Influences of the South China Sea Monsoon Anomalies on Summer Precipitation in China

摘要

In this paper, the intraseasonal variability in the case of early onset and in the case of late onset of the SCSM is analyzed, respectively. The results show that cyclonic anomaly circulations can be found over the region of the SCS, the Western Pacific, the East Indian Ocean and the Bay of Bengal in the case of early onset of the SCSM. The convective activities are active at the same time and westerly wind is very strong along 5°N. On the other hand, in the case of late onset of the SCSM, there are anti-cyclonic anomaly circulations over the Eastern Indian Ocean, the Bay of Bengal and the SCS, the tropical western Pacific, and the convective activities are very weak in these areas. In this paper, the impact of the intraseasonal variability of the SCSM on the summer monsoon rainfall in the Yangtze River Valley and the North China is also analyzed. It is clearly shown that the water vapor transportation in the case of late onset of SCSM is more than that in the case of early onset of the SCSM and the water vapor transportation over North China in the case of late onset of SCSM is less than that in the case of early onset of the SCSM. Therefore, in the case of late onset of SCSM, the convergence of water vapor transportation leads to strong rainfall over the Yangtze River Valley, and the decrease of water vapor transportation in North China leads to drought in there. However, in the case of early onset of SCSM, the divergence of water vapor transportation can cause weak rainfall in the Yangtze River Valley. The stronger convergence of water vapor transportation by a cyclonic shear line over North China can bring the increase of the summer monsoon in North China.