Evapotranspiration estimation using SMAP soil moisture products and Bouchet complementary evapotranspiration over Southern Great Plains

Abstract

Evapotranspiration (ET) is an important water withdrawal in the water balance, particularly in arid and semiarid regions. In this study, a formulation to derive the relative evapotranspiration (β) and ET from in situ and passive microwave data, is presented. The original Komatsu?s β equation was modified by introducing a calibration parameterto eliminate the wind speed effects. Then, a simple formulation to estimate mean daily ET was obtained by combining the β parameter, Bouchet?s complementary relationship, and Priestley-Taylor?s equation. Estimates of β and ET were compared with ground observations in the study area, Southern Great Plains (SGP). These comparisons suggest that β characterizes the relative evapotranspiration behavior in the region. Besides, ET results show a good agreement with ground data, yielding a root mean square error and bias of 28.5 and -6 W/m2, respectively. The proposed approach took advantages of passive microwave images, combining them with ground observations in a simple and robust equation.