台风“韦森特”登陆后暴雨的成因分析

Study on the Cause of Torrential Rain Associated with Landfalling Typhoon Vicente

采用常规气象资料、区域自动站资料以及NCEP/NCAR分辨率1°×1°再分析资料,对2012年1208号台风"韦森特"登陆影响下,珠江三角洲和粤西地区的暴雨过程进行分析。分析了"韦森特"登陆后的高低空环流形势和辐合辐散场、西南季风的活动以及水汽输送情况。结果表明:1)西太副高高压脊西伸加强,且脊线位置维持,抑制了"韦森特"的北上,有利于其登陆后移速不致过快,为"韦森特"西北西行过程中产生持续性暴雨提供了稳定的背景场。2)100°E附近、108°E附近两支越赤道气流及索马里急流的加强,使西南季风进一步发展,为台风登陆后的降水补充大量水汽、热量和动量,有利于其降水发生维持。同时,水汽输送大值带穿过中南半岛,源源不断地向台风环流输送水汽。随着台风登陆后西北移动和西风大值区北抬的影响,水汽通量大值区和水汽通量散度大值区相应北抬,对暴雨增幅的发生有一定的作用。3)台风登陆后,高空辐散明显加强,强于低层辐合,高层流出的气流具有强的抽吸作用,为强降水的发生提供了动力抬升条件。

By using conventional meteorological data, data from regional automatic weather stations, and NECP/NCAR1°×1° 6-hourly reanalysis data, a torrential rain in the Pearl River Delta and western Guangdong province which was under the influence of the landfalling typhoon Vicente （1208） is analyzed. The circulation situation, convergence and divergence condition, Southwest Monsoon activities and water va- por transport are analyzed for the time after Vicente landed. The results are shown as follows： 1 ） As a West Pacific subtropical high pressure ridge was westward and strengthened and the ridge line position maintained, the typhoong northward movement was restrained, being beneficial to its mild post-landing moving speed and providing a stable background field to the persistent rain in Vicente＇ s northwest-bound process. 2） The strengthening of two equatorial flows near 100°E and 108°E and a Somali jet caused the Southwest Monsoon to develop, adding abundant amount of water vapor, heat and momentum to the rainfall after landfall and be- ing beneficial to the maintenance of the rainfall. Meanwhile, a band of high - value water vapor transporta- tion passed through Indochina and supplied water vapor to typhoon circulation continuously. With the effect of the typhoon moving northwest after landing and a band of big values of the westerly moving northwards, a big - value area of water vapor flux and a big - value area of moisture flux divergence were correspondingly moving north, which had a certain role in the increase of heavy rain. 3 ） After landing, the upper divergence significantly strengthened. It was stronger than the low - level convergence. A jet stream flowing out of high levels had a strong sucking effect, which supplied dynamic lifting to the occurrence of heavy precipitation.