Observations of compact intracloud lightning discharges in the northernmost region (51°N) of China

Abstract

Using a three‐station wideband electric and magnetic field measuring network in conjunction with VHF receivers, we recorded the so‐called compact intracloud discharges (CIDs) in the Greater Khingan Range (51°N) in Northeast China. This type of lightning discharge had never been observed in such high‐latitude regions before. During the summer seasons of 2009 and 2010, a total of 493 CIDs with positive electric field pulses (negative charge moving up) occurring in 31 thunderstorms was recorded, with 87% (27/31) of CID‐producing storms generating less than 20 CIDs. The CID occurrence observed at 51°N appears to differ significantly from that in most lower latitude regions. Specifically, CIDs accounted only for 0.034% of the total of 1.4 million recorded lightning events, and no CIDs with negative electric field pulses (positive charge moving up) were observed. A total of 202 CIDs was located and they clustered at altitudes ranging from 5 to 12 km above ground level (agl), with a median height of 7.9 km agl. The effective ionosphere heights ranged from 75 to 95 km during the time period of 15:00–06:00 (local time). The median maximum heights of the 30 dBZ radar echo for convective cells with CIDs and without CIDs were 10.8 and 9.4 km, respectively. We infer that a relatively small vertical extent of thunderclouds, limited by the height of the tropopause, and a lack of vigorous convective surges in higher‐latitude regions might be responsible for the paucity or absence of CIDs in general and apparent suppression of those with negative electric field pulses in particular.