Spatio-Temporal Variations of Evapotranspiration in the Lake Selin Co Basin (Tibetan Plateau) from 2003 to 2012

Abstract:

Over the Tibetan Plateau (TP), lake expansion/shrinkage has been found closely correlated to the changing evapotranspiration (ET) patterns. Lake Selin Co is the largest endorheic lake on the TP, but the spatio-temporal changes of ET and its controlling factors in this lake basin are still not well understood. In this study, the Water and Energy Budget-based Distributed Hydrological Model (WEB-DHM, for land area), Penman-Monteith method (unfrozen period of water area) and a simple sublimation estimation approach (frozen period of water area) were used to estimate the spatio-temporal variations of ET in the Lake Selin Co Basin from 2003 to 2012. The causes for the variations are also discussed. By comparing with MODIS land surface temperature (LST) data, WEB-DHM successfully reproduced the spatial pattern and basin-averaged values of nighttime and daytime LST. Compared with the ET reference values estimated from water balance method, our method showed better performance than global ET products in reproducing annual basin-averaged ET. The modeled ET at point scale matches well with in situ daily measurements from 10 October to 10 November 2012 (RMSE = 0.82 mm/day). The increase of precipitation makes ET from the land area an increasing trend, except in winter. ET from the water area is an integrated effect of climate factors on annual and seasonal scales. The decline of wind speed and the increase of vapor pressure deficit may offset the effect of increasing temperature and contribute to an insignificant decreasing trend of annual ET from the water area.