full text Cite

Velocity asymmetry and turbulent transport closure in smooth- A nd rough-wall boundary layers

Journal Article Physical Review Fluids · October 14, 2020 Sweep and ejection events in turbulent boundary layer flows have been explored for half a century now to describe eddies impacting turbulent stresses. Yet, moving these studies from their current diagnostic phase to a prognostic form remains a formidable c ... Full text Cite

Revisiting the relation between momentum and scalar roughness lengths of urban surfaces

Journal Article Quarterly Journal of the Royal Meteorological Society · October 1, 2020 Large-Eddy Simulations (LESs) of neutral flow over regular arrays of cuboids are conducted to explore connections between momentum (z0m) and scalar (z0s) roughness lengths in urban environments, and how they are influenced by surface geometry. As LES resol ... Full text Cite

Longitudinal dispersal properties of floating seeds within open-channel flows covered by emergent vegetation

Journal Article Advances in Water Resources · October 1, 2020 The effect of emergent stems on the transport of downstream floating particles (e.g., buoyant seeds) is explored theoretically and experimentally at moderate to high Reynolds number (Rd=2Ubas/υ>300) in an open channel, where Ub is the bulk velocity, as is ... Full text Cite

Homogenization of the terrestrial water cycle

Journal Article Nature Geoscience · October 1, 2020 Full text Cite

Contaminant removal efficiency of floating treatment wetlands

Journal Article Environmental Research Letters · October 1, 2020 Floating treatment wetlands are new ecological infrastructures for stormwater treatment. Despite a recent proliferation in their usage, their contaminant removal efficiency e continues to draw research attention. Here, the e from idealized FTWs is numerica ... Full text Cite

Peak grain forecasts for the US High Plains amid withering waters.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · October 2020 Irrigated agriculture contributes 40% of total global food production. In the US High Plains, which produces more than 50 million tons per year of grain, as much as 90% of irrigation originates from groundwater resources, including the Ogallala aquifer. In ... Full text Cite

Data from: Contaminant removal efficiency of floating treatment wetlands

Dataset · September 16, 2020 Full text Cite

Scalewise Return to Isotropy in Stratified Boundary Layer Flows

Journal Article Journal of Geophysical Research: Atmospheres · August 27, 2020 Anisotropic turbulence is ubiquitous in atmospheric and oceanic boundary layers due to differences in energy injection mechanisms. Unlike mechanical production that injects energy in the streamwise velocity component, buoyancy affects only the vertical vel ... Full text Cite

Root-zone soil moisture variability across African savannas: From pulsed rainfall to land-cover switches

Journal Article Ecohydrology · July 1, 2020 The main source of soil moisture variability in savanna ecosystems is pulsed rainfall. Rainfall pulsing impacts water-stress durations, soil moisture switching between wet-to-dry and dry-to-wet states, and soil moisture spectra as well as derived measures ... Full text Cite

Plant hydraulics accentuates the effect of atmospheric moisture stress on transpiration

Journal Article Nature Climate Change · July 1, 2020 Transpiration, the dominant component of terrestrial evapotranspiration (ET), directly connects the water, energy and carbon cycles and is typically restricted by soil and atmospheric (for example, the vapour pressure deficit (VPD)) moisture stresses throu ... Full text Cite

Effects of Gentle Topography on Forest-Atmosphere Gas Exchanges and Implications for Eddy-Covariance Measurements

Journal Article Journal of Geophysical Research: Atmospheres · June 16, 2020 The interpretation of tower-based eddy-covariance (EC) turbulent flux measurements above forests hinges on three key assumptions: (1) steadiness in the flow statistics, (2) planar homogeneity of scalar sources or sinks, and (3) planar homogeneity in the fl ... Full text Cite

Advancing ecohydrology in the 21st century: A convergence of opportunities

Journal Article Ecohydrology · June 1, 2020 Nature-based solutions for water-resource challenges require advances in the science of ecohydrology. Current understanding is limited by a shortage of observations and theories that can further our capability to synthesize complex processes across scales ... Full text Cite

Recovering the Metabolic, Self-Thinning, and Constant Final Yield Rules in Mono-Specific Stands

Journal Article Frontiers in Forests and Global Change · May 27, 2020 Competition among plants of the same species often results in power-law relations between measures of crowding, such as plant density, and average size, such as individual biomass. Yoda's self-thinning rule, the constant final yield rule, and metabolic sca ... Full text Cite

Inverse Cascade Evidenced by Information Entropy of Passive Scalars in Submerged Canopy Flows

Journal Article Geophysical Research Letters · May 16, 2020 Turbulent mixing of scalars within canopies is investigated using a flume experiment with canopy-like rods of height h mounted to the channel bed. The data comprised a time sequence of high-resolution images of a dye recorded in a plane parallel to the bed ... Full text Cite

Resistance Formulations in Shallow Overland Flow Along a Hillslope Covered With Patchy Vegetation

Journal Article Water Resources Research · May 1, 2020 Describing the effects of surface roughness on flow resistance remains a first-order challenge for modeling shallow overland flow using the Saint Venant equations (SVE). This challenge has resulted in a proliferation of roughness schemes relating the prope ... Full text Cite

Global convergence of COVID-19 basic reproduction number and estimation from early-time SIR dynamics

Journal Article · April 14, 2020 AbstractThe SIR (‘susceptible-infectious-recovered’) formulation is used to uncover the generic spread mechanisms observed by COVID-19 dynamics globally, especially in the early phases of infectious spread. During this earl ... Full text Cite

The Duality of Reforestation Impacts on Surface and Air Temperature

Journal Article Journal of Geophysical Research: Biogeosciences · April 1, 2020 Evidence is mounting that temperate-zone reforestation cools surface temperature (Tsurf), mitigating deleterious effects of climate warming. While Tsurf drives many biophysical processes, air temperature (Ta) is an equally important target for climate miti ... Full text Cite

Multiscale analysis of evapotranspiration and carbon assimilation for a long time series of micrometeorological observation in a typical semi-arid Mediterranean ecosystem

Journal Article · March 23, 2020 The evapotranspiration (ET) process is a key term of soil water balance. In the Mediterranean climates ET represents the main loss term, that could ... Full text Cite

Plant hydraulics accentuates the effects of atmospheric moisture stress on transpiration

Journal Article · March 23, 2020 Transpiration directly links the water, energy and carbon cycles. It is commonly restricted by soil (through soil moisture) and atmospheric (through vapor pressure deficit, VPD) moisture stresses governed by the movement o ... Full text Cite

Assessing decoupling of above and below canopy air masses at a Norway spruce stand in complex terrain

Journal Article · March 23, 2020 Concurrent below (0.14 &#8226; canopy height) and above canopy sonic anemometer vertical velocity (w) measurements reveal frequent decoupling events between the air masses below and above the canopy at a dense spru ... Full text Cite

Deriving the sensible heat flux from the air temperature time-series through the flux-variance and the surface renewal methods

Journal Article · March 23, 2020 Eddy covariance (EC) has become the standard method for determining energy fluxes at the soil-plant-atmosphere interface. However, the cost and complexity of EC often limit its widespread deployment, and therefore, alterna ... Full text Cite

An investigation into the influence of high-resolution land-surface heterogeneity on atmospheric dynamics

Journal Article · March 23, 2020 Land-surface heterogeneity is known to play an important role in land surface hydrology and thus the boundary conditions for numerical weather prediction (NWP) and climate modeling. For this reason, there have been conside ... Full text Cite

Seasonal hysteresis of surface urban heat islands.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · March 2020 Temporal dynamics of urban warming have been extensively studied at the diurnal scale, but the impact of background climate on the observed seasonality of surface urban heat islands (SUHIs) remains largely unexplored. On seasonal time scales, the intensity ... Full text Cite

A joint velocity-intermittency analysis reveals similarity in the vertical structure of atmospheric and hydrospheric canopy turbulence

Journal Article Environmental Fluid Mechanics · February 1, 2020 Turbulent flow through and over vegetation continues to draw significant research attention given its relevance to a plethora of applications in earth and environmental science. Canopy flows are characterized by three-dimensional coherent vortical motions ... Full text Cite

Maximizing leaf carbon gain in varying saline conditions: An optimization model with dynamic mesophyll conductance.

Journal Article The Plant journal : for cell and molecular biology · February 2020 While the adverse effects of elevated salinity levels on leaf gas exchange in many crops are not in dispute, representing such effects on leaf photosynthetic rates (A) continues to draw research attention. Here, an optimization model for stomatal conductan ... Full text Cite

The effect of rainfall amount and timing on annual transpiration in grazed savanna grassland

Journal Article · January 10, 2020 Abstract. The role of precipitation (P) variability on evapotranspiration (ET) and its two components transpiration (T) and evaporation (E) rates from savannas continues to draw significant research interest given its relevance to a number of eco-h ... Full text Cite

Global convergence of COVID-19 basic reproduction number and estimation from early-time SIR dynamics.

Journal Article PloS one · January 2020 The SIR ('susceptible-infectious-recovered') formulation is used to uncover the generic spread mechanisms observed by COVID-19 dynamics globally, especially in the early phases of infectious spread. During this early period, potential controls were not eff ... Full text Cite

Reduced resilience as an early warning signal of forest mortality

Journal Article Nature Climate Change · November 1, 2019 Climate-induced forest mortality is being widely observed across the globe. Predicting forest mortality remains challenging because the physiological mechanisms causing mortality are not fully understood and empirical relations between climatology and mort ... Full text Cite

Xylem-phloem hydraulic coupling explains multiple osmoregulatory responses to salt stress.

Journal Article The New phytologist · October 2019 Salinity is known to affect plant productivity by limiting leaf-level carbon exchange, root water uptake, and carbohydrates transport in the phloem. However, the mechanisms through which plants respond to salt exposure by adjusting leaf gas exchange and xy ... Full text Cite

Cospectral budget model describes incipient sediment motion in turbulent flows

Journal Article Physical Review Fluids · September 24, 2019 Relating incipient motion of sediments to properties of turbulent flows continues to draw significant research attention given its relevance to a plethora of applications in ecology, sedimentary geology, geomorphology, and civil engineering. Upon combining ... Full text Cite

Magnitude of urban heat islands largely explained by climate and population.

Journal Article Nature · September 2019 Urban heat islands (UHIs) exacerbate the risk of heat-related mortality associated with global climate change. The intensity of UHIs varies with population size and mean annual precipitation, but a unifying explanation for this variation is lacking, and th ... Full text Cite

A Dynamic Optimality Principle for Water Use Strategies Explains Isohydric to Anisohydric Plant Responses to Drought

Journal Article Frontiers in Forests and Global Change · August 28, 2019 Optimality principles that underlie models of stomatal kinetics require identifying and formulating the gain and the costs involved in opening stomata. While the gain has been linked to larger carbon acquisition, there is still a debate as to the costs tha ... Full text Cite

Mean Velocity and Shear Stress Distribution in Floating Treatment Wetlands: An Analytical Study

Journal Article Water Resources Research · August 1, 2019 Floating treatment wetlands (FTWs) are efficient at wastewater treatment; however, data and physical models describing water flow through them remain limited. A two-domain model is proposed dividing the flow region into an upper part characterizing the flo ... Full text Cite

Submeso Motions and Intermittent Turbulence Across a Nocturnal Low-Level Jet: A Self-Organized Criticality Analogy

Journal Article Boundary-Layer Meteorology · July 1, 2019 One of the hallmarks of the stable boundary layer is the switching between turbulent (active) and non-turbulent (passive) states. In very stable conditions, the boundary layer becomes layered with fully-developed turbulence confined to a shallow region nea ... Full text Cite

Effects of topography on in-canopy transport of gases emitted within dense forests

Journal Article Quarterly Journal of the Royal Meteorological Society · July 1, 2019 The significance of air flow within dense canopies situated on hilly terrain is not in dispute given its relevance to a plethora of applications in meteorology, wind energy, air pollution, atmospheric chemistry and ecology. While the mathematical descripti ... Full text Cite

Large Eddies Regulate Turbulent Flux Gradients in Coupled Stable Boundary Layers

Journal Article Geophysical Research Letters · June 16, 2019 Due to strong mean wind shear, the stable boundary layer (SBL) becomes vertically coupled. In a coupled SBL, large turbulent eddies enhance cross-layer mixing and vertically mix turbulent kinetic energy. However, large gradients in momentum and heat fluxes ... Full text Cite

Turbulence structure in open channel flow with partially covered artificial emergent vegetation

Journal Article Journal of Hydrology · June 1, 2019 An innovative approach was recently proposed to increase water depth and improve navigation in rivers by increasing overall roughness through an adaptive placement of artificial vegetation. In this approach, a section of the river width is covered with art ... Full text Cite

The simultaneous effects of image force and diffusion on ultrafine particle deposition onto vegetation: A wind tunnel study

Journal Article Aerosol Science and Technology · April 3, 2019 Atmospheric ultrafine particles (UFP) and their associated sources and sinks continue to attract significant research attention in climate and air pollution science. Vegetation is an important sink for UFP given its large area coverage. What remains a subj ... Full text Cite

The structure of turbulent flow through submerged flexible vegetation

Journal Article Journal of Hydrodynamics · April 1, 2019 The hydrodynamics of turbulent flow through submerged flexible vegetation is investigated in a flume using acoustic Doppler velocimetery (ADV) measurements. The flow characteristics such as the energetics and momentum transfer derived from conventional spe ... Full text Cite

A Dynamic Optimality Principle for Water Use Strategies Explains Isohydric to Anisohydric Plant Responses to Drought

Journal Article · March 28, 2019 Optimality principles that underlie models of stomatal kinetics require identifying and formulating the gain and the costs involved in opening stomata. While the gain has been linked to larger carbon acquisition, there is still debate as to the costs th ... Full text Cite

A primer on turbulence in hydrology and hydraulics: The power of dimensional analysis

Journal Article Wiley Interdisciplinary Reviews: Water · March 1, 2019 The apparent random swirling motion of water is labeled “turbulence,” which is a per-vasive state of the flow in many hydrological and hydraulic transport phenomena. Water flow in a turbulent state can be described by the momentum conservation equations kn ... Full text Cite

Xylem functioning, dysfunction and repair: a physical perspective and implications for phloem transport.

Journal Article Tree physiology · February 2019 Xylem and phloem are the two main conveyance systems in plants allowing exchanges of water and carbohydrates between roots and leaves. While each system has been studied in isolation for well over a century, the coupling and coordination between them remai ... Full text Cite

Resistance to Flow on a Sloping Channel Covered by Dense Vegetation following a Dam Break

Journal Article Water Resources Research · February 1, 2019 The effect of hydraulic resistance on the downstream evolution of the water surface profile h in a sloping channel covered by a uniform dense rod canopy following the instantaneous collapse of a dam was examined using flume experiments. Near the head of th ... Full text Cite

The anatomy of large-scale motion in atmospheric boundary layers

Journal Article Journal of Fluid Mechanics · January 10, 2019 The atmospheric boundary layer is the level of the atmosphere where all human activities occur. It is a layer characterized by its turbulent flow state, meaning that the velocity, temperature and scalar concentrations fluctuate over scales that range from ... Full text Cite

Aerodynamic resistance parameterization for heterogeneous surfaces using a covariance function approach in spectral space

Journal Article Journal of the Atmospheric Sciences · January 1, 2019 Simulating the influence of heterogeneous surfaces on atmospheric flow using mesoscale models (MSM) remains a challenging task, as the resolution of these models usually prohibits resolving important scales of surface heterogeneity. However, surface hetero ... Full text Cite

Data from: Resistance to flow on a sloping channel covered by dense vegetation following a dam-break

Dataset · December 28, 2018 The effect of hydraulic resistance on the downstream evolution of the water surface profile h in a sloping channel covered by a uniform dense rod canopy following the instantaneous collapse of a dam was examined using flume experiments. Near the head of th ... Full text Cite

On the role of return to isotropy in wall-bounded turbulent flows with buoyancy

Journal Article Journal of Fluid Mechanics · December 10, 2018 High Reynolds number wall-bounded turbulent flows subject to buoyancy forces are fraught with complex dynamics originating from the interplay between shear generation of turbulence (S) and its production or destruction by density gradients (B). For horizon ... Full text Cite

Vertical characterization of highly oxygenated molecules (HOMs) below and above a boreal forest canopy

Journal Article Atmospheric Chemistry and Physics · December 10, 2018 While the role of highly oxygenated molecules (HOMs) in new particle formation (NPF) and secondary organic aerosol (SOA) formation is not in dispute, the interplay between HOM chemistry and atmospheric conditions continues to draw significant research atte ... Full text Cite

Derivation of canopy resistance in turbulent flow from first-order closure models

Journal Article Water (Switzerland) · December 4, 2018 Quantification of roughness effects on free surface flows is unquestionably necessary when describing water and material transport within ecosystems. The conventional hydrodynamic resistance formula empirically shows that the Darcy-Weisbach friction factor ... Full text Cite

A network model links wood anatomy to xylem tissue hydraulic behaviour and vulnerability to cavitation.

Journal Article Plant, cell & environment · December 2018 Plant xylem response to drought is routinely represented by a vulnerability curve (VC). Despite the significance of VCs, the connection between anatomy and tissue-level hydraulic response to drought remains a subject of inquiry. We present a numerical mode ... Full text Cite

Ejective and Sweeping Motions Above a Peatland and Their Role in Relaxed-Eddy-Accumulation Measurements and Turbulent Transport Modelling

Journal Article Boundary-Layer Meteorology · November 1, 2018 The three turbulent velocity components, water vapour (H 2O ), carbon dioxide (CO 2), and methane (CH 4) concentration fluctuations are measured above a boreal peatland and analyzed using conditional sampling and quadrant analysis. The overarching question ... Full text Cite

Similarity in Fog and Rainfall Intermittency

Journal Article Geophysical Research Letters · October 16, 2018 Intermittent fog occurrences supply significant amounts of moisture to plants in the form of fog drip onto the soil surface thereby prompting interest in their statistical behavior at multiple timescales. A comparison of rainfall and fog measurements colle ... Full text Cite

Partitioning Eddy Covariance Water Flux Components Using Physiological and Micrometeorological Approaches

Journal Article Journal of Geophysical Research: Biogeosciences · October 1, 2018 Eddy covariance (EC) provides ecosystem-scale estimates of photosynthesis (Ph) and evapotranspiration (ET; the sum of plant transpiration [T] and evaporation [Es]). Separating ET into its components is becoming necessary for linking plant-water use strateg ... Full text Cite

Drag coefficient estimation using flume experiments in shallow non-uniform water flow within emergent vegetation during rainfall

Journal Article Ecological Indicators · September 1, 2018 Vegetation persistence on low-gradient slopes in dryland regions is presumed to be supported by lateral flow of water originating from bare sites with low permeability soil. The hydrodynamics of these flows, which occur during and immediately following int ... Full text Cite

Transport in a coordinated soil-root-xylem-phloem leaf system

Journal Article Advances in Water Resources · September 1, 2018 Links between the carbon and water economies of plants are coupled by combining the biochemical demand for atmospheric CO2 with gas transfer through stomates, liquid water transport in the soil-xylem hydraulic system and sucrose export in the phloem. We fo ... Full text Open Access Cite

Effects of leaf area index and density on ultrafine particle deposition onto forest canopies: A LES study

Journal Article Atmospheric Environment · September 1, 2018 A framework to describe transport and deposition of ultrafine particles (UFP) within forests using large eddy simulation (LES) is presented. Comparison with measurements collected within and above a Scots pine stand in Southern Finland are used to explore ... Full text Cite

Indoor and Outdoor Radon Concentration Levels in Lebanon.

Journal Article Health physics · September 2018 Lebanon's lung cancer rates, among the highest in the Arab region, contribute to the burden of noncommunicable diseases. A number of studies have shown that lung cancer risk increases when smokers vs. nonsmokers exposed to elevated radon levels are compare ... Full text Cite

Costs and benefits of non-random seed release for long-distance dispersal in wind-dispersed plant species

Journal Article Oikos · September 1, 2018 The dispersal ability of plants is a major factor driving ecological responses to global change. In wind-dispersed plant species, non-random seed release in relation to wind speeds has been identified as a major determinant of dispersal distances. However, ... Full text Cite

A Structure Function Model Recovers the Many Formulations for Air-Water Gas Transfer Velocity

Journal Article Water Resources Research · September 1, 2018 Two ideas regarding the structure of turbulence near a clear air-water interface are used to derive a waterside gas transfer velocity kL for sparingly and slightly soluble gases. The first is that kL is proportional to the turnover velocity described by th ... Full text Cite

Extremes, intermittency, and time directionality of atmospheric turbulence at the crossover from production to inertial scales

Journal Article Physical Review Fluids · September 1, 2018 The effects of mechanical generation of turbulent kinetic energy and buoyancy forces on the statistics of air temperature and velocity increments are experimentally investigated at the crossover from production to inertial range scales. The ratio of an app ... Full text Cite

Distinct Turbulence Structures in Stably Stratified Boundary Layers With Weak and Strong Surface Shear

Journal Article Journal of Geophysical Research: Atmospheres · August 16, 2018 Turbulence structures and exchange of momentum and heat in the nocturnal stable boundary layer (SBL) show distinct features under different stability conditions prompting interest in their connection. Here eddy covariance data collected at four different h ... Full text Cite

Bridging Land-Surface Fluxes and Aerosol Concentrations to Triggering Convective Rainfall

Report · July 24, 2018 Full text Cite

Environmental and biological controls on seasonal patterns of isoprene above a rain forest in central Amazonia

Journal Article Agricultural and Forest Meteorology. · June 2018 The Amazon rain forest is a major global isoprene source, but little is known about its seasonal ambient concentration patterns. To investigate the environmental and phenological controls over isoprene seasonality, we measured isoprene mixing ratios, concu ... Full text Cite

Biometeorology – From agricultural origins to a last frontier in physics

Journal Article Agricultural and Forest Meteorology · May 28, 2018 Full text Cite

Scalewise invariant analysis of the anisotropic Reynolds stress tensor for atmospheric surface layer and canopy sublayer turbulent flows

Journal Article Physical Review Fluids · May 1, 2018 Anisotropy in the turbulent stress tensor, which forms the basis of invariant analysis, is conducted using velocity time series measurements collected in the canopy sublayer (CSL) and the atmospheric surface layer (ASL). The goal is to assess how thermal s ... Full text Cite

Enhanced Temperature-Humidity Similarity Caused by Entrainment Processes With Increased Wind Shear

Journal Article Journal of Geophysical Research: Atmospheres · April 27, 2018 A number of studies already suggested that entrainment of warm/dry air from aloft degrades the similarity between air temperature (T) and specific humidity (q) in the atmospheric surface layer (ASL). Less is known about entrainment of cool/dry air on the A ... Full text Cite

Scaling and similarity of the anisotropic coherent eddies in near-surface atmospheric turbulence

Journal Article Journal of the Atmospheric Sciences · March 1, 2018 The low-wavenumber regime of the spectrum of turbulence commensurate with Townsend's "attached" eddies is investigated here for the near-neutral atmospheric surface layer (ASL) and the roughness sublayer (RSL) above vegetation canopies. The central thesis ... Full text Cite

Intrinsic Constraints on Asymmetric Turbulent Transport of Scalars Within the Constant Flux Layer of the Lower Atmosphere

Journal Article Geophysical Research Letters · February 28, 2018 A widely used assumption in boundary layer meteorology is the z independence of turbulent scalar fluxes Fs throughout the atmospheric surface layer, where z is the distance from the boundary. This assumption is necessary for the usage of Monin-Obukhov Simi ... Full text Cite

Twenty-three-year timeline of ecological stable states and regime shifts in upper Amazon oxbow lakes

Journal Article Hydrobiologia · February 1, 2018 Regime shifts in shallow lakes are often associated with anthropogenic impacts, such as land-use change, non-point source nutrient loading, and overfishing. These shifts have mostly been examined in lakes in temperate and boreal regions and within anthropo ... Full text Cite

Direct numerical simulation of turbulent slope Flows up to Grashof number Gr D2:110¹¹

Journal Article Journal of Fluid Mechanics · October 25, 2017 Stably stratified turbulent flows over an unbounded, smooth, planar sloping surface at high Grashof numbers are examined using direct numerical simulations (DNS). Four sloping angles (α D 15° 30° 60° and 90°) and three Grashof numbers (Gr D 5×1010, 1×1011 ... Full text Cite

Competition for light and water in a coupled soil-plant system

Journal Article Advances in Water Resources · October 1, 2017 It is generally accepted that resource availability shapes the structure and function of many ecosystems. Within the soil-plant-atmosphere (SPA) system, resource availability fluctuates in space and time whereas access to resources by individuals is furthe ... Full text Cite

Boom and bust carbon-nitrogen dynamics during reforestation

Journal Article Ecological Modelling · September 24, 2017 Legacies of historical land use strongly shape contemporary ecosystem dynamics. In old-field secondary forests, tree growth embodies a legacy of soil changes affected by previous cultivation. Three patterns of biomass accumulation during reforestation have ... Full text Open Access Cite

Increasing atmospheric humidity and CO₂ concentration alleviate forest mortality risk.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · September 2017 Climate-induced forest mortality is being increasingly observed throughout the globe. Alarmingly, it is expected to exacerbate under climate change due to shifting precipitation patterns and rising air temperature. However, the impact of concomitant change ... Full text Cite

Role of large eddies in the breakdown of the Reynolds analogy in an idealized mildly unstable atmospheric surface layer

Journal Article Quarterly Journal of the Royal Meteorological Society · July 1, 2017 While the breakdown in similarity between turbulent transport of heat and momentum (or Reynolds analogy) is not disputed in the atmospheric surface layer (ASL) under unstably stratified conditions, the causes of this breakdown are still debated. One reason ... Full text Cite

A reduced order model to analytically infer atmospheric CO2 concentration from stomatal and climate data

Journal Article Advances in Water Resources · June 1, 2017 To address questions related to the acceleration or deceleration of the global hydrological cycle or links between the carbon and water cycles over land, reliable data for past climatic conditions based on proxies are required. In particular, the reconstru ... Full text Cite

On the linkage between the k^-5/3 spectral and k^-7/3 cospectral scaling in high-Reynolds number turbulent boundary layers

Journal Article Physics of Fluids · June 1, 2017 Connections between the "-5/3" spectral and "-7/3" cospectral scaling exponents characterizing the inertial subranges of the wall-normal energy spectrum and the turbulent momentum flux cospectrum are explored in the equilibrium layer of high-Reynolds numbe ... Full text Cite

A Kolmogorov-Brutsaert structure function model for evaporation into a turbulent atmosphere

Journal Article Water Resources Research · May 1, 2017 In 1965, Brutsaert proposed a model that predicted mean evaporation rate Ē from rough surfaces to scale with the 3/4 power law of the friction velocity (u*) and the square-root of molecular diffusivity (Dm) for water vapor. In arriving at these results, a ... Full text Cite

Non-closure of the surface energy balance explained by phase difference between vertical velocity and scalars of large atmospheric eddies

Journal Article Environmental Research Letters · March 16, 2017 It is now accepted that large-scale turbulent eddies impact the widely reported non-closure of the surface energy balance when latent and sensible heat fluxes are measured using the eddy covariance method in the atmospheric surface layer (ASL). However, a ... Full text Cite

Multiple mechanisms generate a universal scaling with dissipation for the air-water gas transfer velocity

Journal Article Geophysical Research Letters · February 28, 2017 A large corpus of field and laboratory experiments support the finding that the water side transfer velocity kL of sparingly soluble gases near air-water interfaces scales as kL∼(νε)1/4, where ν is the kinematic water viscosity and ε is the mean turbulent ... Full text Cite

Manning's formula and Strickler's scaling explained by a co-spectral budget model

Journal Article Journal of Fluid Mechanics · February 10, 2017 Manning's empirical formula in conjunction with Strickler's scaling is widely used to predict the bulk velocity from the hydraulic radius , the roughness size and the slope of the energy grade line in uniform channel and pipe flows at high bulk Reynolds nu ... Full text Cite

The effect of plant water storage on water fluxes within the coupled soil-plant system.

Journal Article The New phytologist · February 2017 In addition to buffering plants from water stress during severe droughts, plant water storage (PWS) alters many features of the spatio-temporal dynamics of water movement in the soil-plant system. How PWS impacts water dynamics and drought resilience is ex ... Full text Cite

On the variability of the ecosystem response to elevated atmospheric CO2 across spatial and temporal scales at the Duke Forest FACE experiment

Journal Article Agricultural and forest meteorology. · January 2017 While the significance of elevated atmospheric CO2 concentration on instantaneous leaf-level processes such as photosynthesis and transpiration is rarely disputed, its integrated effect at ecosystem level and at long-time scales remains a subject of debate ... Full text Cite

The non-local character of turbulence asymmetry in the convective atmospheric boundary layer

Journal Article Quarterly Journal of the Royal Meteorological Society · January 1, 2017 The inadequacy of conventional gradient diffusion in closure modelling of turbulent heat fluxes within the convective atmospheric boundary layer is often alleviated by accounting for non-local transport effects, such as Deardorff's counter-gradient models, ... Full text Cite

Turbulent mixing and removal of ozone within an Amazon rainforest canopy

Journal Article Journal of Geophysical Research · January 1, 2017 Simultaneous profiles of turbulence statistics and mean ozone mixing ratio are used to establish a relation between eddy diffusivity and ozone mixing within the Amazon forest. A one-dimensional diffusion model is proposed and used to infer mixing time scal ... Full text Cite

Do the energy fluxes and surface conductance of boreal coniferous forests in Europe scale with leaf area?

Journal Article Global change biology · December 2016 Earth observing systems are now routinely used to infer leaf area index (LAI) given its significance in spatial aggregation of land surface fluxes. Whether LAI is an appropriate scaling parameter for daytime growing season energy budget, surface conductanc ... Full text Cite

Delay-induced rebounds in CO2 emissions and critical time-scales to meet global warming targets

Journal Article Earth's Future · December 1, 2016 While climate science debates are focused on the attainment of peak anthropogenic CO2 emissions and policy tools to reduce peak temperatures, the human-energy-climate system can hold “rebound” surprises beyond this peak. Following the second industrial rev ... Full text Cite

Linking meteorology, turbulence, and air chemistry in the amazon rain forest

Journal Article Bulletin of the American Meteorological Society · December 1, 2016 A field campaign reveals that the Amazon rain forest produces enough chemical species to undergo oxidation and generate aerosols, which can activate into cloud condensation nuclei and potentially influence cloud formation. ... Full text Cite

Ecohydrology: Modeling water, carbon, and nutrient cycling within the soil-plant atmosphere continuum

Chapter · November 25, 2016 Full text Cite

Climate, not conflict, explains extreme Middle East dust storm

Journal Article Environmental Research Letters · November 8, 2016 The recent dust storm in the Middle East (Sepember 2015) was publicized in the media as a sign of an impending 'Dust Bowl.' Its severity, demonstrated by extreme aerosol optical depth in the atmosphere in the 99th percentile compared to historical data, wa ... Full text Cite

Generalized logarithmic scaling for high-order moments of the longitudinal velocity component explained by the random sweeping decorrelation hypothesis

Journal Article Physics of Fluids · September 1, 2016 Expressions for the logarithmic variations of the normalized turbulent longitudinal velocity (u2p)1/p with normalized distance z/δ from a boundary for high-order (p) moments in the intermediate region of wall bounded flows characterized by thickness d are ... Full text Cite

Deviations from unity of the ratio of the turbulent Schmidt to Prandtl numbers in stratified atmospheric flows over water surfaces

Journal Article Physical Review Fluids · July 20, 2016 Full text Cite

GRADIENT-DIFFUSION CLOSURE AND THE EJECTION-SWEEP CYCLE IN CONVECTIVE BOUNDARY LAYERS

Journal Article Ciência e Natura · July 20, 2016 The inadequacy of conventional gradient-diffusion closure in modeling turbulent heat flux within the convective atmospheric boundary-layer is often alleviated by accounting for nonlocal transport. Such nonlocal effects are a manifestation of the in ... Full text Cite

Soil-plant-atmosphere conditions regulating convective cloud formation above southeastern US pine plantations.

Journal Article Global change biology · June 2016 Loblolly pine trees (Pinus taeda L.) occupy more than 20% of the forested area in the southern United States, represent more than 50% of the standing pine volume in this region, and remove from the atmosphere about 500 g C m-2 per year through net ecosyste ... Full text Cite

Large CO2 effluxes at night and during synoptic weather events significantly contribute to CO2 emissions from a reservoir

Journal Article Environmental Research Letters · May 24, 2016 CO2 emissions from inland waters are commonly determined by indirect methods that are based on the product of a gas transfer coefficient and the concentration gradient at the air water interface (e.g., wind-based gas transfer models). The measurements of c ... Full text Cite

Dissipation Intermittency Increases Long-Distance Dispersal of Heavy Particles in the Canopy Sublayer

Journal Article Boundary-Layer Meteorology · April 1, 2016 The dispersion of heavy particles such as seeds within canopies is evaluated using Lagrangian stochastic trajectory models, laboratory, and field experiments. Inclusion of turbulent kinetic energy dissipation rate intermittency is shown to increase long-di ... Full text Cite

Mean-velocity profile of smooth channel flow explained by a cospectral budget model with wall-blockage

Journal Article Physics of Fluids · March 1, 2016 A series of recent studies has shown that a model of the turbulent vertical velocity variance spectrum (Fvv) combined with a simplified cospectral budget can reproduce many macroscopic flow properties of turbulent wall-bounded flows, including various feat ... Full text Cite

Matching ecohydrological processes and scales of banded vegetation patterns in semiarid catchments

Journal Article Water Resources Research · March 1, 2016 While the claim that water-carbon interactions result in spatially coherent vegetation patterning is rarely disputed in many arid and semiarid regions, the significance of the detailed water pathways and other high frequency variability remain an open ques ... Full text Cite

Persistence and memory timescales in root-zone soil moisture dynamics

Journal Article Water Resources Research · February 1, 2016 The memory timescale that characterizes root-zone soil moisture remains the dominant measure in seasonal forecasts of land-climate interactions. This memory is a quasi-deterministic timescale associated with the losses (e.g., evapotranspiration) from the s ... Full text Cite

The k^-1 scaling of air temperature spectra in atmospheric surface layer flows

Journal Article Quarterly Journal of the Royal Meteorological Society · January 1, 2016 A number of atmospheric surface layer (ASL) experiments reported a k-1 scaling in air temperature spectra ETT(k) at low wavenumber k but other experiments did not. Occurrence of this scaling law in ETT(k) in an idealized ASL flow across a wide range of atm ... Full text Cite

A spectral budget model for the longitudinal turbulent velocity in the stable atmospheric surface layer

Journal Article Journal of the Atmospheric Sciences · January 1, 2016 A spectral budget model is developed to describe the scaling behavior of the longitudinal turbulent velocity variance σ2u with the stability parameter ζ=z/L and the normalized height z/δ in an idealized stably stratified atmospheric surface layer (ASL), wh ... Full text Cite

On the variability of the Priestley-Taylor coefficient over water bodies

Journal Article Water Resources Research · January 1, 2016 Deviations in the Priestley-Taylor (PT) coefficient αPT from its accepted 1.26 value are analyzed over large lakes, reservoirs, and wetlands where stomatal or soil controls are minimal or absent. The data sets feature wide variations in water body sizes an ... Full text Cite

Closure schemes for stably stratified atmospheric flows without turbulence cutoff

Journal Article Journal of the Atmospheric Sciences · January 1, 2016 Two recently proposed turbulence closure schemes are compared against the conventional Mellor-Yamada (MY) model for stably stratified atmospheric flows. The Energy- and Flux-Budget (EFB) approach solves the budgets of turbulent momentum and heat fluxes and ... Full text Cite

The Spatio-temporal Statistical Structure and Ergodic Behaviour of Scalar Turbulence Within a Rod Canopy

Journal Article Boundary-Layer Meteorology · December 1, 2015 Connections between the spatial and temporal statistics of turbulent flow, and their possible convergence to ensemble statistics as assumed by the ergodic hypothesis, are explored for passive scalars within a rod canopy. While complete ergodicity is not ex ... Full text Cite

Wind-induced leaf transpiration

Journal Article Advances in Water Resources · December 1, 2015 While the significance of leaf transpiration (fe) on carbon and water cycling is rarely disputed, conflicting evidence has been reported on how increasing mean wind speed (U) impacts fe from leaves. Here, conditions promoting enhancement or suppression of ... Full text Cite

Steady nonuniform shallow flow within emergent vegetation

Journal Article Water Resources Research · December 1, 2015 Surface flow redistribution on flat ground from crusted bare soil to vegetated patches following intense rainfall events elevates plant available water above that provided by rainfall. The significance of this surface water redistribution to sustaining veg ... Full text Cite

Introduction to a special section on ecohydrology of semiarid environments: Confronting mathematical models with ecosystem complexity

Journal Article Water Resources Research · November 1, 2015 Current literature provides large number of publications about ecohydrological processes and their effect on the biota in drylands. Given the limited laboratory and field experiments in such systems, many of these publications are based on mathematical mod ... Full text Cite

The dual role of soil crusts in desertification

Journal Article Journal of Geophysical Research: Biogeosciences · October 1, 2015 Vegetation cover in dry regions is a key variable in determining desertification. Soils exposed to rainfall by desertification can form physical crusts that reduce infiltration, exacerbating water stress on the remaining vegetation. Paradoxically, field st ... Full text Cite

Coupling boreal forest CO2, H2O and energy flows by a vertically structured forest canopy - Soil model with separate bryophyte layer

Journal Article Ecological Modelling · September 4, 2015 A 1-dimensional multi-layer, multi-species soil-vegetation-atmosphere transfer model APES (Atmosphere-Plant Exchange Simulator) with a separate moss layer at the forest floor was developed and evaluated for a boreal Scots pine forest situated in Hyytiälä, ... Full text Cite

Bottlenecks in turbulent kinetic energy spectra predicted from structure function inflections using the Von Kármán-Howarth equation.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · September 2015 Featured Publication The compensated three-dimensional turbulent kinetic energy spectrum exhibits a peculiar bump at wave numbers in the vicinity of the crossover from inertial to viscous regimes due to pile up in turbulent kinetic energy, a phenomenon referred to as the bottl ... Full text Cite

Cross-scale impact of climate temporal variability on ecosystem water and carbon fluxes

Journal Article Journal of Geophysical Research: Biogeosciences · September 1, 2015 While the importance of ecosystem functioning is undisputed in the context of climate change and Earth system modeling, the role of short-scale temporal variability of hydrometeorological forcing (∼1 h) on the related ecosystem processes remains to be full ... Full text Cite

Characteristics of gravity waves over an Antarctic Ice sheet during an Austral Summer

Journal Article Atmosphere · September 1, 2015 While occurrences of wavelike motion in the stable boundary layer due to the presence of a significant restoring buoyancy force are rarely disputed, their modalities and interaction with turbulence remain a subject of active research. In this work, the cha ... Full text Cite

The hysteresis response of soil CO2 concentration and soil respiration to soil temperature

Journal Article Journal of Geophysical Research: Biogeosciences · August 1, 2015 Diurnal hysteresis between soil temperature (Ts) and both CO2 concentration ([CO2]) and soil respiration rate (Rs) were reported across different field experiments. However, the causes of these hysteresis patterns remain a subject of debate, with biotic an ... Full text Cite

Separating physical and biological controls on long-term evapotranspiration fluctuations in a tropical deciduous forest subjected to monsoonal rainfall

Journal Article Journal of Geophysical Research: Biogeosciences · July 1, 2015 Evapotranspiration (ET), especially in the mainland of the Indochina Peninsula, can impact and is impacted by the Asian monsoonal (AM) system, thereby prompting interest in its long-term variability. To separate the physical and biological factors controll ... Full text Cite

Suppressed convective rainfall by agricultural expansion in southeastern Burkina Faso

Journal Article Water Resources Research · July 1, 2015 With the "green economy" being promoted as a path to sustainable development and food security within the African continent, the influx of agricultural land is proliferating at a rapid pace often replacing natural savannah forests. Where agriculture is pri ... Full text Cite

Revisiting the formulations for the longitudinal velocity variance in the unstable atmospheric surface layer

Journal Article Quarterly Journal of the Royal Meteorological Society · July 1, 2015 Because of its non-conformity to Monin-Obukhov Similarity Theory (MOST), the effects of thermal stratification on scaling laws describing the streamwise turbulent intensity σu normalized by the turbulent friction velocity (u*) continue to draw research att ... Full text Cite

Footprint Estimation for Multi-Layered Sources and Sinks Inside Canopies in Open and Protected Environments

Journal Article Boundary-Layer Meteorology · May 1, 2015 A multi-layered flux footprint model is developed for a canopy situated within a protected environment such as a screenhouse. The model accounts for the vertically distributed sources and sinks within the canopy as well as modifications introduced by the s ... Full text Cite

Effects of different representations of stomatal conductance response to humidity across the African continent under warmer CO2-enriched climate conditions

Journal Article Journal of Geophysical Research: Biogeosciences · May 1, 2015 General circulation models (GCMs) forecast higher global vapor pressure deficit (VPD) but unchanged global relative humidity (RH) in future climates. A literature survey revealed that 50% of Earth system models and land surface models embedded within GCMs ... Full text Cite

Abiotic and biotic controls of soil moisture spatiotemporal variability and the occurrence of hysteresis

Journal Article Water Resources Research · May 1, 2015 An expression that separates biotic and abiotic controls on the temporal dynamics of the soil moisture spatial coefficient of variation Cv(θ) was explored via numerical simulations using a mechanistic ecohydrological model, Tethys-Chloris. Continuous soil ... Full text Cite

The influence of water table depth and the free atmospheric state on convective rainfall predisposition

Journal Article Water Resources Research · April 1, 2015 A mechanistic model for the soil-plant system is coupled to a conventional slab representation of the atmospheric boundary layer (ABL) to explore the role of groundwater table (WT) variations and free atmospheric (FA) states on convective rainfall predispo ... Full text Cite

The Doomsday Equation and 50 years beyond: new perspectives on the human-water system

Journal Article WIREs Water · March 1, 2015 In 1960, von Foerster et al. humorously predicted an abrupt transition in human population growth to occur in the mid-21st century. Their so-called ‘Doomsday’ emerged from either progressive degradation of a finite resource or faster-than-exponential growt ... Full text Link to item Cite

Flume experiments on wind induced flow in static water bodies in the presence of protruding vegetation

Journal Article Advances in Water Resources · February 1, 2015 The problem of wind-induced flow in inland waters is drawing significant research attention given its relevance to a plethora of applications in wetlands including treatment designs, pollution reduction, and biogeochemical cycling. The present work address ... Full text Cite

The effects of leaf size and microroughness on the branch-scale collection efficiency of ultrafine particles

Journal Article Journal of Geophysical Research · January 1, 2015 Wind tunnel experiments were performed to explore how leaf size and leaf microroughness impact the collection efficiency of ultrafine particles (UFP) at the branch scale. A porous media model previously used to characterize UFP deposition onto conifers (Pi ... Full text Cite

Revisiting the turbulent prandtl number in an idealized atmospheric surface layer

Journal Article Journal of the Atmospheric Sciences · January 1, 2015 Cospectral budgets are used to link the kinetic and potential energy distributions of turbulent eddies, as measured by their spectra, to macroscopic relations between the turbulent Prandtl number (Prt) and atmospheric stability measures such as the stabili ... Full text Cite

Turbulent Energy Spectra and Cospectra of Momentum and Heat Fluxes in the Stable Atmospheric Surface Layer

Journal Article Boundary-Layer Meteorology · 2015 © 2015, Springer Science+Business Media Dordrecht.The turbulent energy spectra and cospectra of momentum and sensible heat fluxes are examined theoretically and experimentally with increasing flux Richardson number (Rf) in the stable atmospheric surface la ... Full text Cite

On the effects of temporal meteorological variability on ecosystem water and carbon fluxes across scales: A modeling approach

Conference Rainfall in Urban and Natural Systems - Proceedings of the 10th International Workshop on Precipitation in Urban Areas, UrbanRain 2015 · January 1, 2015 Climate varies across a wide range of temporal and spatial scales and this variability affects and is affected by ecosystem responses. There is strong evidence from observations and climate model projections that due to anthropogenic influences, climate va ... Cite

Streamwise turbulent intensity under unstable atmospheric stratification explained by a spectral budget

Conference Proceedings - 15th European Turbulence Conference, ETC 2015 · January 1, 2015 © TU Delft. Because of its non-conformity to Monin-Obukhov Similarity Theory (MOST), the effects of thermal stratification on scaling laws describing the stream-wise turbulent intensity σu normalized by the turbulent friction velocity (u∗) continues to dra ... Cite

Streamwise turbulent intensity under unstable atmospheric stratification explained by a spectral budget

Conference Proceedings - 15th European Turbulence Conference, ETC 2015 · January 1, 2015 Because of its non-conformity to Monin-Obukhov Similarity Theory (MOST), the effects of thermal stratification on scaling laws describing the stream-wise turbulent intensity σu normalized by the turbulent friction velocity (u∗) continues to draw research a ... Cite

Cospectral budget of turbulence explains the bulk properties of smooth pipe flow.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · December 2014 Connections between the wall-normal turbulent velocity spectrum E(ww)(k) at wave number k and the mean velocity profile (MVP) are explored in pressure-driven flows confined within smooth walls at moderate to high bulk Reynolds numbers (Re). These connectio ... Full text Cite

Radiative and precipitation controls on root zone soil moisture spectra

Journal Article Geophysical Research Letters · November 16, 2014 Temporal variability in root zone soil moisture content (w) exhibits a Lorentzian spectrum with memory dictated by a damping term when forced with white-noise precipitation. In the context of regional dimming, radiation and precipitation variability are ne ... Full text Cite

Invariant soil water potential at zero microbial respiration explained by hydrological discontinuity in dry soils

Journal Article Geophysical Research Letters · October 28, 2014 Soil microbial respiration rates decrease with soil drying, ceasing below water potentials around -15-MPa. A proposed mechanism for this pattern is that under dry conditions, microbes are substrate limited because solute diffusivity is halted due to breaki ... Full text Cite

Interpreting three-dimensional spore concentration measurements and escape fraction in a crop canopy using a coupled Eulerian–Lagrangian stochastic model

Journal Article Agricultural and Forest Meteorology. · August 2014 Plant disease epidemics caused by pathogenic spores are common threat to agricultural crops. Pathogenic spores are often produced and released inside plant canopies but are transported out of the canopy region by turbulent motions and advected longitudinal ... Full text Cite

Momentum balance of katabatic flow on steep slopes covered with short vegetation

Journal Article Geophysical Research Letters · July 16, 2014 Katabatic flows over alpine mountainous terrain differ from their forested or bare slope counterparts due to the presence of well-ventilated, short vegetation. The impact of a grass canopy and larger-scale pressure perturbations on the one-dimensional mean ... Full text Cite

Increasing water use efficiency along the C3 to C4 evolutionary pathway: a stomatal optimization perspective.

Journal Article Journal of experimental botany · July 2014 C4 photosynthesis evolved independently numerous times, probably in response to declining atmospheric CO2 concentrations, but also to high temperatures and aridity, which enhance water losses through transpiration. Here, the environmental factors controlli ... Full text Cite

A theoretical analysis of microbial eco-physiological and diffusion limitations to carbon cycling in drying soils

Journal Article Soil Biology and Biochemistry. · June 2014 Soil microbes face highly variable moisture conditions that force them to develop adaptations to tolerate or avoid drought. Drought conditions also limit the supply of vital substrates by inhibiting diffusion in dry conditions. How these biological and phy ... Full text Cite

Tree root systems competing for soil moisture in a 3D soil-plant model

Journal Article Advances in Water Resources · April 1, 2014 Competition for water among multiple tree rooting systems is investigated using a soil-plant model that accounts for soil moisture dynamics and root water uptake (RWU), whole plant transpiration, and leaf-level photosynthesis. The model is based on a numer ... Full text Cite

Mechanistic modeling of seed dispersal by wind over hilly terrain

Journal Article Ecological Modelling · February 24, 2014 Seed dispersal is the main movement mechanism used by plants. The last decade saw rapid progress in understanding the underlying processes, especially for dispersal by wind, in part due to new mechanistic modeling approaches that account for turbulent fluc ... Full text Cite

Erratum: Two phenomenological constants explain similarity laws in stably stratified turbulence (Physical Review E - Statistical, Nonlinear, and Soft Matter Physics (2014) 89 023007))

Journal Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics · February 21, 2014 Full text Cite

Two phenomenological constants explain similarity laws in stably stratified turbulence.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · February 2014 Featured Publication In stably stratified turbulent flows, the mixing efficiency associated with eddy diffusivity for heat, or equivalently the turbulent Prandtl number (Pr(t)), is fraught with complex dynamics originating from the scalewise interplay between shear generation ... Full text Cite

Vegetation collection efficiency of ultrafine particles: From single fiber to porous media

Journal Article Journal of Geophysical Research · January 16, 2014 A number of parameterization schemes are available to determine the collection efficiency of ultrafine particles (UFP) onto vegetated surfaces. One approach represents the vegetated elements as a fibrous filter with a characteristic fiber size that is diff ... Full text Cite

A Velocity-Dissipation Lagrangian Stochastic Model for Turbulent Dispersion in Atmospheric Boundary-Layer and Canopy Flows

Journal Article Boundary-Layer Meteorology · January 1, 2014 An extended Lagrangian stochastic dispersion model that includes time variations of the turbulent kinetic energy dissipation rate is proposed. The instantaneous dissipation rate is described by a log-normal distribution to account for rare and intense burs ... Full text Cite

The hysteretic evapotranspiration - Vapor pressure deficit relation

Journal Article Journal of Geophysical Research: Biogeosciences · January 1, 2014 Diurnal hysteresis between evapotranspiration (ET) and vapor pressure deficit (VPD) was reported in many ecosystems, but justification for its onset and magnitude remains incomplete with biotic and abiotic factors invoked as possible explanations. To place ... Full text Cite

Particle deposition to forests: An alternative to K-theory

Journal Article Atmospheric Environment · January 1, 2014 It has been known for some time that flux-gradient closure schemes (or K-theory), widely used to model the aerosol sized particle turbulent diffusivity, are problematic within canopies. Reported momentum transport in a zero- or counter-mean velocity gradie ... Full text Cite

An ecohydrological perspective on drought-induced forest mortality

Journal Article Journal of Geophysical Research: Biogeosciences · January 1, 2014 Regional-scale drought-induced forest mortality events are projected to become more frequent under future climates due to changes in rainfall patterns. The occurrence of these mortality events is driven by exogenous factors such as frequency and severity o ... Full text Cite

A dynamical system perspective on plant hydraulic failure

Journal Article Water Resources Research · January 1, 2014 Photosynthesis is governed by leaf water status that depends on the difference between the rates of transpiration and water supply from the soil and through the plant xylem. When transpiration increases compared to water supply, the leaf water potential re ... Full text Cite

Ecohydrological flow networks in the subsurface

Journal Article Ecohydrology · January 1, 2014 Preferential flow in hillslope systems through subsurface networks developed from a range of botanical, faunal and geophysical processes have been observed and inferred for decades and may provide a large component of the bulk transport of water and solute ... Full text Cite

Optimal plant water-use strategies under stochastic rainfall

Journal Article Water Resources Research · January 1, 2014 Plant hydraulic traits have been conjectured to be coordinated, thereby providing plants with a balanced hydraulic system that protects them from cavitation while allowing an efficient transport of water necessary for photosynthesis. In particular, observa ... Full text Cite

Secondary dispersal driven by overland flow in drylands: Review and mechanistic model development.

Journal Article Movement ecology · January 2014 Seed dispersal alters gene flow, reproduction, migration and ultimately spatial organization of dryland ecosystems. Because many seeds in drylands lack adaptations for long-distance dispersal, seed transport by secondary processes such as tumbling in the w ... Full text Cite

Bayesian estimation of methane emission rates from a single high-frequency gas sensor

Conference Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA · January 1, 2014 In onshore oil and gas exploration and production, new tools are needed to support environmentally responsible development of these key national energy assets. Concerns for air pollution emissions from this sector include the unintentional release of produ ... Cite

Correction: Secondary dispersal driven by overland flow in drylands: Review and mechanistic model development.

Journal Article Movement ecology · January 2014 Full text Cite

Logarithmic scaling in the longitudinal velocity variance explained by a spectral budget

Journal Article Physics of Fluids · December 2, 2013 A logarithmic scaling for the streamwise turbulent intensity σu2/u*2 = B1 - A1 ln (z/δ) was reported across several high Reynolds number laboratory experiments as predicted from Townsend's attached eddy hypothesis, where u* is the friction velocity and z i ... Full text Cite

Optimization of stomatal conductance for maximum carbon gain under dynamic soil moisture

Journal Article Advances in Water Resources · December 1, 2013 Featured Publication Optimization theories explain a variety of forms and functions in plants. At the leaf scale, it is often hypothesized that carbon gain is maximized, thus providing a quantifiable objective for a mathematical definition of optimality conditions. Eco-physiol ... Full text Cite

The role of coherent turbulent structures in explaining scalar dissimilarity within the canopy sublayer

Journal Article Environmental Fluid Mechanics · December 1, 2013 Scalar similarity is widely assumed in models and interpretation of micro-meteorological measurements. However, in the air space within and just above the canopy (the so-called canopy sublayer, CSL) scalar similarity is generally violated. The scalar dissi ... Full text Cite

A perspective on optimal leaf stomatal conductance under CO2 and light co-limitations

Journal Article Agricultural and Forest Meteorology. · December 2013 To describe stomatal response to micro-environmental variations, optimization theories for canopy gas exchange are often used as alternatives to empirical or mechanistic but complex models of stomatal function. Solutions for optimal stomatal conductance ha ... Full text Cite

Buoyancy effects on the integral lengthscales and mean velocity profile in atmospheric surface layer flows

Journal Article Physics of Fluids · October 23, 2013 Within the diabatic atmospheric surface layer (ASL) under quasi-stationary and horizontal homogeneous conditions, the mean velocity profile deviates from its conventional logarithmic shape by a height-dependent universal stability correction function φ{sym ... Full text Cite

Katul Receives 2012 Hydrologic Sciences Award: Response

Journal Article Eos, Transactions American Geophysical Union · October 2013 Thank you, Marc, for the kind comments and unwavering support as a mentor and friend. I am honored by this award, which I share with many people. ... Full text Cite

Katul Receives 2012 Hydrologic Sciences Award: Citation

Journal Article Eos, Transactions American Geophysical Union · October 2013 I am delighted to present Professor Gabriel Katul of Duke University with the 2012 Hydrologic Sciences Award. He has made massive contributions to the understanding and prediction of hydrology, and it is for his work that we (Professors Poporato, H ... Full text Cite

Mean Flow Near Edges and Within Cavities Situated Inside Dense Canopies

Journal Article Boundary-Layer Meteorology · October 1, 2013 A streamfunction-vorticity formulation is used to explore the extent to which turbulent and turbulently inviscid solutions to the mean momentum balance explain the mean flow across forest edges and within cavities situated inside dense forested canopies. T ... Full text Cite

The effects of leaf area density variation on the particle collection efficiency in the size range of ultrafine particles (UFP).

Journal Article Environmental science & technology · October 2013 Carbonaceous particles were generated during a "sooting burn" experiment to explore how heterogeneity in horizontal leaf area density (LAD) within the canopy impacts the ultrafine particle (UFP) collection efficiency at the branch-scale. To address this go ... Full text Cite

Root controls on water redistribution and carbon uptake in the soil-plant system under current and future climate

Journal Article Advances in Water Resources · October 1, 2013 Understanding photosynthesis and plant water management as a coupled process remains an open scientific problem. Current eco-hydrologic models characteristically describe plant photosynthetic and hydraulic processes through ad hoc empirical parameterizatio ... Full text Cite

Co-spectrum and mean velocity in turbulent boundary layers

Journal Article Physics of Fluids · September 18, 2013 Featured Publication Connections are explored between spectral descriptions of turbulence and the mean velocity profile in the equilibrium layer of wall-bounded flows using a modeled budget for the co-spectral density. Using a standard model for the wall normal velocity varian ... Full text Cite

Seed dispersal by wind: Towards a conceptual framework of seed abscission and its contribution to long-distance dispersal

Journal Article Journal of Ecology · July 1, 2013 Diaspore abscission determines many aspects of seed dispersal by wind. While there is yet no complete mechanistic framework for understanding abscission by wind, empirical studies to date have suggested that abscission generally (i) occurs above some thres ... Full text Cite

Are atmospheric surface layer flows ergodic?

Journal Article Geophysical Research Letters · June 28, 2013 The transposition of atmospheric turbulence statistics from the time domain, as conventionally sampled in field experiments, is explained by the so-called ergodic hypothesis. In micrometeorology, this hypothesis assumes that the time average of a measured ... Full text Cite

Implications of nonrandom seed abscission and global stilling for migration of wind-dispersed plant species.

Journal Article Global change biology · June 2013 Migration of plant populations is a potential survival response to climate change that depends critically on seed dispersal. Biological and physical factors determine dispersal and migration of wind-dispersed species. Recent field and wind tunnel studies d ... Full text Cite

Partitioning ozone fluxes between canopy and forest floor by measurements and a multi-layer model

Journal Article Agricultural and Forest Meteorology. · May 2013 Ozone uptake by plant leaves is essential to studies investigating atmospheric air pollution and plant injury. A major challenge to these investigations is the up-scaling of leaf-level stomatal processes to the ecosystem level, the accounting for forest fl ... Full text Cite

Flume Experiments on Turbulent Flows Across Gaps of Permeable and Impermeable Boundaries

Journal Article Boundary-Layer Meteorology · April 1, 2013 Laser Doppler anemometery and laser-induced fluorescence techniques were used to explore the spatial structure of the flow within and above finite cavities created within porous and solid media. The cavities within these two configurations were identical i ... Full text Cite

Hydraulic limits on maximum plant transpiration and the emergence of the safety-efficiency trade-off.

Journal Article New Phytol · April 2013 Featured Publication Soil and plant hydraulics constrain ecosystem productivity by setting physical limits to water transport and hence carbon uptake by leaves. While more negative xylem water potentials provide a larger driving force for water transport, they also cause cavit ... Full text Link to item Cite

Erratum: Mean scalar concentration profile in a sheared and thermally stratified atmospheric surface layer (Physical Review E (2013) 87 (023004) DOI:10.1103/PhysRevE.87.023004)

Journal Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics · March 22, 2013 Full text Cite

On the complementary relationship between marginal nitrogen and water-use efficiencies among Pinus taeda leaves grown under ambient and CO2-enriched environments.

Journal Article Annals of botany · March 2013 Background and aimsWater and nitrogen (N) are two limiting resources for biomass production of terrestrial vegetation. Water losses in transpiration (E) can be decreased by reducing leaf stomatal conductance (g(s)) at the expense of lowering CO(2) ... Full text Cite

Fifty years to prove Malthus right.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · March 2013 Full text Cite

Mean scalar concentration profile in a sheared and thermally stratified atmospheric surface layer.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · February 2013 Using only dimensional considerations, Monin and Obukhov proposed a "universal" stability correction function φ(c)(ζ) that accounts for distortions caused by thermal stratification to the mean scalar concentration profile in the atmospheric surface layer w ... Full text Cite

Scalar Turbulence within the Canopy Sublayer

Chapter · January 1, 2013 The exchange of scalars between the biosphere and the atmosphere has direct bearing on a large number of problems such as climate change, air and water quality, agricultural management and food security, landscape ecology, and decision making for environme ... Full text Cite

A Wavelet-Based Correction Method for Eddy-Covariance High-Frequency Losses in Scalar Concentration Measurements

Journal Article Boundary-Layer Meteorology · January 1, 2013 Eddy-covariance (EC) scalar-flux measurements suffer from unavoidable biases introduced by high-frequency losses in the sampled scalar concentration fluctuations. This bias alone leads to an underestimation of scalar fluxes by as much as 20% in some cases, ... Full text Cite

Biological constraints on water transport in the soil-plant-atmosphere system

Journal Article Advances in Water Resources · January 1, 2013 An effective description of water transport in the soil-plant-atmosphere continuum (SPAC) is needed for wide-ranging applications in hydrology and climate-vegetation interactions. In this contribution, the theory of water movement within the SPAC is review ... Full text Cite

Advances in Water Resources: 35th Anniversary Issue Preface

Journal Article Advances in Water Resources · January 1, 2013 Full text Cite

The role of coherent turbulent structures in explaining scalar dissimilarity within the canopy sublayer

Journal Article Environmental Fluid Mechanics · 2013 Cite

Hydraulic determinism as a constraint on the evolution of organisms and ecosystems

Journal Article Journal of Hydraulic Research · December 4, 2012 The interaction between plant hydraulics and plant structure was documented by Leonardo da Vinci, and its importance as a regulator of vegetation and ecosystem function remains of vital contemporary interest. It is proposed that hydraulics deterministicall ... Full text Cite

Existence of k⁻¹ power-law scaling in the equilibrium regions of wall-bounded turbulence explained by Heisenberg's eddy viscosity.

Journal Article Physical review. E, Statistical, nonlinear, and soft matter physics · December 2012 The existence of a "-1" power-law scaling at low wavenumbers in the longitudinal velocity spectrum of wall-bounded turbulence was explained by multiple mechanisms; however, experimental support has not been uniform across laboratory studies. This letter sh ... Full text Cite

Mean velocity and temperature profiles in a sheared diabatic turbulent boundary layer

Journal Article Physics of Fluids · October 3, 2012 In the atmospheric surface layer, modifications to the logarithmic mean velocity and air temperature profiles induced by thermal stratification or convection are accounted for via stability correction functions Φm and Φh, respectively, that vary with the s ... Full text Cite

Turbulent transport efficiency and the ejection-sweep motion for momentum and heat on sloping terrain covered with vineyards

Journal Article Agricultural and Forest Meteorology. · September 2012 In boundary layer flows, it is now recognized that the net momentum and mass exchange rates are dominated by the statistical properties of ejecting and sweeping motion often linked to the presence of coherent turbulent structures. Over vineyards, three mai ... Full text Cite

Evapotranspiration: A process driving mass transport and energy exchange in the soil-plant-atmosphere-climate system

Journal Article Reviews of Geophysics · September 1, 2012 The role of evapotranspiration (ET) in the global, continental, regional, and local water cycles is reviewed. Elevated atmospheric CO2 , air temperature, vapor pressure deficit (D), turbulent transport, radiative transfer, and reduced soil moist ... Full text Cite

A phenomenological model to describe turbulent friction in permeable-wall flows

Journal Article Geophysical Research Letters · July 28, 2012 Describing the canonical properties of turbulent flows over rough-permeable walls such as gravel beds, vegetatedor snow-covered surfaces have, to date, resisted complete theoretical treatment. The major complication in describing such geophysical flows is ... Full text Cite

Increased resin flow in mature pine trees growing under elevated CO2 and moderate soil fertility.

Journal Article Tree physiology · June 2012 Warmer climates induced by elevated atmospheric CO(2) (eCO(2)) are expected to increase damaging bark beetle activity in pine forests, yet the effect of eCO(2) on resin production--the tree's primary defense against beetle attack--remains largely unknown. ... Full text Cite

On the scaling laws of the velocity-scalar cospectra in the canopy sublayer above tall forests

Journal Article Boundary-Layer Meteorology · May 30, 2012 The scaling laws of the vertical (Fwc) and longitudinal (Fuc) velocity-scalar cospectra within the inertial subrange are explored using dimensional arguments and a simplified cospectral budget in the canopy sublayer above three distinct forested ecosystems ... Full text Cite

A branch scale analytical model for predicting the vegetation collection efficiency of ultrafine particles

Journal Article Atmospheric Environment · May 1, 2012 The removal of ultrafine particles (UFP) by vegetation is now receiving significant attention given their role in cloud physics, human health and respiratory related diseases. Vegetation is known to be a sink for UFP, prompting interest in their collection ... Full text Cite

Causality and persistence in ecological systems: a nonparametric spectral granger causality approach.

Journal Article The American naturalist · April 2012 Abstract Directionality in coupling, defined as the linkage relating causes to their effects at a later time, can be used to explain the core dynamics of ecological systems by untangling direct and feedback relationships between the different components o ... Full text Cite

The Effect of the Screen on the Mass, Momentum, and Energy Exchange Rates of a Uniform Crop Situated in an Extensive Screenhouse

Journal Article Boundary-Layer Meteorology · March 1, 2012 The area of crops cultivated in extensive screenhouses is rapidly growing, especially in semi-arid and arid regions. Water vapour, carbon dioxide, and sensible heat released or taken up by crops within such protected environments can substantially alter th ... Full text Cite

Multiple mechanisms generate Lorentzian and 1/f ^α power spectra in daily stream-flow time series

Journal Article Advances in Water Resources · March 1, 2012 Power-law scaling is an ubiquitous feature of the power spectrum of streamflow on the daily to monthly timescales where the spectrum is most strongly affected by hydrologic catchment-scale processes. Numerous mechanistic explanations for the emergence of t ... Full text Cite

A phenomenological model for the flow resistance over submerged vegetation

Journal Article Water Resources Research · February 29, 2012 The bulk velocity U b in streams is conventionally estimated from Manning's equation, but difficulties remain in parameterizing the roughness coefficient n when the streambed is covered with vegetation. A two-layer velocity model is proposed to determine n ... Full text Cite

The effects of gentle topographic variation on dispersal kernels of inertial particles

Journal Article Geophysical Research Letters · February 1, 2012 Seed dispersal kernels of wind-dispersed species imprint the initial spatial template over which later demographic processes such as establishment or re-colonization operate from. A major knowledge gap in seed dispersal modeling by wind is the role of comp ... Full text Cite

The role of surface characteristics on intermittency and zero-crossing properties of atmospheric turbulence

Journal Article Journal of Geophysical Research Atmospheres · January 1, 2012 Clustering and intermittency in atmospheric turbulent flows above different natural surfaces are investigated with reference to their dependency on surface roughness and thermal stratification. The dualism between active and quiescent phases within measure ... Full text Cite

Mean velocity profile in a sheared and thermally stratified atmospheric boundary layer.

Journal Article Phys Rev Lett · December 23, 2011 Featured Publication A stability correction function φ(m)(ζ) that accounts for distortions to the logarithmic mean velocity profile (MVP) in the lower atmosphere caused by thermal stratification was proposed by Monin and Obukhov in the 1950s using dimensional analysis. Its uni ... Full text Link to item Cite

Empirical and optimal stomatal controls on leaf and ecosystem level CO2 and H2O exchange rates

Journal Article Agricultural and Forest Meteorology. · December 2011 Linkage between the leaf-level stomatal conductance (gâ) response to environmental stimuli and canopy-level mass exchange processes remains an important research problem to be confronted. How various formulations of gâ influence canopy-scale mean scala ... Full text Cite

Drought sensitivity of patterned vegetation determined by rainfall-land surface feedbacks

Journal Article Journal of Geophysical Research: Biogeosciences · December 1, 2011 Vegetation pattern morphology is suggested as one indicator of system closeness to desertification. Using pattern morphology as an indicator requires understanding the timescales at which patterned vegetation systems respond to drought. Modeling these time ... Full text Cite

Leaf conductance and carbon gain under salt-stressed conditions

Journal Article Journal of Geophysical Research: Biogeosciences · December 1, 2011 Exposure of plants to salt stress is often accompanied by reductions in leaf photosynthesis and in stomatal and mesophyll conductances. To separate the effects of salt stress on these quantities, a model based on the hypothesis that carbon gain is maximize ... Full text Cite

Observed increase in local cooling effect of deforestation at higher latitudes.

Journal Article Nature · November 2011 Deforestation in mid- to high latitudes is hypothesized to have the potential to cool the Earth's surface by altering biophysical processes. In climate models of continental-scale land clearing, the cooling is triggered by increases in surface albedo and i ... Full text Cite

Effects of stomatal delays on the economics of leaf gas exchange under intermittent light regimes.

Journal Article The New phytologist · November 2011 • Understory plants are subjected to highly intermittent light availability and their leaf gas exchanges are mediated by delayed responses of stomata and leaf biochemistry to light fluctuations. In this article, the patterns in stomatal delays across biome ... Full text Cite

Inferring ecosystem parameters from observation of vegetation patterns

Journal Article Geophysical Research Letters · October 1, 2011 Spatial organization of vegetation into periodic, coherent patterns arises from the interaction of positive and negative ecological feedbacks. Naturally, the patterns reflect the characteristics of the ecological processes that underlie their formation. Di ... Full text Cite

A flow resistance model for assessing the impact of vegetation on flood routing mechanics

Journal Article Water Resources Research · September 7, 2011 The specification of a flow resistance factor to account for vegetative effects in the Saint-Venant equation (SVE) remains uncertain and is a subject of active research in flood routing mechanics. Here, an analytical model for the flow resistance factor is ... Full text Cite

Unsteady overland flow on flat surfaces induced by spatial permeability contrasts

Journal Article Advances in Water Resources · August 1, 2011 Lateral redistribution of surface water in patchy arid ecosystems has been hypothesized to contribute to the maintenance of vegetation patches through the provision of a water subsidy from bare sites to vegetated sites. Such runon-runoff processes occur du ... Full text Cite

Evaporation from a reservoir with fluctuating water level: Correcting for limited fetch

Journal Article Journal of Hydrology · July 11, 2011 Operational water reservoirs are used to manage the supply of water according to the local demand and availability. Hence, such reservoirs are characterized by large variability in the water level due to variations in inflow and outflow rates, thereby comp ... Full text Cite

A note on aerosol sized particle deposition onto dense and tall canopies situated on gentle cosine hills

Journal Article Tellus, Series B: Chemical and Physical Meteorology · July 1, 2011 Micrometeorological measurements of aerosol sized dry particle deposition velocity (Vd) onto forested canopies have significantly advanced over the past two decades and now include both-airborne and stationary platforms. However, the interpretation of thes ... Full text Cite

A wavelet-based spectral method for extracting self-similarity measures in time-varying two-dimensional rainfall maps

Journal Article Journal of Time Series Analysis · July 1, 2011 Many environmental time-evolving spatial phenomena are characterized by a large number of energetic modes, the occurrence of irregularities, and self-organization over a wide range of space or time scales. Precipitation is a classical example characterized ... Full text Cite

Optimizing stomatal conductance for maximum carbon gain under water stress: a meta-analysis across plant functional types and climates

Journal Article Functional ecology · June 2011 1. Quantification of stomatal responses to environmental variables, in particular to soil water status, is needed to model carbon and water exchange rates between plants and the atmosphere. 2. Models based on stomatal optimality theory successfully describ ... Full text Cite

First passage time statistics of Brownian motion with purely time dependent drift and diffusion

Journal Article Physica A: Statistical Mechanics and its Applications · June 1, 2011 Systems where resource availability approaches a critical threshold are common to many engineering and scientific applications and often necessitate the estimation of first passage time statistics of a Brownian motion (Bm) driven by time-dependent drift an ... Full text Cite

Mechanistic models of seed dispersal by wind

Journal Article Theoretical Ecology · May 1, 2011 Over the past century, various mechanistic models have been developed to estimate the magnitude of seed dispersal by wind, and to elucidate the relative importance of physical and biological factors affecting this passive transport process. The conceptual ... Full text Cite

The Role of Wake Production on the Scaling Laws of Scalar Concentration Fluctuation Spectra Inside Dense Canopies

Journal Article Boundary-Layer Meteorology · April 1, 2011 The scalar concentration fluctuations within a plane parallel-to-the-ground surface were measured inside a model canopy composed of densely arrayed rods using the laser-induced fluorescence technique. Two-dimensional scalar concentration spectra were compu ... Full text Cite

Maximum discharge from snowmelt in a changing climate

Journal Article Geophysical Research Letters · March 16, 2011 Predicted changes in precipitation and air temperature patterns can lead to major alterations in timing and volume of mountain snowmelt runoff with a possible increased incidence of catastrophic events such as flooding and summer droughts. Here, the role o ... Full text Cite

Modeling the vegetation-atmosphere carbon dioxide and water vapor interactions along a controlled CO2 gradient

Journal Article Ecological Modelling · February 10, 2011 Ecosystem functioning is intimately linked to its physical environment by complex two-way interactions. These two-way interactions arise because vegetation both responds to the external environment and actively regulates its micro-environment. By altering ... Full text Cite

The effects of the canopy medium on dry deposition velocities of aerosol particles in the canopy sub-layer above forested ecosystems

Journal Article Atmospheric Environment · February 1, 2011 Understanding how the leaf area density (a(z)) and its depth integrated value, the leaf area index (LAI), modify dry deposition velocities (Vd) of aerosol particles within the canopy sub-layer is needed for progressing on a plethora of aerosol related prob ... Full text Cite

Spread of North American wind-dispersed trees in future environments

Journal Article Ecology Letters · 2011 P>Despite ample research, understanding plant spread and predicting their ability to track projected climate changes remain a formidable challenge to be confronted. We modelled the spread of North American wind-dispersed trees in current and future (c. 206 ... Cite

How well do stomatal conductance models perform on closing plant carbon budgets? A test using seedlings grown under current and elevated air temperatures

Journal Article Journal of Geophysical Researach · 2011 Cite

Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations

Journal Article AGRICULTURAL AND FOREST METEOROLOGY · January 2011 More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems provide a ... Full text Cite

The effects of plant pathogens on tree recruitment in the Western Amazon under a projected future climate: a dynamical systems analysis

Journal Article The Journal of ecology · November 2010 1. Climate change predictions in the Amazon have largely focused on carbon-water relations, while the impacts of increased air temperature and reduced precipitation on host-pathogen relationships have not been extensively explored. These relationships are ... Full text Cite

Estimation of long-term basin scale evapotranspiration from streamflow time series

Journal Article Water Resources Research · October 29, 2010 We estimated long-term annual evapotranspiration (ETQ) at the watershed scale by combining continuous daily streamflow (Q) records, a simplified watershed water balance, and a nonlinear reservoir model. Our analysis used Q measured from 11 watersheds (area ... Full text Open Access Cite

The rainfall-no rainfall transition in a coupled land-convective atmosphere system

Journal Article Geophysical Research Letters · July 1, 2010 A one-dimensional representation of the atmospheric boundary layer (ABL) depth is coupled to a soil moisture bucket model to dynamically explore the relative roles of surface and free atmospheric conditions on convective precipitation occurrence and result ... Full text Open Access Cite

Role of microtopography in rainfall-runoff partitioning: An analysis using idealized geometry

Journal Article Water Resources Research · July 1, 2010 Microtopography, consisting of small-scale excursions in the elevation of the land surface on millimeter to centimeter scales, is ubiquitous on hillslopes, but its effects are rarely incorporated into hydrological analyses of rainfall-runoff partitioning. ... Full text Open Access Cite

What's good for you may be good for me: evidence for adaptive introgression of multiple traits in wild sunflower.

Journal Article The New phytologist · July 2010 Full text Cite

Biotic and abiotic factors act in coordination to amplify hydraulic redistribution and lift.

Journal Article The New phytologist · July 2010 Full text Cite

Scaling Properties of Biologically Active Scalar Concentration Fluctuations in the Atmospheric Surface Layer over a Managed Peatland

Journal Article Boundary-Layer Meteorology · June 16, 2010 The higher-order scalar concentration fluctuation properties are examined in the context of Monin-Obukhov similarity theory for a variety of greenhouse gases that have distinct and separate source/sink locations along an otherwise ideal micrometeorological ... Full text Cite

Vegetation‐infiltration relationships across climatic and soil type gradients

Journal Article Journal of Geophysical Research: Biogeosciences · June 2010 The enhancement of infiltration capacity in the presence of vegetation is well documented in arid ecosystems where it can significantly impact the water balance and vegetation spatial organization. To begin progress toward developing a theory of ve ... Full text Open Access Cite

Evaluation of the Turbulent Kinetic Energy Dissipation Rate Inside Canopies by Zero- and Level-Crossing Density Methods

Journal Article Boundary-Layer Meteorology · May 17, 2010 Inferring the vertical variation of the mean turbulent kinetic energy dissipation rate (ε) inside dense canopies remains a basic research problem to be confronted. Using detailed laser Doppler anemometry (LDA) measurements collected within a densely arraye ... Full text Cite

The influence of hilly terrain on aerosol-sized particle deposition into forested canopies

Journal Article Boundary-Layer Meteorology · April 1, 2010 Virtually all reviews dealing with aerosol-sized particle deposition onto forested ecosystems stress the significance of topographic variations, yet only a handful of studies considered the effects of these variations on the deposition velocity (Vd). Here, ... Full text Cite

An analytical model for the distribution of CO2 sources and sinks, fluxes, and mean concentration within the roughness sub-Layer

Journal Article Boundary-Layer Meteorology · April 1, 2010 A one-dimensional analytical model that predicts foliage CO2 uptake rates, turbulent fluxes, and mean concentration throughout the roughness sub-layer (RSL), a layer that extends from the ground surface up to 5h, where h is canopy height, is proposed. The ... Full text Cite

Interannual Invariability of Forest Evapotranspiration and Its Consequence to Water Flow Downstream

Journal Article Ecosystems. · April 2010 Although drought in temperate deciduous forests decreases transpiration rates of many species, stand-level transpiration and total evapotranspiration is often reported to exhibit only minor interannual variability with precipitation. This apparent contradi ... Full text Cite

A stomatal optimization theory to describe the effects of atmospheric CO2 on leaf photosynthesis and transpiration.

Journal Article Annals of botany · March 2010 Background and aimsGlobal climate models predict decreases in leaf stomatal conductance and transpiration due to increases in atmospheric CO2. The consequences of these reductions are increases in soil moisture availability and continental scale r ... Full text Cite

Albedo estimates for land surface models and support for a new paradigm based on foliage nitrogen concentration

Journal Article Global Change Biology. · February 2010 Vegetation albedo is a critical component of the Earth's climate system, yet efforts to evaluate and improve albedo parameterizations in climate models have lagged relative to other aspects of model development. Here, we calculated growing season albedos f ... Full text Cite

A sensitivity analysis of the nocturnal boundary-layer properties to atmospheric emissivity formulations

Journal Article Boundary-Layer Meteorology · January 1, 2010 A one-dimensional model for the mean potential temperature within the nocturnal boundary layer (NBL) was used to assess the sensitivity of three NBL properties (height, thermal stratification strength, and near-surface cooling) to three widely used atmosph ... Full text Cite

Estimation of in-canopy ammonia sources and sinks in a fertilized Zea mays field

Journal Article Environmental Science and Technology · 2010 Open Access Cite

Predicting the dry deposition of aerosol-sized particles using layer-resolved canopy and pipe flow analogy models: Role of turbophoresis

Journal Article Journal of Geophysical Research Atmospheres · January 1, 2010 A number of synthesis activities, mathematical modeling, and experiments on dry deposition of aerosol-sized particles over forested surfaces point to three disjointed findings: (1) deposition velocities measured over tall forests do not support a clearly d ... Full text Open Access Cite

Causality across rainfall time scales revealed by continuous wavelet transforms

Journal Article Journal of Geophysical Research Atmospheres · January 1, 2010 Rainfall variability occurs over a wide range of time scales owing to processes initiated by cloud microphysics and sustained by atmospheric circulation. A central topic in rainfall research is to determine whether rainfall variability at a given scale is ... Full text Open Access Cite

Scale-wise evolution of rainfall probability density functions fingerprints the rainfall generation mechanism

Journal Article Geophysical Research Letters · January 1, 2010 The cross-scale probabilistic structure of rainfall intensity records collected over time scales ranging from hours to decades at sites dominated by both convective and frontal systems is investigated. Across these sites, intermittency build-up from slow t ... Full text Open Access Cite

A continuous measure of gross primary production for the conterminous United States derived from MODIS and AmeriFlux data

Journal Article Remote Sensing of Environment · 2010 Cite

Climate control of terrestrial carbon exchange across biomes and continents

Journal Article Environmental Research Letters · 2010 Cite

Turbulent pressure and velocity perturbations induced by gentle hills covered with sparse and dense canopies

Journal Article Boundary-Layer Meteorology · November 1, 2009 How the spatial perturbations of the first and second moments of the velocity and pressure fields differ for flow over a train of gentle hills covered by either sparse or dense vegetation is explored using large-eddy simulation (LES). Two simulations are i ... Full text Cite

Revisiting rainfall clustering and intermittency across different climatic regimes

Journal Article Water Resources Research · November 1, 2009 One of the vexing questions in rainfall research is the role of intermittency and its nonuniversal signature in anomalous scaling functions. Whether this lack of universal behavior is due to the bursting patterns in rainfall intensity or the alternation be ... Full text Cite

Hydraulic resistance of submerged rigid vegetation derived from first-order closure models

Journal Article Water Resources Research · October 1, 2009 The past decade witnessed rapid developments in remote sensing methods that now permit an unprecedented description of the spatial variations in water levels (Hw), canopy height (hc), and leaf area density distribution (a) at large spatial scales. These de ... Full text Cite

Increases in air temperature can promote wind-driven dispersal and spread of plants.

Journal Article Proceedings. Biological sciences · September 2009 Long-distance dispersal (LDD) of seeds and pollen shapes the spatial dynamics of plant genotypes, populations and communities. Quantifying LDD is thus important for predicting the future dynamics of plants exposed to environmental changes. However, environ ... Full text Cite

Nocturnal evapotranspiration in eddy-covariance records from three co-located ecosystems in the Southeastern U.S.: Implications for annual fluxes

Journal Article Agricultural and Forest Meteorology. · September 2009 Nocturnal evapotranspiration (ET N ) is often assumed to be negligible in terrestrial ecosystems, reflecting the common assumption that plant stomata close at night to prevent water loss from transpiration. However, recent evidence across a wide range of s ... Full text Cite

The Duke University helicopter observation platform

Journal Article Bulletin of the American Meteorological Society · August 26, 2009 To establish a helicopter observation platform (HOP), Duke University has purchased a Bell 206 "Jet Ranger" helicopter, which has been equipped with a three-dimensional, high-frequency positioning and attitude-recording system, a data acquisition and real- ... Full text Cite

Leaf stomatal responses to vapour pressure deficit under current and CO(2)-enriched atmosphere explained by the economics of gas exchange.

Journal Article Plant, cell & environment · August 2009 Using the economics of gas exchange, early studies derived an expression of stomatal conductance (g) assuming that water cost per unit carbon is constant as the daily loss of water in transpiration (f(e)) is minimized for a given gain in photosynthesis (f( ... Full text Cite

The effects of elevated atmospheric CO₂ and nitrogen amendments on subsurface CO₂ production and concentration dynamics in a maturing pine forest

Journal Article Biogeochemistry. · July 2009 Profiles of subsurface soil CO₂ concentration, soil temperature, and soil moisture, and throughfall were measured continuously during the years 2005 and 2006 in 16 locations at the free air CO₂ enrichment facility situated within a temperate loblolly pine ... Full text Cite

Exploring the effects of microscale structural heterogeneity of forest canopies using large-eddy simulations

Journal Article Boundary-Layer Meteorology · June 30, 2009 The Regional Atmospheric Modeling System (RAMS)-based Forest Large-Eddy Simulation (RAFLES), developed and evaluated here, is used to explore the effects of three-dimensional canopy heterogeneity, at the individual tree scale, on the statistical properties ... Full text Cite

Spatial organization of vegetation arising from non-local excitation with local inhibition in tropical rainforests

Journal Article Physica D: Nonlinear Phenomena · June 15, 2009 The Janzen-Connell (JC) effect, which hypothesizes that recruitment and growth of seedlings is positively correlated to the distance from the parent tree, is shown to generate highly organized vegetation biomass spatial patterns when coupled to a revised F ... Full text Cite

The relationship between reference canopy conductance and simplified hydraulic architecture

Journal Article Advances in Water Resources · June 1, 2009 Terrestrial ecosystems are dominated by vascular plants that form a mosaic of hydraulic conduits to water movement from the soil to the atmosphere. Together with canopy leaf area, canopy stomatal conductance regulates plant water use and thereby photosynth ... Full text Cite

Soil moisture feedbacks on convection triggers: The role of soil-plant hydrodynamics

Journal Article Journal of Hydrometeorology · May 5, 2009 The linkages between soil moisture dynamics and convection triggers, defined here as the first crossing between the boundary layer height (hBL) and lifting condensation level (hLCL), are complicated by a large number of interacting processes occurring over ... Full text Cite

Predicting population survival under future climate change: density dependence, drought and extraction in an insular bighorn sheep.

Journal Article The Journal of animal ecology · May 2009 1. Our understanding of the interplay between density dependence, climatic perturbations, and conservation practices on the dynamics of small populations is still limited. This can result in uninformed strategies that put endangered populations at risk. Mo ... Full text Cite

AmeriFlux Radiological and Meteorological Data for Fermi Prairie Site

Dataset · April 14, 2009 Full text Cite

AmeriFlux Radiological and Meteorological Data for Duke Forest Hardwoods Site

Dataset · April 14, 2009 Full text Cite

AmeriFlux Radiological and Meteorological Data for Duke Forest Open Field

Dataset · April 14, 2009 Full text Cite

AmeriFlux Radiological and Meteorological Data for Fermi Agricultural Site

Dataset · April 14, 2009 Full text Cite

An analytical model for the two-scalar covariance budget inside a uniform dense canopy

Journal Article Boundary-Layer Meteorology · February 25, 2009 The two-scalar covariance budget is significant within the canopy sublayer (CSL) given its role in modelling scalar flux budgets using higher-order closure principles and in estimating the segregation ratio for chemically reactive species. Despite its impo ... Full text Cite

The effects of thermal stratification on clustering properties of canopy turbulence

Journal Article Boundary-Layer Meteorology · February 12, 2009 The intermittent structure of turbulence within the canopy sublayer (CSL) is sensitive to the presence of foliage and to the atmospheric stability regime. How much of this intermittency originates from amplitude variability or clustering properties remains ... Full text Cite

Secondary seed dispersal and its role in landscape organization

Journal Article Geophysical Research Letters · January 28, 2009 [1] Mathematical models of banded vegetation patterns predict rapid upslope migration of vegetated patches not realized in field observations, a key point of disagreement between theory and observation. It is shown that the disagreement between model resul ... Full text Cite

Evapotranspiration

Chapter · January 1, 2009 The importance of evapotranspiration (ET) in sustaining the global- and continental-scale hydrologic cycle and replenishing the world's freshwater resources has been recognized for thousands of years. State-of-the-art climate models and even the old ninete ... Full text Cite

The Lagrangian stochastic model for estimating footprint and water vapor fluxes over inhomogeneous surfaces.

Journal Article International journal of biometeorology · January 2009 This study investigated a two-dimensional Lagrangian stochastic dispersion model for estimating water vapor fluxes and footprint over homogeneous and inhomogeneous surfaces. Over the homogeneous surface, particle trajectories were computed from a 2-D Lagra ... Full text Cite

Flume experiments on intermittency and zero-crossing properties of canopy turbulence

Journal Article Physics of Fluids · January 1, 2009 How the presence of a canopy alters the clustering and the fine scale intermittency exponents and any possible connections between them remains a vexing research problem in canopy turbulence. To begin progress on this problem, detailed flume experiments in ... Full text Cite

Biosphere-atmosphere exchange of CO2 in relation to climate: A cross-biome analysis across multiple time scales

Journal Article Biogeosciences · January 1, 2009 The net ecosystem exchange of CO2 (NEE) varies at time scales from seconds to years and longer via the response of its components, gross ecosystem productivity (GEP) and ecosystem respiration (RE), to physical and biological drivers. Quantifying the relati ... Full text Cite

Roughness effects on fine-scale anisotropy and anomalous scaling in atmospheric flows

Journal Article Physics of Fluids · January 1, 2009 The effects of surface roughness on various measures of fine-scale intermittency within the inertial subrange were analyzed using two data sets that span the roughness "extremes" encountered in atmospheric flows, an ice sheet and a tall rough forest, and s ... Full text Cite

Analysis of soil carbon transit times and age distributions using network theories

Journal Article Journal of Geophysical Research: Biogeosciences · January 1, 2009 The long-term soil carbon dynamics may be approximated by networks of linear compartments, permitting theoretical analysis of transit time (i.e., the total time spent by a molecule in the system) and age (the time elapsed since the molecule entered the sys ... Full text Open Access Cite

Energy, water, and carbon fluxes in a loblolly pine stand: Results from uniform and gappy canopy models with comparisons to eddy flux data

Journal Article Journal of Geophysical Research: Biogeosciences · January 1, 2009 This study investigates the impacts of canopy structure specification on modeling net radiation (Rn), latent heat flux (LE) and net photosynthesis (An) by coupling two contrasting radiation transfer models with a two-leaf photosynthesis model for a maturin ... Full text Open Access Cite

Vegetation pattern shift as a result of rising atmospheric CO2 in arid ecosystems.

Journal Article Theoretical population biology · December 2008 Arid ecosystems are expected to be among the ecosystems most sensitive to climate change. Here, we explore via model calculations how regular vegetation patterns, widely observed in arid ecosystems, respond to projected climatic shifts as provided by gener ... Full text Cite

Understanding strategies for seed dispersal by wind under contrasting atmospheric conditions.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · December 2008 Traits associated with seed dispersal vary tremendously among sympatric wind-dispersed plants. We used two contrasting tropical tree species, seed traps, micrometeorology, and a mechanistic model to evaluate how variation in four key traits affects seed di ... Full text Cite

Ameriflux Biological Data Template for Duke Forest Loblolly Pine Site

Dataset · November 2008 Full text Cite

Ameriflux Biological Data Template for Duke Forest Open Fields Site

Dataset · October 2008 Full text Cite

Ameriflux Biological Data Template for Duke Forest Hardwoods Site

Dataset · October 2008 Full text Cite

Turbulent intensities and velocity spectra for bare and forested gentle hills: Flume experiments

Journal Article Boundary-Layer Meteorology · October 1, 2008 To investigate how velocity variances and spectra are modified by the simultaneous action of topography and canopy, two flume experiments were carried out on a train of gentle cosine hills differing in surface cover. The first experiment was conducted abov ... Full text Cite

Role of biomass spread in vegetation pattern formation within arid ecosystems

Journal Article Water Resources Research · October 1, 2008 The spatial organization of biomass resulting from plant-water feedbacks in arid ecosystems, "patterned vegetation," provides a macroscopic signal of nonlinear plant-water interactions and ecosystem health. Current models that reproduce such patterning ass ... Full text Cite

AmeriFlux Radiological and Meteorological Data for Duke Forest Loblolly Pine Site

Dataset · September 13, 2008 Full text Cite

The structure of turbulence near a tall forest edge: the backward-facing step flow analogy revisited.

Journal Article Ecological applications : a publication of the Ecological Society of America · September 2008 Flow disturbances near tall forest edges are receiving significant attention in diverse disciplines including ecology, forest management, meteorology, and fluid mechanics. Current theories suggest that near a forest edge, when the flow originates from a fo ... Full text Cite

Estimating daytime subcanopy respiration from conditional sampling methods applied to multi-scalar high frequency turbulence time series

Journal Article Agricultural and Forest Meteorology · July 4, 2008 This study presents a new method to estimate daytime respiration from the subcanopy of forests directly from conventional eddy covariance (EC) measurements. The method primarily considers the respiration signal from root, litter and microbial respiration, ... Full text Cite

The effect of canopy roughness density on the constitutive components of the dispersive stresses

Journal Article Experiments in Fluids · July 1, 2008 How to represent the effects of variable canopy morphology on turbulence remains a fundamental challenge yet to be confronted. Planar averaging over some minimal area can be applied to average-out this sort of spatial variability in the time-averaged mean ... Full text Cite

On the anomalous behaviour of scalar flux-variance similarity functions within the canopy sub-layer of a dense alpine forest

Journal Article Boundary-Layer Meteorology · July 1, 2008 Within the canopy sub-layer (CSL), variability in scalar sources and sinks are known to affect flux-variance (FV) similarity relationships for water vapour (q) and carbon dioxide (C) concentrations, yet large-scale processes may continue to play a signific ... Full text Cite

Investigating a hierarchy of eulerian closure models for scalar transfer inside forested canopies

Journal Article Boundary-Layer Meteorology · July 1, 2008 Modelling the transfer of heat, water vapour, and CO2 between the biosphere and the atmosphere is made difficult by the complex two-way interaction between leaves and their immediate microclimate. When simulating scalar sources and sinks inside canopies on ... Full text Cite

Effects of canopy heterogeneity, seed abscission and inertia on wind-driven dispersal kernels of tree seeds

Journal Article Journal of Ecology · July 1, 2008 1. Understanding seed dispersal by wind and, in particular, long-distance dispersal (LDD) is needed for management of plant populations and communities, especially in response to changes in climate, land use and natural habitats. Numerical models designed ... Full text Cite

A stochastic model for daily subsurface CO2 concentration and related soil respiration

Journal Article Advances in Water Resources · July 1, 2008 Near-surface soil CO2 gas-phase concentration (C) and concomitant incident rainfall (Pi) and through-fall (Pt) depths were collected at different locations in a temperate pine forest every 30 min during the 2005 and 2006 growing seasons (and then averaged ... Full text Cite

Analytical models for the mean flow inside dense canopies on gentle hilly terrain

Journal Article Quarterly Journal of the Royal Meteorological Society · July 1, 2008 Simplifications and scaling arguments employed in analytical models that link topographic variations to mean velocity perturbations within dense canopies are explored using laboratory experiments. Laser Doppler anemometry (LDA) measurements are conducted i ... Full text Cite

Surface heterogeneity and its signature in higher-order scalar similarity relationships

Journal Article Agricultural and Forest Meteorology · June 30, 2008 Over the past three decades, a number of field experiments have suggested that land-cover heterogeneity (LCH) impacts Monin and Obukhov (M-O) scaling, when applied to second-order statistics of temperature (T), water vapor (q), and CO2 (c) fluctuations. To ... Full text Cite

On the anomalous behavior of the Lagrangian structure function similarity constant inside dense canopies

Journal Article Atmospheric Environment · June 1, 2008 The choice of the Kolmogorov constant (C0) in Lagrangian Stochastic Models (LSMs) for canopy flows remains a subject of debate and uncertainty. This uncertainty stems from the fact that canopy flows are highly dissipative, lack a well-defined inertial subr ... Full text Cite

Role of vegetation in determining carbon sequestration along ecological succession in the southeastern United States

Journal Article Global Change Biology. · June 2008 Vegetation plays a central role in controlling terrestrial carbon (C) exchange, but quantifying its impacts on C cycling on time scales of ecological succession is hindered by a lack of long-term observations. The net ecosystem exchange of carbon (NEE) was ... Full text Cite

Plant propagation fronts and wind dispersal: an analytical model to upscale from seconds to decades using superstatistics.

Journal Article The American naturalist · April 2008 Scale separation crossing many orders of magnitude is a consistent challenge in the ecological sciences. Wind dispersal of seed that generates plant propagation fronts is a typical case where timescales range from less than a second for fast turbulent proc ... Full text Cite

Spectral short-circuiting and wake production within the canopy trunk space of an alpine hardwood forest

Journal Article Boundary-Layer Meteorology · March 1, 2008 Using synchronous multi-level high frequency velocity measurements, the turbulence spectra within the trunk space of an alpine hardwood forest were analysed. The spectral short-circuiting of the energy cascade for each velocity component was well reproduce ... Full text Cite

The effects of canopy leaf area index on airflow across forest edges: Large-eddy simulation and analytical results

Journal Article Boundary-Layer Meteorology · March 1, 2008 The structure of turbulent flows along a transition between tall-forested canopies and forest clearings continues to be an active research topic in canopy turbulence. The difficulties in describing the turbulent flow along these transitions stem from the f ... Full text Cite

The temperature-humidity covariance in the marine surface layer: A one-dimensional analytical model

Journal Article Boundary-Layer Meteorology · February 1, 2008 An analytical model that predicts how much of the temperature-humidity covariance within the marine atmospheric surface layer (ASL) originates just above the ASL and just near the surface is proposed and tested using observations from the Risø A ir S ea Ex ... Full text Cite

Micro- and macro-dispersive fluxes in canopy flows

Journal Article Acta Geophysica · January 1, 2008 Resolving every detail of the three-dimensional canopy morphology and its underlying topography remains untenable when modeling high Reynolds number geophysical flows. How to represent the effects of such a complex morphological variability and any concomi ... Full text Cite

Evaporation from three water bodies of different sizes and climates: Measurements and scaling analysis

Journal Article Advances in Water Resources · January 1, 2008 Evaporation from small reservoirs, wetlands, and lakes continues to be a theoretical and practical problem in surface hydrology and micrometeorology because atmospheric flows above such systems can rarely be approximated as stationary and planar-homogeneou ... Full text Cite

Onset of water stress, hysteresis in plant conductance, and hydraulic lift: Scaling soil water dynamics from millimeters to meters

Journal Article Water Resources Research · January 1, 2008 Estimation of water uptake by plants and subsequent water stress are complicated by the need to resolve the soil-plant hydrodynamics at scales ranging from millimeters to meters. Using a simplified homogenization technique, the three-dimensional (3-D) soil ... Full text Cite

Estimation of net ecosystem carbon exchange for the conterminous United States by combining MODIS and AmeriFlux data

Journal Article AGRICULTURAL AND FOREST METEOROLOGY · 2008 Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify th ... Cite

Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks

Journal Article PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA · 2008 The availability of nitrogen represents a key constraint on carbon cycling in terrestrial ecosystems, and it is largely in this capacity that the role of N in the Earth's climate system has been considered. Despite this, few studies have included continuou ... Cite

Stochastic dynamics of plant-water interactions

Journal Article Annual Review of Ecology, Evolution, and Systematics · December 1, 2007 Describing water flow from soil through plants to the atmosphere remains a formidable scientific challenge despite years of research. This challenge is not surprising given the high dimensionality and degree of nonlinearity of the soil-plant system, which ... Full text Cite

Separating the effects of albedo from eco-physiological changes on surface temperature along a successional chronosequence in the southeastern United States

Journal Article Geophysical Research Letters · November 16, 2007 In the southeastern United States (SE), the conversion of abandoned agricultural land to forests is the dominant feature of land-cover change. However, few attempts have been made to quantify the impact of such conversion on surface temperature. Here, this ... Full text Cite

Vertical variability and effect of stability on turbulence characteristics down to the floor of a pine forest

Journal Article Tellus, Series B: Chemical and Physical Meteorology · November 1, 2007 Among the fundamental problems in canopy turbulence, particularly near the forest floor, remain the local diabatic effects and linkages between turbulent length scales and the canopy morphology. To progress on these problems, mean and higher order turbulen ... Full text Cite

Dual length scale two-equation modelling of the canopy turbulent kinetic energy wake budget

Journal Article Comptes Rendus - Mecanique · November 1, 2007 Within vegetation canopies, the turbulent kinetic energy (k) budget is mainly modelled through source terms added to the free-air state formulation. The dependence of the modelled source term coefficients upon a dimensionless ratio (λ) between the mixing l ... Full text Cite

An experimental investigation of the mean momentum budget inside dense canopies on narrow gentle hilly terrain

Journal Article Agricultural and Forest Meteorology. · May 2007 Full text Cite

Turbulent flows on forested hilly terrain: The recirculation region

Journal Article Quarterly Journal of the Royal Meteorological Society · April 1, 2007 A number of analytical and numerical studies employing first-order closure principles have suggested that canopy flows on gentle sinusoidal hills feature a recirculation region, situated on the lee side, that can dramatically affect scalar transfer between ... Full text Cite

The ejection-sweep cycle over bare and forested gentle hills: A laboratory experiment

Journal Article Boundary-Layer Meteorology · March 1, 2007 Progress on practical problems such as quantifying gene flow and seed dispersal by wind or turbulent fluxes over nonflat terrain now demands fundamental understanding of how topography modulates the basic properties of turbulence. In particular, the modula ... Full text Cite

Radon measurements in well and spring water in Lebanon

Journal Article Radiation Measurements · January 1, 2007 The variation of dissolved radon (222Rn) levels in water supplies remains of interest because of the radiation-induced public health hazards. A large part of the Lebanese population relies on springs and wells for their drinking water. 222Rn measurements i ... Full text Cite

An experimental investigation of turbulent flows over a hilly surface

Journal Article Physics of Fluids · January 1, 2007 Gentle topographic variations significantly alter the mass and momentum exchange rates between the land surface and the atmosphere from their flat-world state. This recognition is now motivating basic studies on how a wavy surface impacts the flow dynamics ... Full text Cite

Simplified expressions for adjusting higher-order turbulent statistics obtained from open path gas analyzers

Journal Article Boundary-Layer Meteorology · January 1, 2007 When density fluctuations of scalars such as CO2 are measured with open-path gas analyzers, the measured vertical turbulent flux must be adjusted to take into account fluctuations induced by 'external effects' such as temperature and water vapour. These ad ... Full text Cite

Hydrologic and atmospheric controls on initiation of convective precipitation events

Journal Article WATER RESOURCES RESEARCH · 2007 The pathway to summertime convective precipitation remains a vexing research problem because of the nonlinear feedback between soil moisture content and the atmosphere. Understanding this feedback is important to the southeastern U.S. region, given the hig ... Cite

On the spectrum of soil moisture from hourly to interannual scales

Journal Article WATER RESOURCES RESEARCH · 2007 {[}1] The spectrum of soil moisture content at scales ranging from 1 hour to 8 years is analyzed for a site whose hydrologic balance is primarily governed by precipitation (p), and evapotranspiration (ET). The site is a uniformly planted loblolly pine stan ... Cite

Eco-hydrological controls on summertime convective rainfall triggers

Journal Article GLOBAL CHANGE BIOLOGY · 2007 Triggers of summertime convective rainfall depend on numerous interactions and feedbacks, often compounded by spatial variability in soil moisture and its impacts on vegetation function, vegetation composition, terrain, and all the complex turbulent entrai ... Cite

Are ecosystem carbon inputs andoutputs coupled at short time scales? A case study from adjacent pine and hardwood forests using impulse-response analysis

Journal Article Plant, Cell and Environment · 2007 Cite

An evaluation of models for partitioning eddy covariance-measured net ecosystem exchange into photosynthesis and respiration

Journal Article Agricultural and Forest Meteorology. · December 2006 Full text Cite

Restoration of hydrologic and biogeochemical functions in bottomland hardwoods

Journal Article Hydrology and Management of Forested Wetlands - Proceeding of the International Conference · December 1, 2006 The degraded state and loss of ecological functions in many bottomland hardwood swamps and riparian wetlands in the United States are directly related to severe alteration of hydrologic flows in streams, with a concomitant loss of hydric soil conditions du ... Cite

Two-dimensional scalar spectra in the deeper layers of a dense and uniform model canopy

Journal Article Boundary-Layer Meteorology · November 1, 2006 The turbulent flow inside dense canopies is characterized by wake production and short-circuiting of the energy cascade. How these processes affect passive scalar concentration variability in general and their spectral properties in particular remains a ve ... Full text Cite

Net ecosystem exchange of grassland in contrasting wet and dry years

Journal Article Agricultural and Forest Meteorology. · October 2006 Full text Cite

The relative importance of ejections and sweeps to momentum transfer in the atmospheric boundary layer

Journal Article Boundary-Layer Meteorology · September 1, 2006 Using an incomplete third-order cumulant expansion method (ICEM) and standard second-order closure principles, we show that the imbalance in the stress contribution of sweeps and ejections to momentum transfer (δSo) can be predicted from measured profiles ... Full text Cite

Soil moisture and vegetation controls on evapotranspiration in a heterogeneous Mediterranean ecosystem on Sardinia, Italy

Journal Article Water Resources Research · August 1, 2006 Micrometeorological measurements of evapotranspiration (ET) can be difficult to interpret and use for validating model calculations in the presence of land cover heterogeneity. Land surface fluxes, soil moisture (θ), and surface temperatures (Ts) data were ... Full text Cite

Multiscale model intercomparisons of CO₂ and H₂O exchange rates in a maturing southeastern US pine forest

Journal Article Global Change Biology. · July 2006 We compared four existing process-based stand-level models of varying complexity (physiological principles in predicting growth, photosynthesis and evapotranspiration, biogeochemical cycles, and stand to ecosystem carbon and evapotranspiration simulator) a ... Full text Cite

Denoising ozone concentration measurements with BAMS filtering

Journal Article Journal of Statistical Planning and Inference · July 1, 2006 We propose a method for filtering self-similar geophysical signals infected by an autoregressive noise using a combination of non-decimated wavelet transform and a Bayesian model. In the application part, we consider separating the instrumentation noise fr ... Full text Cite

Estimating the uncertainty in annual net ecosystem carbon exchange: spatial variation in turbulent fluxes and sampling errors in eddy-covariance measurements

Journal Article Global Change Biology. · May 2006 Above forest canopies, eddy covariance (EC) measurements of mass (CO₂, H₂O vapor) and energy exchange, assumed to represent ecosystem fluxes, are commonly made at one point in the roughness sublayer (RSL). A spatial variability experiment, in which EC meas ... Full text Cite

Modeling nighttime ecosystem respiration from measured CO2 concentration and air temperature profiles using inverse methods

Journal Article Journal of Geophysical Research Atmospheres · April 27, 2006 A major challenge for quantifying ecosystem carbon budgets from micrometeorological methods remains nighttime ecosystem respiration. An earlier study utilized a constrained source optimization (CSO) method using inverse Lagrangian dispersion theory to infe ... Full text Cite

An analysis of intermittency, scaling, and surface renewal in atmospheric surface layer turbulence

Journal Article Physica D: Nonlinear Phenomena · March 15, 2006 Turbulent velocity and scalar concentration time series were collected in the atmosphere above an ice sheet, a mesic grassland, and a temperate pine forest, thereby encompassing a wide range of roughness conditions encountered in nature. Intermittency and ... Full text Cite

The porous media model for the hydraulic system of a conifer tree: Linking sap flux data to transpiration rate

Journal Article Ecological Modelling · February 5, 2006 Linking sap flow in tree boles to plant transpiration continues to be a fundamental and practical research problem in physiological ecology and forest hydrology. Many models have been proposed to describe water movement within trees with varying degrees of ... Full text Cite

Scalar dispersion within a model canopy: Measurements and three-dimensional Lagrangian models

Journal Article Advances in Water Resources · February 1, 2006 Modeling scalar transport within canopies remains a vexing research problem in eco-hydrology and eco-hydraulics. Canopy turbulence is inhomogeneous, non-Gaussian, and highly dissipative, thereby posing unique challenges to three-dimensional Lagrangian Disp ... Full text Cite

Modeling seed dispersal distances: implications for transgenic Pinus taeda.

Journal Article Ecological applications : a publication of the Ecological Society of America · February 2006 Predicting forest-tree seed dispersal across a landscape is useful for estimating gene flow from genetically engineered (GE) or transgenic trees. The question of biocontainment has yet to be resolved, although field-trial permits for transgenic forest tree ... Full text Cite

Dispersal of Transgenic Conifer Pollen

Chapter · 2006 Full text Cite

A remote sensing observatory for hydrologic sciences: A genesis for scaling to continental hydrology

Journal Article WATER RESOURCES RESEARCH · 2006 {[} 1] Uncertainties in assessing the effects of global-scale perturbations on the climate system arise primarily from an inadequate understanding of the hydrological cycle: on land, in oceans, and in the atmosphere and biosphere. Because of this uncertain ... Cite

The influence of hilly terrain on canopy-atmosphere carbon dioxide exchange

Journal Article Boundary-Layer Meteorology · January 1, 2006 Topography influences many aspects of forest-atmosphere carbon exchange; yet only a small number of studies have considered the role of topography on the structure of turbulence within and above vegetation and its effect on canopy photosynthesis and the me ... Full text Cite

Buoyancy and the sensible heat flux budget within dense canopies

Journal Article Boundary-Layer Meteorology · January 1, 2006 In contrast to atmospheric surface-layer (ASL) turbulence, a linear relationship between turbulent heat fluxes (FT and vertical gradients of mean air temperature within canopies is frustrated by numerous factors, including local variation in heat sources a ... Full text Cite

A multi-site analysis of random error in tower-based measurements of carbon and energy fluxes

Journal Article Agricultural and Forest Meteorology. · January 2006 Measured surface-atmosphere fluxes of energy (sensible heat, H, and latent heat, LE) and CO(2) (FCO(2)) represent the “true” flux plus or minus potential random and systematic measurement errors. Here, we use data from seven sites in the AmeriFlux network, ... Full text Cite

Separating the effects of climate and vegetation on evapotranspiration along a successional chronosequence in the southeastern US

Journal Article GLOBAL CHANGE BIOLOGY · 2006 We combined Eddy-covariance measurements with a linear perturbation analysis to isolate the relative contribution of physical and biological drivers on evapotranspiration (ET) in three ecosystems representing two end-members and an intermediate stage of a ... Cite

Finite element tree crown hydrodynamics model (FETCH) using porous media flow within branching elements: A new representation of tree hydrodynamics

Journal Article Water Resources Research · November 1, 2005 [1] Estimating transpiration and water flow in trees remains a major challenge for quantifying water exchange between the biosphere and the atmosphere. We develop a finite element tree crown hydrodynamics (FETCH) model that uses porous media equations for ... Full text Cite

Mechanistic analytical models for long-distance seed dispersal by wind.

Journal Article The American naturalist · September 2005 We introduce an analytical model, the Wald analytical long-distance dispersal (WALD) model, for estimating dispersal kernels of wind-dispersed seeds and their escape probability from the canopy. The model is based on simplifications to well-established thr ... Full text Cite

Photosynthetic responses of a humid grassland ecosystem to future climate perturbations

Journal Article Advances in Water Resources · September 1, 2005 Increases in atmospheric CO2 concentration not only affects climate variables such as precipitation and air temperature, but also affects intrinsic ecosystem physiological properties such as bulk stomatal conductance and intercellular CO2 concentration. De ... Full text Cite

Resampling hierarchical processes in the wavelet domain: A case study using atmospheric turbulence

Journal Article Physica D: Nonlinear Phenomena · July 15, 2005 There is a growing need for statistical methods that generate an ensemble of plausible realizations of a hierarchical process from a single run or experiment. The main challenge is how to construct such an ensemble in a manner that preserves the internal d ... Full text Cite

Foliage shedding in deciduous forests lifts up long-distance seed dispersal by wind.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · June 2005 Seed terminal velocity and release height are recognized as key biotic determinants of long-distance dispersal (LDD) of seeds by wind. Yet, potential determinants at the ecosystem level, such as seasonal dynamics in foliage density characterizing many deci ... Full text Cite

Eulerian-Lagrangian model for predicting odor dispersion using instrumental and human measurements

Journal Article Sensors and Actuators, B: Chemical · April 29, 2005 A Eulerian-Lagrangian model was used to predict the trajectory and spatial distribution of odor and odorants downwind from an industrial facility with multiple sources of odor emissions. Specifically, the model was used to simulate the dispersion of odor f ... Full text Cite

Long-distance biological transport processes through the air: Can nature's complexity be unfolded in silico?

Journal Article Diversity and Distributions · March 1, 2005 Understanding and predicting complex biological systems are best accomplished through the synthesis and integration of information across relevant spatial, temporal and thematic scales. We propose that mechanistic transport models, which integrate atmosphe ... Full text Cite

Assessing the effects of atmospheric stability on the fine structure of surface layer turbulence using local and global multiscale approaches

Journal Article Physics of Fluids · January 1, 2005 The conceptual framework for modeling the inertial subrange is strongly influenced by the Richardson cascade, now the subject of various reinterpretations. One apparent departure from the Richardson cascade is attributed to boundary conditions influencing ... Full text Cite

Contrasting responses to drought of forest floor CO2 efflux in a loblolly pine plantation anda nearby oak-hickory forest

Journal Article Global Change Biology · 2005 Cite

Temporal variability in (13)C of respired CO(2) in a pine and a hardwood forest subject to similar climatic conditions.

Journal Article Oecologia · January 2005 Temporal variability in the (13)C of foliage (delta(13)C(F)), soil (delta(13)C(S)) and ecosystem (delta(13)C(R)) respired CO(2) was contrasted between a 17.2-m tall evenly aged loblolly pine forest and a 35-m tall unevenly aged mature second growth mixed b ... Full text Cite

Variability in net ecosystem exchange from hourly to inter-annual time scales at adjacent pine and hardwood forests: a wavelet analysis

Journal Article TREE PHYSIOLOGY · 2005 Orthonormal wavelet transformation (OWT) is a computationally efficient technique for quantifying underlying frequencies in nonstationary and gap-infested time series, such as eddy-covariance-measured net ecosystem exchange of CO2 (NEE). We employed OWT to ... Cite

Carbon and water cycling in a Bornean tropical rainforest under current and future climate scenarios

Journal Article Advances in Water Resources · December 1, 2004 We examined how the projected increase in atmospheric CO2 and concomitant shifts in air temperature and precipitation affect water and carbon fluxes in an Asian tropical rainforest, using a combination of field measurements, simplified hydrological and car ... Full text Cite

One- and two-equation models for canopy turbulence

Journal Article Boundary-Layer Meteorology · October 1, 2004 The predictive skills of single- and two-equation (or K-ε) models to compute profiles of mean velocity (U), turbulent kinetic energy (K), and Reynolds stresses (u′w′) are compared against datasets collected in eight vegetation types and in a flume experime ... Full text Cite

Organised motion and radiative perturbations in the nocturnal canopy sublayer above an even-aged pine forest

Journal Article Boundary-Layer Meteorology · July 1, 2004 Using time series measurements of velocity, carbon dioxide and water vapour concentration, and temperature collected just above a 15 m tall even-aged pine forest, we quantify the role of organized motion on scalar and momentum transport within the nocturna ... Full text Cite

The effect of vegetation density on canopy sub-layer turbulence

Journal Article Boundary-Layer Meteorology · June 1, 2004 The canonical form of atmospheric flows near the land surface, in the absence of a canopy, resembles a rough-wall boundary layer. However, in the presence of an extensive and dense canopy, the flow within and just above the foliage behaves as a perturbed m ... Full text Cite

Momentum transfer and turbulent kinetic energy budgets within a dense model canopy

Journal Article Boundary-Layer Meteorology · June 1, 2004 Second-order closure models for the canopy sublayer (CSL) employ a set of closure schemes developed for 'free-air' flow equations and then add extra terms to account for canopy related processes. Much of the current research thrust in CSL closure has focus ... Full text Cite

A note on the contribution of dispersive fluxes to momentum transfer within canopies

Journal Article Boundary-Layer Meteorology · June 1, 2004 Dispersive flux terms are formed when the time-averaged mean momentum equation is spatially averaged within the canopy volume. These fluxes represent a contribution to momentum transfer arising from spatial correlations of the time-averaged velocity compon ... Full text Cite

Impact of elevated atmospheric CO2 on forest floor respiration in a temperate pine forest

Journal Article Global Biogeochemical Cycles · June 1, 2004 The effects of elevated atmospheric CO2 (COe2) on soil respiration were evaluated using inverse models and static chamber measurements collected over 4.5 years in a maturing loblolly pine forest. The chamber measurements of forest floor CO2 efflux showed t ... Full text Cite

Interaction between large and small scales in the canopy sublayer

Journal Article Geophysical Research Letters · March 16, 2004 Two characteristics that distinguish canopy sublayer (CSL) turbulence from its atmospheric surface layer (ASL) counterpart are short-circuiting of the energy cascade and formation of Kelvin-Helmholtz (KH) vortices near the canopy top. These two phenomena l ... Full text Cite

Water cycling in a Bornean tropical rain forest under current and projected precipitation scenarios

Journal Article Water Resources Research · January 1, 2004 Southeastern Asian tropical rain forests are among the most important biomes in terms of annual productivity and water cycling. How their hydrologic budgets are altered by projected shifts in precipitation is examined using a combination of field measureme ... Full text Cite

Determinants of long-distance seed dispersal by wind in grasslands

Journal Article Ecology · January 1, 2004 Long-distance seed dispersal is an important topic in ecology, but notoriously difficult to quantify. Previous modeling approaches have failed to simulate long-distance dispersal, and it has remained unclear which mechanisms determine long-distance dispers ... Full text Cite

Human effects on long-distance wind dispersal and colonization by grassland plants

Journal Article Ecology · January 1, 2004 Human effects on plant colonization capacity have not been studied mechanistically because a crucial component of colonization capacity, long-distance seed dispersal, could not be quantified. Now, development of mechanistic models has progressed sufficient ... Full text Cite

Gap-filling missing data in eddy covariance measurements using multiple imputation (MI) for annual estimations.

Journal Article Agricultural and Forest Meteorology. · January 2004 Full text Cite

Carbon dioxide and water vapor exchange in a warm temperate grassland.

Journal Article Oecologia · January 2004 Grasslands cover about 40% of the ice-free global terrestrial surface, but their contribution to local and regional water and carbon fluxes and sensitivity to climatic perturbations such as drought remains uncertain. Here, we assess the direction and magni ... Full text Cite

Diurnal centroid of ecosystem energy and carbon fluxes at FLUXNET sites

Journal Article Journal of Geophysical Research: Atmospheres · November 16, 2003 Data from a network of eddy covariance stations in Europe and North America (FLUXNET) were analyzed to examine the diurnal patterns of surface energy and carbon fluxes during the summer period across a range of ecosystems and climates. Diurnal trends were ... Full text Cite

Predicting scalar source-sink and flux distributions within a forest canopy using a 2-D Lagrangian stochastic dispersion model

Journal Article Boundary-Layer Meteorology · November 1, 2003 This study proposes a two-dimensional Lagrangian stochastic dispersion model for estimating spatial and temporal variation of scalar sources, sinks, and fluxes within a forest canopy. Carbon dioxide and heat dispersion experiments were conducted for field ... Full text Cite

Exposure to an enriched CO2 atmosphere alters carbon assimilation and allocation in a pine forest ecosystem

Journal Article Global Change Biology · October 1, 2003 We linked a leaf-level CO2 assimilation model with a model that accounts for light attenuation in the canopy and measurements of sap-flux-based canopy conductance into a new canopy conductance-constrained carbon assimilation (4C-A) model. We estimated cano ... Full text Cite

Reduction of forest floor respiration by fertilization on both carbon dioxide-enriched and reference 17-year-old loblolly pine stands

Journal Article Global Change Biology · June 1, 2003 Elevated atmospheric carbon dioxide (CO2e) increases soil respiration rates in forest, grassland, agricultural and wetland systems as a result of increased growth, root biomass and enhanced biological activity of soil microorganisms. Less is known about ho ... Full text Cite

Partitioning interannual variability in net ecosystem exchange between climatic variability and functional change.

Journal Article Tree physiology · May 2003 Interannual variability (IAV) in net ecosystem exchange of carbon (NEE) is a critical factor in projections of future ecosystem changes. However, our understanding of IAV is limited because of the difficulty in isolating its numerous causes. We proposed th ... Full text Cite

Modelling sources and sinks of CO2, H2O and heat within a Siberian pine forest using three inverse methods

Journal Article Quarterly Journal of the Royal Meteorological Society · April 1, 2003 Source/sink distributions of heat, CO2 and water vapour in a Siberian Scots pine forest were estimated from measured concentration and temperature profiles using three inverse analysis methods. These methods include: a Eulerian second-order closure model ( ... Full text Cite

Quantifying organization of atmospheric turbulent eddy motion using nonlinear time series analysis

Journal Article Boundary-Layer Meteorology · March 1, 2003 Using three methods from nonlinear dynamics, we contrast the level of organization in the vertical wind velocity (ω) time series collected in the atmospheric surface layer (ASL) and the canopy sublayer (CSL) for a wide range of atmospheric stability (ξ) co ... Full text Cite

Relationship between plant hydraulic and biochemical properties derived from a steady-state coupled water and carbon transport model

Journal Article Plant, Cell and Environment · March 1, 2003 There is growing evidence that plant stomata have evolved physiological controls to satisfy the demand for CO2 by photosynthesis while regulating water losses by leaves in a manner that does not cause cavitation in the soil-root-xylem hydraulic system. Whe ... Full text Cite

Are the effects of large scale flow conditions really lost through the turbulent cascade?

Journal Article Geophysical Research Letters · February 15, 2003 The conceptual framework for modeling the inertial subrange is strongly influenced by the Kolmogorov cascade phenomena, which is nowadays the subject of significant reinterpretation. It has been argued that the effects of boundary conditions influence larg ... Full text Cite

Phase and amplitude of ecosystem carbon release and uptake potentials as derived from FLUXNET measurements

Journal Article Agricultural and Forest Meteorology · December 2, 2002 As length and timing of the growing season are major factors explaining differences in carbon exchange of ecosystems, we analyzed seasonal patterns of net ecosystem carbon exchange (FNEE) using eddy covariance data of the FLUXNET data base (http://www-eosd ... Full text Cite

Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation

Journal Article Agricultural and Forest Meteorology · December 2, 2002 The objective of this research was to compare seasonal and annual estimates of CO2 and water vapor exchange across sites in forests, grasslands, crops, and tundra that are part of an international network called FLUXNET, and to investigating the responses ... Full text Cite

Seasonality of ecosystem respiration and gross primary production as derived from FLUXNET measurements

Journal Article Agricultural and Forest Meteorology · December 2, 2002 Differences in the seasonal pattern of assimilatory and respiratory processes are responsible for divergences in seasonal net carbon exchange among ecosystems. Using FLUXNET data (http://www.eosdis.ornl.gov/FLUXNET) we have analyzed seasonal patterns of gr ... Full text Cite

Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites

Journal Article Water Resources Research · December 1, 2002 The warm season (mid-June through late August) partitioning between sensible (H) and latent (LE) heat flux, or the Bowen ratio (β = H/LE), was investigated at 27 sites over 66 site years within the international network of eddy covariance sites (FLUXNET). ... Full text Cite

A mixing layer theory for flow resistance in shallow streams

Journal Article Water Resources Research · November 1, 2002 A variety of surface roughness characterizations have emerged from nineteenth and twentieth century studies of channel hydraulics. When the water depth h is much larger than the characteristic roughness height ks, roughness formulations such as Manning's n ... Full text Cite

Hydrologic balance in an intact temperate forest ecosystem under ambient and elevated atmospheric CO2 concentration.

Journal Article Global Change Biology. · September 2002 Full text Cite

Modeling Heat, Water Vapor, and Carbon Dioxide Flux Distribution Inside Canopies Using Turbulent Transport Theories

Journal Article Vadose Zone Journal · August 2002 This study reports recent developments in mulitlayer turbulent transport methods to compute distributions of strengths of scalar sources and sinks Sc as well as turbulent fluxes F Full text Cite

Quantifying net ecosystem exchange by multilevel ecophysiological and turbulent transport models

Journal Article Advances in Water Resources · August 1, 2002 To quantify the interplay between scalar sources and sinks (Sc) and net ecosystem exchange (NEE), "forward" and "inverse" approaches have been proposed. The canonical form of forward approaches is a one-dimensional ecophysiological-radiative transfer schem ... Full text Cite

Mechanisms of long-distance dispersal of seeds by wind.

Journal Article Nature · July 2002 Long-distance dispersal (LDD) is central to species expansion following climate change, re-colonization of disturbed areas and control of pests. The current paradigm is that the frequency and spatial extent of LDD events are extremely difficult to predict. ... Full text Cite

Estimating heat sources and fluxes in thermally stratified canopy flows using higher-order closure models

Journal Article Boundary-Layer Meteorology · April 1, 2002 Over the past two decades, several inverse methods have been proposed to estimate scalar source and sink strengths from measured mean concentration profiles within the canopy volume (hereafter termed the 'inverse' problem). These inverse methods commonly a ... Full text Cite

Modelling night-time ecosystem respiration by a constrained source optimization method

Journal Article Global Change Biology. · February 2002 One of the main challenges to quantifying ecosystem carbon budgets is properly quantifying the magnitude of night-time ecosystem respiration. Inverse Lagrangian dispersion analysis provides a promising approach to addressing such a problem when measured me ... Full text Cite

Modelling the limits on the response of net carbon exchange to fertilization in a south-eastern pine forest

Journal Article Plant, Cell and Environment · January 1, 2002 Using a combination of model simulations and detailed measurements at a hierarchy of scales conducted at a sandhills forest site, the effect of fertilization on net ecosystem exchange (NEE) and its components in 6-year-old Pinus taeda stands was quantified ... Full text Cite

Modeling heat, water vapor, and carbon dioxide flux distribution inside canopies using turbulent transport theories

Journal Article Vadose Zone Journal · January 1, 2002 This study reports recent developments in mulitlayer turbulent transport methods to compute distributions of strengths of scalar sources and sinks Sc as well as turbulent fluxes Fc within the plant-atmosphere continuum. In particular, we focus on the so-ca ... Full text Cite

Evapotranspiration intensifies over the conterminous United States

Journal Article Journal of Water Resources Planning and Management · November 1, 2001 Using long-term (1948-1996) pan evaporation measurements, a 6% increase in warm-season (May-October) actual evapotranspiration (ET) is computed over the conterminous United States between 1949 and 1996 via the complementary hypothesis. This predicted incre ... Full text Cite

Relative importance of local and regional controls on coupled water, carbon, and energy fluxes

Journal Article Advances in Water Resources · November 1, 2001 This paper reports the first effort to include carbon, water, and heat exchange in a Large Eddy Simulation (LES) model for 3D canopy flows with dynamic response of leaf temperature and stomatal aperture. The LES model simulates eddy motion from 3D, transie ... Full text Cite

Multiscale analysis of vegetation surface fluxes: From seconds to years

Journal Article Advances in Water Resources · November 1, 2001 The variability in land surface heat (H), water vapor (LE), and CO2 (or net ecosystem exchange, NEE) fluxes was investigated at scales ranging from fractions of seconds to years using eddy-covariance flux measurements above a pine forest. Because these flu ... Full text Cite

Sensible heat flux estimation by flux variance and half-order time derivative methods

Journal Article Water Resources Research · September 12, 2001 This study is the first to contrast two similarity theory methods, the flux variance and the half-order time derivative, over a wide range of atmospheric stability and surface roughness conditions. These two methods were selected because they require only ... Full text Cite

Soil fertility limits carbon sequestration by forest ecosystems in a CO2-enriched atmosphere.

Journal Article Nature · May 2001 Northern mid-latitude forests are a large terrestrial carbon sink. Ignoring nutrient limitations, large increases in carbon sequestration from carbon dioxide (CO2) fertilization are expected in these forests. Yet, forests are usually relegated to sites of ... Full text Cite

Carbon sequestration and southern pine forests

Journal Article JOURNAL OF FORESTRY · April 1, 2001 Link to item Cite

Meeting Global Policy Commitments: Carbon Sequestration and Southern Pine Forests

Journal Article Journal of Forestry · April 1, 2001 In managed forests, the amount of carbon further sequestered will be determined by (1) the increased amount of carbon in standing biomass (resulting from land-use changes and increased productivity); (2) the amount of recalcitrant carbon remaining below gr ... Cite

Gap filling strategies for defensible annual sums of net ecosystem exchange

Journal Article Agricultural and Forest Meteorology · March 1, 2001 Heightened awareness of global change issues within both science and political communities has increased interest in using the global network of eddy covariance flux towers to more fully understand the impacts of natural and anthropogenic phenomena on the ... Full text Cite

Short communication: Gap filling strategies for long term energy flux data sets

Journal Article Agricultural and Forest Meteorology · March 1, 2001 At present a network of over 100 field sites are measuring carbon dioxide, water vapor and sensible heat fluxes between the biosphere and atmosphere, on a nearly continuous basis. Gaps in the long term measurements of evaporation and sensible heat flux mus ... Full text Cite

Modeling dynamic understory photosynthesis of contrasting species in ambient and elevated carbon dioxide.

Journal Article Oecologia · February 2001 Dynamic responses of understory plants to sunflecks have been extensively studied, but how much differences in dynamic light responses affect daily photosynthesis (A day) is still the subject of active research. Recent models of dynamic photosyn ... Full text Cite

Estimating global and local scaling exponents in turbulent flows using discrete wavelet transformations

Journal Article Physics of Fluids · January 1, 2001 The inertial subrange structure of turbulence, were investigated by using high frequency longitudinal velocity measurements. The local and global intermittency buildup in the inertial subrange were investigated over a wide range of atmospheric stability co ... Full text Cite

Estimating CO2 source/sink distributions within a rice canopy using higher-order closure models

Journal Article Boundary-Layer Meteorology · January 1, 2001 Source/sink strengths and vertical flux distributions of carbon dioxide within and above a rice canopy were modelled using measured mean concentration profiles collected during an international rice experiment in Okayama, Japan (IREX96). The model utilizes ... Full text Cite

Gross primary productivity in duke forest: Modeling synthesis of co2 experiment and eddy-flux data

Journal Article Ecological Applications · January 1, 2001 This study was designed to estimate gross primary productivity (GPP) in the Duke Forest at both ambient and elevated CO2 (ambient + 200 μL/L) concentrations using a physiologically based canopy model. The model stratified the canopy of loblolly pine (Pinus ... Full text Cite

FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities

Journal Article Bulletin of the American Meteorological Society · January 1, 2001 FLUXNET is a global network of micrometeorological flux measurement sites that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere. At present over 140 sites are operating on a long-term and continuous basi ... Full text Cite

Carbon sequestration and southern pine forests (vol 99, pg 14, 2001)

Journal Article JOURNAL OF FORESTRY · 2001 Cite

Quantifying the complexity in mapping energy inputs and hydrologic state variables into land-surface fluxes

Journal Article Geophysical Research Letters · January 1, 2001 This study explores the complexity (or disorder) in mapping energy (Rn) forcing to land surface fluxes of sensible heat (Hs), water vapor (LE), and carbon dioxide (or net ecosystem exchange, NEE) for different soil water states (θ). Specifically, we ask, d ... Full text Cite

Estimating scalar sources, sinks, and fluxes in a forest canopy using Lagrangian, Eulerian, and hybrid inverse models

Journal Article Journal of Geophysical Research Atmospheres · December 27, 2000 A new method was developed to estimate canopy sources and sinks from measured mean concentration profiles within the canopy (referred to as the "inverse" problem). The proposed method combined many of the practical advantages of the Lagrangian localized ne ... Full text Cite

Multiscale denoising of self-similar processes

Journal Article Journal of Geophysical Research Atmospheres · November 27, 2000 A practical limitation to investigating self-similarity in geophysical phenomena from their measured state variables is that measured signals are typically convolved with instrumentation noise at multiple scales. This study develops and tests a multiscale ... Full text Cite

Modeling CO2 and water vapor turbulent flux distributions within a forest canopy

Journal Article Journal of Geophysical Research Atmospheres · November 16, 2000 One-dimensional multilayer biosphere-atmosphere models (e.g., CANVEG) describe ecosystem carbon dioxide (CO2) and water vapor (H2O) fluxes well when cold temperatures or the hydrologic state of the ecosystem do not induce stomatal closure. To investigate t ... Full text Cite

An approximate analytical model for footprint estimation of scalar fluxes in thermally stratified atmospheric flows

Journal Article Advances in Water Resources · June 1, 2000 An approximate analytical model was developed to estimate scalar flux footprint in thermally stratified atmospheric surface layer flows. The proposed model was based on a combination of Lagrangian stochastic dispersion model results and dimensional analysi ... Full text Cite

The dynamic role of root-water uptake in coupling potential to actual transpiration

Journal Article Advances in Water Resources · January 11, 2000 The relationship between actual (E(act)) and potential (E(p)) transpiration above a grass-covered forest clearing was investigated numerically and experimentally from simultaneous measurements of soil moisture content profiles, mean meteorological conditio ... Full text Cite

Modelling assimilation and intercellular CO2 from measured conductance: A synthesis of approaches

Journal Article Plant, Cell and Environment · January 1, 2000 A spectrum of models that estimate assimilation rate A from intercellular carbon dioxide concentration (Ci) and measured stomatal conductance to CO2 (gc) were investigated using leaf-level gas exchange measurements. The gas exchange measurements were perfo ... Full text Cite

Modelling vegetation-atmosphere CO2 exchange by a coupled Eulerian-Langrangian approach

Journal Article Boundary-Layer Meteorology · January 1, 2000 A Eulerian-Lagrangian canopy microclimate model was developed with the aim of discerning physical from biophysical controls of CO2 and H2O fluxes. The model couples radiation attenuation with mass, energy, and momentum exchange at different canopy levels. ... Full text Cite

Survey and synthesis of intra- and interspecific variation in stomatal sensitivity to vapour pressure deficit

Journal Article Plant, Cell and Environment · December 1, 1999 Responses of stomatal conductance (g(s)) to increasing vapour pressure deficit (D) generally follow an exponential decrease described equally well by several empirical functions. However, the magnitude of the decrease - the stomatal sensitivity - varies co ... Full text Cite

Spatial variability of turbulent fluxes in the roughness sublayer of an even-aged pine forest

Journal Article Boundary-Layer Meteorology · December 1, 1999 The spatial variability of turbulent flow statistics in the roughness sublayer (RSL) of a uniform even-aged 14 m (= h) tall loblolly pine forest was investigated experimentally. Using seven existing walkup towers at this stand, high frequency velocity, tem ... Full text Cite

Analytical approximation to the solutions of Richards' equation with applications to infiltration, ponding, and time compression approximation

Journal Article Advances in Water Resources · October 11, 1999 A recent approach to solve Richards' equation is further improved. This approach brings understanding into the physical processes of infiltration and ponding. In particular we apply it to analyze the standard hydrologic tool of Time Compression Approximati ... Full text Cite

Modeling CO2 sources, sinks, and fluxes within a forest canopy

Journal Article Journal of Geophysical Research Atmospheres · March 27, 1999 A practical method to infer CO2 sources, sinks, and fluxes from measured mean concentration profiles is proposed and field-tested in a uniform pine forest using eddy covariance measurements. The proposed method computes the velocity statistics from a secon ... Full text Cite

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

Journal Article Advances in Water Resources · February 24, 1999 A new, parameter-free method, based on orthonormal wavelet expansions is proposed for calculating the principal time scale of coherent structures in atmospheric surface layer measurements. These organized events play an important role in the exchange of he ... Full text Cite

A note on the flux-variance similarity relationships for heat and water vapour in the unstable atmospheric surface layer

Journal Article Boundary-Layer Meteorology · January 1, 1999 Atmospheric surface layer (ASL) experiments over the past 10 years demonstrate that the flux-variance similarity functions for water vapour are consistently larger in magnitude than their temperature counterpart. In addition, latent heat flux calculations ... Full text Cite

Principal length scales in second-order closure models for canopy turbulence

Journal Article Journal of Applied Meteorology · January 1, 1999 Triaxial sonic anemometer velocity measurements vertically arrayed at six levels within and above a pine forest were used to examine the performance of two second-order closure models put forth by Wilson and Shaw and by Wilson. Based on these measurements, ... Full text Cite

An investigation of higher-order closure models for a forested canopy

Journal Article Boundary-Layer Meteorology · December 1, 1998 Simultaneous triaxial sonic anemometer velocity measurements vertically arrayed at six levels within and above a uniform pine forest were used to examine two parameterization schemes for the triple-velocity correlation tensor employed in higher-order closu ... Full text Cite

Water Balance Delineates the Soil Layer in Which Moisture Affects Canopy Conductance

Journal Article Ecological Applications · November 1998 Full text Cite

Canopy conductance of Pinus taeda, Liquidambar styraciflua and Quercus phellos under varying atmospheric and soil water conditions.

Journal Article Tree physiology · May 1998 Sap flow, and atmospheric and soil water data were collected in closed-top chambers under conditions of high soil water potential for saplings of Liquidambar styraciflua L., Quercus phellos L. and Pinus taeda L., three co-occurring species in the southeast ... Full text Cite

Identification of low-dimensional energy containing / flux transporting eddy motion in the atmospheric surface layer using wavelet thresholding methods

Journal Article Journal of the Atmospheric Sciences · February 1, 1998 The partitioning of turbulent perturbations into a "low-dimensional" active part responsible for much of the turbulent energy and fluxes and a "high-dimensional" passive part that contributes little to turbulent energy and transport dynamics is investigate ... Full text Cite

Spectral scaling of static pressure fluctuations in the atmospheric surface layer: The interaction between large and small scales

Journal Article Physics of Fluids · January 1, 1998 Static pressure fluctuations measured in the atmospheric surface layer over a grass covered forest clearing are studied in the context of Townsend's 1961 hypothesis regarding the effect of the outer region on the inner region. It is shown that large-scale ... Full text Cite

Active turbulence and scalar transport near the forest-atmosphere interface

Journal Article Journal of Applied Meteorology · January 1, 1998 Turbulent velocity, temperature, water vapor concentration, and other scalars were measured at the canopyatmosphere interface of a 13-14-m-tall uniform pine forest and a 33-m-tall nounuiform hardwood forest. These measurement were used to investigate wheth ... Full text Cite

A theoretical and experimental investigation of energy-containing scales in the dynamic sublayer of boundary-layer flows

Journal Article Boundary-Layer Meteorology · January 1, 1998 The existence of universal power laws at low wavenumbers (K) in the energy spectrum (Eu) of the turbulent longitudinal velocity (u) is examined theoretically and experimentally for the near-neutral atmospheric surface layer. Newly derived power-law solutio ... Full text Cite

Skin temperature perturbations induced by surface layer turbulence above a grass surface

Journal Article Water Resources Research · January 1, 1998 High-frequency (5 Hz) atmospheric surface layer (ASL) turbulent velocity (u') and infrared skin temperature perturbations (T'(s)) were measured above a grass-covered forest clearing and analyzed for cloud free conditions. These measurements were used to in ... Full text Cite

Scaling xylem sap flux and soil water balance and calculating variance: A method for partitioning water flux in forests

Journal Article Annales des Sciences Forestieres · January 1, 1998 To partition evapotranspiration between canopy and subcanopy components in a 12-m-tall Pinus taeda forest and to assess certain aspects of environmental regulation of canopy transpiration, we quantified water flux in a forest using three approaches: 1) mea ... Full text Cite

Water balance delineates the soil layer in which moisture affects canopy conductance

Journal Article Ecological Applications · January 1, 1998 To link variation in canopy conductance to soil moisture in the rooting zone, measurements of throughfall (P(T)), volumetric soil moisture (θ) to 0.7 m, transpiration from trees >10 mm in diameter (E(C)), and vapor pressure deficit (D) were made in a fores ... Full text Cite

Estimation of groundwater evaporation and salt flux from Owens Lake, California, USA

Journal Article Journal of Hydrology · December 15, 1997 Groundwater evaporation and subsequent precipitation of soluble salts at Owens Lake in eastern California have created one of the single largest sources of airborne dust in the USA, yet the evaporation and salt flux have not been fully quantified. In this ... Full text Cite

Time constant for water transport in loblolly pine trees estimated from time series of evaporative demand and stem sapflow

Journal Article Trees - Structure and Function · August 1, 1997 The use of stem sap flow data to estimate diurnal whole-tree transpiration and canopy stomatal conductance depends critically upon knowledge of the time lag between transpiration and water flux through the stem. In this study, the time constant for water m ... Full text Cite

Dissipation methods, Taylor's hypothesis, and stability correction functions in the atmospheric surface layer

Journal Article Journal of Geophysical Research Atmospheres · July 27, 1997 The traditional dissipation method and the new approaches suggested by Albertson et al. [1996] and Hsieh et al. [1996] to estimate momentum and heat fluxes were compared using velocity and temperature measurements in the atmospheric surface layer. These me ... Full text Cite

Lagrangian dispersion model for predicting CO2 sources, sinks, and fluxes in a uniform loblolly pine (Pinus taeda L.) stand

Journal Article Journal of Geophysical Research Atmospheres · April 27, 1997 A canopy Lagrangian turbulent scalar transport model for predicting scalar fluxes, sources, and sinks within a forested canopy was tested using CO2 concentration and flux measurements. The model formulation is based on the localized near-field theory (LNF) ... Full text Cite

Estimation of surface heat and momentum fluxes using the flux-variance method above uniform and non-uniform terrain - Reply

Journal Article BOUNDARY-LAYER METEOROLOGY · 1997 Cite

The Lagrangian stochastic model for fetch and latent heat flux estimation above uniform and nonuniform terrain

Journal Article Water Resources Research · January 1, 1997 A Lagrangian stochastic model was used to estimate the fetch and latent heat flux above a nonuniform grass-covered forest clearing site at the Duke Forest, in Durham, North Carolina, and an irrigated bare soil patch at the University of California in Davis ... Full text Cite

Energy-inertial scale interactions for velocity and temperature in the unstable atmospheric surface layer

Journal Article Boundary-Layer Meteorology · January 1, 1997 Triaxial sonic anemometer velocity and temperature measurements were used to investigate the local structure of the velocity and temperature fluctuations in the unstable atmospheric surface layer above a grass-covered forest clearing. Despite the existence ... Full text Cite

The ejection-sweep character of scalar fluxes in the unstable surface layer

Journal Article Boundary-Layer Meteorology · January 1, 1997 In the atmospheric surface layer, it is widely accepted that ejection and sweep eddy motions, typically associated with coherent structures, are responsible for much of the land-surface evaporation, sensible heat, and momentum fluxes. The present study ana ... Full text Cite

Turbulent eddy motion at the forest-atmosphere interface

Journal Article Journal of Geophysical Research Atmospheres · January 1, 1997 Ejection and sweep eddy motions in the atmospheric surface layer (ASL) are widely accepted as being responsible for much of land surface evaporation, sensible heat flux, and momentum flux; however, less is known about this type of eddy motion within the ca ... Full text Cite

Soil water depletion by oak trees and the influence of root water uptake on the moisture content spatial statistics

Journal Article Water Resources Research · January 1, 1997 The space-time statistical structure of soil water uptake by oak trees was investigated in a 3.1-m-diameter closed top chamber using a three-dimensional measurement grid of soil moisture and pressure, and measurements of tree transpiration. Using the time ... Full text Cite

The random sweeping decorrelation hypothesis in stratified turbulent flows

Journal Article International Journal of Multiphase Flow · December 1996 Full text Cite

The "inactive" eddy motion and the large-scale turbulent pressure fluctuations in the dynamic sublayer

Journal Article Journal of the Atmospheric Sciences · September 1, 1996 The statistical structure of the turbulent pressure fluctuations was measured in the dynamic sublayer of a large grass-covered forest clearing by a free air static pressure probe and modeled using Townsend's hypothesis. Townsend's hypothesis states that th ... Full text Cite

Estimation of momentum and heat fluxes using dissipation and flux- variance methods in the unstable surface layer

Journal Article Water Resources Research · August 1, 1996 Dissipation and flux-variance methods, derived from the turbulent kinetic energy and temperature variance budget equations in conjunction with Monin-Obukov similarity theory, were used to estimate surface fluxes of momentum and sensible heat. To examine th ... Full text Cite

Probability density functions of turbulent velocity and temperature in the atmospheric surface layer

Journal Article Water Resources Research · June 1, 1996 The probability density functions (pdf's) for the longitudinal and vertical velocities, temperature, their derivatives, and momentum and sensible heat fluxes were measured in the atmospheric surface layer for a wide range of atmospheric stability condition ... Full text Cite

The local effect of intermittency on the inertial subrange energy spectrum of the atmospheric surface layer

Journal Article Boundary-Layer Meteorology · January 1, 1996 Orthonormal wavelet expansions are applied to atmospheric surface layer velocity measurements. The effect of intermittent events on the energy spectrum of the inertial subrange is investigated through analysis of wavelet coefficients. The local nature of t ... Full text Cite

The partitioning of attached and detached eddy motion in the atmospheric surface layer using Lorentz wavelet filtering

Journal Article Boundary-Layer Meteorology · January 1, 1996 Proposes and tests a methodology for separating the attached and detached eddy motion from time series measurements of velocity and temperature. The proposed methodology is based on the time-frequency localization and filtering capabilities of the orthonor ... Full text Cite

An investigation of the conditional sampling method used to estimate fluxes of active, reactive, and passive scalars

Journal Article Journal of Applied Meteorology · January 1, 1996 The conditional sampling flux measurement technique was evaluated for four scalars (temperature, water vapor, ozone, and carbon dioxide) by comparison with direct eddy correlation measurements at two sites. The empirical constant β relating the turbulent f ... Full text Cite

Latent and sensible heat flux predictions from a uniform pine forest using surface renewal and flux variance methods

Journal Article Boundary-Layer Meteorology · January 1, 1996 A surface renewal model that links organized eddy motion to the latent and sensible heat fluxes is tested with eddy correlation measurements carried out in a 13 m tall uniform Loblolly pine plantation in Duke Forest, Durham, North Carolina. The surface ren ... Full text Cite

The spatial structure of turbulence at production wavenumbers using orthonormal wavelets

Journal Article Boundary-Layer Meteorology · July 1, 1995 Orthonormal wavelet expansions are applied to surface-layer measurements of vertical wind speed under various atmospheric, stability conditions. The orthonormal wavelet transform allows for the unfolding of these measurements into space and scale simultane ... Full text Cite

Estimation of surface heat and momentum fluxes using the flux-variance method above uniform and non-uniform terrain

Journal Article Boundary-Layer Meteorology · May 1, 1995 Eddy-correlation measurements above an uneven-aged forest, a uniform-irrigated bare soil field, and within a grass-covered forest clearing were used to investigate the usefulness of the fluxvariance method above uniform and non-uniform terrain. For this pu ... Full text Cite

Watershed Scale Shear Stress From Tethersonde Wind Profile Measurements Under Near Neutral and Unstable Atmospheric Stability

Journal Article Water Resources Research · January 1, 1995 Mean wind speed profiles were measured in the atmospheric surface layer, using a tethersonde system, above the Ojai Valley Watershed in southern California. The valley is mainly planted with mature avocado and orange trees. The surface shear stress and lat ... Full text Cite

Local isotropy and anisotropy in the sheared and heated atmospheric surface layer

Journal Article Boundary-Layer Meteorology · January 1, 1995 Longitudinal velocity and temperature measurements above a uniform dry lakebed were used to investigate sources of eddy-motion anisotropy within the inertial subrange. Rather than simply test the adequacy of locally isotropic relations, we investigated dir ... Full text Cite

The random sweeping decorrelation hypothesis in stratified turbulent flows

Journal Article Fluid Dynamics Research · January 1, 1995 Longitudinal velocity measurements above a uniform dry lakebed were carried out to investigate the applicability of the random sweeping decorrelation hypothesis to thermally stratified turbulent flow. The higher order velocity structure functions of order ... Full text Cite

Analysis of Land Surface Heat Fluxes Using the Orthonormal Wavelet Approach

Journal Article Water Resources Research · January 1, 1995 Heat fluxes under unstable atmospheric conditions are measured and analyzed using orthonormal wavelet expansions. Both wavelet and Fourier power spectra display a −1 power law that can be derived from dimensional arguments for latent and sensible heat flux ... Full text Cite

Low-wavenumber spectral characteristics of velocity and temperature in the atmospheric surface layer

Journal Article Journal of Geophysical Research · January 1, 1995 The structure of atmospheric surface layer turbulence at low wavenumbers was analyzed using 56 Hz triaxial velocity and temperature measurements above a uniform dry lake bed. A key feature of this experiment was the small roughness length of the surface th ... Cite

Sensible Heat Flux From Arid Regions: A Simple Flux‐Variance Method

Journal Article Water Resources Research · January 1, 1995 Similarity models in the inner region of the unstable atmospheric boundary layer (ABL) are generally based on four dimensional parameters: buoyancy, friction velocity, surface heat flux, and the height above the land surface. in the free convection limit t ... Full text Cite

Low-wavenumber spectral characteristics of velocity and temperature in the atmospheric surface layer

Journal Article Journal of Geophysical Research · 1995 The structure of atmospheric surface layer turbulence at low wavenumbers was analyzed using 56 Hz triaxial velocity and temperature measurements above a uniform dry lake bed. A key feature of this experiment was the small roughness length of the surface th ... Cite

Observations on the growth of an internal boundary layer with a Lidar technique

Journal Article Proceedings of the Symposium on Fundamentals and Advancements in Hydraulic Measurements and Experimentation · December 1, 1994 The distribution of atmospheric water vapor across a step change in surface humidity (dry-wet) was observed by a Lidar measurement technique under neutral atmospheric stability condition. The technique uses multiple elevation scans from a scanning water Ra ... Cite

A model for sensible heat flux probability density function for near-neutral and slightly-stable atmospheric flows

Journal Article Boundary-Layer Meteorology · October 1, 1994 The probability density function for sensible heat flux was measured above a uniform dry lakebed (Owens lake) in Owens Valley, California. It was found that for moderately stable to near neutral atmospheric stability conditions, the probability density fun ... Full text Cite

On the Active Role of Temperature in Surface-Layer Turbulence

Journal Article Journal of the Atmospheric Sciences · August 1994 Full text Cite

Intermittency in Atmospheric Surface Layer Turbulence: The Orthonormal Wavelet Representation

Journal Article · January 1, 1994 Orthonormal wavelet expansions are applied to atmospheric surface layer velocity measurements that exhibited about three decades of inertial subrange energy spectrum. A direct relation between the nth order structure function and the wavelet coefficients i ... Full text Cite

Sensible and latent heat flux predictions using conditional sampling methods

Journal Article Water Resources Research · January 1, 1994 The conditional sampling formulation typically used in eddy accumulation flux measurements was tested at two sites using velocity, temperature, and specific humidity time series measurements. The first site was at Owen's Lake in southern California, and th ... Full text Cite

Intermittency, local isotropy, and non-Gaussian statistics in atmospheric surface layer turbulence

Journal Article Physics of Fluids · January 1, 1994 Orthonormal wavelet expansions are applied to atmospheric surface layer velocity and temperature measurements above a uniform bare soil surface that exhibit a long inertial subrange energy spectrum. In order to investigate intermittency effects on Kolmogor ... Full text Cite

Conditional sampling, bursting, and the intermittent structure of sensible heat flux

Journal Article Journal of Geophysical Research · January 1, 1994 Sensible heat flux measurements were carried out to examine the characteristics related to frequency and duration of extreme flux events above a desert surface. First, the flux bursts were identified by a modified hyperbolic hole "quadrant analysis'. Secon ... Full text Cite

Conditional sampling, bursting, and the intermittent structure of sensible heat flux

Journal Article Journal of Geophysical Research · 1994 Sensible heat flux measurements were carried out to examine the characteristics related to frequency and duration of extreme flux events above a desert surface. First, the flux bursts were identified by a modified hyperbolic hole "quadrant analysis'. Secon ... Cite

Estimation of in situ hydraulic conductivity function from nonlinear filtering theory

Journal Article Water Resources Research · January 1, 1993 A method based on an optimal nonlinear filtering technique is proposed and tested for the determination of the hydraulic conductivity function from a field drainage experiment. Simplifications to Richards's equation lead to a Langevin type differential equ ... Full text Cite

Evaporation and the field scale soil water diffusivity function

Journal Article Water Resources Research · January 1, 1993 Simplifications to the depth‐integrated soil water transport equation lead to an Ito stochastic differential equation where the evaporation is related to the stored water by the nonlinear soil water diffusivity function. From the derived equation the diffu ... Full text Cite

Determination of average field scale soil surface temperature from meteorological measurements

Journal Article Soil Science · January 1, 1993 A simple procedure is presented for the determination of field scale soil surface temperature using meteorological and surface energy measurements. An advectionaridity evaporation model, in conjunction with the surface energy budget, is used to solve for t ... Full text Cite

A nonlinear filtering approach for determining hydraulic conductivity functions in field soils

Journal Article Soil Science · January 1, 1993 A nonlinear Extended Kalman Filter approach is used to explicitly account for measurement and model uncertainty in field soil hydraulic conductivity function determination. The standard deviation that such a procedure provides for hydraulic conductivity, a ... Full text Cite

Application of a scanning, water Raman-Lidar as a probe of the atmospheric boundary layer

Journal Article IEEE Transactions on Geoscience and Remote Sensing · 1993 A scanning water Raman-lidar has been designed and constructed to study surface-atmosphere processes with high spatial and temporal resolution. Analytical methods are also being developed to analyze the information this lidar can take. The lidar is able to ... Full text Cite

Revision of Oregon crop water use and irrigation requirements

Journal Article Management of Irrigation and Drainage Systems : Integrated Perspectives · January 1, 1993 A project to revise the crop water use estimates and irrigation requirements for the state at Oregon is described. The FAO modified Blaney-Criddle method was applied in this project since this method has been shown to have the lowest estimation error of al ... Cite

Physical basis for a time series model of soil water content

Journal Article Water Resources Research · January 1, 1992 A first‐order autoregressive Markovian model AR(1) is formulated on the basis of the hydrologic budget and soil water transport equation. The model predictions compared well with neutron probe measurements of soil moisture content, and the statistical mome ... Full text Cite

Analysis of evaporative flux data for various climates

Journal Article Journal of Irrigation and Drainage Engineering · January 1, 1992 Estimation of evapotranspiration is a key requirement of hydrologic balance studies and climate analysis. The study reported involved collection of precise weighing lysimeter and meteorological data from three sites representing distinct climates. The comb ... Full text Cite

Estimation of bare soil evaporation using skin temperature measurements

Journal Article Journal of Hydrology · January 1, 1992 A simple model based on the Monin-Obukhov surface layer similarity theory of heat and momentum transport can be used to predict the latent heat flux for a variety of atmospheric and soil moisture conditions. Experiments were carried out on the Campbell Tra ... Full text Cite

Estimation of the diurnal variation of potential evaporation from a wet bare soil surface

Journal Article Journal of Hydrology · January 1, 1992 Potential evaporation from a wet bare soil field was measured with a large sensitive weighing lysimeter on a 20 min time step for 5 days at Davis, California. The diurnal evaporation rate modeled with the Penman-Brutsaert model for potential evaporation wi ... Full text Cite

A Penman‐Brutsaert Model for wet surface evaporation

Journal Article Water Resources Research · January 1, 1992 An atmospheric stability Penman‐Brutsaert model for wet surface evaporation is developed for short time prediction of the diurnal latent heat flux. Monin‐Obukhov similarity theory is used in conjunction with a theoretical scalar roughness length for bluff ... Full text Cite

An advection‐aridity evaporation model

Journal Article Water Resources Research · January 1, 1992 Actual evaporation is calculated by means of an advection‐aridity complementary model which requires, as input, the meteorological data used in classical combination models. The main advantage of the model is that it does not require site‐specific calibrat ... Full text Cite

A technique for the continuous recording of tick feeding electrograms and temperature by telemetry from free-ranging cattle.

Journal Article International journal for parasitology · August 1976 Full text Cite