台风与冷空气对“13.10”上海特大暴雨过程的影响分析

The combined effects of typhoon Fitow and Danas together with cool air on an excessive heavy rain from October 7 to 8 in 2013 in Shanghai

2013年10月7—8日上海地区发生特大暴雨过程。利用常规天气资料、FY-2E卫星云图、风廓线雷达资料、NCEP再分析资料以及国内所使用的主要业务模式预报资料,分析台风与冷空气对其发生发展的影响。结果表明,登陆减弱的1323号台风"菲特"低压环流与1324号台风"丹娜丝"北侧外围强东风急流为该过程强降水区提供了充足的水汽和能量;北方扩散南下冷空气、台风低压环流、"丹娜丝"北侧外围强东风急流三者的结合使切变辐合抬升得到加强;分析风廓线雷达资料发现,低层切变线在上海长时间维持是该地产生特大暴雨的主要原因;长时间维持的切变线反映在卫星云图上,为先后5个β中尺度对流云团生成、合并,并造成持续强降水。各业务模式预报结果检验表明,因其不能精确描述各台风的位置、强度和结构,对降水落区、强度以及最强降水时段预报均存在较大误差。对于模式预报误差,要重视实时资料的应用,尤其是组网风廓线雷达资料可作为大暴雨短时预警的重要参考依据。

Based on routine weather maps, FY-2E satellite cloud images, wind profiler radar data, reanalysis data from NCEP and operation- al numerical forecast data, we have analyzed the effects of typhoon FITOW （1323） and DANAS （1324） together with cool air on an excessive heavy rain event occurred in Shanghai from October 7 to 8 in 2013. The results show that the plentiful supply of water vapor and energy required for the event comes from the low pressure circulation with typhoon FITOW that is weaken after its making landfall and the strong easterly jet in the north side of typhoon DANAS. The meeting of cold air spreading from north to south, low pressure circulation with typhoon and strong easterly jet mentioned above strengthens the upward motion induced by convergence. Analysis of wind-profile radar data found that shear line in the low-level continued for a long time over Shanghai, which is the main reason that leads to an excessive heavy rain event in this region. In the satellite cloud images near the shear line that lasted for a long time, it can be found that 5 meso- 13 scale convective cloud clusters successively originated and merged, and hence cause the severe precipitation continuing. Forecast verification of different numerical prediction models indicates that there are remarkable forecast errors in distribution, intensity and time interval of rain among these numerical prediction products because they cannot accurately predict location, intensity and structure of typhoons. In order to reduce forecast errors from models, we should devote much attention to the application of real time observations, particularly the use of wind profile radar network data for short term early warning of extra heavy rain.