大气折射对甚高频闪电定位的影响分析

利用GPS探空仪实测数据计算大气折射率的高度廓线,建立大气折射误差模型。并分析大气折射效应对方向交汇、到达时间差以及综合法3种甚高频闪电定位方法测量精度的影响。结果表明,对于定位距离,大气折射对方向交汇法的影响最大,误差最大值可达到116.52m,平均误差为30.18m;大气折射对时间差法的影响最小,误差最大值约为44.70m,平均值为12.32m;对综合法的影响介于二者之间,误差最大值约为58.90m,平均值为16.74m。在综合法中,选取离闪电源较远测站进行方向交汇的定位误差是选取较近站点的定位误差的1.6倍,因此应当选取近站点。考虑到GPS授时误差,要保证大气折射对闪电定位造成定位误差小于GPS时间同步带来的误差,3种闪电定位方法的站间距应分别不大于28km、60km、45km。

Effect of atmospheric refraction on VHF lightning location

By using the vertical profile of atmospheric refraction calculated by GPS sonde data, the error model induced by atmospheric refraction was proposed. Moreover, the effect of atmospheric refraction on lightning location methods(Direction Finder(DF), Time-Of-Arrival(TOA) and Improved Accuracy using Combined Technology(IMPACT)) were also analyzed. Results show that for the location precision, the atmospheric refraction has the greatest impact on the DF method with the maximum error value of 116.52 m and the mean error of 30.18 m;whereas it has the least impact on the TOA method with the maximum error of 44.70 m and the mean error of 12.32 m;the maximum error and the mean error of the IMPACT method are 58.90 m and 16.74 m, respectively. For the IMPACT method, the location error of far station is 1. 6 times of the location error of more nearby station, hence, the nearby station should be chosen to locate the lightning. To ensure the error induced by the atmospheric refraction less than that induced by timing error of GPS, the station distances of the DF, TOA and IMPACT system should be less than 28 km, 60 km and 45 km, respectively.