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A surface energy balance method for partitioning evapotranspiration data into plant and soil components for a surface with partial canopy cover
Author(s) -
Massman W. J.
Publication year - 1992
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/92wr00217
Subject(s) - evapotranspiration , environmental science , canopy , energy balance , bowen ratio , steppe , atmospheric sciences , hydrology (agriculture) , soil science , soil water , potential evaporation , eddy covariance , available energy , ecosystem , energy (signal processing) , geology , ecology , mathematics , statistics , geotechnical engineering , biology
An objective, data‐based method for partitioning evapotranspiration (ET) measurements into soil and plant contributions is proposed and applied to a semiarid shortgrass steppe site in northeastern Colorado. This method requires fairly standard micrometeorological/surface energy balance measurements and relies on a two‐source Penman‐Monteith model of ET and a submodel (proposed and developed in this study) that relates the soil evaporation resistance to the soil Bowen ratio. Assuming that these soil parameters do not vary much during any given day, their daily values are determined by an optimization procedure which exploits the diurnal change in the meteorological data. Once the soil resistance and soil Bowen ratio are determined, the available energy and the ET data are partitioned into soil and plant components and then the canopy resistance and the within‐canopy aerodynamic resistance (herein referred to as the subcanopy resistance) are determined. Comparisons between the present results and other observations made in the shortgrass steppe ecosystem provide support for the validity of the present methods.