Analysis of Environmental Field Characteristics of Convective Initiation Triggered by Thunderstorm Gust Fronts in Beijing Area

Abstract

In order to enhance the understanding of the environmental field characteristics of the convective regeneration triggered by thunderstorm gust fronts.Based on Beijing sounding observation， automatic stations， S-band Doppler radar and new detection data to analyse environmental field characteristics of two typical cases in which convection initiation triggered by thunderstorm gust fronts.The results show that： （1） One type is convection triggered by collision of multiple gust fronts or the encounter of gust fronts with other boundary layer convergence lines in the region with high Convective Available Potential Energy （CAPE） and sufficient water vapor （collision triggering）.In this type， the vertical velocity of two collision gust fronts is much larger than that of a single gust front.Strong upward movement is easy to provide good lifting conditions for the triggering of convection， and convection is easy to trigger.（2） The other type is the gust front triggers convection in the unstable region （non-collision trigger）.In this type， the low-level wind direction is perpendicular to the gust front， which is conducive to the strong convergence between the ambient wind near the ground and the gust front.Meanwhile， the updraft of the convection triggered by the gust front tends to be vertical， which is beneficial to convective initiation.（3） By comparing the environmental field of gust fronts trigger and non-trigger Convective Initiation （CI） cases， the results show that there are deep wet convection potential with high CAPE and low Convective Inhibition （CIN） of the environment field in these cases which CI are triggered by gust fronts.The wind profile and microwave radiometer observations indicate that there are cold dry advection at the upper level and warm wet advection at the lower level in most cases CI triggered by the gust fronts.In most cases which gust fronts trigger CI occur at the wind speed or wind direction convergence areas with high CAPE.（4） In cases which non-triggered CI， vertical distribution of environmental field is not conducive to the regeneration and development of convection， and gust fronts pass the area which are divergence or there are low CAPE and high CIN.These conditions are adverse to convection triggering.

Keywords

• gust front
• convective initiation
• environmental field
• nowcasting