2010年7—8月东北地区强降雨过程分析和预报技术探讨

Analysis and Forecasting Technology on the Heavy Rainfall Processes in the Northeast China During July to August 2010

2010年7月19日至8月底,我国东北地区的吉林省和辽宁省先后共出现10次强降雨过程,造成严重洪涝灾害,降雨具有过程频繁、降水量大、落区重复的特点。利用地面、高空、卫星、雷达等常规观测资料和地面区域站资料及T639、NCEPFNL业务全球分析资料针对上述特点进行了分析。结果表明:稳定而异常的环流形势导致了较强偏南暖湿气流与冷空气在吉林中东部和辽宁中东部交汇,形成持续不断的降雨过程。造成强降雨的主要高空系统有低涡(切变)北上类和冷涡(低槽)东移类,两类的环流形势特点、水汽来源、冷空气作用不尽相同。两类系统的个例分析表明,降雨云团反复生成并经过同一地区是造成较大累积降雨量的主要原因。两个个例的对流云团生成机制不同,7月20日过程对流云团发生于沿低空急流带上超地转偏差风辐合区、高空冷锋前部的上升运动区和位势不稳定区,7月27日夜间过程的上升运动主要是近地层锋面抬升即冷暖空气辐合的结果;生成后对流系统的移动方向可用Corfidi向量法判断。上述分析结果对东北暴雨预报具有参考价值,分析方法同样也适用于我国其他各地的暴雨分析和预报。

Ten heavy rainfall processes,which caused severe flooding in Jilin and Liaoning Provinces of Northeast China,occurred during July to August in 2010.The total precipitation is characterized by frequent processes,large amount precipitation and co-located rainfall area.By using the observational data of surface,upper-air,satellite,Doppler radar,regional AWS and the operational NWP analysis data of T639 and NCEP FNL,the causes for the above characteristics are presented.The main results are as follows： （1） The frequent rainfall processes are mainly caused by the convergence of westerly cold air flow and strong warm,moist southerly air flow,which are supported by a stable and abnormal general circulation. （2） The ten rainfall processes can be divided into two categories based on the most important upper-air influence weather system,category one is about low vortex（including shear line） mainly occurring at low levels,category two is about cold vortex（including trough） mainly occurring at middle to higher levels. The circulation characteristics,water vapor source and the role of cold air are different for each category. （3） Case study of each category shows that the large amount precipitation is caused by the convective cells, which initiated at almost the same place and moved through the concerned place frequently.（4） The mechanism of cells initiated is different for two cases.The case＂7.20＂convective cells are initiated at the ascent and potential unstable zone of geostrophic deviation wind convergence and ahead of cold front aloft;the case＂7.27＂convective cells are mainly triggered by surface front.（5）The Corfidi vector method provided a good estimate of the motion of the most active elements of the convection system.The above results are valuble to heavy rainfall forecasting of the Northeast China.The analysis method can be also applied to the heavy rain forecasting of other places.