南海夏季风与登陆我国大陆初旋的关系

Relationship between the South China Sea summer monsoon and the first-landfall tropical cyclone over mainland of China

利用1948—2009年南海夏季风指数、NCEP/NCAR月平均再分析位势高度场、风场资料,首次分析了南海夏季风与每年登陆中国大陆的首个热带气旋(初旋)的关系.结果表明:初旋的登陆日、登陆纬度、生成纬度与当年登陆中国大陆热带气旋的频数、活动期、强度等相关性较好;强(弱)南海夏季风指数年份,登陆大陆热带气旋数偏多(少)、初旋登陆日偏迟(早)、初旋登陆点偏南(北).从流场上看,强(弱)南海夏季风指数年份,对应的季风槽偏强(弱),其异常风场和初旋路径也截然不同.从年际变化上看,南海夏季风指数明显呈减弱趋势,而初旋登陆点则有一定北移.

This study investigates the relationship between the South China Sea summer monsoon and the first tropical cyclone （TC） of the season to make landfall over China's Mainland （in short, the first-landfall TC） using the South China Sea summer monsoon index, NCEP/NCAR reanalysis monthly average data, and best-track TC data from Joint Typhoon Warning Center （JTWC） for 1948-2009. The results show that the characteristics of the first-landfall TC are closely associated with the frequency, active stage, and strength of subsequent landfall TCs in the same year. In detail, a stronger （weaker） South China Sea summer monsoon index year corresponds to more （fewer） landfall TCs over China's Mainland, a later （earlier） date of the first-landfall TC, a lower （higher）-latitude landing point of the first-landfall TC, and a stronger （weaker） monsoon trough. The anomalous wind field and the track of the first-landfall TC are also significantly related to the strength of the index. The location of the first-landfall TC has shows a gradual trend toward higher latitudes over the analysis period, and there is a decreasing trend in the variability of the South China Sea summer monsoon index.