高原雷暴地闪回击辐射场特征分析

CHARACTERISTICS OF THE RADIATION FIELDS FROM RETURN STROKES IN PLATEAU THUNDERSTORMS

该文主要利用微秒量级时间分辨率的慢天线电场变化仪资料,对甘肃平凉地区雷暴过程中云地闪电首次回击和继后回击的远区辐射场特征进行了观测研究,并与国内外结果进行了对比分析。发现高原夏季雷暴过程中的闪电特征具有较大的独特性,平均而言,高原雷暴正负地闪首次回击辐射场波形的过零时间分别为63ms、66ms;正负地闪首次回击负反冲深度分别为20%、31%,其二者均介于美国夏季雷暴和日本冬季雷暴之间。负地闪首次回击和继后回击初始峰值之后,通常叠加有明显的次峰现象,而正地闪相对较少,相邻次峰间隔依次增大,相对强度依次减小。

Characteristics of cloud-to-ground(CG) lightning flashes in Pingliang have been analyzed by using the data obtained from a broadband slow antenna system with a time resolution of 1MHz from June to August, 2001. It has been found that lightning discharges in plateau summer thunders-torms usually present some special characteristics compared with Americal summer thunderstorms and Japanese winter thunderstorms. On the average, The zero crossing time of the firt stroke radition fields is 63祍 and 66祍 for positive and negative CG flashes, respectively. The overshoot depth is 20% and 31%, respectively. The initial peak of the return stroke radiation field is followed by several subsidiary peaks. The time interval between the successive peaks increases whereas their amplitudes decrease by order.