北京地区大气电场的特征及雷电预警中的订正分析

Characteristics of Atmospheric Electric Field and Their Application to Lightning Warning in Beijing

利用北京市气象局4个大气电场仪2009年春季、夏季和秋季的监测资料，分析了本地区大气电场各季节日变化、晴天和雷暴天气下的变化特征，分析结果表明：北京地区全年大气电场具有“双峰双谷”的日变化特征，峰值出现在07—09时和20—23时，谷值出现在04—06时和15—17时，全年大气电场的平均值为0．31kV／m；全年晴天大气电场的日变化规律要比年平均更为明显，其电场值要比全年日平均值大40％左右；雷电的发生与电场仪的快变抖动之间存在着很好的对应关系。根据大气电场的变化特征和所对应的雷暴过程对大气电场的雷电预警阈值进行了订正，研制出新的三级雷电警报闽值分别为2．84kV／m、5．58kV／m、8．29kV／m，并对警报阈值进行可靠性检验，即将新的三级警报阈值的准确率和电场仪默认的警报闽值的准确率进行比较分析；分析结果指出，夏季三个级别警报阂值的准确率分别为67．4％、78．4％和90．6％，一级警报阈值的准确率提高了约25％，二级和三级警报阈值的准确率提高了5％～20％。最后，结合闪电定位资料和北京城八区局地电场监测网分析了2009年6月16日一次雷云经过本市的放电过程，为在其他气象探测资料（雷达、探空、闪电定位等）无法提供的或者通信电力无法保障的地区使用电场仪预警雷电的发生提供参考。

The characteristics of atmospheric electric field in the Beijing area were investigated. Diurnal variation in the atmospheric electric field in spring, summer, fall and total year indicated double peak and double valley. The peak occurred at 7～9,20～23 o＇clock and the valley occurred at 4～6,15～17 o＇clock, respectively. The annual averaged value of the atmospheric electric field was 0.31kV/m . The amplitude of double peak and double valley for the fine weather was larger about 40% than the annual average. The occurrence of lightning was closely related to the frequently irregular dithering of electric field. Based on the variation of atmospheric electric field and the lightning process, the new warning threshold values for the three levels that were 2.84 kV/m, 5.58kV/m and 8.29kV/m were obtained. And the accuracy of new warning threshold values compared with the old ones were analyzed in this paper. The results showed that the accuracy of the three warning thresholds in summer were 67.4% ,78.4% and 90.6% ,respectively. The accuracy of the first warning threshold was improved by 25%, while the second and third were improved by 5% to 20%. Finally, combining with lightning location data and the data from the local atmospheric electric field monitoring network in eight districts of Beijing, the lightning process on 16 June 2009 was analyzed to prove the experiment of the atmospheric electric field data in lightning warning.