An analysis of the characteristics of lightning activities, radar reflectivity and ice scattering for tropical cyclones over the western North Pacific

Using the data from the precipitation radar (PR), lightning imaging sensor (LIS), and passive microwave imaging(TMI) onboard on the Tropical Rainfall Measuring Mission (TRMM) satellite, the characteristics of lightning activities, radar reflectivity and ice scattering of the 46 China landfalling tropical cyclones from 1998 to 2008 are analyzed, and the relationships among lightning occurence and radar reflectivity and ice scattering are investigated. The tropical cyclones are divided into the six intensity periods according to the maximum sustained wind near the eyewall. The results indicate that lightnings are more likely to happen in the weaker intensity period of tropical cyclones compared with the stronger ones. After a tropical cyclone reaches the tropical storms intensity, the stronger it is, the fewer flashes are. There are different spatial distributions of lightning activities in the different intensity periods of tropical cyclones. The largest flash rate occurs in eyewall regions during tropical storm, severe typhoon and super severe typhoon periods, while it occurs in outer rainband regions during the other periods. As a whole, the precipitation in tropical cyclones is dominated by stratiform rains. The radar reflectivity is sharply decreased and the ice scattering signature is weaker as well above the freezing level. Though the strongest convective signatures appear in eyewall regions, there are fewer lightning flashes in eyewall regions than in outer rainband regions. Given the same radar reflectivity, lightning flashes are more likely to occur in typhoon and severe tropical storm periods with a maximum threshold of radar reflectivity found in super typhoon periods. The electrical activities are closely related to ice crystal, graupel, supercooled water and convective updraft, so to some extent, lightning data can give us some information about the microphysical and dynamic processes in tropical cyclones. 