圣帕台风暴雨的非地转湿Q矢量的诊断分析

利用WRF中尺度模式模拟了台风"圣帕"登陆后减弱成热带低压造成湖南省大暴雨的过程,使用模拟输出的高分辨率资料,借助非地转湿Q矢量对这次暴雨过程做了详细的诊断分析.结果表明:非地转湿Q矢量能比较清楚地揭示此次暴雨演变过程,尤其700 hPa的非地转湿Q矢量散度场对降水预报具有较好的指示意义,其散度辐合区域对应着降水的落区,散度辐合强度变化指示着降水强度的变化趋势,并且非地转湿Q矢量散度辐合强度的大小可预示着未来3～6 h降水的强弱,是具有预报价值的;非地转湿Q矢量散度是非地转ω方程的强迫项,并与地形条件共同作用激发了地面中尺度系统的发展与次级环流的形成,是此次暴雨得以发展与维持的机制.

Analysis on ageostrophic wet Q vector of the rainstorm caused by typhoon "Sepat"

Mesoscale model WRF has been used to simulate the course of heavy rainstorm caused by typhoon "Sepat" being weakened to tropic cyclone after landing in Hunan province, which provides the high resolution output data, detailed diagnostic analysis on the rainstorm is done with method of ageostrophic wet Q vector. It shows that, the ageostrophic wet Q vector can reveal the evolvement of rainstorm clearly, especially at the 700hPa layer it has good direction for precipitation forecast, its convergence area corresponds to precipitation area and its convergence intensity gives guidance for the variation of precipitation intensity, besides its convergence intensity can foreeast precipitation in the coming 3～6 hours; the divergence of ageostrophic wet Q vector was taken as an only forcing term in the whole ω-equation, which motivates development of surface mesoscale system and formation of secondary circulation accompanied with terrain. Both factors are the mechanism to maintain rainstorm.