Estimation of annual daily averaged evapotranspiration across China during 1996–2015 using passive microwave observations

Accurate characterization of land surface evaporation is essential for understanding climate dynamics and the terrestrial ecosystem productivity because it is closely related to energy transfer processes. A practical all-weather method for estimating the annual daily averaged evapotranspiration (ET) was proposed using the passive microwave brightness temperature (22 and 37 GHz) and latitude, and a favorable accuracy with RMSE = 0.27 mm/day was obtained. Moreover, the annual daily averaged ET across China from 1996 to 2015 was calculated using the proposed method. The results showed that annual daily averaged ET decreases from southeast to northwest China. The annual ET over all of China ranges from 128 to 1223mm/yr. The interannual variability of ET showed a slightly increase from 1996 to 2007, a sudden decrease in 2008 and a relatively increase from 2008 to 2015. The mean annual ET over all of China ranges from 340 to 400 mm/yr.