Relationships between the prophase spring latent heat flux anomalies in the western North Pacific and autumn rainfalls over South China and its possible physical mechanism

Based on the Indian-Pacific Ocean heat flux data provided by the Institute of Oceanology in Chinese Academy of Sciences,a study is conducted with focus on the relationship between spring latent heat flux anomalies in the western North Pacific and autumn rainfalls over South China. Accordingly, the possible physical mechanism involved is discussed. The results show that there is a high positive corre1ation between the autumn rainfall anomaly over South China and the previous April latent heat flux anomaly in the western North Pacific (15°-30°N, 150°-170°E). When the prophase April latent heat flux in the key area is higher (lower) than normal, South China would receive more (less) than normal rainfall during the subsequent autumn. It is found that the high latent heat flux in the key area is due to the cyclonic wind shear in the western North Pacific. Northeasterly anomalies north of the anomalous cyclone enhance the wind speed,which would cause a cooling in heat content. The associated westerly anomalies south of the anomalous cyclone lead to the occurrence of anomalous warm heat content near the date line. After that, the anomalous warm heat content is transported eastward through the warming Kelvin Wave effect. Correspondingly, the anomalous cold heat content migrates westward accompanied by the Rossby wave. When the Rossby wave reaches the western tropical Pacific, it motivates the anomalous Philippine Sea anticyclone. It is conductive to more water vapor being transported towards South China and thus more rainfall appears over southern China during autumn.This research suggests a potential signal for predicting the autumn precipitation over South China two seasons in advance.