夏季季节内振荡对西北太平洋台风活动的影响

EFFECTS OF THE BOREAL SUMMER INTRASEASONAL OSCILLATION ON TROPICAL CYCLONE ACTIVITY IN THE NORTHWEST PACIFIC OCEAN

关键词:  天气学  台风  台风密集度  北半球夏季季节内振荡  西北太平洋

Key words:  synoptic meteorology  typhoon  tropical cyclone density  BSISO  the northwest Pacific Ocean

摘要:

利用夏季季节内振荡(Boreal Summer Intraseasonal Oscillation, BSISO) 指数和台风密集度分析了夏季季节内振荡和西北太平洋台风活动的关系。台风密集度定义为一天内500 km范围内台风出现的概率，与台风经纬度位置相比，台风密集度可更灵活地表达台风生成及移动特征。结果表明夏季季节内振荡对台风活动有明显的调制作用。当夏季季节内振荡指数1(BSISO1)处于第1、5、6、7、8位相时，南海及菲律宾以东海域台风活动明显增强；当夏季季节内振荡指数2(BSISO2)处于第2、3、4位相时，西北太平洋台风活动也明显增强。当夏季季节内振荡处于这些位相时，台风活动增强与南海及菲律宾以东海域环流气旋式异常、对流活动正异常相一致。

Abstract:

The present research uses the Boreal Summer Intraseasonal Oscillation (BSISO) indices and tropical cyclone density to analyze the relationship between BSISO and tropical cyclone activity in the northwestern Pacific Ocean. Tropical cyclone density is defined as the probability of a tropical cyclone occurring within 500 km of a specific location in one day. The use of tropical cyclone density can depict the generation and migration characteristics of tropical cyclones more flexibly compared with using their position information directly. The results show that BSISO has a significant modulation effect on tropical cyclone activity. When BSISO1 is in phases 1, 5, 6, 7 and 8, the tropical cyclone activity in the South China Sea and the ocean to the east of the Philippines is significantly enhanced. When BSISO2 is in phases 2, 3, and 4, the tropical cyclone activity in the northwestern Pacific is also significantly enhanced. The enhanced tropical cyclone activity in BSISO phases mentioned above is consistent with the cyclonic circulation anomalies and the enhanced active convection anomalies in the South China Sea and east of Philippines.