全球变暖背景下西北太平洋热带气旋生成位置及路径变化

On the Variation of Genesis Locations and Paths of Tropical Cyclones in Western North Pacific Under the Background of Global Warming

利用JTWC 6 h热带气旋Best track资料、Hadley中心的月平均SST资料及NECP的再分析资料,对1979—2013年西北太平洋热带气旋生成位置及路径的变化进行了研究,分析了各环境场变量的作用。结果表明:1979—2013年间西北太平洋热带气旋生成位置向北、向西发生了移动。影响全年生成位置变化的环境变量为SST升高、垂直风切变减弱、700 hPa相对湿度增大、850 hPa相对涡度增大,前季、盛季和后季的影响因素各不相同。全年、盛季和后季西行路径减少,西北行及转向路径增多,而前季西北行路径减少,西行、转向路径增多。路径的变化与对流层中层引导气流的变化密切相关,而生成位置的北移,也使得热带气旋的路径更容易受到副高的影响,从而发生变化。

Using the 6 h best track data of tropical cyclones from JTWC, monthly mean SST data from the Hadley center and reanalysis from NCEP, this work studies the variation of the genesis locations and paths of the tropical cyclones in the western North Pacific from 1979 to 2013 and analyzes the roles played by individual variables of the environmental field. The result is shown as follows. During the period from 1979 to 2013, the genesis locations of the tropical cyclones in the western North Pacific shifted towards the north and west. Annually, governing variables of the environmental field include the rise of sea surface temperature, weakening of the vertical wind shear, increases of both the relative humidity at 700 hPa and the relative vorticity at 850 hPa. The governing factors differ for the early, prevailing and late stages of the season. For the whole year, prevailing season and late season, the westward paths decrease while the northwestward and turning paths increase;for the early season, the northwestward paths decrease while the westward and turning paths increase. The variation of paths is closely correlated with that of the steering current in the middle layer of the troposphere, and the northward shift of the genesis location also makes the paths of the tropical cyclones more likely to be affected by the subtropical high to vary.