Characteristics of atmospheric electricity of thunderclouds accompanied by severe hailfall

In recent years, it has been pointed out that there has been an increase in the number of localised heavy rain and hailstorms in urban areas, which are thought to be caused by climate change and extreme weather. It is said to be difficult to distinguish whether a thundercloud (cell) that causes localised hailstorms or heavy rain is a cell that will produce hailstorms or heavy rain, based on observations of the reflection intensity of the weather radar alone. In this study, we consider extreme weather events that cause hailstorms and heavy rain from the perspective of lightning discharges, distinguishing between cells that lead to hailstorms and cells that do not lead to hailstorms but only to heavy rain. We compared two cells in the same meteorological field in three cases that occurred in the Tokyo metropolitan area. We compared the cells that led to hailstorms with the control cells that only led to heavy rain. As a result, we found the following common characteristics.

1) The number of ±CG strokes in cells with heavy rain but no hail is larger than in cells with hail.

2) The volume of ice calculated from polarimetric radar in cells with hail is larger than in cells with heavy rain but no hail.

As a result, the possibility of discriminating between cells with and without hail has increased. This study is a re-evaluation of the results obtained by Fujiwara et al, (J. Atmos. Electriciy, 2021; 2023).