The climatic features of the tropical cyclone activity off the shore of China and its relationship with largescale environmental fields

The primary features of tropical cyclone activity within 300 nautical miles of the China coast line are investigated using the 54 a (1949~2004) tropical cyclone data in this study.The differences of the tropical cyclone activities north and south of 25°N and the associated differences in the sea surface temperature (SST) and 500 hPa geopotential height, especially on the interannual and interdecadal time scales, are examined.The tropical cyclone activities north and south of 25°N are different.Increasing (decreasing) tropical cyclones affected the region north (south) of 25°N since the 1980s.The compositing large scale environmental fields for the above (below) average years indicate significant differences for these two categories.In addition, the correlation analysis of the large scale fields leads to some useful predictors for longterm tropical cyclone prediction.