Infrasound from lightning measured in Ivory Coast

Previous measurement campaign, realized in France in 2005, has shown that an infrasound station can clearly measure thunder when lightning occur within 75 km from the station. In this paper, infrasound data recorded in Ivory Coast since 2005 are analyzed and compared to WWLLN data in order to quantify statistically the main trends observed in 2005. The main results are : (1) the (infrasonic) thunder can be measured in direct propagation up to 50-70 km (depending on the direction of the wind) from the lightning, (2) the thunder amplitude, measured in direct propagation, decreases of one order of magnitude in a range of 50 km, (3) thunder can be also detected when lightning occur in the so called “shadow zone” (70-200 km), and (4) up to 60% of the WWLLN events are correlated with an infrasound event when their location are less than 50 km while about the detection efficiency is about 5% when lightning occur in the shadow zone. To explain these results intensive calculations of thunder shock wave propagation taking into account a real meteorology during 1 year have been performed.