A mesoscale analysis of low level vortex disturbance initiating severe convective weather
ZHANG Yuanzhi1, SU Tao2, SHEN Hangfeng3, ZHAI Guoqing2
1. Zhejiang Air Traffic Management Sub-Bureau of CAAC, Hangzhou 311207, China;
2. School of Earth Sciences, Zhejiang University, Hangzhou 310027, China;
3. Hangzhou Meteorology Bureau of Zhejiang, Hangzhou 310051, China
Abstract:Mesoscale analysis on a disastrous convective weather event is presented. This event occurred in north Anhui on June 5th 2009, causing large economic loss and casualties. Satellite data, radar data, automatic weather station data, and Japan reanalysis data are used to analyze this case. The results showed that there was a stationary mesoscale convergence line formed by the southwest flow and the northwest flow in north Anhui in that day afternoon. The respective low-level wind field and convergence field showed that a disturbance was embedded in the southwest background flow near the convergence line. By applying the Shuman-Shapiro smoothing filtering method to the Japan reanalysis data, the disturbance characterized by a horizontal vortex circulation is revealed. The vortex disturbance corresponded with a low-level mesoscale convergence zone and convergence center, as well as a strongest upward flow near the convergence center. Radar and satellite pictures showed that new convection occurred near the vortex disturbance by 1500 LST. The mesoscale disturbance features had a good corresponding relationship with the genesis of the first echo of the convection, indicating that convection was more likely to initiate in the center and east of the mesoscale disturbance vortex or the convection was triggered by the upward flow of the vortex.
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