川藏铁路西藏段地闪活动时空分布特征分析

Temporal and Spatial Distribution of Ground Lightning Activity in Xizang along Sichuan-Xizang Railway

利用2009—2021年地闪定位网观测数据,研究了川藏铁路沿线西藏段区域的地闪活动规律。结果表明:川藏铁路沿线西藏段地闪活动的季节变化呈单峰型,负地闪峰值出现在7月,占年平均负地闪数的25%,正地闪的峰值出现在9月,占年平均正地闪数的22%,正地闪峰值相对于负地闪延迟了2个月,而正地闪比例呈冬季最高,11月占50.7%;地闪日变化最活跃时段为14:00—22:00时,正、负地闪在达到峰值后,出现较为缓慢的减少,一直持续到第二天10:00左右达到最低值;空间分布上,西藏段铁路沿线地闪活动季节变化出现不一致性,但7月最为频繁;而地闪活动日变化最活跃时段出现在下午的16:00—18:00时;地闪密度呈北强南弱,拉萨大部、山南北部、林芝北部、昌都东北部一带的地闪活动较为频繁;正、负地闪回击电流强度呈南强北弱,沿喜马拉雅山南麓一带正、负地闪回击电流强度较大。

Utilizing ground flash location network observational data from 2009 to 2021,we investigated the characteristics of ground lightning activity along the Xizang section of the Sichuan-Xizang Railway.The results indicate that the seasonal variation of ground lightning activity in this region exhibits a unimodal pattern.The peak of negative ground lightning occurs in July,accounting for 25% of the annual average,while the peak of positive ground lightning appears in september,representing 22% of the annual average.The peak of positive ground lightning is delayed by two months compared to that of negative ground lightning.Moreover,the proportion of positive ground lightning is highest in winter,reaching 50.7% in November.The most active period for daily variation in ground lightning is between 14:00 and 22:00,with both positive and negative ground lightning showing a gradual decrease after reaching their peaks until reaching the minimum around 10:00 at the next day.In terms of spatial distribution,the seasonal variation of ground lightning activity along the Xizang section of the railway exhibits inconsistency,but is most frequent in July.The most active period for daily variation in ground lightning occurs in the afternoon from 16:00 to 18:00(Beijing time).Ground lightning density shows a north-south gradient,with more frequent activity in the areas of north Lhasa,the northern part of Shannan,the northern part of Nyingchi,and the northeastern part of Chamdo.The intensity of positive and negative ground lightning return stroke currents shows a south-north gradient,with higher intensities along the southern foothills of the Himalayas.