Characteristics of Intracloud Lightning to Cloud-to-ground Lightning Ratio in Thunderstorms over Eastern and Southern China

This study investigates the characteristics of intracloud lightning to cloud-to-ground lightning (IC:CG) ratios in eastern and southern China, as well as their relationships to convective intensity. IC:CG is not only examined on the 0.5o grid scale but also uniquely on the thunderstorm scale (convective features), using coincident satellite-based and ground-based lightning observations from 2009 to 2014. The grid-scale IC:CG climatology in eastern and southern China shows a mean value of 3.97, consistent to the worldwide reported values. The IC:CG distribution exhibits two maxima (8–10) over North China Plain (NCP) and the southwest hilly Guangxi Province (GXP), and a low-value band (2–4) located along the Mei-Yu rainband in central China including Sichuan Basin (SCB) and the Yangtze River Basin (YRB). The IC:CG ratios over different regions all maximize in the spring and decrease toward the middle summer. Storm-scale analyses further indicate that the SCB/YRB thunderstorms are weaker but own relatively higher CG frequency, leading to a low IC:CG. This is likely because the SCB/YRB storms are more organized with broader stratiform precipitation. Moreover, IC:CG increases with stronger convective intensity following a power-law relation, and the power is the strongest over GXP and weakest over SCB. In short, our results reveal unique IC:CG characteristics and their relationships with convective intensity for monsoonal thunderstorms, therefore providing insights on thunderstorms' electrification structures under monsoon environments.