大尺度背景下西北太平洋热带气旋的统计分析

利用大尺度再分析资料和静止卫星云图资料，对1995-2004年西北太平洋热带气旋（TC）形成的大尺度环流背景进行了分类研究。在这10a期间，有27．5％的西北太平洋TC形成于赤道辐合带，45．6％形成于季风槽，10．1％形成于东风波，10．4％形成于热带对流层上部槽，6．3％形成于斜压性扰动条件下。统计分析表明，斜压性扰动背景下形成的TC在生命史、强度方面均明显弱于其他情况，平均生命史为108．60h，平均强度为39．250kn，其余4种情况平均生命史约为200h，平均强度为70～80kn。季风槽情况下形成的TC每3个就有一个会登陆我国，其次是东风波情况下的TC，斜压性扰动背景下形成的TC必须在南海附近生成才有可能登陆我国。

Statistical Analysis of Large-Scale Backgrounds Classification Associated with Tropical Cyclone Formations in the Western North Pacific

Using large-scale reanalysis files and stationary satellite cloud pictures, we analyzed respectively the lager-scale circulation backgrounds associated with tropical cyclone formations in the Western North Pacific between 1995 and 2004. And we got a conclusion that about 27.5% of tropical cyclogenesis cases in the past ten years were attributed to the Intertropical Convergence Zone（ITCZ） ,45.6% occured in monsoon troughs, 10. 1% occurred in easterly waves, 10.4% occured under Tropical Upper Tropospheric Trough（ TUTT）, and 6.3 % occurred in baroclinic disturbances. We analyzed the characters of tropical cyclones under different large-scale circulation backgrounds, such as life cycle, origion, intensity, horizontal scale, and landfall, and finally found that TCs of baroclinic disturbance category had a shorter life and was weaker than any other category of TCs. The average life cycle of the baroclinic disturbance category of tropical cyclones was 108.60 h ,and the average intensity 39.250 kn,while the average of others was about 200 h and 70-80 kn respectively. 1/3 of the monsoon trough category of tropical cyclones would land in China, which is of the highest possibility. The secondary was the easterly wave category. TCs of baroclinic disturbance category were of least possibility. Only those that formed in the South China Sea might land in China.