Investigating the potential of X-band multi-parameter radar to detect convective storm associated with cloud-to-ground lightning in the warm season in Kanto region, Japan

Spatial distribution of cloud microphysical properties relates to electrification and charge structure in a thunderstorm. Multi-parameter radar provides information about characteristics of precipitation particle. The multi-parameter radar is expected to be utilized for detection and nowcast of lightning activity.

National Research Institute for Earth Science and Disaster Prevention, Japan (NIED) carried out intensive observation of thunderstorm with two X-band polarimetric Doppler radar (MP-X) in the Kanto region, Japan during the summer of 2011-2013. The MP-X performed sector scans to collect volume scan data within 2 minutes. Cloud-to-ground lightning data (CG) obtained by Japan Lightning Detection Network (JLDN) was used for analysis.

Based on previous studies, we compared the following six kinds of indicators of lightning probability (ILP): reflectivity threshold at some temperature in the atmosphere, reflectivity lapse rate in the temperature range from 0 to -20℃, graupel volume, volume of upward wind with more than certain upward wind speed, and maximum upward wind speed. To extract graupel, we referred to two different methods proposed by Palucki et al. (2011) and Suzuki et al. (2012). We investigated the threshold values with the highest percent correct (PC) in each ILP.b The ILPs were investigated for a thunderstorm which brought a tornado on 2 September 2013 in Kanto region, Japan. The ILP using upward wind speed (volume with 2 m/s upward wind) was the highest PC among the six ILP. The PC of the ILP using polarimetric parameters was higher than that of the ILP using reflectivity. We will accumulate case studies to investigate the most suitable ILP and its threshold value for thunderstorms in the warm season in Kanto region, Japan.