一次西南涡路径预报偏差分析及数值模拟

The Analysis of Forecast Deviation of the Southwest Vortex Track and Numerical Simulation

2008年7月21—23日,在川东的西南涡移出后东北上。参考各数值模式对22—23日西南涡路径预报后,河南省气象台于21日发布暴雨预报,出现了落区偏差。为加深对西南涡移动路径机理的认识,利用常规和NCEP资料,从大气环流、热力、动力等方面对这次西南涡移动路径特征进行探讨;对数值预报产品作天气学检验;利用WRF模式对本次过程进行模拟。结果表明:(1)这次西南涡呈现南掉—东北上—东东北再东北上的曲折路径;(2)低涡结构显示了中尺度特征,涡度轴向、K指数等对低涡的移动路径有指示意义;(3)由于过于依赖数值预报,加之对东北南下冷空气影响考虑不足,是造成这次低涡路径预报偏差的主要原因;(4)WRF模式对这次低涡路径有较好的预报能力。

The southwest vortex （21-23 July, 2008） moved northeastward from east of Sichuan. Henan Meteorological Observatory published rainstorm forecast at 21st with reference to several numerical weather prediction （NWP） commonly used, and the forecast showed regional deviation. For the further understanding on the mechanism of the moving route of the southwest vortex, it is discussed in some aspects such as atmospheric circulation, thermal, dynamics based on the formal and NCEP datasets. Synoptic test on numerical forecast products has been done, and the process is simulated by WRF. The results show that： （1） the route of the southwest vortex changes sharply, firstly southward, then northeastward, and then eastward, finally northeastward. （2） The structure of the vortex is of mesoscale characteristics. K index and axial direction of the vortex have instructions on the moving of the vortex. （3） The main reasons of the deviation are more rely on the NWP and less consideration to the influence of the cool air from northeast. （4） The forecast of the vortex’s route by WRF is better.