CHARACTERISTICS OF PRECIPITATION IN SOUTH CHINA IN JUNE AND ATMOSPHERIC CIRCULATION ANALYSES
中国华南地区6月降水变化特征及大气环流条件分析

The precipitation of June over South China has significant periods of 2-year,4-year,9-year and 30-year.The circulation anomalies greatly influence the precipitation in June in South China.The precipitation of June over South China has a remarkable positive correlation with the low-level southwesterly flow over coastal areas of South China,indicating that the stronger southwesterly flow over coastal areas of South China is favorable for the flow cyclonic convergence over South China.The intensity and longitudinal position of the subtropical high in the Western Pacific(SHWP) decide the southwesterly flow in its north side.When the SHWP is stronger and extends westward,the southwesterly flow over coastal areas of South China becomes stronger. So the rainfall of June in South China increases.If the cross equator flow around 120°E is stronger,the SHWP is weaker.So the stronger cross equator flow around 120°E is unfavorable for the rainfall of June in South China.The Somali cross equator flow can influence the precipitation of June over the South China through the southwesterly flow.When the Somali cross equator flow is stronger,the rainfall increases.In addition,the precipitation of June over South China is significantly related to the trough in the northwest side of the SHWP. The warm and wet air by southwesterly flow converges with the cold air by the trough over South China continuously,which is favorable for the occurrence of continuous rain.There is a wave train along the jet stream over high level.When the precipitation of June over South China increases,an anticyclonic anomalous circulation locates over the northwest side of the Tibetan Plateau and a cyclonic anomalous circulation situates from the East Tibetan Plateau to East China,high-level divergence over South China increases.