中文摘要：

在普查1979—2005年热带气旋（TC）个例的基础上,建立了生成于西北太平洋季风槽的热带气旋（简称MTTC）序列,统计发现1979—2005年的5—10月南海和西太平洋TC总频数为672个,其中MTTC频数为491个,占总频数的73.1%,占登陆我国TC频数的79.2%,可见,MTTC的活动规律反映了西太平洋TC以及影响我国TC的主要活动规律。分析了逐日环流场,将季风槽分为5种主要形态：南海季风槽型、南海-西太平洋季风槽型、反向季风槽型、三气流型和西太平洋季风槽型。根据每年5—10月的季风槽、副高以及越赤道气流等系统的强弱和位置,将1979—2005年分为4种年型：季风槽西南型、西北型、偏东型和正常年型,针对前3种季风槽异常年型,诊断分析了有利于TC形成的海温场、大尺度环流场、水汽输送、大气视热源和视水汽汇以及纬向风垂直切变的特征,发现不同季风槽年型,由于太平洋海温场的差异,引起哈得来环流和Walker环流的差异以及西太平洋副高、南亚高压等大尺度系统位置以及越赤道气流强度的差异,导致有利于TC生成的热力条件、动力条件和环境条件的不同,致使MTTC生成位置、频数、路径以及在我国的登陆点有着显著差异。

英文摘要：

A general survey was made of 1979--2005 tropical cyclones （TC） before a sequence is established of the western North Pacific monsoon trough （MT） tropical cyclones （MTTC）. Statistics show that in May October, 1979-2005, TCs originating from the South China Sea （SCS） and western North Pacific （WNP） totaled 672, of which 491 had the origin in the monsoon trough （i. e., MTTCs）, making up 73.1 % of the total and 79.2 % of the TCs landing on China in this period. It follows that grasp of their activity features means the grasp of the main activity laws of WNP and China--landing TCs. Based on the a- nalysis of day--to--day circulation fields the MTs are categorized as （1） SCS type, （2） SCS--WNP type, （3） reversal type, （4） triple-flow type and （5） WNP type. In terms of the strength and position of May to October monsoon troughs, subtropical highs and cross--equatorial flows on an annual basis, the 1979-- 2005 monsoon troughs are separated into such annual types as the southwest-- northwest--, and eastward of mean as well as normal. For the first three MT anomalous annual types diagnostic study is conducted of TC formation favorable SST and large-scale circulation fields, vapor transport, atmospheric apparent heat sources, apparent vapor sinks, and zonal wind vertical shear, indicating that for the different MT annual types differences in Pacific SST fields cause the disparity in the intensity of the Hadley and Walker circulations, the positions of western Pacific subtropical high and South Asian high as well as the intensity of cross-equatorial flows, thus producing TC genesis favorable thermal, dynamic and environmental conditions, leading to remarkable differences in MTTC genesis area, frequency, track and TC China--landing location.