A comparison of lightning activity and convective indices over some monsoon-prone areas of China

Using 10-year lightning localization data observed by the TRMM (Tropical Rainfall Measuring Mission) Lightning Imaging Sensor (LIS), the relationship between lightning activity and a series of convective indices was investigated over nine monsoon-prone areas of China in which high-impact weather (HIW) events are frequently observed.Two methods were used to verify and reconstruct LIS lightning data. First, LIS lightning flash data were verified by both surface thunderstorm reports and ground-based lightning detection data. Seasonal, monthly, and 5-day distributions of LIS observed lightning activity agree well with the surface reports and ground-based lightning observations. Second, due to LIS's low sampling frequency, a data reconstruction and compensation scheme for LIS lightning observations was designed using both LIS lightning seasonal diurnal cycles and surface thunderstorm reports. After data reconstruction, five lightning products were derived: daily mean and maximum LIS flash rate, daily mean and maximum LIS lightning cell rate, and number of lightning days per five day period.Then, a series of convective indices describing convection conditions were derived from radiosonde data according to atmospheric instability and convective potential analysis. Correlation analysis for each study region was done between 10-year lightning derived products and corresponding convective indices by 5-day periods. The correlation analysis results show that higher lightning flash rate and lightning probability are associated with more unstable air and smaller vertical wind shear in a nearly saturated lower layer in most of the study regions. But the correlation varies from region to region. The best correlation between lightning activity and convective indices was found in eastern and southern China, whereas the correlation is lowest in some inland or basin topography regions in which topographic effects are more significant. Moreover, ambient moisture plays a much more important role in the convective development of thunderstorms in southern China than other regions. Thunderstorm development mechanism differences among regions were also discussed.Based on the close relationship between lightning activity and convective indices, some regression equations for forecasting 5-day mean or maximum LIS lightning flash rate and lightning area (a thunderstorm cell) rate, and 5-day lightning days for the study regions were developed using convective indices as predictors. The verifications show that the convective index-based lightning forecast methods can provide a reasonable lightning outlook including probability and lightning flash rate forecasts for a 5-day period.