Search

The authors have carried out measurement of the current waveforms associated with lightning discharges to wind turbines near the coast of the Sea of Japan in Tohoku. In this paper, measured waveforms in winter from 2013 to 2018 are investigated and the charge transfer of lightning flash initiated by upward propagating leaders is studied. The charge transfer associated with bipolar lightning is higher than that associated with unipolar lightning. The lightning charge transfer of the typical winter atmospheric pressure pattern thunderstorms (TWPs) with relatively low −10 °C isotherm altitude is less than that of OTT (other thunderstorms than the TWP) at Nikaho and in Tohoku. In Hokuriku, another winter lightning area, the charge transfer of the lightning flash is almost the same regardless of the above-mentioned two types of the thunderstorms as well as the −10 °C isotherm altitude. As the result, it is pointed out that the charge transfer is dependent on the −10 °C isotherm altitude and types of thunderstorms, and that characteristics of winter lightning depend on the region. It is commonly found that the charge transfer exceeding 300 C occurs when the altitude of −10 °C isotherm is between 1000 and 2500 m above the sea level. [ABSTRACT FROM AUTHOR]

Subject matter of this paper is the analysis of the total of six upward positive lightning initiated from the Peissenberg Tower, Germany. All of them occurred during the cold season from February to April in the years 1997 to 1999. Three of them were initiated without nearby preceding lightning activity (called “self-initiated” upward lightning) and the other three occurred during nearby lightning activity (called “other-triggered” up-ward lightning). The analysis suggests that the other-triggered upward lightning is a downward lightning involving a relatively long upward connecting leader. The first current component, however, was different from the current of a first return stroke of a positive cloud-to-ground flash. On average, the duration was 15.7 ms, the maximum was 4.37 kA, and the charge was 13.3 C. Due to the long duration and the relatively low current, the first current component is more consistent with the initial continuous current (ICC) of an upward lightning. The initial period of the ICC exhibits a slowly rising portion lasting about 1 ms. During that period, the ICC was superimposed by weak current pulses. The arithmetic means of the pulse peak and the pulse duration were 0.49 kA and 9.6 μs, respectively. The average leader velocity was \bf \bf 2.3 \, \bm \times \,\bf 10^\bf 5 m/s and the average leader charge density was \bf 1.02 \, \bf \times\, \bf 10^\bf -3 C/m. Much stronger current pulses were observed after that initial period. Then, the arithmetic means were 5.3 kA for the pulse peak and 46.6 μs for the pulse duration. The ICC of the self-initiated upward lightning did not exhibit such an initial slowly rising portion with weak superimposed current pulses. The ICC immediately increased to several kilo-amperes involving strong current pulsation. For the ICC, the arithmetic means were 58 ms for the duration, 6.4 kA for the maximum, and 105 C for the charge. For the current pulses, the arithmetic means were 5.7 kA for the pulse peak and 19 μs for the pulse duration. The leader charge density was estimated to be up to several 10 mC/m. [ABSTRACT FROM PUBLISHER]