Abstract:
Based on the detection data of S-band dual-polarization Doppler weather radar in Xinle, Shijiazhuang, conventional meteorological observation data and regional automatic weather station observation data, the evolution characteristics of dual-polarization structure of supercell storm with long life history caused by large hail in central Hebei on June 25,2020 were analyzed. The results show that the supercell storm occurs in a strong thermal instability and strong vertical wind shear environment. The effective growth layer thickness of hail The effective growth layer thickness of hail is about 3 km and the thickness ratio of cold and warm clouds exceeds 2.3. The height of maximum thermal buoyancy height is located in the effective growth layer, and the intensity of maximum thermal buoyancy intensity is greater than 4 °C, which is conducive to the formation of large hail. In the strong echo center of the low-level supercell storm, large wet ( or dry ) hail coexists with heavy precipitation, and the reflectivity factor exceeds 65 dBz, corresponding to small differential reflectivity and correlation coefficient, and the differential phase shift rate is not displayed in a large range. The large wet ( or dry ) hail in the low-level strong echo center of the supercell storm coexists with heavy precipitation, and the reflectivity factor exceeds 65 dBz. Corresponding to the differential reflectivity and correlation coefficient, the large range of differential phase shift rate is not shown. The strong echo area on the left side of before and after the supercell storm is weak rainfall and a small amount of melted hail. The reflectivity factor is between 50 ~ 55 dBz, and the differential reflectivity is large, the correlation coefficient and the differential phase shift rate are large. The ZDR columnring, CC low value arearing and KDP column in the middle layer of the supercell storm are located on the left and right sides of the bounded weak echo area, and the left CC low value arearing is stronger and located in the center of the strong echoin the strong echo center. Due to the existence of mixed phase and large structural differences, the correlation coefficient is smaller. The right KDP column is stronger and located in the bounded weak echo area. The narrow ZDR column in the upper layer is located on the right edge of the strong echo center, and the CC low value area is located in the the strong echo center center. There is a strong updraft in the strong echo center area and the bounded weak echo area and the strong echo center area in the middle and upper layers. When the large hail falls, the height of CC low value area and CC ring corresponding to the strong echo center decreases rapidly and the intensity decreases obviously. , Tthe ZDR hole expands to the lowest elevation angle and the width increases, which can be used as the basis for judgingcriterion for the imminent landing of large hail. When a large hail falls, the height of the ZDR ring, ZDDR column and CC low value area decreases, and the intensity weakens. However, the ZDR column, ZDR ring and CC low value area in the weak echo area on the right side of the supercell always exist, and the low-level ZDR arc is strengthened, the middle-level rotation is weakened, but the low-level rotation is strengthened, and the strong updraft always exists, so the supercell can maintain for a long time.The height and intensity of the ZDR ring, ZD ring and CC low value area decreased when the large hail fell, but the ZDR ring, ZDR ring and CC were low in the weak echo area on the right side of the supercell.