Abstract

Lightning activity during winter thunderstorms around the Hokuriku coast was observed by SAFIR. The SAFIR system has been operating with three detection stations since 1991. To improve the operation and detection efficiency, an additional detection station was installed at the end of November 1996. Thirty-five thunderstorm days and 4427 flashes were recorded during the last winter thunderstorm season from December through late February, and the statistics on lightning activity are derived from various features. The total number of cloud-to-ground flashes (CG) are 975 of which 42.3% have positive polarity. The diurnal variation in lightning discharges is obtained, and its periodicity is revealed. Maximum lightning activity is observed just before dawn and coincidentally with the nighttime land-breeze convergence along the coast. The relation between the thunderstorm occurrence and the meteorological conditions is investigated. Stronger monsoons accompanying greater lightning activity are observed. Another observation is that both multiplicity and multipoint strikes exhibit lognormal distributions with an average of 1.4 for multiplicity and 1.2 for multipoint strikes. Furthermore, this is the first paper providing a statistical discussion of multipoint strikes. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 30–37, 2000

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