Estimating evapotranspiration with land data assimilation systems

Advancements in both land surface models (LSMs) and land surface data assimilation, especially over the last decade, have substantially advanced the ability of land data assimilation systems (LDASs) to estimate evapotranspiration (ET). This article provides a historical perspective on international LSM intercomparison efforts and the development of LDASs, both of which have improved LSM ET skill. In addition, an assessment of ET estimates for current LDASs is provided along with current research that demonstrates improvement in LSM ET estimates due to assimilating satellite-based soil moisture products. Using the Ensemble Kalman Filter in the Land Information System, we assimilate both NASA and Land Parameter Retrieval Model soil moisture products into the Noah LSM Version 3.2 with the North American LDAS Phase 2 (NLDAS-2), forcing to mimic the NLDAS-2 configuration. Through comparisons with two global reference ET products, one based on interpolated flux tower data and one from a new satellite ET algorithm, over the NLDAS-2 domain, we demonstrate improvement in ET estimates only when assimilating the LPRM soil moisture product. Copyright (C) 2011 John Wiley & Sons, Ltd.