Activity characteristics of the cloud-to-ground lightning in a severe convective weather event in Arksu of Xinjiang

Abstract

A severe convective weather event occurred in the Arksu area of Xinjiang on 7 June 2017. In this event, two α-mesoscale convection systems (MCS) and their merging and development caused gale, hailstorm, and short-time heavy precipitation at several stations. The objective of this study is to determine the distribution characteristics of cloud-to-ground (CG) lightning and its relationship with cloud top brightness temperature (TBB) and the development of radar echo and convective system in this event, and to deepen the understanding of the characteristics of CG lightning activity. Using the lightning locating data over Xinjiang, the TBB data from FY-4A, the Doppler weather radar data, and other data, we conducted an analysis of the characteristics of CG lightning activity during this event. The results show that (1) the CG lightning activity concentrates on the warm advection side of the low-level shear line due to the obviously wetter lower and middle troposphere and the stability and continuance of the mesoscale shear line in the lower troposphere. (2) During the event, the CG lightning is mainly negative CG lightning, and its intensity is higher in the east and lower in the west of the Arksu area. There is a certain negative correlation between the CG lightning intensity and the CG lighting density. The large-scale strong wind near the ground has a strong linear correlation with the leap of CG lightning frequency and the decreasing of positive CG lightning proportion. (3) Most of CG lightning distributes in the areas where TBB is less than or equal to -40℃. The frequency of CG has positive and negative correlations with the cloud cluster areas with TBB ≤ -40℃ and the TBB minimum value, respectively. (4) During the period affected by MCS, most of the negative and positive CG lightning occur in the echo areas of 6-20 dBz and 11-15 dBz, respectively. Both the generation and development and the mature stages of convection, the peak value of vertical integrated liquid water content (VIL) appears 12-20 min earlier than the sharp increasing of CG lightning frequency. There are positive and negative correlations between CG lightning frequency and echo top height at the generation and development and the mature stages of convection, respectively.

Keywords

• severe convection
• cloud-to-ground lightning
• brightness temperature of cloud top
• radar echo
• low-level jet stream