Seasonal variations of heat and water balances have been estimated by using a multi-layer soil model for the Tibetan Plateau in 1997-1998. Input data was from routine meteorological data, and calculation was carried out for 14 stations in 1997 and 17 stations in 1998.
Compared with 1997, annual precipitation was smaller in northwestern and larger in southeastern Tibet in 1998. The variations of latent heat flux from the ground surface, connected with the changes of soil water content that are controlled by change of precipitation. Thus, the latent heat flux of 1998 was larger than that of 1997 in southeast Tibet, but in northwest Tibet, the situation was reversed. The calculation result for Wetness Index (WI), showed that from 1997 to 1998, the climate in northwest Tibet become more dry, and southeast Tibet wetter. The climatic difference became more severe between those two regions.
In northeast Tibet, soil water contents were smaller and sensible heat flux was larger in 1998, than in 1997, because the precipitation was relatively small in the springtime of 1998. In southeast Tibet, the amount of the precipitation were almost the same in the springtime of 1997 and 1998, but the rainfall amount became larger, and concentrated in the latter monsoon season in 1998, this led to the increase in soil water contents, and the amount of evaporation. Those increases were not as sharp as the changes of precipitation, and most of the precipitation contributed to sharply increase the run off, and flowed into the rivers. After monsoon seasons, the differences between the amount of precipitation in 1997 and 1998 became very small, and the soil water contents were almost the same in the end of those two years. Soil water contents changed with the precipitation.