The Implication of Heat and Water Balance Changes in a Lake Basin on the Tibetan Plateau

Abstract

The numerous lakes found throughout the Tibetan Plateau have a large effect on evaporation from the plateau. We analyzed variation in the water cycle in Yamdrok Yumtso Lake basin under the temperature increase of 1.13°C during the 45 years from 1961‒2005. Both vapor pressure and relative humidity increased by approximately 17%, resulting in a 13.7% increase in longwave radiation flux and a smaller daily range of surface air temperature. A 5.7% decrease in sunshine duration caused solar radiation flux to decrease by 3%. Heat and water balances were simulated over land and the lake. The lake covers 10% of the total basin area. Evaporation from the lake was larger than that from land, with lake evaporation making up 26% of the basin total. Evaporation from the lake decreased 7% (May‒ September) over the study period, and observed small pan evaporation also decreased. This trend was not found in the evaporation from land and from precipita- tion. With water vapor in the air increasing and evapor- ation from the ground surface (lake and land) decreas- ing, the water vapor may have come from areas outside the basin and possibly even beyond the plateau.