The Effect Of Winter Snow Cover Vver Tibetan Plateau To The Summer Precipitation At The Yellow River Basin

This paper uses the meteorology stations snow cover day data in China, the summer precipitation data at Yellow River Basin, the NCEP/NCAR reanalysis data and the NOAA sea surface temperature data and make use of the methods of EOF and MTM-SVD etc.First of all we analyzed the spatiotemporal variation characteristics of snow cover in China and summer precipitation at Yellow River Basin and then revealed the typical cycle between winter snow cover over Tibet Plateau and the summer precipitation at Yellow River Basin. At last we discussed the influential mechanism by means of atmospheric circulation.The results showed that:1) The distribution of snow cover days and the depth in China is inhomogeneous and mostly influenced by the underlying surface. And the direct influence factors are latitude and altitude. The snow cover days and the depth increase from south to north in China except Tibet Plateau. The three large value areas are northern Xinjiang, northeast and eastern Tibet Plateau.2) In recent50years, there was a slowly decreasing trend of the snow cover days and the maximum depth in spring and autumn, but it was opposite in winter, especially in the areas of snow cover big value in China such as north of the northeast, north of Xinjiang and central and eastern of Tibet Plateau. There are significant interannual and interdecadal characteristic of winter snow cover at Tibet Plateau, and have2.5～2.7-year and2.9～3.1-year cycle.3) There is a response of the summer precipitation at the Yellow River Basin to the previous winter snow cover days over Tibetan Plateau at quasi-three year period. When the previous snow cover days over Tibetan Plateau is abnormal more(less), there is abnormal less (more) of precipitation in the next summer at Yellow River Basin. This response has decadal variation, the most significant period appears before1983and there is an adjustment stage between1983and1993, which appears significantly after1993.4) The typical cycle of winter snow cover at Tibetan Plateau influence summer precipitation at Yellow River Basin is:The first year, the snow cover days is more than normal (The Siberia High is strong, north wind is strong, sst is high from the Philippine to the east Japanese), the precipitation at Yellow River Basin is less than normal. The second year, the snow cover days is more than normal (The Tibetan Plateau High is strong, the Bay of Bengal south wind is strong, sst is high from the Philippine to the east Japanese), the precipitation at Yellow River Basin is less than normal. The third year, the snow cover days is less than normal (The Siberia High is weak, south wind is strong, more water vapor flux over Yellow River Basin, sst is high from the Philippine to the east Japanese), the precipitation at Yellow River Basin is more than normal.