Study of the correlation between lightning activity and convective rain over Equatorial Africa

Abstract

The paper examines the reciprocal relationships between lightning activity (number of lightning flashes) and convective rain of mesoscale convective systems in the Equatorial African region and quantify them. The results of this study include: The dependence of lightning activity on convective rain varies from one region to another, as shown by correlation or coherence wavelet studies. The relationship between lightning activity and convective rain has a linear character in the two sub-regions of Equatorial Africa; a very good positive and significant correlation for both the North region <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{(\mathrm{R}=0.899)}$</tex> and the South one <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{(\mathrm{R}=0.934)}$</tex> of Equatorial Africa. This correlation is even stronger in the South region than in the North region of Equatorial Africa, although the electric activity is much more important in the North than in the South. The two models thus established are very well suited to both the “number of lightning flashes and convective rain” data of one or the other sub-region and explains 81 % (resp. 85 %) of the variability of the response data around the mean, in the North (resp. South) of Equatorial Africa. Number of lightning flashes and convective rain show very high trends in both sub-regions and are in an average ratio of about 94297:1 and 93102:1 (flashes/mm), respectively in the north region and in the south one of Equatorial Africa. This reveals the approximately invariant nature of the relationship between lightning activity and convective rain, both locally and globally. Similarly, the degree of linearity between the two signals <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{S}_{1}$</tex> , lightning activity and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{S}_{2}$</tex> , convective rain in the Equatorial African region, both in the North and in the South, 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 0° (in phase).