Variation of South China Rainfall in June and Its Association with the East Asia-Pacific Teleconnection

Based on the atmospheric circulation and rainfall data from 1959 to 2010, the variations of summer monsoon rainfall in the pre-rainy season in South China, i.e., rainfall in June, are analyzed in this study. The results show that the South China rainfall anomaly in June is significantly related to the East Asia-Pacific (EAP) teleconnection pattern with a correlation coefficient of 0.35. When the EAP index is positive, above-normal rainfall occurs over the areas south of the middle and lower reaches of the Yangtze River, and below-normal rainfall occurs over the areas between the Yangtze River and the Yellow River. Furthermore, the South China rainfall in June is divided into two time series: one is dependent on the EAP pattern and the other is independent of the EAP pattern. Comparisons between the two corresponding atmospheric circulation anomalies are followed up. The atmospheric circulation anomalies corresponding to rainfall time series dependent on the EAP pattern are similar to the distributions of EAP related circulation anomalies. When the EAP rainfall is above-normal, there is a combination of anti-cyclonic, cyclonic, and anti-cyclonic anomalies from low latitudes to high latitudes over the tropical western North Pacific and East Asia in the lower troposphere. The southerly and northerly anomalies meet over South China, leading to above-normal rainfall there. Meanwhile, the Huaihe River basin is occupied by northerly anomalies, resulting in below-normal rainfall. By contrast, the atmospheric anomalies corresponding to the above-normal rainfall time series that is independent of the EAP pattern are characterized by an obvious anti-cyclonic anomaly over the tropical western North Pacific and southwesterly anomalies over South China, which favor water vapor transportation and resultant above-normal rainfall.