Characteristics Of Negative Return Stroke Charge Using Guangzhou Lightning Slow Electric Field Array

The cloud-to-ground flash return stroke has received widespread attention due to its ability to transfer a large amount of electric charge to the ground.In this paper,the thunderstorm electric field continuously collected by the Guangzhou Lightning Slow Field Array,combined with the strike location and other meteorological data provided by the Guangdong-Hong Kong-Macao Lightning Location System(GHMLLS),studied the temporal and spatial development characteristics of the charge source of the negative cloud-to-ground flash return stroke in the transit thunderstorm in Guangzhou area,and obtained the following conclusions:(1)After analyzing 379 return strokes(RS)of 80 cloud-to-ground flashes(CG)in this transit thunderstorm,it was found that the number of RSs from CG ranged from 1 to 13,with an average value of 4.7±2.7.The time interval between RSs is between 16.5 ms and 795.2 ms,with an average value of 117.6 ms±91.7 ms,and the time interval will gradually increase with the development of the lightning process.(2)Analyzing the amount of charge transferred by the negative RS and its peak current,it is found that the amount of charge in the RS is between-0.20 C～-11.02 C,with an average value of-2.16 C±1.57 C,and the total amount of charge transferred during the CG is between-0.56 C～-23.78 C,the average value is-9.15 C±6.25 C.The peak return current is between-2.2 kA～-117.2 kA,and the average value is-25.7 kA ± 17.4 kA.The first RS has a higher intensity,which is manifested by more charge transferred and a higher peak current.With the development of the lightning process,the amount of transferred charges and the peak current of the RS gradually decrease,and there is a positive correlation between the amount of charge neutralized by the RS and its peak current.(3)The spatial characteristics of the charge source of the negative RS were analyzed,and it was found that the height of the charge source was between 4.43 km and 8.30 km,with an average value of 6.42 km±0.70 km,and about 98%of the height was in the temperature range of 0℃ to-15℃ inside.The horizontal distance from the charge source to its corresponding strike point is between 0.43 km and 11.36 km,with an average value of 5.36 km±2.36 km.The first RS is closer to the grounding point than the subsequent RSs.With the development of the lightning process,the height of the charge source does not change much,and the charge source will gradually move away from its strike point.(4)After analyzing the lightning process of different number of RSs,it is found that when the number of RSs increases,the average charge transferred by the RSs will gradually decrease,the average height will fluctuate and decrease,and the average horizontal distance from the charge source to the strike point will gradually get farther away.