Thunder-day Climatology Using Modern Lightning Location Data

A thunder-day is defined as a 24-hour period of time during which thunder is heard. Records of thunder-days for specific locations go back more than 100 years, making this one of the few measurements suitable for long term lightning climatology studies. More recently, lightning climatology studies have used lightning flash density instead of thunder-days (e.g. Cecil et al. 2014, Hodanish et al. 1997). Since lightning location systems have been operationally available for only a handful of decades, the history available with the measurements is much shorter and prone to biases due to ever improving detection technology. Further, for inter-seasonal analysis measurements of flash density are arguably worse than thunder days because the number of flashes observed in any particular location in a season is frequently dominated by a small number of thunderstorms. This requires flash density observations to be averaged over longer periods of time to smooth out the variability. Luckily, it is possible to generate a synthetic thunder-day measurement using the stroke locations of a lightning location system. As an added benefit, these synthetic measurements heavily reduce the effects of temporally and spatially varying detection efficiency inherent in ground based lightning location systems. Thunder-day observations are also more intuitive and meaningful to a general audience, and still make stunning visualizations. In this study, we will develop a synthetic thunder-day product, apply the technique to stroke data from multiple lightning location systems, and compare the results to direct thunder observations available in NOAA’s Global Historical Climatology Network, as well as other thunder-day sources. We will then show maps of multiple years of thunder activity for a number of locations on the globe, and demonstrate the utility of these maps for inter-seasonal trend analysis.

Cecil, Daniel J., Dennis E. Buechler, and Richard J. Blakeslee. "Gridded lightning climatology from TRMM-LIS and OTD: Dataset description." Atmospheric Research 135 (2014): 404-414.

Hodanish, Stephen, et al. "A 10-yr monthly lightning climatology of Florida: 1986–95." Weather and forecasting12.3 (1997): 439-448.