Evapotranspiration (ET) is a critical process that regulates the heat and water transfer between the land and atmosphere. Instantaneous satellite data can provide area-wide daily ET measurements. Surface energy budgets used in satellite-based calculations generally overpredict daily net radiation and the related ET. Our objective was to improve the accuracy of satellite-based daily evapotranspiration by correcting the overprediction of net radiation.
To do so, we introduced a routine for calculating the downward longwave radiation on cloudy days. This new algorithm removed the upward bias in the predicted net radiation at seven ChinaFlux sites. Then, using previously developed methods for converting instantaneous measurement into daily averages, we found that evapotranspiration rates were predicted more accurately than existing methods at the same ChinaFlux sites. In addition, our evapotranspiration rates compared well with watershed ET and other calibrated and validated spatiotemporal gridded data products in China