江苏一次大暴雨高低空急流的数值研究

A numerical study of the high/low level jets' effect on the one heavy rainfall in Jiangsu Province

本文运用我国新一代中尺度数值模式(GRAPES)对2004年6月23—25日长江中下游地区大暴雨过程进行了数值模拟研究,数值模拟和诊断分析结果表明,暴雨的落区和强度与高低空急流的位置及强度密切相关,低空急流位置北(南)移,垂直上升运动中心的位置也随之北(南)移,对应暴雨的落区也随之移动,暴雨中心强度与垂直上升运动的强度变化趋势一致,上升运动中心强,对应暴雨中心的雨量大。因此,改变高低空急流位置及强度,实际上是改变高空辐散和低空辐合区的位置及强度,改变了高低空急流耦合的位置,主要是影响了垂直上升运动的位置和强度,进而影响了暴雨的落区和强度。高低空急流耦合及上升运动加强,是暴雨发生和雨量增幅的一种重要物理机制。

Using the new generation numerical prediction model GRAPES,the paper simulated the heavy rainfall occurred in middle-lower Yangtze River from Jule 23 to 25,2004.The results indicate that the intensity and location of the this heavy rainfall is closely related to that of the high/low level jets,and the high/low level jets of the model initial field move northward（sourthward）,so do the center of the ascending movement in the meridional cross section and the region of the heavy rainfall.The change of rainfall intensity is consistent with that of the ascending movement.The more the center of ascending movement becomes intensive,the heavier the rainfall occurs in rainfall center.So changing the intensity and positon of the high/low level jets in model initial field is actually changing that of the divergence at high level and convergence at low level,and is also changing of the coupled position between high level jet and low level jet.All of the changes affect the vertically ascending movement position and intensity so as to the region and intensity of the heavy rainfall.Thereby the coupling of the high/low level jets which increases the ascending movement is an important physical mechanism to cause and amplify the heavy rainfall.