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

文章来源: 发布时间:2014-06-26

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Abstract
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.
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