西北太平洋热带气旋发生的时空变化特征

利用中国气象局整编的1949-1988年的《台风年鉴》和1989-2000年的《热带气旋年鉴》资料，统计分析了西北太平洋热带气旋的主要发生源地、各强度等级热带气旋发生的经纬度变化特征、各强度等级热带气旋发生源地和发生频率的季节变化特征。结果表明：西北太平洋有三个热带气旋的主要发生地，分别是南海中北部偏东洋面、菲律宾以东至加罗林群岛之间的洋面、加罗林群岛一带洋面；热带气旋强度越强，发生位置越偏南、偏东；热带气旋平均发生源地存在明显的季节变化特征，冬季平均发生源地偏南偏东，以后逐渐向北向西偏移，夏季以后又向南向东偏移；各强度等级热带气旋2月平均发生频率最小，8月平均发生频率最大，全年TC较集中地发生在7～10月期间。

SPATIAL-TEMPORAL VARIATION FEATHER OF OCCURRENCE OF TROPICAL CYCLONE IN WESTERN NORTH PACIFIC

A brief study on the sources, geographic and seasonal variation of sources and seasonal variation of occurring frequencies of the tropical cyclone in Western North Pacific is made by using tropical cyclone data from 1949~2000. The results are as follows: (1) There are three sources of tropical cyclone in Western North Pacific, namely South sea of China, sea areas between Philippines and Caroline Islands and sea areas nearby Caroline Islands. The stronger the tropical cyclone is, the more southeastern its occurrence place is. (2) The seasonal variation of tropical cyclone's sources is obvious. The average occurrence place in winter tends toward south and east. Thereafter, the average occurrence place tends toward north and west gradually. After summer, the average occurrence place tends to south and east again. (3) The average occurrence frequency of tropical cyclone is the smallest in February and is the biggest in August. Tropical cyclone mainly occurs in four months from July to October.