Characteristics of Winter Lightning Frequency in Wakasa Bay, Japan

Abstract

Based on LIDEN (Lightning Detection Network System) data for four winters from 2017/18 to 2020/21, the distribution of lightning frequency was investigated in the Hokuriku to San’in regions including Wakasa Bay. The results showed that the density of lightning strikes was high along the coast of the Japan Sea from the western Noto Peninsula to the Echizen Coast and near Tsuruga, while the density was low in Wakasa Bay. Thus, we investigated typical cases in which lightning strikes were lower in Wakasa Bay than in the surrounding areas, especially around Mikuni area. The results showed that when thunderclouds approached Mikuni area, they tended to develop and form a stronger precipitation area than the surrounding, and the frequency of lightning strikes also increased. This suggests that the topography of the Mikuni area contributes to enhanced precipitation and lightning in this region. On the other hand, in the Wakasa Bay area, surface winds blowing into the Wakasa Bay from the surrounding land were frequently observed. Near Tsuruga on the east side of Wakasa Bay, the topography of the area makes the area near the ground a convergence field, and precipitation and lightning strikes are relatively strong. In contrast, the central to western part of Wakasa Bay tends to be a divergence field, which may contribute to the suppression of convection in this area. The relatively steep topography around Wakasa Bay may have contributed to the formation of this divergence field near the ground.