Characteristic Analysis of Primary SquallLine Gales Under Weak Vertical Wind Shear
Using the observation data of 7 national observatories and 266 regional observatories in Xuancheng,NCEP reanalysis,radiosonde data,Fengyun satellite and S band Doppler radar obser-vation data to analyze the squall line process on July 26,2022.The results indicate that:1)the squall line system of this process occurs near the 500 hPa high altitude trough,located at the edge of the subtropical high.Before the process,the Xuancheng area was in front of the trough and near the trough line,with an increase in positive vorticity advection.then,the high altitude trough passed through and it turned into a northwest airflow,and the injection of dry and cold air triggered the re-lease of unstable energy.2)The radiosonde data shows that during the development period of the squall line,the stratification is dry at the top and wet at the bottom,and there is a shallow inversion layer near the stratum,which is conducive to energy storage and triggering.The corrected convective effective potential energy of more than 4 000 J/kg and the K index above 35℃indicate that energy condition are very good,while the vertical wind shear at 0～6 km is only about 14 m/s,indicating that this process is triggered under the environment of strong unstable energy and weak shear.The downward momentum of the incoming jet stream behind the squall line and the involvement of dry and cold air promote evaporation,resulting in a strong sinking airflow,which promotes the rapid movement of the cold pool and causes strong winds on the ground.3)The radar characteristics of the regional level 10 thunderstorm gale are obvious:the bow echo before the squall line passes through,with a central intensity of 55～60 dBZ.Two gust fronts successively move rapidly in front of the squall line,and meet near Xuancheng railway station to trigger the convection to strengthen again.The radial velocity in the lower layer is blurred,forming a large area of radial velocity.4)The obvi-ous radial convergence in the middle layer and strong divergence at the storm crest both have indica-tive significance for surface strong winds.
squall linethunderstorms and strong windsweak vertical wind shearspeed ambigui-tygust front
国家科技期刊平台
NSTL
万方数据
维普
