变形场锋生对0108登陆台风温带变性和暴雨形成作用的诊断分析

THE TRANSFIGURATION FRONTOGENESIS ANALYSES ON 0108 LANDFALL TYPHOON EXTRATROPICAL TRANSITION AND HEAVY RAIN STRUCTURE

文中利用MM5模式对0108(桃芝)台风温带变性特征及暴雨的发生发展机制进行了诊断分析。分析表明0108(桃芝)台风登陆后其大风区向外扩展,中心区以外的气压仍有下降。由于锋面的斜压作用其温度场结构发生了明显变化,由对称的暖心结构演变为半暖半冷的温带气旋非对称结构,相对应的高度场、流场特征亦表现出非对称结构。通过计算变形向量、锋生函数及非地转风的分布,发现在锋生函数中变形项所起作用比散度项和倾斜项要早、要大,对台风温带变性有重要的作用。而锋生结果加强了风场的非地转性并强迫出锋面垂直次级环流,造成强烈的辐合上升运动,引起台风暴雨的增幅。

A heavy rain process over Jiangsu province caused by typhoon 0108（Toraji） was studied with the aid of MM5 model. By the analyses of its height, temperature and winds field features, it was found that after typhoon landfall, the center pressure increased but its gale areas still have expending tendency, formatting strong wind transfiguration. Due to the frontal barocline,its temperature field structure evolved from symmetric warm center to asymmetric half cold and half warm extratropical cyclone. And the winds field also has such asymmetric structure. After calculation of every items distribution of frontogenesis function, it was found that in the early stage of raining the effects of transfiguration item on frontogenesis function was earlier,larger than the others, played important role to typhoon＇s transition. The result of frontogenesis forced strong convergence, upward motion and geostrophic departure. Then the 0108 typhoon was re-intensification. In the right back area of upper south- west Jet there existed obviously geostrophic departure positive divergence, which developed and maintained heavy rainfall.