Interannual and decadal variations of snow cover over Qinghai-Xizang Plateau and their relationships to summer monsoon rainfall in China

Interannual and decadal variations of winter snow cover over the Qinghai-Xi zang Plateau (QXP) are analyzed by using monthly mean snow depth data set o f 60 stations over QXP for the period of 1958 through 1992. It is found tha t the winter snow cover over QXP bears a pronounced quasi-biennial oscillat ion, and it underwent an obvious decadal transition from a poor snow cover period to a rich snow cover period in the late 1970's during the last 40 ye ars. It is shown that the summer rainfall in the eastern China is closely associ ated with the winter snow cover over QXP not only in the interannual variat ion but also in the decadal variation. A clear relationship exists in the q uasi-biennial oscillation between the summer rainfall in the northern part of North China and the southern China and the winter snow cover over QXP. F urthermore, the summer rainfall in the four climate divisions of Qinling-Da ba Mountains, the Yangtze-Huaihe River Plain, the upper and lower reaches o f the Yangtze River showed a remarkable transition from drought period to r ainy period in the end of 1970's, in good correspondence with the decadal t ransition of the winter snow cover over QXP.