Environmental Background And Radar Echo Characteristics On Severe Wind

Conventional ground observation,soundings and Doppler weather radar data are used to compare the key environmental parameters of cases of severe wind which known as convective wind and ordinary deep convection without strong weather without strong convection which also known as ordinary deep moist convection in China in 2002-2017,with 95 cases in each,revealing the key environmental parameters of severe wind events.The results show that,mean convective available potential energy of severe wind which is 1820 J/kg obviously larger than the average of ordinary thunderstorm which is only 470 J/kg,that is mainly related to the larger vertical temperature lapse rate in the middle and lower troposphere of severe wind.The mean vertical temperature lapse rate of events is 6.7 ?/km in the middle and lower troposphere which is obviously larger than that of ordinary thunderstorm which is 5.5 ?/km.The vertical wind shear of severe wind is significantly larger than the corresponding value of ordinary thunderstorm.The wind vector difference of 0-6 km is 18.1m/s and 14.3m/s respectively,and the wind vector difference of 0-3 km is 13.2 m/s and 10.5 m/s respectively,means that the convective system that produces severe wind has significantly stronger deep and low vertical wind shear,and thus has a higher organization and a longer life history.The low-level moisture layer of severe wind is obviously shallower than that of ordinary thunderstorm,the difference of the ground dew point temperature between sever wind and ordinary thunderstorm is not significant,however,the average precipitable water of the latter is 37 mm,significantly lower than that of the former which is 51 mm.Severe wind occurs in a relatively dry environment and tropospheric mid-level dry air intensity is significantly greater compared with ordinary deep moist convection,the single-layered maximum depression of dew point of severe wind is 25.7 °C and the average depression of dew point is 13.6 °C,This is in sharp contrast with the corresponding values of ordinary deep moist convection whose are 16.2 °C and 6.5 °C.Severe wind has strong convective available potential energy of downdraft and entrainment zone mean wind speed compared with ordinary deep moist convection.Convective available potential energy of downdraft is another indicator of downdraft potential and entrainment zone mean wind speed is one of the indicators of the horizontal momentum down-conversion potential with strong downdraft.The average convective available potential energy of downdraft and entrainment zone mean wind speed of severe wind are 1110 J/kg and 15.7 m/s,respectively,significantly higher than the corresponding value of ordinary thunderstorm whose are 620 J/kg and 11.9 m/s respectively.Statistics show that in the 95 cases of severe wind,the severe multicell storms accounted for 22.6% among the convective storms that caused severe wind,the squall line accounted for 51.2% and the supercell storm accounted for 26.2%.Some environmental parameters of the three types are different.The severe multicell storms have the best water vapor conditions and the convective available potential energy is the largest.The temperature decline rate in the middle and lower troposphere,the deep vertical wind shear and the median entrainment zone mean wind speed of supercell storm are larger.The paper also selects two typical severe wind processes,analyzes their circulation backgrounds and radar echo characteristics,and deepens the understanding of severe wind.