“海棠”台风(2005)暴雨过程数值模拟及位涡分析

采用WRF模式对2005年"海棠"台风登陆福建省前后24h内所造成的降水过程进行了数值模拟,在此基础上,利用模式输出结果,借助位涡理论分析位涡与台风低压流场及降水的关系,并结合对风场、相当位温、相对湿度等诊断量的分布特征分析,探讨了台风强降水的发展和维持机制。结果表明,310K等熵面上高位涡发展演变较好反映了台风低压系统路径移动以及强度变化的过程。暴雨中心主要出现在位涡大值区及其偏东北方向,且位涡气块回旋少动,与暴雨的发展维持密切相关。高位涡区主要位于等熵面坡度和梯度最大处,当等熵面上下贯通,对流层高层的高位涡沿等熵面下传,形成位涡柱时,有利于暴雨增幅。台风环流内水汽充足,上升运动强烈,也有助于此次台风降水强度持续强大。

NUMERICAL SIMULATION AND PONTENTIAL VORTICITY ANALYSIS OF TYPHOON HAITANG(2005)RAINSTORM

Typhoon Haitang has given rise to a significant 24-hour rainfall process during its landing Fujian province. This rainfall process is simulated by the WRF model. Based on simulated outputs, the relationship between isobaric potential vorticity （PV） and typhoon depression, the relationship between PV and rainfall, and the distribution characteristics of flow, equivalent potential temperature, upward motion and relative humidity, the mechanism of development and maintenance for heavy rainfall of typhoon are discussed. The results show that evolution of high PV at 310 K isentropic surface reflects well of the change process of typhoon depression＇s track and intensity. Rainstorm center lies mainly in the high PV area and in the northeast of its center. PV air parcel convolutes and moves little, and it closely relates to the development and maintenance of rainstorm. High PV center lies where the gradient and slope of isentropic surface are max. When the top and bottom of isentropic surface connects, high PV of upper troposphere moves downward along the isentropic surface and PV column forms, storm will increase. Sufficient water vapors as well as strong upward motion are also two important factors for the maintenance of the strong typhoon rainstorm.