四川盆地特殊地形下基于加密观测的一次低涡暴雨水汽结构分析

利用NCEP 1°×1°再分析资料、常规观测资料以及汛期西南涡加密观测资料,分析了2012年7月7~10日由西南涡引发的四川暴雨天气过程。结果表明:结合加密观测资料能更好表现四川盆地复杂地形下低涡附近的水汽来源及其与实际降雨的关系,由于地形阻挡作用,气流在大巴山以南堆积,引发了四川、陕西交界处的暴雨。运用西南区域数值预报系统(SWCWARMS),与控制试验(不同化观测资料)相比,同化试验(同化西南涡加密观测资料)可使预报降雨与实况更为接近。通过同化加密观测资料,初始时刻四川北部出现了偏南气流,这有利于西南涡的初生,对比试验中的西南涡范围与强度也比控制试验更大更强,并且,试验验证了盆地东北部的水汽堆积现象。因此,西南涡加密观测资料在天气诊断及数值预报业务应用中都具有重要作用。 

A Comparative Experimental Study of an Extreme Rainstorm Caused by the Southwest China Vortex during the Intensive Observation Period

A rainstorm caused by the Southwest China vortex (SWCV) in Sichuan during 7 July-10 July 2012 is analyzed by using the NCEP data of 1°×1° with 6-hour interval,the conventional observed data and the intensive observed data of SWCV experiment during flood season. The results show combined with the intensive observed data,it has a better performance on the vapor source near the vortices and the connection with actual precipitation,In addition,there is a phenomenon that airflow heaps up at the south side of Daba Mountain due to the blocking function of terrain,which causes rainstorm at the border of Sichuan and Shanxi. Using the Southwest Center-WRF ADAS Real-time Modeling System (SWCWARMS),compared with the control experiment,the distribution of rainfall in assimilation experiment is more similar with the actual precipitation. By assimilating intensive observed data,the southerly flow exists in northern Sichuan in initial time,which benefits for the newborn of SWCV. Contrast research shows the strength and the range of SWCV are much larger than them in control experiment and it proves the water vapor heaping up at the northeast of the Sichuan Basin. So,the intensive observed data can play an important role in synoptic diagnosis and regional modeling system.