The Abnormal Weather and Its Circulation in Summer of 2009

The main weather processes and their related circulations in summer 2009, including the South China Sea monsoon and the precipitation features over South China, the YangtzeHuaihe River basin, and northeast China, are discussed. There were not widearea floods, but serious heat wave and drought were reported over southern China. The South China Sea monsoon began at the fourth pentad of May. The Indian Monsoon was extremely abnormal than usual which may influenced the variation of rainband in China. The typical circulation and the related strong precipitation during the Meiyu period over the Yangtze River basin did not appeared, however, the westerlies troughs and landing typhoons brought several rainfall processes to the YangtzeHuaihe River basin. The total precipitation over North China was below normal. The vortices over northeastern China were very active in the summer of 2009, which resulted in the more precipitation and low temperature in that area. In addition, the heat wave and drought occurred in southern China during 8 to 24 July and 15 August to 14 September, and both of the periods were associated with the western Pacific subtropical high.