Characteristics of positive cloud‐to‐ground lightning in Da Hinggan Ling forest region at relatively high latitude, northeastern China

Abstract

[1] In 2009 and 2010, a multistation network of fast and slow antennas was installed on the edge of a relatively high latitude forest region in Da Hinggan Ling (50.4°N, 124.1°E) of northeastern China. The documented 185 positive cloud-to-ground (CG) flashes containing 196 return strokes were analyzed in the paper. It was found that 71.89% of the positive CG flashes contained continuing current. The average duration of continuing current was short with an arithmetic mean value of 33.29 ms and a geometric mean value of 16.74 ms; only one continuing current lasted longer than 150 ms, probably because of the small size of the storm cell in this relatively high latitude region. The vast majority (94.59%) of positive CG flashes was characterized by a single stroke, and the average number of stroke per flash is 1.06. The average charge transferred by positive stroke and continuing current, based upon the analysis of five flashes with well-documented simultaneous measurements of more than five stations, was +5.2 C from a height of 6.0 km (above ground) and +10.2 C from a height of 6.4 km, respectively. The charge moment for +CG strokes ranged from +13.7 C km to +55.9 C km, while that for continuing current ranged from +29.0 C km to +96.9 C km, respectively. The preliminary breakdown process in positive CG flashes can be classified into three types, namely type S (same), type D (different), and type C (chaotic) according to the disparities in the initial polarity of bipolar pulses from the return stroke, which account for 62.92%, 23.60%, and 13.48%, respectively. According to the electric field waveforms indicative (or not indicative) of intracloud (IC) discharge, positive CG flashes are classified into four types, i.e., ordinary positive CG flash (63.78%), hybrid +CG-IC flash (21.08%), hybrid IC-+CG flash (5.41%), and hybrid IC-+CG-IC flash (9.73%). About 15.14% of the recorded positive CG flashes were byproduct of IC lightning discharge.

O bserved Electric Field Changes o f Positive Lightning Flashes Preceded b y Preliminary Breakdown i n Padang

“…Our AM PB-RS separation was smaller than the mean values found by Schumann et al [10], Zhang et al [17] and Qie et al [11]. We suspect that the difference may be caused by the charge configurations at the observation locations and the small number of samples.…”

“…The corresponding AM values from previous studies conducted in Japan, Sweden, Brazil, Beijing, Guangzhou and Da Hinggan Lin were 54.2 s, 96 s, 280 s, 141 s, 256 s, and 148.72 s, respectively [7,9,10,11,17]. Our AM pulse separation was longer than that in the studies conducted at higher latitudes.…”

“…In Table 1 respectively [7,9,10,11,17]. Our AM pulse duration was slightly longer than in the previous studies.…”

“…It has been found that in positive ground flashes, the initial pulse polarity of the electric field that is preceded by the PB process is sometimes different from that of the following RS [6][7][8][9][10]. The initiating mechanism of the positive lightning discharge remains a mystery because the charge structure of thunderclouds that create positive lightning is more complex than in the case of negative lightning [1,2,11,12]. In addition, only few studies have been reported about lightning flashes in tropical regions compared to temperate regions [13][14].…”

Features of Ground Flashes before and after the Massive Earthquake Observed from Kathmandu, Nepal

“…According to Williams (1989), the lightning activity itself follows a specific pattern with the intracloud (IC) lightning normally appearing in the developing stage followed by the cloud-to-ground (CG) lightning during the mature stage, whereas, both types of lightning can occur in the decaying stage of thunderstorms. Lightning in thunderstorms is strongly linked to the microphysics and dynamics of thunderstorms and, hence, changes in the lightning activity can tell us about changes in the internal processes within the thunderstorms (Price, 2008;Qie et al, 2013). Positive ground flashes are of much interest to the lightning community because of their possible association with the upper atmospheric discharges, such as sprites, and due to the magnitude of current possessed by them.…”