Investigation and Evaluation of Lightning Indices with X-band Polarimetric Radars in the Warm Season in Japan

This study evaluates lightning indices (LIs) using radar parameters for cloud-to-ground lightning in Japan. National Research Institute for Earth Science and Disaster Resilience, Japan (NIED) has carried out intensive observations of thunderstorm with two X-band polarimetric radars (MP-X) in the Kanto region, Japan in the summer seasons since 2011. The MP-Xs performed sector scans to collect volume scan data within 1 or 2 minutes.

From the analysis using MP-Xs data in 2012 and 2013, the Lightning Indices (LIs) of updraft volumes were found to be well correlated with CG lightning frequency for threshold values of updraft speeds of > 5 and > 10 m s−1; this result supports the findings of a previous study in the North America. The LIs derived from updraft strength studied here, updraft volumes at vertical velocities of > 0, > 5, and > 10 m s−1 and maximum updraft speed, were also well correlated with the occurrence of CG lightning. We will also show the results on LIs of polarimetric parameters in the warm season in Kanto region, Japan.

Sector scans were performed by manually during the summer seasons of 2011-2013. In 2016, we are performing sector scans by automatically. Results of the automatic adaptive scan will be shown in this presentation.