Estimation and comparison of evapotranspiration from MODIS and AVHRR sensors for clear sky days over the Southern Great Plains

Evapotranspiration (ET) cannot be measured directly from satellite observations but remote sensing can provide a reasonably good estimate of evaporative fraction (EF), defined as the ratio of ET and available radiant energy. It is feasible to estimate EF using a contextual interpretation of radiometric surface temperature (T-o) and normalized vegetation index (NDVI) from multiple satellites. Recent studies have successfully estimated net radiation (R-n) over large heterogeneous areas for clear sky days using only remote sensing observations. With distributed maps of EF and R-n, it is now possible to explore the feasibility and robustness of ET estimation from multiple satellites. Here we present the results of an extensive inter-comparison of spatially distributed ET and related variables (NDVI, T-o, EF and R-n) derived from MODIS and AVHRR sensors onboard EOS Terra, NOAA14 and NOAA16 satellites respectively. Our results show that although, NDVI and T. differ with the sensor response functions and overpass times, contextual space of NDVI-T-o diagram gives comparable estimates of EF. The utility of different sensors is demonstrated by 2 validating the estimated ET results to ground flux stations over the Southern Great Plains with a root mean square error of 53, 51 and 56.24 Wm(-2), and a correlation of 0.84, 0.79 and 0.77 from MODIS, NOAA16 and NOAA14 sensors respectively. (c) 2006 Elsevier Inc. All rights reserved.