RELATIONSHIP BETWEEN THE 30 TO 60 DAY OSCILLATION OF ATMOSPHERIC HEAT SOURCE AND THE DROUGHT AND FLOOD EVENTS IN JUNE IN THE SOUTH OF CHINA

Based on the NCEP/NCAR reanalysis data and the observed precipitation data in the south of China from 1958 to 2000, the impact of 30 to 60 day oscillation of atmospheric heat sources on the drought and flood events in June in the south of China is discussed. During the flood (drought) events, there exists an anomalous low-frequency anticyclone (cyclone) at the low level of the troposphere over the South China Sea and the northwestern Pacific, accompanied with anomalous low-frequency heat sinks (heat sources), while there exists an anomalous low-frequency cyclone (anticyclone) with anomalous heat sources (sinks) over the area from the south of China to the south of Japan. On average, the phase evolution of the low-frequency in drought events is 7 to 11 days ahead of that in flood events in May to June in the south of China. In flood events, low-frequency heat sources and cyclones are propagated northward from the southern South China Sea, northwestward from the warm pool of the western Pacific and westward from the northwestern Pacific around 140°E, which have very important impact on the abundant rainfall in June in the south of China. However, in drought events, the northward propagations of the low-frequency heat sources and cyclones from the South China Sea and its vicinity are rather late compared with those in flood events, and there is no obvious westward propagation of the heat sources from the northwestern Pacific. The timing of the low-frequency heat source propagation has remarkable impact on the June rainfall in the south of China.