Convective Properties of A Landfalling Typhoon as Revealed by Lightning and Numerical Simulation

Abstract:

Our knowledge about lightning activities in tropical cyclones (TCs) has been increasing during the last few years. Previous studies showed variation of spatial and temporal characteristics of TC lightning, and indicated the potential of using lightning data to predict changes of storm intensity and evolution of structure. Typhoon Molave (2009) exhibited strong convection and intense lightning during its landfall in China. In this work, lightning data from the World Wide Lightning Location Network (WWLLN), as well as data from S-band Radar were utilized to study the evolution of lightning during landfall and to investigate its relationship to TC convection. Simulation results from the Weather Research and Forecast (WRF) mesoscale model (version 3.2.1) were used to focus on the convective properties of Molave. The model reproduced well the strong convections in the inner core and rainbands, and featured the horizontal and vertical characteristics of convection evolution of the typhoon.

Our results showed that lightning in the inner core outbreak prior to the maximum intensity of the storm and the bursts could be a good indicator of the imminent intensification of the storm. The large concentrations and increased distribution height of graupel and cloud water particles in the inner core, and the enhancement of updraft velocity were the main reasons for lightning outbreak in the inner core. The increased concentration of ice phase particles and the emergence of strong convection nuclear in the outer rainbands caused the peak frequency of TC lightning at the maximum intensity of the storm.