Characteristics of the Lightning Activity During a Thunderstorm Process in Xi'an
Based on lightning location data of Shaanxi Province,Doppler radar data and hourly pre-cipitation data,this paper analyzes the relation characteristics among lightning,precipitation,radar echo,and airflow shear during a thunderstorm process in Xi'an on August 9,2018,and conducts a comparative analysis of the characteristics.The results show that the frequency of lightning increased gradually after the initial lightning occurred at about 15:00,and decreased gradually after the highest lightning frequency at 17:54.In the whole thunderstorm process,the proportion of positive CG(Cloud-to-Ground)flashes is higher,accounting for 23.8％.There were two obvious peak values of lightning frequency,with the highest frequency of 124 times in 6 min from 17:48 to17:54.The lightning was mainly concentrated in the area and time period of heavy precipitation.Lightning activity occurred before the precipitation,and positive CG flashes was closely related to precipitation.The reflectance area above 60 dBZ was consistent with the lightning frequency over time.The appearance and disappearance of 65 dBZ strong reflectance were accompanied by the increase and decrease of lightning frequency.At the same time,there was a good correspondence between lightning frequency and the reflectance contours of 50 dBZ and 40 dBZ.Positive and negative CG flashes had different concentration degrees in different reflectance ranges.The positive CG flashes were active in the front and rear parts of the strong echo zone and mainly occurred after the developed thunderstorm clouds,while the negative CG flashes were mainly concentrated in the central and rear parts of the strong echo zone.The occurrence area of CG flashes was closely related to the updraft and wind shear area,but it did not occur entirely in the updraft area.The proportion of negative CG flashes in the updraft and downdraft areas had a certain indication for the developing stage of convective system.The above comparative analyses suggest that the correlation between precipitation and positive ground flashes,as well as the relationship between lightning and radar reflectivity in three thunderstorm events have simi-lar features with those of the thunderstorms in Xi'an.
lightningprecipitationradar reflectivityairflow and shear
NETL
NSTL
万方数据
