Characterizing the dynamic movement of thunderstorms using VLF/LF total lightning data over the Pearl River Delta region

This paper reveals the characteristics of thunderstorm dynamic movement using total lightning data obtained from the VLF/LF measurement. Eight thunderstorms, which was evenly distributed in the morning, midday, afternoon and evening, are selected to compare the different kinematic features around the Pearl River Delta (PRD) region in the south of China from 17 May to 23 May 2014. The connected-neighborhood labeling method is used to identify lightning clusters and obtain the centroids. Significant characterization parameters are put forward as metrics to reveal the kinematic features of thunderstorms, including the duration, valid area (VA), velocity, direction, and farthest distance in longitude and latitude during the life cycle of storm. A common trend is that the storms initiate in the west of the PRD region, moving to the east and disappearing after the thunderstorm travels around 106.5 km in longitude. There are two kinds of distribution to depict the property of valid area, which are one-peak distribution with the maximum in the mature stage and two-peak distribution with a relatively smaller peak in the early time of storm. The velocity does not show the same trend as the variation of VA which shows the steady increase or decrease during the lifetime of thunderstorm. The biggest VA and highest velocity are 891 km2 occurred on the evening of 17 May and 204.8 km h−1 occurred on the morning of 20 May. The 19 May evening storm was the weakest, with the maximum of VA and velocity being 253 km2 and 115.3 km h−1, respectively. The motion of storms shows a distinct pattern, as the spread of direction distributes tightly in the range of 0°–90° and 270°–360°. The movement characteristics of thunderstorm and the associated parameters may help to improve the nowcasting and forecasting system of thunderstorms in this region.