Effect of Surface Temperature Variation of Tibetan Plateau in Early Spring on the Precipitation in Mid-and Lower-Reaches of Yangtze River

Based on NCEP/NCAR reanalysis data and precipitation data of 160 stations in China,the correlation between variations of surface temperature in the Tibetan Plateau(TP) from February to March and precipitation in the mid-and lower-reaches of Yangtze River in June has been studied.The results show that the main spatial distribution of the increamen of surface temperature in TP from February to March is higher in its edge and lower in its center,but highter in low sea level elevation and vice versa.There is obvious negative correlation between the increamen of surface temperature and precipitation in the southern part of the mid-and lower-reaches of Yangtze River.When the increasmen of surface temperature is high,precipitation in the southern part of mid-and lower-reaches of Yangtze River reduces,and vice versa.Further research indicates,when the increasmen of surface temperature is low,the atmospheric circulation and synoptic system provide favorable vapor,dynamic and thermodynamic conditions for precipitation in the southern part of mid-and lower-reaches of Yangtze River.The south Asia high on 100 hPa becomes strong and spreads meridianal,the polar vortex on 500 hPa turns strong and eastward,the ridge between the Baikal and the Okhotsk strengthens and the west Pacific subtropical high spreads westward,which must be the most important reasons of the precipitation increasing.