Statistical Relationships of Precipitation Rate and Wind Gust Intensity to Lightning Activity in Japan

This study examined the relationships of precipitation rate and wind gust intensity to lightning activity in Japan by using data recorded at ~1,000 automatic weather stations and a lightning detection network at 10 minute intervals for three years from June 2009 to May 2012. The relationships were evaluated by correlation analyses in 11 climatologically distinct areas of Japan. To investigate the frequency of simultaneous occurrences of precipitation, gusts, and lightning activity, observations were subjectively divided into four categories, based on their distributions in a plot of precipitation and gust data versus lightning activity. There were weak positive correlations between cloud-to-ground (CG) lightning activity and precipitation rate in summer, except in northern Japan, but no significant correlations between CG lightning activity and precipitation rate in winter. High precipitation rate was associated with 5%–40% of occurrences of high lightning activity, suggesting that lightning activity has only limited application as an indicator of high precipitation rate in summer. There were no significant correlations of lightning activity with wind gusts in summer or winter in any of the 11 areas. Only 0%–11% of occurrences of high lightning activity were accompanied by strong gusts in winter, indicating that lightning activity is not a useful indicator of strong wind gusts in winter.