Characteristics of a supercell storm with long life cycle based on analysis of weather radar data

Using datasets of routine upper-air and surface weather observations,surface automatic weather station,Doppler weather radar at Shijiazhuang,dual-polarization radar at Raoyang and other relevant data,we have conducted a detailed analysis on the atmospheric circulation environment and radar observed characteristics of a supercell storm with long life cycle that affected the central and southern Hebei on 13 June 2018. The main results are as follow. (1) This supercell occurred under the atmospheric circulation of the revising of a transverse trough at the back of vortex. (2) The life cycle of the storm is 204 min long,during which the supercell lasted for 138 min,and the maximum radar reflectivity factor is basically maintained above 65 dBz during this period. (3) The deep and strong development of a mesocyclone is an important dynamic mechanism for the development and maintenance of the supercell storm. The bottom of the mesocyclone can reach the bottom of the storm,and the top height of the mesocyclone had little changes. The formation and development of both low-centroid and high-centroid mesocyclone may cause hail on the ground,and the supercell weakened temporarily during the corresponding hail period. (4) During the maintenance period of supercell,the vortex pairs of cyclones and anticyclones are always accompanied,and the cyclonic vortex is dominant. The hook echo characteristics of the supercell are obvious,which shows the typical vertical structure of echo wall-weak echo region-hanging echo. The structure such as convergence in the low-level,divergence in the upper level,and divergence in the upper level being greater than convergence in the low-level,is conducive to the strong rotation and ascending movement within the supercell. There are obvious three body scatter signature (TBSS) and sidelobe echo,and the longest TBSS is more than 60 km and its duration is as long as 150 min. (5) Dual polarization radar detection shows that the reflectivity factor of the supercell is greater than or equal to 55 dBz,the differential reflectivity in the corresponding position is from -0.5 dB to 0.5 dB,the differential propagation phase shift rate is only between 1.5°/km and 2.0°/km,and the correlation coefficient is from 0.75 to 0.92,which indicates that there are droplets and large hails within the supercell at the same time.