1.Suzhou Meteorology Bureau;2.State Key Laboratory of Sever Weather Chinese Academy of Meteorological Sciences;3.China
Based on the S-band dual polarization Doppler weather radar of Xuzhou and Nanjing, the single polarization radar of Suqian and Huaian, and the reanalysis data, this paper analyzes the circulation background, instability mechanism dynamic, uplift conditions, radar echo and the evolution characteristics of dual polarization radar parameters and the wind inversion technology of dual radar of a wide range hailstorm process accompanied by thunderstorm and short-term heavy rainfall occured in Jiangsu Xuzhou, Suqian, Huaian, Nanjing and Changzhou on July 6, 2019. The results show that the wide range strong convective weather occurred when the cold vortex falling on high level and horizontal trough swing south, the trough line swept across Jiangsu from north to south before midnight on the 6th，the lower layer warm and humid air flow moved northward，under the background of strong unstable circulation on upper and lower layers, and the low pressure slowly moved eastward and the South pressure provided the convergence and uplift conditions. The vertical dry and cold air over Jiangsu is superimposed on the warm and wet air flow, the convective instability layer where θse decreasing with height from ground to 600hPa and the strong vertical wind shear of 0-6km provide strong thermal and dynamic instability conditions for the process. The intensity of radar echo is generally over 50 dBZ, and the echo top is always above 10 km in this procedure. What's more, it appears a significant Three Body Scattering Spikes, cyclonic convergence and storm top divergence. Hail storm can be identified by the polarization parameters (such as ZDR, KDP, CC). Hail storm usually exist in the area with strong reflectivity、low value of ZDR, and CC. The typical value of ZDR is usually between -1.0 and 0.2 and the value of CC is less than 0.85. In addition, ZDR and KDP columns help to identify hail, thunderstorm, and short-term heavy rainfall. The characteristics of the above two polarization parameters have great potential in the application of strong convection short-term approach prediction and hail recognition. Using the double radar wind inversion technology to study the hail period, it is found that there is obvious downdraft in the hail period. The three-dimensional flow field structure of the hailstorm supercell is as follows: the cyclonic air flow in the front of the storm moves into the storm, then gradually inclines to the top of the storm to form the anticyclonic air flow, and gradually forms the downdraft; in the weakening stage of the system, there is a strong downdraft, strong echo bottom and ground. Dual radar can retrieve the fine structure of three-dimensional wind of hailstorm supercell, which is helpful to deepen the understanding of hailstorm cloud structure and improve the prediction and early warning ability of severe convective weather such as hail storm.
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