A PRELIMINARY ANALYSIS OF THE REGULARITY IN FLOOD, DROUGHT AND SNOWSTORM IN TIBETAN PLATEAU DURING HISTORICAL TIMES

In this paper, the natural disasters on the Tibetan plateau recorded in the historical official files by thousand of Tibet local government officers are collected and a preliminary analysis of the flood, drought and snowstorm on the plateau is made. Tne main features are summarized as follows: 1.During recent 100 years, the flood and drought appeared alternately, with 3 rainy periods and 3 dry periods. The dry period might become longer in the future. 2. 2.6-3.6 years periodicities in the change of the flood and drought over the Tibet were found 3.When the rainfall is smaller than normal rainfall by 100 mm, severe dry damage could occur in some sites. 4.It is expected that it may become drier and warmer over the plateau. 5.In Qiangtang area, the snowstorm was one of the main damage, the drought frequency was small and the almost no flood.