Radar Characteristics of Straight-line Damaging Wind Producing Supercell Storms

Based on S-band Doppler weather radar data and damaging wind gust records, 56 damaging straight-line winds events from 2002 to 2020 above 25 m·s^-1 caused by supercell storms are investigated. The relationship between Doppler weather radar echo characteristics and damaging straight-line winds caused by supercell storm is analyzed to obtain quantitative description of the structural characteristics. The results will be benefit for subjective and objective monitoring and warning of damaging straight-line winds produced by supercell storms. Superstorm is a highly organized strong convective storm with a long-life history, according to the statistical results, and it is possible to judge the potential of supercell storms that produce damaging gale by the Doppler weather radar echo structures. It shows that, in the supercell storm that produces damaging straight-line winds, the strong reflectivity echo above 60 dBZ is deep, and the average echo thickness of strong reflectivity is 5.5 km. The core height of the strong reflectivity of most supercell storms are above 6 km which indicate that the updraft in this kind of supercell storms can be very strong. The mid altitude radial convergence (MARC), the reflectivity core decline and rear inflow jet (RIJ) are important for warning of damaging straight-line winds features. The MARC is significant, the largest speed difference of the MARC is above 29 m·s^-1 in most cases. The mesocyclone is mainly of medium intensity, the rotating speed of mesocyclone is 18.4 m·s^-1 on average, which can extend up to the upper troposphere (7 km). The descending of supercell storm reflectivity core, the descending of mesocyclone core, the MARC which can exist for a long time with 29 m·s^-1 largest radar radial speed difference and the decrease of vertically integrated liquid water content (VIL) value can be used as the warning indices of the damaging straight-line winds. Among them, the descending of supercell storm reflectivity core can give 15-minute precursor signal, the descending of mesocyclone core can give 8-minute precursor signal, the significant MARC can give 30-minute precursor signal, and the descending of VIL value can give 17-minute early warning signal of damaging winds. Based on narrow-band echo, the proportion that can be recognized as gust front of the supercell storm is low, and only a few damaging straight-line winds can be identified from the moving speed of storm or gust front characteristics. There are only 4 obvious low-level divergence velocity pairs identified in 56 cases, which indicate that most supercell storms produce asymmetric downburst because of horizontal movements.