Journal articleGeophysical Research Letters · July 16, 2026
Fog prediction remains challenging because the physical processes governing its life cycle evolve across time scales and do not follow reversible or stationary dynamics. Using high-frequency visibility observations from Sable Island, Canada, this study ana ...
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Journal articleJournal of Geophysical Research Atmospheres · June 16, 2026
The longitudinal turbulent heat flux is central to the description of vertical momentum and energy transport in stratified atmospheric boundary layers, yet its scaling behavior with respect to thermal stratification remains uncertain in comparison to bette ...
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Journal articleJournal of Fluid Mechanics · April 20, 2026
The variance and spectra of wall-normal velocities are investigated for direct numerical simulations of turbulent flow in a channel, pipe and zero-pressure-gradient boundary layer across a decade of friction Reynolds numbers. Spectra along the spanwise wav ...
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Journal articleGeophysical Research Letters · January 16, 2026
Glacial cycles emerged with a 41-kyr period after the Pliocene and later intensified with a 100-kyr period in the mid-Pleistocene, which were attributed to Earth's orbital variations. However, no significant changes in the orbital forcing were found at the ...
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Journal articleNature Climate Change · January 1, 2026
Rising concentrations of atmospheric CO2 (ca) increase plant photosynthesis (An) and reduce stomatal conductance (gs). This increases the intrinsic water-use efficiency (iWUE = An/ gs), a ma ...
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Journal articleWater Resources Research · December 1, 2025
Theories for flow conveyance within aquatic vegetation have predominantly been developed for impermeable beds thereby overlooking key interactions between hydraulic and hydrologic drivers. To begin addressing this overlook, the hydrodynamic properties of e ...
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Journal articleQuarterly Journal of the Royal Meteorological Society · October 1, 2025
The influence of thermal stratification on the turbulent kinetic energy balance has been widely studied; however, its influence on the turbulent stress remains less explored in the presence of tall vegetated canopies and less ideal micrometeorological cond ...
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Journal articleReviews of Geophysics · September 1, 2025
Stemflow hydrodynamics is the study of water movement along the exterior surface area of plants. Its primary goal is to describe water velocity and water depth along the stem surface area. Its significance in enriching the rhizosphere with water and nutrie ...
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Journal articleEcological Indicators · September 1, 2025
A wide array of bark surfaces sheath wooded plants in rural and urban areas alike. Much work has examined the function and role of bark in different contexts and different environs, including urban areas, finding that it is rich in life and can play a role ...
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Journal articleAgricultural and Forest Meteorology · August 15, 2025
Modifications to the spectra of turbulent velocity and scalars and co-spectra of vertical fluxes of momentum and scalars due to patchy landscape heterogeneity and non-stationarity are explored for a Mediterranean ecosystem. About 9 months of high frequency ...
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Journal articleGeophysical Research Letters · June 16, 2025
The measured variations in the turbulent static pressure structure function (Formula presented.) with scale (Formula presented.) in the roughness sublayer above a subarctic forest are empirically shown to exhibit exponents that are smaller than (Formula pr ...
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Journal articleJournal of Fluid Mechanics · May 13, 2025
The attached-eddy model (AEM) predicts that the mean streamwise velocity and streamwise velocity variance profiles follow a logarithmic shape, while the vertical velocity variance remains invariant with height in the overlap region of high Reynolds number ...
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Journal articleGeophysical Research Letters · March 16, 2025
Top-down entrainment shapes the vertical gradients of sensible heat, latent heat, and CO2 fluxes, influencing the interpretation of eddy covariance (EC) measurements in the unstable atmospheric surface layer (ASL). Using large eddy simulations f ...
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Journal articleJournal of Geophysical Research Atmospheres · February 28, 2025
The turbulent static pressure spectrum (Formula presented.) as a function of longitudinal wavenumber (Formula presented.) in the roughness sublayer of forested canopies is of interest to a plethora of problems such as pressure transport in the turbulent ki ...
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Journal articleAdvances in Water Resources · January 1, 2025
Describing flow resistance using the physical properties of an underlying surface is a recalcitrant problem in overland flow models. If discharge measurements are available, an equivalent roughness (e.g., Manning's n) can be calibrated to represent the eff ...
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Journal articleWater Resources Research · January 1, 2025
Describing flow resistance from the properties of an underlying surface is a challenge in surface hydrology. Runoff models must specify a resistance formulation or “roughness scheme”—describing the functional relationship between flow resistance and flow d ...
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Journal articleJournal of Fluid Mechanics · December 18, 2024
Empirical evidence is provided that within the inertial sublayer (i.e. logarithmic region) of adiabatic turbulent flows over smooth walls, the skewness of the vertical-velocity component Sw displays universal behaviour, being a positive constant ...
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Journal articleBoundary Layer Meteorology · November 1, 2024
Turbulent flows over a large surface area (S) covered by n obstacles experience an overall drag due to the presence of the ground and the protruding obstacles into the flow. The drag partition between the roughness obstacles and the ground is analyzed usin ...
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Journal articleWater Resources Research · November 1, 2024
In inland water covering lakes, reservoirs, and ponds, the gas exchange of slightly soluble gases such as carbon dioxide, dimethyl sulfide, methane, or oxygen across a clean and nearly flat air-water interface is routinely described using a water-side mean ...
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Journal articlePhysics of Fluids · November 1, 2024
One of the main features of near-neutral atmospheric boundary layer (ABL) turbulence is the positive vertical velocity skewness S k w above the roughness sublayer or the buffer region in smooth-walls. The S k w variations are receiving renewed interest in ...
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Journal articleJournal 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 ...
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Journal articleThe 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 ...
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Journal articleAtmospheric 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 ...
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Journal articleRemote 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 ...
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Journal articlePhysics 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 ...
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Journal articleScience 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 ...
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Journal articleAgu 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 ...
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Journal articleEarth 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 ...
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Journal articleGeophysical 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 w ...
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Journal articleCurrent 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 ...
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Journal articleGeophysical 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 ...
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Journal articleAgricultural and Forest Meteorology. · November 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 ...
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Journal articleCatena · 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 ...
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Journal articleAgricultural and Forest Meteorology. · October 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 ...
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Journal articleInternational 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 ...
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Journal articleJournal 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 partia ...
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Journal articlePhysics 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 ...
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Journal articleGeophysical 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 ...
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Journal articleAtmosphere · 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 ...
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Journal articleEarth 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. ...
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Journal articleAgricultural and forest meteorology · April 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 ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articlePhysics 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 ...
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Journal articleBoundary 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 ...
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Journal articleAtmospheric 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 ...
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Journal articleHydrology 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 ...
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Journal articlePhysica 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 rol ...
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Journal articleJournal 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 ...
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Journal articleBoundary 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 ...
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Journal articleQuarterly 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 ...
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Journal articleBiogeosciences · 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 ...
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Journal articlePlant, 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. ...
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Journal articlePlant 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleGlobal 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articlePhysical 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 ...
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Journal articleAgricultural 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 ...
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Journal articleGlobal 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 ...
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Journal articleWater 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 ...
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Journal articleThe 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 ...
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Journal articleGlobal 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 ...
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Journal articleGeophysical 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 ...
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Journal articlePhysics 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) ...
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Journal articleChemical 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 re ...
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Journal articleEnvironmental 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 ...
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Journal articleProceedings 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 ...
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Journal articlePhysical 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( ...
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Journal articleJournal 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 ...
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Journal articleAtmospheric 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 ...
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Journal articleProceedings 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 ...
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Journal articlePhysical 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 ...
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Journal articlePhysical 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 ...
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Journal articleGeophysical 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 ...
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Journal articleJournal 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 ...
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Journal articleRemote 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 r ...
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Journal articleGeophysical 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 urgen ...
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Journal articleAgricultural 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 patt ...
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Journal articleGeological 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 plet ...
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Journal articleJournal 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 ...
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Journal articleAgricultural 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 ...
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Journal articleJournal 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 ...
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Journal articleGeophysical 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 ...
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Journal articleApplied 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleAgricultural 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 ...
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Journal articleProceedings. 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 ...
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Journal articleJournal 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 ...
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Journal articlePhysical 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 ...
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Journal articleQuarterly 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 ...
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Journal articleAdvances 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, wher ...
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Journal articleEnvironmental 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 ...
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Journal articleProceedings 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 ...
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Journal articleJournal 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 ...
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Journal articleEcohydrology · 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 ...
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Journal articleNature 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 ...
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Journal articleJournal 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 ...
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Journal articleEcohydrology · 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 ...
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Journal articleFrontiers 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 ...
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Journal articleGeophysical 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 ...
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Journal articleWater 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 ...
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Journal article · April 14, 2020
Abstract
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 ...
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Journal articleJournal 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 ...
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Journal article · March 23, 2020
<p>The evapotranspiration (<em>ET</em>) process is a key term of soil water balance. In the Mediterranean climates <em>ET </em>represents the main loss term, that could ...
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Journal article · March 23, 2020
<p>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 ...
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Journal article · March 23, 2020
<p>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 ...
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Journal article · March 23, 2020
<p>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 ...
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Journal article · March 23, 2020
<p>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 ...
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Journal articleProceedings 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 ...
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Journal articleEnvironmental 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 ...
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Journal articleThe 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 ...
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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 ...
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Journal articlePloS 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 ...
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Journal articleNature 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 ...
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Journal articleThe 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 ...
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Journal articlePhysical 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 ...
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Journal articleNature · 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 ...
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Journal articleFrontiers 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 ...
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Journal articleWater 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 ...
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Journal articleBoundary 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 ...
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Journal articleQuarterly 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 ...
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Journal articleGeophysical 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 ...
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Journal articleJournal 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 ...
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Journal articleAerosol 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 ...
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Journal articleJournal 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 ...
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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 ...
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Journal articleWiley 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 ...
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Journal articleTree 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 ...
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Journal articleWater 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleAtmospheric 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 ...
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Journal articleWater 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 ...
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Journal articlePlant, 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 ...
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Journal articleBoundary 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 a ...
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Journal articleGeophysical 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 ...
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Journal articleJournal 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 p ...
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Journal articleEcological 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 ...
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Journal articleAdvances 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 ph ...
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Journal articleAtmospheric 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 ...
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Journal articleHealth 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 ...
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Journal articleOikos · 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, ...
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Journal articleWater 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 ve ...
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Journal articlePhysical 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 ...
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Journal articleJournal 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 ...
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Journal articleAgricultural 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 ...
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Journal articlePhysical 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleGeophysical 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-O ...
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Journal articleHydrobiologia · 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 ...
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Journal articleJournal 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
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Journal articleAdvances 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 ...
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Journal articleEcological 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 ...
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Journal articleProceedings 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 ...
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Journal articleQuarterly 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 ...
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Journal articleAdvances 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 ...
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Journal articlePhysics 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 ...
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Journal articleWater 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 ...
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Journal articleEnvironmental 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 ...
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Journal articleGeophysical 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 visco ...
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Journal articleJournal 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 ...
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Journal articleThe 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 ...
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Journal articleAgricultural 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 ...
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Journal articleQuarterly 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, ...
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Journal articleJournal 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 ...
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Journal articleGlobal 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 ...
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Journal articleEarth 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 ind ...
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Journal articleBulletin 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. ...
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Journal articleEnvironmental 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 ...
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Journal articlePhysics 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 characteriz ...
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Journal articleCiência 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 ...
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Journal articleGlobal 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 ...
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Journal articleEnvironmental 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 measur ...
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Journal articleBoundary 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 ...
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Journal articlePhysics 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 v ...
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Journal articleWater 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 ...
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Journal articleWater 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 ...
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Journal articleQuarterly 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 AS ...
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Journal articleJournal 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 s ...
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Journal articleWater 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 bo ...
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Journal articleJournal 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 ...
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Journal articleBoundary 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 ...
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Journal articleAdvances 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 enhancem ...
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Journal articleWater 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 ...
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Journal articleWater 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 ...
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Journal articleJournal 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 ...
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Journal articleEcological 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, ...
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Journal articlePhysical review. E, Statistical, nonlinear, and soft matter physics · September 2015
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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 ...
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Journal articleJournal 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 ...
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Journal articleAtmosphere · 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 ...
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Journal articleJournal 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 pattern ...
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Journal articleJournal 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 ...
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Journal articleWater 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 ...
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Journal articleQuarterly 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*) continu ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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. Conti ...
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Journal articleWater 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 ...
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Journal articleWIREs 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 ...
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Journal articleAdvances 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articlePhysical 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 ...
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Journal articleGeophysical 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 ...
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Journal articleGeophysical 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 ...
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Journal articleAgricultural 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 ...
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Journal articleGeophysical 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 ...
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Journal articleJournal 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 ...
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Journal articleSoil 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 ...
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Journal articleAdvances 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 ...
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Journal articleEcological 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 ...
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Journal articlePhysical 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 ...
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Journal articleJournal 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 ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articleAtmospheric 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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 ...
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Journal articleEcohydrology · 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 ...
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Journal articleWater 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 ...
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Journal articleMovement 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 ...
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Journal articlePhysics 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 hypothesi ...
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Journal articleAdvances in Water Resources · December 1, 2013
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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 ...
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Journal articleEnvironmental 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 ...
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Journal articleAgricultural 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 ...
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Journal articlePhysics 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 ...
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Journal articleEos, 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. ...
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Journal articleEos, 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 ...
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Journal articleBoundary 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 ...
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Journal articleEnvironmental 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 ...
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Journal articleAdvances 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 ...
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Journal articlePhysics of Fluids · September 18, 2013
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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 ...
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Journal articleJournal 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 ...
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Journal articleGeophysical 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 ...
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Journal articleGlobal 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 ...
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Journal articleAgricultural 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 ...
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Journal articleBoundary 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 ...
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Journal articleNew Phytol · April 2013
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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 ...
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Journal articleAnnals 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) ...
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Journal articlePhysical 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 ...
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Journal articleBoundary 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, ...
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Journal articleAdvances 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 ...
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Journal articleJournal 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 ...
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Journal articlePhysical 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 ...
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Journal articlePhysics 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 ...
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Journal articleAgricultural 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 ...
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Journal articleReviews 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 ...
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Journal articleGeophysical 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 ...
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Journal articleTree 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. ...
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Journal articleBoundary 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 distin ...
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Journal articleAtmospheric 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 ...
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Journal articleThe 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 ...
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Journal articleBoundary 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 ...
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Journal articleAdvances 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 ...
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Journal articleWater 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 ...
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Journal articleGeophysical 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 ...
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Journal articleJournal 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 ...
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Journal articlePhys Rev Lett · December 23, 2011
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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 ...
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Journal articleAgricultural 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleNature · 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 ...
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Journal articleThe 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 ...
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Journal articleGeophysical 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 ...
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Journal articleWater 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 ...
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Journal articleAdvances 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 ...
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Journal articleJournal 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 ...
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Journal articleTellus 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 interpretat ...
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Journal articleJournal 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 ...
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Journal articleFunctional 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 ...
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Journal articlePhysica 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 ...
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Journal articleTheoretical 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 ...
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Journal articleBoundary 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 ...
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Journal articleGeophysical 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 ...
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Journal articleEcological 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 ...
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Journal articleAtmospheric 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 r ...
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Journal articleEcology 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 ...
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Journal articleAGRICULTURAL 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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 water ...
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Journal articleGeophysical 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 ...
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Journal articleWater 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. ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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
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Journal articleBoundary 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 pro ...
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Journal articleEcosystems. · 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 ...
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Journal articleAnnals 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 ...
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Journal articleGlobal 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 ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleGeophysical 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 ...
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Journal articleBoundary 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 ...
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Journal articleWater 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 ...
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Journal articleWater 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 sp ...
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Journal articleProceedings. 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 ...
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Journal articleAgricultural 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 ...
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Journal articleBulletin 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- ...
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Journal articlePlant, 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( ...
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Journal articleBiogeochemistry. · 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 ...
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Journal articleBoundary 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 ...
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Journal articlePhysica 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 ...
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Journal articleAdvances 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 ...
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Journal articleJournal 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 pr ...
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Journal articleThe 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleGeophysical 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 ...
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Journal articleInternational 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 ...
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Journal articlePhysics 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 ...
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Journal articleBiogeosciences · 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 ...
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Journal articlePhysics 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 photosynthes ...
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Journal articleTheoretical 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 ...
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Journal articleProceedings 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 ...
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Journal articleBoundary 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 ...
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Journal articleWater 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 ...
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Journal articleEcological 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 ...
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Journal articleAgricultural 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, ...
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Journal articleExperiments 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articleAdvances 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 gr ...
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Journal articleQuarterly 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 ...
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Journal articleAgricultural 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) fluct ...
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Journal articleAtmospheric 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 in ...
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Journal articleGlobal 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 ...
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Journal articleThe 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleActa 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 ...
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Journal articleAdvances 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 ...
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Journal articleWater 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 ...
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Journal articleAGRICULTURAL 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 ...
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Journal articlePROCEEDINGS 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 ...
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Journal articleAnnual 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 ...
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Journal articleGeophysical 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 ...
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Journal articleTellus 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 ...
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Journal articleComptes 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 ...
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Journal articleQuarterly 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 ...
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Journal articleBoundary 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 ...
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Journal articleRadiation 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. 222< ...
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Journal articlePhysics 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 ...
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Journal articleBoundary 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 vapou ...
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Journal articleWATER 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 ...
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Journal articleWATER 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 ...
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Journal articleGLOBAL 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 ...
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Journal articleHydrology 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 measure ...
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Journal articleWater 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 ...
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Journal articleGlobal 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 ...
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Journal articleJournal 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 ...
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Journal articleGlobal 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 ...
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Journal articleJournal 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 ...
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Journal articlePhysica 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 ...
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Journal articleEcological 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 ...
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Journal articleAdvances 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 ...
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Journal articleEcological 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 ...
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Journal articleWATER 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 hea ...
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Journal articleAgricultural 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, ...
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Journal articleGLOBAL 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 ...
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Journal articleWater 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 ...
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Journal articleThe 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 ...
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Journal articleAdvances 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
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Journal articlePhysica 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 ...
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Journal articleProceedings 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 ...
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Journal articleSensors 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 ...
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Journal articleDiversity 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 ...
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Journal articlePhysics 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 ...
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Journal articleOecologia · 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 ...
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Journal articleTREE 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 ...
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Journal articleAdvances 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 hydrologi ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleGlobal 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 ...
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Journal articleGeophysical 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 ...
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Journal articleWater 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 ...
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Journal articleEcology · 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 ...
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Journal articleEcology · 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 ...
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Journal articleOecologia · 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 ...
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Journal articleJournal 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 ...
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Journal articleBoundary 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 ...
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Journal articleGlobal 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 est ...
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Journal articleGlobal 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. ...
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Journal articleTree 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 ...
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Journal articleQuarterly 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 clos ...
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Journal articleBoundary 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 ...
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Journal articlePlant 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 ...
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Journal articleGeophysical 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 ...
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Journal articleAgricultural 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 ...
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Journal articleAgricultural 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 ...
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Journal articleAgricultural 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 ...
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Journal articleWater 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). ...
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Journal articleWater 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 ...
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Journal articleVadose 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 ...
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Journal articleAdvances 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 tra ...
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Journal articleNature · 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. ...
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Journal articleBoundary 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 ...
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Journal articleGlobal 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 ...
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Journal articlePlant 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 ...
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Journal articleVadose 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, ...
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Journal articleJournal 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 ...
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Journal articleAdvances 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 ...
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Journal articleAdvances 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. Becaus ...
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Journal articleWater 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 ...
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Journal articleNature · 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 ...
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Journal articleJournal 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 ...
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Journal articleAgricultural 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 ...
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Journal articleAgricultural 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 ...
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Journal articleOecologia · 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 ...
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Journal articlePhysics 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 ...
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Journal articleBoundary 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 ...
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Journal articleEcological 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 ...
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Journal articleBulletin 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 ...
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Journal articleGeophysical 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). S ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 clo ...
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Journal articleAdvances 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 ...
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Journal articleAdvances 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 ...
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Journal articlePlant 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 ...
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Journal articleBoundary 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 dif ...
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Journal articlePlant 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 ...
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Journal articleBoundary 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 ...
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Journal articleAdvances 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 ...
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Journal articleJournal 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 f ...
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Journal articleAdvances 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 ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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, ...
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Journal articleBoundary 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 ...
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Journal articleTree 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 ...
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Journal articleJournal 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 ...
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Journal articlePhysics 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 ...
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Journal articleJournal 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 ...
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Journal articleBoundary 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- ...
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Journal articleWater 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 ...
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Journal articleAnnales 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 ...
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Journal articleEcological 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 ...
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Journal articleJournal 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 ...
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Journal articleTrees 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 t ...
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Journal articleWater 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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 ...
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Journal articleWater 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleJournal 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleBoundary 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 ...
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Journal articleWater 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 ...
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Journal articleBoundary 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 ...
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Journal articleFluid 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 ...
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Journal articleWater 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleProceedings 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 ...
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Journal articleBoundary 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 ...
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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 coe ...
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Journal articleWater 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 ...
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Journal articlePhysics 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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 ...
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Journal articleWater 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 ...
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Journal articleSoil 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 ...
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Journal articleSoil 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 ...
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Journal articleIEEE 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 ...
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Journal articleManagement 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 ...
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Journal articleWater 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleJournal 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 ...
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Journal articleWater 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 ...
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Journal articleWater 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 ...
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https://orcid.org/0000-0001-9768-3693