重庆地区复杂地形影响下地闪活动特征分析

CHARACTERISTICS OF CLOUD-TO-GROUND LIGHTNING ACTIVITIESUNDER INFLUENCE OF COMPLEX TERRAIN IN CHONGQING

关键词:  地闪活动  复杂地形  重庆地区  时空分布

Key words:  cloud-to-ground lightning activity  complex terrain  Chongqing  spatial-temporal distribution

摘要:

利用DEM高程数据和2008—2020年重庆地区ADTD闪电定位资料，研究了重庆地区复杂地形影响下的地闪活动特征。结果表明：（1） 重庆地区地闪活动空间分布具有明显的区域性差异，且与地形及海拔高度密切相关，整体表现为自西向东，由盆地、丘陵到高山山地区域地闪活动逐渐减弱，正地闪占比逐渐增大的特征；（2） 重庆地区地闪活动年际变化分布不均，月变化呈单峰型，7月为峰值，主要集中在4—9月，占全年的96.3%，日变化呈双峰型，夜间峰值集中在00:00—04:00，白天峰值集中在14:00—18:00，08:00—12:00为地闪活动最弱时段；（3） 地闪活动月、季节尺度变化主要受大尺度天气系统支配，地形及海拔高度对地闪活动影响主要体现在日变化的显著差异上，在海拔1 000 m以下的盆地、丘陵和低山区域，夜间地闪频数明显多于白天，具有夜间主导型特征，海拔1 000 m以上的高山山地区域，白天地闪频数多于夜间，具有白天主导型特征，海拔高度越高，闪电越易出现在白天；（4）正地闪强度明显大于负地闪，地形及海拔高度变化对地闪强度影响不明显。

Abstract:

Based on DEM terrain elevation data and ADTD lightning location data of Chongqing from 2008 to 2020, the temporal and spatial distribution characteristics of cloud-to-ground (CG) lightning activities under the influence of complex terrain in Chongqing were studied. The results showed that: (1) The spatial distribution of CG lightning activities in Chongqing exhibited significant differences, and it was closely related to topography and altitude. From west to east, the CG lightning activities in Chongqing gradually weakened from basins to hills and to the mountainous areas with high altitudes, and the proportion of positive CG lightning gradually increased. (2) The inter-annual variation of CG lightning activities was unevenly distributed. The monthly variation of CG lightning activity was unimodal. The peak was in July, and the lightning activities mainly occurred from April to September, accounting for 96.3% of all the activities in the whole year. The diurnal variation of lightning activity was characterized by double peaks. The peak at night was concentrated at 00:00-04:00, and the peak at daytime was concentrated at 14:00-18:00. The number of CG lightning activity during 08:00-12:00 was the lowest. The monthly and seasonal changes in CG lightning activity were mainly dominated by large-scale weather systems. (3) The influence of topography and altitude on CG lightning activity was mainly reflected in the significant differences in diurnal changes. In basins, hills, and low mountainous areas with an altitude less than 1000 m, the frequency of CG lightning at nighttime was significantly higher than that in the daytime. In high mountainous areas with an altitude more than 1000 m above sea level, the frequency of CG lightning during the day was more than that at night. The higher the altitude, the more likely lightning would occur during the day. (4) The current intensity of the positive CG lightning was obviously greater than that of negative CG lightning, and the influence of terrain and altitude changes on the current intensity of the CG lightning was not obvious.