台风“利奇马”(1909)影响期间上海强降水成因诊断分析

DIAGNOSIS OF SEVERE PRECIPITATION IN SHANGHAI UNDER INFLUENCE OF TYPHOON LEKIMA (2019)

关键词:  台风“利奇马”  强降水  边界  Q矢量分解  诊断分析

Key words:  Typhoon Lekima  severe precipitation  boundary  Q vector decomposition  diagnosis

摘要:

2019年第9号台风“利奇马”(1909)在8月9—11日影响上海期间造成了严重的风雨影响。基于ERA5逐小时再分析资料和上海区域高时空分辨率的地面观测资料，采用非地转Q矢量分解等方法诊断分析了此次强降水成因。结果表明，台风“利奇马”在上海造成的强降水主要来自台风东侧的螺旋雨带。强降水区东南西北各边界的相对湿度在垂直方向上随时间的变化差异明显，水汽的垂直输送和大气整层水汽含量在台风强降水中起重要作用。进一步利用非地转Q矢量分解方法揭示了东边界的大尺度和北边界的中尺度系统在强降水中起主要作用。台风登陆时呈现出整层大气被抬升之后最大强迫中心由高层向低层下传的态势，且此下传效应中尺度比大尺度强迫更加明显，从而有利于强降水的发生。

Abstract:

Typhoon Lekima (2019), the 9th typhoon in 2019, caused severe rainstorm during its impact on Shanghai from August 9 to 11, 2019. Based on the ERA-5 hourly reanalysis datasets and the ground observational data with high spatial and temporal resolution in Shanghai, the present study analyzed the causes of the severe precipitation by using the ageostrophic Q-vector decomposition method. The results showed that the severe precipitation associated with Lekima (2019) in Shanghai dominantly came from the spiral rainbands on the east side of the typhoon. The relative humidity at each boundary of the severe precipitation area varied significantly with time in the vertical direction. The vertical transport of water vapor and the water vapor flux in the whole atmosphere played an important role in this severe precipitation event. Furthermore, ageostrophic Q-vector decomposition was used to reveal that the large-scale system on the eastern boundary and the mesoscale system on the northern boundary played a major role. The maximum forcing center descended from the upper to the lower atmosphere after the whole atmosphere was uplifted when the typhoon made landfall, and the mesoscale forcing effect was more obvious than that of the large-scale forcing, which was conducive to the occurrence of severe precipitation.