The Influences of Anomalous Atmospheric Circulation over Mid-High Latitudes and the Activities of 30-60 d Low Frequency Convection over Low Latitudes on the Onset of the South China Sea Summer Monsoon
中高纬大气环流异常和低纬30～60天低频对流活动对南海夏季风爆发的影响

The influences on the onset of South China Sea summer monsoon(SCSSM) of anomalous atmospheric circulation over mid-high latitude areas and the activities of 3060 d low frequency convection over low latitude areas are studied by using the NCEP/NCAR-2 reanalysis data,CMAP(NOAA NCEP Climate Prediction Center Merged Analysis of Precipitation) precipitation data and NOAA OLR(outgoing longwave radiation) data.The results show that when there exists a anomalous wave train with negative anomalies of geopotential height field(low frequency cyclone) over the Ural Mountains and its western region and along the seacoast of eastern Asia,the positive anomaly(anomalous anticyclone) over middle latitude continent and the Sea of Okhotsk during May 115,the ridge of subtropical high will withdraws from the South China Sea(SCS) earlier.At the same time,low-frequency convection(LFC) over the eastern part of the Bay of Bengal is active and moves eastward,that around the Philippines develops and moves westward,that over South China is active and moves southward and that over Kalimantan is also active and moves northward.In this case,the establishment of SCSSM is earlier.On the other hand,when there exists a anomalous wave train with positive anomalies of geopotential height field(low frequency anticyclone) over the Ural Mountains and its western region and along the seacoast of eastern Asia,the negative anomaly(anomalous cyclone) over middle latitude continent and the Sea of Okhotsk during the first half month of May,the ridge of subtropical high will withdraws from the South China Sea(SCS) later.At the same time,the low-frequency convection(LFC) over the eastern part of the Bay of Bengal is not active and moves eastward later,that around the Philippines is also not active and its westward movement is opposite in phase with the eastward movement of the LFC over the eastern part of the Bay of Bengal,that over South China is not active and the intensity of that over Kalimantan is also weak.In this case,the establishment of SCSSM is later.