Bridging the polarimetric structure and lightning activity of isolated thunderstorm cells during the cloud life cycle

Abstract

Polarimetric structures detected by radar can characterize cloud microphysics and dynamics. Many studies have indicated that differential reflectivity (ZDR) and specific differential phase (KDP) columns, which serve as proxies for updraught strength, are related to lightning activity; moreover, the quantities of ice and supercooled liquid water strongly influence the occurrence of lightning flashes via non-inductive charging. However, the sequence or interactions among these factors with dynamics and microphysics from the perspective of the cloud life cycle are uncertain. Here, we improve the “3D mapping columns” method to identify and quantify the ZDR/KDP columns, which is based on Cartesian grid datasets; this method is sensitive in the early phase of cloud formation. Our study bridges the polarimetric structure and lightning activity within 15 isolated thunderstorms during the cloud life cycle. The results indicate that microphysical variations in supercooled liquid water and graupel yield better correlation coefficients for the lightning activity prediction at short warning times (e.g. 6 min) than dynamical variations in the ZDR column volume do; however, the trend of the ZDR column volume implies good performance at longer warning times (e.g. 12 min). The KDP column is probably absent in the early phase of convection development; however, it will occur in the later stage with heavily cold cloud processes, replacing the ZDR column to indicate updraughts within the reflectivity core when obvious graupels and hailstones occur. Our study improves the understanding of the polarimetric structure, which is related to dynamics and microphysics, and is also associated with lightning activity.