A 5 Year Global Lightning Climatology using ENGLN Thunder Hour Data

Abstract:

A thunder hour is defined as an hour during which thunder can be heard from a given location.

Thunder hours are an intuitive measure of lightning since the one-hour interval represents the

life span of most airmass thunderstorms. Examining long-term lightning patterns in the context

of thunder hours lends insight into thunderstorm activity without being heavily influenced by

individual storm intensity, shedding light on patterns in storm activity associated with weaker

thunderstorms. Thunder hour observations also reduce network performance dependencies in the

dataset, making thunder hours particularly useful for studying climatology.

Thunder hours have been calculated for the entire globe using 5 years of data from the Earth

Networks Global Lightning Network (ENGLN). To convert from lightning flash locations to

thunder hours, we converted the entire globe to a 0.05° grid, and we have slightly modified the

definition of thunder-hour to an UTC hour during which lightning was located within 15 km of a

given grid point. The 15 km criteria here is based on the approximate range at which thunder can

be heard from a lightning flash. ENGLN TH data were also compared with TRMM-LIS data in

order to determine the ENGLN thunderstorm detection efficiency, which was found to be > 83%

for much of the globe. This study will examine global thunderstorm activity, highlighting diurnal

and seasonal patterns observed across the globe, including seasonal drift in the intertropical

convergence zone, sea breeze storms, regional monsoons, and large-scale storm motions.