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Title: Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site

Abstract

The purpose of this paper is to examine the mechanism that controls the variation of surface energy partitioning between latent and sensible heat fluxes at a temperate deciduous forest site in central Missouri, USA. Taking advantage of multiple micrometeorological and ecophysiological measurements and a prolonged drought in the middle of the 2005 growing season at this site, we studied how soil moisture, atmospheric vapor pressure deficit (VPD), and net radiation affected surface energy partitioning. We stratified these factors to minimize potential confounding effects of correlation among them. We found that all three factors had direct effects on surface energy partitioning, but more important, all three factors also had crucial indirect effects. The direct effect of soil moisture was characterized by a rapid decrease in Bowen ratio with increasing soil moisture when the soil was dry and by insensitivity of Bowen ratio to variations in soil moisture when the soil was wet. However, the rate of decrease in Bowen ratio when the soil was dry and the level of soil moisture above which Bowen ratio became insensitive to changes in soil moisture depended on atmospheric conditions. The direct effect of increased net radiation was to increase Bowen ratio. The direct effectmore » of VPD was very nonlinear: Increased VPD decreased Bowen ratio at low VPD but increased Bowen ratio at high VPD. The indirect effects were much more complicated. Reduced soil moisture weakened the influence of VPD but enhanced the influence of net adiation on surface energy partitioning. Soil moisture also controlled how net radiation influenced the relationship between surface energy partitioning and VPD and how VPD affected the relationship between surface energy partitioning and net radiation. Furthermore, both increased VPD and increased net radiation enhanced the sensitivity of Bowen ratio to changes in soil moisture and the effect of drought on surface energy partitioning. The direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning identified in this paper provide a target for testing atmospheric general circulation models in their representation of land-atmosphere coupling.« less

Authors:
 [1];  [2];  [3];  [1];  [1];  [4];  [3];  [1];  [1];  [1]
  1. ORNL
  2. NOAA ATDD
  3. University of Missouri
  4. ATDD, NOAA
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931353
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Geophysical Research - Atmospheres; Journal Volume: 111; Journal Issue: D16
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; DROUGHTS; FORESTS; GENERAL CIRCULATION MODELS; MISSOURI; MOISTURE; RADIATIONS; SEASONS; SENSITIVITY; SOILS; SURFACE ENERGY; TARGETS; TESTING; VAPOR PRESSURE

Citation Formats

Gu, Lianhong, Meyers, T. P., Pallardy, Stephen G., Hanson, Paul J, Yang, Bai, Heuer, Mark, Hosman, K. P., Riggs, Jeffery S, Sluss, Daniel Wayne, and Wullschleger, Stan D. Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site. United States: N. p., 2006. Web. doi:10.1029/2006JD007161.
Gu, Lianhong, Meyers, T. P., Pallardy, Stephen G., Hanson, Paul J, Yang, Bai, Heuer, Mark, Hosman, K. P., Riggs, Jeffery S, Sluss, Daniel Wayne, & Wullschleger, Stan D. Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site. United States. doi:10.1029/2006JD007161.
Gu, Lianhong, Meyers, T. P., Pallardy, Stephen G., Hanson, Paul J, Yang, Bai, Heuer, Mark, Hosman, K. P., Riggs, Jeffery S, Sluss, Daniel Wayne, and Wullschleger, Stan D. Sun . "Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site". United States. doi:10.1029/2006JD007161.
@article{osti_931353,
title = {Direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning revealed by a prolonged drought at a temperate forest site},
author = {Gu, Lianhong and Meyers, T. P. and Pallardy, Stephen G. and Hanson, Paul J and Yang, Bai and Heuer, Mark and Hosman, K. P. and Riggs, Jeffery S and Sluss, Daniel Wayne and Wullschleger, Stan D},
abstractNote = {The purpose of this paper is to examine the mechanism that controls the variation of surface energy partitioning between latent and sensible heat fluxes at a temperate deciduous forest site in central Missouri, USA. Taking advantage of multiple micrometeorological and ecophysiological measurements and a prolonged drought in the middle of the 2005 growing season at this site, we studied how soil moisture, atmospheric vapor pressure deficit (VPD), and net radiation affected surface energy partitioning. We stratified these factors to minimize potential confounding effects of correlation among them. We found that all three factors had direct effects on surface energy partitioning, but more important, all three factors also had crucial indirect effects. The direct effect of soil moisture was characterized by a rapid decrease in Bowen ratio with increasing soil moisture when the soil was dry and by insensitivity of Bowen ratio to variations in soil moisture when the soil was wet. However, the rate of decrease in Bowen ratio when the soil was dry and the level of soil moisture above which Bowen ratio became insensitive to changes in soil moisture depended on atmospheric conditions. The direct effect of increased net radiation was to increase Bowen ratio. The direct effect of VPD was very nonlinear: Increased VPD decreased Bowen ratio at low VPD but increased Bowen ratio at high VPD. The indirect effects were much more complicated. Reduced soil moisture weakened the influence of VPD but enhanced the influence of net adiation on surface energy partitioning. Soil moisture also controlled how net radiation influenced the relationship between surface energy partitioning and VPD and how VPD affected the relationship between surface energy partitioning and net radiation. Furthermore, both increased VPD and increased net radiation enhanced the sensitivity of Bowen ratio to changes in soil moisture and the effect of drought on surface energy partitioning. The direct and indirect effects of atmospheric conditions and soil moisture on surface energy partitioning identified in this paper provide a target for testing atmospheric general circulation models in their representation of land-atmosphere coupling.},
doi = {10.1029/2006JD007161},
journal = {Journal of Geophysical Research - Atmospheres},
number = D16,
volume = 111,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}