我国近海热带气旋活动的气候特征及其与大尺度环境场的关系

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

利用1949-2004年共54a的热带气旋资料，通过对历年影响我国近海（距海岸线30012mile范围内）25°N以北及以南热带气旋的基本要素特征值的分析，发现我国近海25°N以北与以南热带气旋影响的频数和年代际变化不一致，尤其是20世纪80年代中期以来呈现反位相特征，近海25°N以北TC偏多，强度强；25°N以南TC偏少，强度弱．对热带气旋个数偏多年与偏少年对应的夏季海温场、高度场的合成分析，发现25°N以北偏多年比以南偏多年的东太平洋海温负距平强度大、范围广，高度距平场上反映出25°N以北偏多年西太平洋（包括南海）负高度距平区更为偏北、偏东；25°N以北TC偏少年时，中东太平洋海温为正距平区，高度场上太平洋低纬区域基本为正距平区，太平洋高纬区域是负距平区，而以南TC偏少年中东太平洋海温是负距平区，高度场上太平洋高纬区域是正距平区．文中还对当年前期各月海温场、高度场与当年以北、以南热带气旋个数分别作了相关分析，得出了一些实用有效的预报因子．

The primary features of tropical cyclone activity within 300 nautical miles of the China coastline 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 long-term tropical cyclone prediction.