Comparative study of lightning activity over north vs south Equatorial Africa

Abstract

The aims of this paper is to compare the lightning activity (number of lightning flashes) of mesoscale convective systems over North and South Equatorial Africa. It examines also the correlation between the lightning activity in the Northern Equatorial Africa and that in the Southern one. Indeed, spatial observations have shown that the highest concentrations of lightning on the Earth are mostly located in Equatorial Africa. This study has been made using data processing, descriptive statistical analysis and wavelet coherence analysis. The obtained results show that there is more lightning activity in the North region of Equatorial Africa than in the South one, in an average ratio of about 1.12 to 1. At the same time, a North-South regional contrast in lightning activity is observed over the Equatorial Africa. Concerning their relationships, it has been found that the lightning activity is strongly and negatively correlated (R=-0.588) between the two hemispheres. Furthermore, using the wavelet method we have obtained the same results. The degree of linearity between the lightning activity signals S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> of the Northern Equatorial Africa and S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> of the Southern one has been characterized (linear correlation level between 0 and 1) for any time-scale location and shows that the interactions between the two signals are at sub-annual and seasonal scales, with a relative phase difference of 180° (in phase opposition). Thus, the two signals are negatively correlated. Lightning activity shows very high trends in both sub-regions and the variation in its monthly as well as seasonal mean could be explained given the strong convection and thunderstorms throughout the region.