A Study on the Intra-annual Variation and the Spatial Distribution of Lightning Activity Over Greece

Abstract

The intra-annual variation and the spatial distribution of lightning activity over Greece is studied for the 10-year period 2005–14, on a 15-day basis, using Zeus 0.5° × 0.5° data. Factor Analysis (S-mode and T-mode) is applied to the average lightning activity for each fortnight of the year and for each grid box, for the studied period. (i) For the intra-annual variation of lightning activity, 3 sub-regions are defined, presenting characteristic modes of variation: In the first one, over the mainland, a broad maximum appears during late spring–early summer; in the second, mainly over the Ionian Sea, a maximum is seen during early autumn; while in the third, mainly over the central and south Aegean Sea, two maxima are found, one in middle autumn and another in late May. (ii) For the spatial distribution of lightning activity, 4 main patterns are revealed: the ‘summer’ pattern (1/5–15/8), characterized by a maximum over the mainland; the ‘autumn’ pattern (1/9–15/10), with maxima over the north Ionian Sea and the north Aegean Sea; the ‘winter’ pattern (15/12–15/2), with maxima over the south Ionian Sea and Dodecanese Islands; and a low variance ‘transitional’ pattern (1/4–30/4 and 1/12–15/12), with maximum over the central Aegean Sea.