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United States Department of Agriculture

Agricultural Research Service

Title: The Differing Efficacy of the Alpha and Beta Method for Parameterizing Evaporation from Non-Vegetated Surfaces

Authors
item Cahill, Anthony - JOHNS HOPKINS UNIVERSITY
item Parlange, Marc - JOHNS HOPKINS UNIVERSITY
item Jackson, Thomas
item O"neill, Peggy - NASA
item Schmugge, Thomas

Submitted to: Journal of Applied Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 1999
Publication Date: N/A

Interpretive Summary: Two alternative approaches to parameterizing evaporation form bare soil were evaluated. One approach was found to be compatible with using remotely sensed soil moisture data while the other was found to depend on a variable that could not be directly measured. These results clearly show that the preferred parameterization science is very robust. This result provides valuable information on how to construct evaporation models that can be incorporated in large scale hydrology and water management.

Technical Abstract: Remotely-sensed soil moisture has been shown to hold promise for estimation of evaporation. We investigated two widely-used parmeterizations of evaporation which use surface soil moisture, the alpha method and the beta method. It is shown that while remotely-sensed soil moisture in combination with the beta method yields good estimates of evaporation, the alpha methods does not. The poor performance of the alpha method is related to factors beyond surface soil moisture which affect the soil surface specific humidity.

Last Modified: 11/27/2014
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