LF lightning location system (BOLT) in Osaka area and its applications

A LF lightning location system called BOLT was installed from the year of 2012 to 2013. This paper presents preliminary results of observations during one winter and one summer. During the winter of 2012-2013, a special type of lightning discharges producing large bipolar electric field change waveforms were observed. Such discharge event has not been reported before and we call it “large bipolar event” (LBE). Almost all LBEs were located on land area and they were inferred to be associated with high grounded objects such as towers and wind mills. During the summer of 2013, hundreds of narrow bipolar events (NBEs) were observed. Some NBEs were found as the initiation process of normal intracloud and cloud-to-ground lightning flashes. These NBEs were all positive polarity and were followed by positive pulse trains similar to those of preliminary breakdown pulses. One major difference between these “initiator NBEs” and other regular NBEs was that source heights of “initiator NBEs” were generally lower than other NBEs.