Environmental Parameter Characteristics of Severe Wind with Extreme Thunderstorm

Cases of severe wind with extreme thunderstorm and ordinary thunderstorm without strong convection in various regions of China are analyzed to study characteristics of environmental element of the severe wind, and 95 cases are selected for each type from 2002 to 2017. The comparison of key environmental parameters of severe wind with extreme thunderstorm and ordinary thunderstorm reveal the key environmental parameter characteristics. Results show that severe wind occurs in a relatively dry environment in the middle troposphere. The single-layered maximum depression of dew point of severe wind is 25.7℃ and the average depression of dew point is 13.6℃ when those of ordinary thunderstorm are 16.2℃ and 6.5℃, respectively. Differences between their ground dew point temperature are not significant, when the mean ground dew point temperature of severe wind is 20.2℃, and the mean of ordinary thunderstorm is 21℃. However, the average precipitable water of the former is 37 mm, significantly lower than that of the latter which is 51 mm due to the discrepancy in moisture layer. The moisture layer thickness of the former is below 2 km in most of cases, obviously shallower than the average thickness of ordinary thunderstorm moisture layer, which is 3.6 km. The mean vertical temperature lapse rate in the middle and lower troposphere of severe wind is larger than that of ordinary thunderstorm. Its average temperature difference between 850 hPa and 500 hPa is 28.2℃, obviously larger than that of ordinary events, which is 23.3℃. At the same time, as the ground dew point temperature is not much different, the mean convective available potential energy of severe wind is 1820 J·kg^-1, larger than the average of ordinary thunderstorm which is only 470 J·kg^-1. The convective inhibition for two types of thunderstorms are not significantly different, the average convective inhibition of severe wind is 79 J·kg^-1, comparing to 55 J·kg^-1 of ordinary thunderstorms. 0-6 km vertical wind shear of severe wind is 18.1 m·s^-1 and 0-3 km vertical wind shear is 13.2 m·s^-1 comparing to 14.3 m·s^-1 and 10.5 m·s^-1, respectively. The convective available potential energy of downdraft of severe wind is larger whose average value is 1110 J·kg^-1 while the mean convective available potential energy of downdraft of ordinary thunderstorm is 620 J·kg^-1. And the median entrainment zone mean wind speed of severe wind is 14 m·s^-1. It is slightly larger than that of ordinary thunderstorm, which is 12 m·s^-1. In addition, there is also discrepancy in the height of characteristic layer of severe wind with extreme thunderstorm and ordinary thunderstorm, such as 0℃ layer, -20℃ layer, and the lifting condensation level.