关键词: 热带扰动, 频数, 季风槽, 低层涡度, 潜热释放

Abstract: Based on the Tropical Storm and Hurricane WX products ( WX-TROPL) , 596 tropical disturbances generated over the Northwestern Pacific during 2000-2008 are analyzed, 456 of which occur in summer half year (May to October). The frequency peaks in August ( 11. 6 per year in average) . There are 369 disturbances generated in the monsoon trough. The average development rate of disturbances is 43. 8% , while the peak value 54. 8% appears in August, and the neap value 20% appears in February. The ENSO3. 4 index at the end of year has a high negative correlation with the frequency of disturbances in the next summer half year, and the coefficient reaches 76. 1% . The stronger peak value of La Nina's signal appears, and the longer it lasts, the higher frequency of disturbances in the next summer half year turns up. Over the Northwestern Pacific, most disturbances generate in the South of 15°N in winter half year, and scatter between 0°-35°N in summer half year. Using data derived from satellites, it is implied that the tropical disturbances over the Northwestern Pacific all generate in the high value areas of lower level vorticity and latent heat release.

Key words: tropical disturbances, frequency, monsoon trough, vorticity at lower level, the latent heat release