Preliminary analysis of total lightning activity in atmosphere of a squall line over Beijing

Abstract

Based on the 3d lightning location data and Doppler radar data, we analyzed the total lightning of a squall line that occurred in Beijing on July 1, 2021. A squall line is a mesoscale convection system in the atmosphere, which is extremely destructive in the process of occurrence, accompanied by lightning, hail, and other extreme weather, people need to take more precautions. The results show that intracloud lightning (IC) dominates the entire squall line process, accounting for about 74.3% of the total lightning. Both IC and cloud-to-ground strokes (CG) are dominated by negative lightning, accounting for 68.75% and 74.3%, respectively. When the convective units merged, the frequency of lightning increased rapidly, and the frequency of IC and CG reached their peak at the end of the squall line development phase. With the loosening of the structure of the strong echo zone, the frequency of IC and CG gradually decreases, and the IC and CG exhibit a singlepeak structure throughout the process. The lightning process is in good agreement with the radar strong echo area and accumulated precipitation. Lightning mostly occurs in the area where the echo >45dBz. The lightning development trend moves from northwest to southeast, which coincides with the entire squall line process. The number of positive CG and negative CG inhibited each other during the squall line, but the general trend was the same. The positive IC has a violent jump at the beginning of the development stage. This may be due to the strong ascending movement that raised the main negative charge area to a higher height, and it collided with the positive charge violently. With the consumption of a large amount of positive charge, the frequency of positive IC dropped rapidly thereafter.