Climate‐related trends of actual evapotranspiration over the Tibetan Plateau (1961–2010)

ABSTRACT Actual evapotranspiration (ETa) is an important component of the hydrologic cycle. In this study, ETa on the Tibetan Plateau (TP) is calculated using the advection‐aridity model (AA model) with data from 86 meteorological stations during the period from 1961 to 2010. Results show that the mean annual ETa over the TP was 543 mm and range from 147 to 687 mm, with higher values in the southern part and lower values in the northern part of the TP. During 1961–2010, annual and seasonal mean ETa show statistically increasing trend at most all stations. Annual ETa in area‐averaged over the TP changed +1.01 mm year−1. Among the four seasons, the changes were most pronounced in March, April, May (MAM) and June, July, August (JJA). ETa variation is significantly and positively correlated with a drought index, defined as the difference between precipitation (P) and potential evapotranspiration (ETp), i.e. P − ETp, showing that the ETa increases over the TP tend to be affected by an increasing soil water supply associated with global warming, such as the retreat of permafrost, increase in P, and decline of ETp.