| Popis: |
Phased-array dual polarization weather radar has the capability on high spatial-temporal resolution detection and microphysical analysis, and it is deemed a new approach of strong convection monitoring and research. If applied in hail suppression operation, it is expected to improve the ability of operation command and effect evaluation. Hence, a case study is carried out on a hail suppression operation by anti-aircraft gun in Xi County, Linfen City, Shanxi Province on 28 June 2021. A phased array dual polarization weather radar is used, which outputs a volume scan data every minute consisting of 21 elevation levels. The radial resolution is 30 m, and the elevation resolution is 1.8°. Based on such high spatial-temporal resolution observations, the phenomenon and mechanisms of the severe convective cell before and after operation are analyzed, including the time series of reflectivity top height and the dynamic and microphysics features in the RHI(range height indicator) profiles. The top height of 55 dBZ reflectivity declines rapidly within 1 min after hail suppression operation, steeping down 2 km to below 0℃ height and maintains. After that, the top height of reflectivity has a short recovery due to the effect of cells merging, but then gradually decreases. 1 min after the operation, the vertical structure of high horizontal reflectivity (ZH) is fractured near 0℃ layer. The parameter of radial velocity divergence (RVD) is proposed to diagnose the vertical airflow structure, showing that the convergence areas in the front and rear of the cell weaken or disappear. The differential reflectivity (ZDR) increases near ground, and the specific phase shift (KDP) increases in the middle and low layers. The ZDR column disappears. There is a column of co-polar correlation coefficient (CC) with the value 0.94-0.96 from the near ground level to 0℃ layer. The small area of the supercooled water in the upper part of the cell core disappears. Below 0℃ layer, the mixed columnar distribution of rain and hail, graupel, wet snow and various rain changes to heavy rain in the low-level. Therefore, these short-term and obvious changes can support the theories of hail suppression by explosion. |
