Characteristics of Climate Change of South Asia High in Summer and Its Impact on Precipitation in Eastern China

Based on the temperature and precipitation data of surface observations from 1961 to 2008,the geopotential height data of upper-air observations from 1971 to 2000 and NCEP reanalysis data,the climate change of South Asia High(SAH) and its impact on precipitation in eastern China are studied.The results show that: (1) Temperature and geopotential height of NCEP reanalysis data have the same characteristic of the climate change in the whole China with observation data,so it is applicable to the study of Chinese climate changes.(2) SAH has obvious interannual and interdecadal changes,the change of SAH area index and east elongation index are almost the same,and the influence on precipitation in China are almost the same.(3) The SVD and correlation analysis shows that when the area index of SAH is larger,south and its ridge line is located east,the precipitation of Yangtze River basin increase;when the area index of SAH is smaller,north and its ridge line is located west,the precipitation of Yangtze River basin is less than normal rainfall.The physical mechanism is that,when the SAH is strong,south and its ridge line is located east,South China and Western Pacific are under control of anti-cyclonic circulation,so it′s conducive to warm and humid air transport to the Yangtze River basin,and the Yangtze River is a flow convergence zone,then the precipitation in the Yangtze River basin increase.When the SAH is weak,north and its ridge line is located west,water vapor transport is poor to the Yangtze River basin,and the Yangtze River is a flow divergence zone,so the precipitation in the Yangtze River basin down.