The Relationship between Interannual Variations of Summer Precipitation in Eastern China and the SST Anomalies in the East China Sea and Its Adjacent Seas

The relationship between the interannual variations of summer precipitation in eastern China and the SST anomalies in the East China Sea and its adjacent seas is analysed by using the methods of composite and correlation analyses and the daily data of summer (June－August) precipitation at 756 stations of China, GPCP2.1 and HadISST datasets from 1979 to 2008. The results show that when the SST of the East China Sea and its adjacent seas is in warm (cold) anomalies in summer, there are less (more) rainfall in the middle and lower reaches of the Yangtze River and the Yangtze River/Huaihe River valley (Jianghuai valley) and more (less) rainfall in the southern part of Northeast China. Moreover, a regional climate model (RegCM3) is used to examine the above-mentioned relationship. The simulation results indicate that the warm (cold) SST anomalies in the East China Sea and its adjacent seas can contribute to less (more) rainfall in the middle and lower reaches of the Yangtze River, the Yangtze River/Huaihe River valley (Jianghuai valley), and most of North China, and more (less) precipitation in South China, the southeast part of Northeast China, and the Korean Peninsula. Besides, the processes of atmospheric circulation variability over East Asia caused by the SST anomalies in these sea regions are explored based on the NCEP/NCAR reanalysis data and numerical simulation. The result shows that increase or decrease of SST in the above-mentioned seas has remarkable effect on zonal and meridional circulations over East Asia. When the SST of the East China Sea and its adjacent seas is above normal, a downward motion with a divergence at low levels and a convergence at upper levels can appear over the middle and lower reaches of the Yangtze Rive and the Yangtze River/Huaihe River valley (Jianghuai valley), and most of North China, which contributes to the decrease of summer rainfall in these areas, in addition to an upward motion with a strong convergence at low levels and a remarkable divergence at upper levels can be caused over the region to the east of these seas. And an upward motion with strong convergence at low levels and remarkable divergence at upper levels is caused in South China, the southern part of Northeast China, and the Korean Peninsula, thus, the summer precipitation increase obviously in these regions. When the SST of the East China Sea and its adjacent seas is below normal, the opposite phenomena appear in the above-mentioned areas. Consequently, it is suggested that the thermal state of the East China Sea and its adjacent seas may be one of the important factors affecting the summer precipitation in East China.