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Impact of Amazonian evapotranspiration on moisture transport and convection along the eastern flanks of the tropical Andes

Publication ,  Journal Article
Sun, X; Barros, AP
Published in: Quarterly Journal of the Royal Meteorological Society
October 1, 2015

The Weather Research and Forecasting (WRF) model was used to investigate the impact of Amazonian evapotranspiration (ET) on moisture transport and convection along the eastern flanks of the Andes (EADS). To isolate the role of surface ET, quasi-idealized simulations down to 1.2 km grid spacing were conducted, where over the Amazon lowlands (AMZL) and at every time step the surface sensible-heat effects are identical to the realistic reference runs while surface latent heat fluxes are prevented from entering the atmosphere. The results show that, without surface ET, daily precipitation within the AMZL decreases by as much as ~75%, but nearly doubles over the surrounding mountainous regions. This dramatic influence is attributed to a dipole structure of convergence-divergence anomalies over the AMZL, primarily due to the considerable cooling of the troposphere associated with suppressed convection. Further examination of moist static energy evolution indicates that the net decrease in convective available potential energy over the AMZL is due to the removal of surface ET that is only partially compensated by related regional circulation changes. Because of the concave shape of the Andean mountain range, enhanced low-level divergence promotes air mass accumulation to the east of the central EADS. This perturbation becomes sufficiently strong around nightfall and produces significant eastward low-level pressure gradient force, rendering stronger winds away from the Andes. Moisture convergence and convection over the EADS vary accordingly, strengthened in the day but attenuated at night. Nocturnal convective motion is, however, more widespread. Analytical solutions of simplified diagnostic equations of convective fraction suggest that reduction of lower troposphere evaporation is the driving mechanism. Additional exploratory experiments with varied surface ET magnitude demonstrate that the connection between the AMZL ET and EADS precipitation is robust.

Duke Scholars

Published In

Quarterly Journal of the Royal Meteorological Society

DOI

EISSN

1477-870X

ISSN

0035-9009

Publication Date

October 1, 2015

Volume

141

Issue

693

Start / End Page

3325 / 3343

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 3701 Atmospheric sciences
  • 0406 Physical Geography and Environmental Geoscience
  • 0405 Oceanography
  • 0401 Atmospheric Sciences
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Sun, X., & Barros, A. P. (2015). Impact of Amazonian evapotranspiration on moisture transport and convection along the eastern flanks of the tropical Andes. Quarterly Journal of the Royal Meteorological Society, 141(693), 3325–3343. https://doi.org/10.1002/qj.2615
Sun, X., and A. P. Barros. “Impact of Amazonian evapotranspiration on moisture transport and convection along the eastern flanks of the tropical Andes.” Quarterly Journal of the Royal Meteorological Society 141, no. 693 (October 1, 2015): 3325–43. https://doi.org/10.1002/qj.2615.
Sun X, Barros AP. Impact of Amazonian evapotranspiration on moisture transport and convection along the eastern flanks of the tropical Andes. Quarterly Journal of the Royal Meteorological Society. 2015 Oct 1;141(693):3325–43.
Sun, X., and A. P. Barros. “Impact of Amazonian evapotranspiration on moisture transport and convection along the eastern flanks of the tropical Andes.” Quarterly Journal of the Royal Meteorological Society, vol. 141, no. 693, Oct. 2015, pp. 3325–43. Scopus, doi:10.1002/qj.2615.
Sun X, Barros AP. Impact of Amazonian evapotranspiration on moisture transport and convection along the eastern flanks of the tropical Andes. Quarterly Journal of the Royal Meteorological Society. 2015 Oct 1;141(693):3325–3343.
Journal cover image

Published In

Quarterly Journal of the Royal Meteorological Society

DOI

EISSN

1477-870X

ISSN

0035-9009

Publication Date

October 1, 2015

Volume

141

Issue

693

Start / End Page

3325 / 3343

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 3701 Atmospheric sciences
  • 0406 Physical Geography and Environmental Geoscience
  • 0405 Oceanography
  • 0401 Atmospheric Sciences