Sun Yat-Sen University
By using the ERA-Interim reanalysis data and daily precipitation observation from 756 stations over China, the extreme winter precipitation over South China during 1979-2015 are identified. They could be classified into five groups according to their spatial distribution via k-means clustering method. That is, the extreme precipitation occurs over the Yangtze River valley, central South China, southeastern South China, Huaihe River Valley and Southwest China. To disclose the causes of the widespread extreme winter precipitation over South China, the extreme precipitation with an eastward migration from Southwest China to the coastal Southeast China have been further analyzed, by comparing with that occurs locally over Southwest China. The results show that the main differences in the trigger and maintenance mechanisms of winter extreme precipitation between the local and eastward migrating cases, are the confliction between warm and moist advection by India-Burma trough and intensity of cold air activity. For the local cases, active cold air activity inhibits the development of India-Burma trough, resulting in the constraint of extreme precipitation over Southwest China. On the contrary, the warm and moist advection by India-Burma trough move eastward continuously in the eastward migration cases along with weak cold air activity. The cooperation of high-latitude wave train and South Asian jet wave train is crucial to the confliction between cold air activity and warm advection. When these two wave trains develop synchronously, the cold air activity over South China will be strong and the warm advection from the Bay of Bengal will be confined over Southwest China, so does the resulting precipitation. However, when the high-latitude wave train developed ahead of South Asian jet wave train, and the cold air activity is weak when the India-Burma trough is enhanced by the South Asian jet wave train, the warm advection from the Bay of Bengal could move eastward continuously, resulting in the eastward migration of precipitation from Southwest China to the coastal Southeast China.