Climatological Comparison of Small- and Large-Current Cloud-to-Ground Lightning Flashes over Southern China

摘要

The first climatological comparison of small-current cloud-to-ground (SCCG; peak current = 50 kA) and large-current cloud-to-ground (LCCG; peak current >50 kA, >75 kA, and >100 kA) lightning flashes is presented for southern China. The LCCG lightning exhibits an apparent preference to occur over the sea. The percentage of positive LCCG lightning during the nonrainy season was more than twice that during the rainy season, while the percentage of positive SCCG lightning showed small seasonal differences. Positive cloud-to-ground (PCG) lightning was more likely to feature a large peak current than was negative cloud-to-ground (NCG) lightning, especially during the nonrainy season and over land. Distinct geographical differences are found between SCCG and LCCG lightning densities and between their own positive and negative discharges. Furthermore, the percentages of positive lightning from LCCG and SCCG lightning exhibit distinctly different geographical and seasonal (rain and nonrainy season) distributions. The diurnal variations in SCCG and LCCG lightning are clearly different over the sea but similar over land. Diurnal variations in the percentage of positive lightning are functions of the peak current and underlying Earth's surface. In combination with the University of Utah precipitation feature (PF) dataset, it is revealed that thunderstorms with relatively weak convection and large precipitation areas are more likely to produce the LCCG lightning, and the positive LCCG lightning is well correlated with mesoscale convective systems in the spatial distribution during nonrainy season.