区域海拔高度对云地闪电参数分布的影响

为进一步研究雷电参数随海拔高度的分布特征,为雷电防护工程设计和雷击风险评估提供参考,根据湖北省雷电定位系统(lightning location system, LLS)2007年1月至2017年12月监测资料,采用数理统计方法,对不同海拔高度的频次、极性、雷电流幅值和波前陡度等参数进行了统计分析。结果表明:负地闪和总地闪频次随海拔高度增加呈线性减少,海拔2 700 m的地闪频次约是300 m处的1/3,正地闪频次随海拔高度变化大致呈"V"字形,海拔800 m处相对最少。海拔在800~2 700 m时,正地闪比例随海拔高度增加而明显增加,2 700 m处的正地闪比例约是800 m处的3.7倍。负地闪和总地闪中值雷电流幅值随海拔高度变化大致呈"V"字形,海拔1 500 m时,负地闪和总地闪中值雷电流幅值相对最小。海拔1 200~1 700 m的高山,负地闪和总地闪≤20 kA的小雷电流幅值比例较高,是海拔200 m处的2倍以上;海拔1 500 m以上的高山地区,大于100 kA大雷电流幅值平均比例大于低山丘陵和平原地区。正地闪、负地闪和总地闪平均雷电流波前陡度随高度增加呈自然对数减少。上述研究表明:海拔1 500 m以上的中高山地区的大雷电流幅值所引起的反击概率大于岗地和平原地区,在1 200~1 700 m的高山地区,小雷电流绕击相对较高。相对于中高山地区,低山丘陵和平原地区的雷电电磁感应的危害性相对较大。

Influence of Regional Altitude on the Distribution of Cloud-to-ground Lightning Parameters

To further investigate the distribution characteristics of lightning parameters with altitude, and provide references for the design of lightning protection engineering and lightning risk assessment, the parameters such as frequency, polarity, amplitude of lightning current and gradient of wave front at different altitudes were analyzed by a mathematical statistics method based on the data monitored by lightning location system(LLS) in Hubei province from January 2007 to December 2017. The results show that the frequency of negative cloud-to-ground(CG) lightning and total CG lightning decreases linearly with increasing height, the frequency of CG lightning at the altitude of 2 700 m is about 1/3 that at 300 m, and the frequency of positive CG lightning roughly presents a trend of "V shape" with altitude, and a relative minimum occurs at the altitude of 800 m. At the altitude of 800~2 700 m, the proportion of positive CG lightning increases significantly with altitude, and the positive CG lightning ratio at 2 700 m is about 3.7 times that at 800 m. The amplitude of negative CG lightning and total CG lightning median current present a trend of roughly "V shape" with altitude, and when the altitude is 1 500 m, negative CG lightning and total CG lightning median current amplitude are relatively minimal. In the high mountains with altitude of 1 200~1 700 m, negative CG lightning and total CG lightning less than or equal to 20 kA have a higher proportion of the current amplitude, which is more than twice the altitude of 200 m. Over 1 500 m above sea level, the average ratio of lightning current amplitude larger than that of 100 kA is greater than that of low hill and plain area. The average gradient of wave front for positive CG lightning, negative CG lightning and total CG lightning decreases with natural logarithm as the height increases. According to the above research, the probability of counter attack caused by the large lightning current in the middle and high mountain areas above 1 500 m is higher than that in the hills and plains, while in the high mountain area of 1 200~1 700 m, the small lightning current is relatively high. Compared with the middle and high mountains, the lightning electromagnetic induction in the low hills and plains are relatively harmful.