一次辽宁大暴雨发生发展的动力和热力机制

Dynamical and Thermodynamic Mechanism of Genesis and Development of a Heavy Rainfall in Liaoning Province

利用WRF模式预报,对2013年8月16日辽宁东北部地区发生的大暴雨过程,进行逐小时的中尺度分析,旨在找出此次大暴雨发生发展的动力和热力机制。结果表明:(1)该地出现如此罕见的大量级降水,是中β尺度对流系统造成的。在辽宁东北部地区形成"列车效应",跟随中低层的引导气流,使强对流性天气系统依次通过该地,致使造成重大灾害;(2)抚顺山区地形的强迫抬升及对流层高层的正涡度平流辐散启动了大暴雨的产生;(3)中层的偏西干冷气流配合低层的西南暖湿急流辐合系统之间的相互作用形成了聚能机制。暴雨区中低空的上升运动和近地面的动力锋生,使中低层的潜在不稳定加剧。潜在不稳定的触发机制为中高层产生的上升运动。

Using the WRF model data, a heavy rainfall on August 16, 2013 in the northeast of Liaoning Province was analyzed in meso-scale for the dynamical and thermodynamic mechanism of genesis and development of a heavy rainfall. The results showed that：（1） the reason of the heavy rainfall was meso-βconvective weather system, the＂train effect＂made the convective weather system following steering flow abovelower atmosphere through northeast of Liaoning Province, that was the main reason of the flooding calamity;（2）the topographic force and positive vorticity advection divergence started the heavy rain;（3） the instable energy was deposited through the middle-level west cold dry airflow with low-level southwest warm humidity airflow,the vertical ascending motion and dynamical frontogenesis in the low level played a positive role in potential instability. Triggering mechanism of the latent instability was the ascending motion at the upper level.