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The Aggregate Description of Semi-Arid Vegetation with Precipitation-Generated Soil Moisture HeterogeneityMeteorological measurements in the Walnut Gulch catchment in Arizona were used to synthesize a distributed, hourly-average time series of data across a 26.9 by 12.5 km area with a grid resolution of 480 m for a continuous 18-month period which included two seasons of monsoonal rainfall. Coupled surface-atmosphere model runs established the acceptability (for modelling purposes) of assuming uniformity in all meteorological variables other than rainfall. Rainfall was interpolated onto the grid from an array of 82 recording rain gauges. These meteorological data were used as forcing variables for an equivalent array of stand-alone Biosphere-Atmosphere Transfer Scheme (BATS) models to describe the evolution of soil moisture and surface energy fluxes in response to the prevalent, heterogeneous pattern of convective precipitation. The calculated area-average behaviour was compared with that given by a single aggregate BATS simulation forced with area-average meteorological data. Heterogeneous rainfall gives rise to significant but partly compensating differences in the transpiration and the intercepted rainfall components of total evaporation during rain storms. However, the calculated area-average surface energy fluxes given by the two simulations in rain-free conditions with strong heterogeneity in soil moisture were always close to identical, a result which is independent of whether default or site-specific vegetation and soil parameters were used. Because the spatial variability in soil moisture throughout the catchment has the same order of magnitude as the amount of rain failing in a typical convective storm (commonly 10% of the vegetation's root zone saturation) in a semi-arid environment, non-linearitv in the relationship between transpiration and the soil moisture available to the vegetation has limited influence on area-average surface fluxes.
Document ID
19970021687
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
White, Cary B. (Arizona Univ. Tucson, AZ United States)
Houser, Paul R. (Arizona Univ. Tucson, AZ United States)
Arain, Altaf M. (Arizona Univ. Tucson, AZ United States)
Yang, Zong-Liang (Arizona Univ. Tucson, AZ United States)
Syed, Kamran (Arizona Univ. Tucson, AZ United States)
Shuttleworth, W. James (Arizona Univ. Tucson, AZ United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1997
Publication Information
Publication: Hydrology and Earth Systems Sciences
Publisher: European Geophysical Society
Volume: 1
Subject Category
Earth Resources And Remote Sensing
Report/Patent Number
NAS 1.26:204814
NASA-CR-204814
Accession Number
97N22585
Funding Number(s)
CONTRACT_GRANT: NAG5-3854
CONTRACT_GRANT: IDP-88-086
CONTRACT_GRANT: NAGw-4165
CONTRACT_GRANT: NGT-30303
Distribution Limits
Public
Copyright
Public Use Permitted.

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