地面中-β尺度强锋区激发的特大暴雨过程分析

ANALYSIS ON A COURSE OF STORM RAINFALLCAUSED BY STRONG MESO-P SCALEFRONT ON SURFACE

受0012号台风（派比安）外围影响,2000年8月30日02时至31日08时,在江苏省东北部产生了一次具有局域性、突发性、高强度、超历史、灾情重等特征的特大暴雨。分析研究发现,在台风外围第二象限,江苏东北部地面存在中-β尺度的能量锋区,此能量锋区是构成产生、维持特大暴雨的中-β尺度的天气系统。利用锋生函数对此能量锋区的发生发展进行诊断,结果表明,锋生函数的变形项起了决定性作用,辐合项也有较明显的贡献,非绝热加热在锋生初期有作用,但对锋区的维持,其贡献并不明显。进一步用二维中尺度方程对锋区进行了数值模拟,结果显示,在能量锋附近驱动产生了涡旋,在涡旋上升支,将高能区的暖湿空气向上输送而成云致雨,在涡旋下沉支,通过下沉气流使雨迅速下落,同时拖曳冷空气使地面降温,使得锋区维持和加强,致使雨强增幅。综合分析表明,中-β尺度能量锋区形成以后,通过锋区附近的中-β尺度的辐合线、中低压、中高压以及锋区附近驱动的扰动涡旋等中-β尺度的天气系统间的相互作用,导致了这次江苏省东北部高强度的特大暴雨。

Affected by No. 0012 typhoon (Prapiroon) ,a unprecedented heavy rain process, with the characters of locality, intensity and abruptness, occurred in the northeast of Jiangsu province from 0200GTM 30 to 0800GTM 31 August. The study shows that the meso-β scale surface energy front was the meso-β scale synoptic system which had the storm rainfall formed and maintatined in the northeast of Jiangsu province i. e the second quadrant of typhoon periphery. The diagnoses which come from the genesis and development of energy front by the frontogenetical function indicates that the deformation item played a crucial role,the convergence item offered obviously contribution too,the diabatic heating item had some effect in the initial stages of frontogensis,however hardly contributed to the front duration. Furthermore, the results of numerical simulation by the two-dimension mesoscale e-quation display that the vortex was drived by the energy front,the warm moisture in high energy area became cloud and rain by the elevation in the ascensive branch of vortex,oppositely, the rain dropped rapidly by the sinking stream in the descensive branch of vortex, meanwhile, the surface was cooling by the cold air,so the front maintained and strengthened,the rain intensity amplified. The integrative analysis illuminated that the interactions of meso-β scale synoptic systems,such as convergence line near front,meso depression,meso anticylone and disturbance vortex drived by front after the formation of meso-β scale energy front resulted in the storm rainfall in the northeast of Jiangsu province.