Analysis of Distribution Characteristics of Cloud-to-ground Lightning at Different Spatiotemporal Scales

Lightning strikes are the primary cause of transmission network failures. Strengthening the monitoring and research of lightning activities contributes to the scientific protection against lightning strikes in power grids. Therefore, based on the lightning detection results of the State Grid of China from 2012 to 2021, this article analyzes the spatiotemporal distribution characteristics of lightning at different scales, and proposes a thunderstorm intensity parameter to measure the intensity of lightning activity. The results indicate that the number of total return stroke in the State Grid region from 2012 to 2021 was approximately 166 million, 2.1 times the number of first return stroke. The monthly variation showed a unimodal distribution, with June to August being the peak period of lightning activity. The spatial distribution of lightning activities was uneven, showing a distribution trend of more in east, central, and north China, while less in northwest and northeast China. The positive-polarity ratio of the first return stroke in various regions was greater than that of total return stroke, with east and central China being the most obvious. The median current in north China and east China was relatively small, and the median current of the first and all return stroke was comparable. The median current in central China, northeast China, and northwest China was relatively large, and the median current of the first return stroke was slightly greater than the median current of all return strokes. The results show that 30 min and $0.3^{\circ}\times 0.3^{\circ}$ can be initially selected as the statistical time $\Delta {\mathrm{t}}$ and grid area for dense thunderstorms to measure the time intensity of lightning activity. The trend of changes in the number of lightning strikes was basically consistent with the number of dense thunderstorms.