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 precipitation. With water vapor in the air increasing and evaporation from the ground surface (lake and land) decreasing, the water vapor may have come from areas outside the basin and possibly even beyond the plateau.