Storms and Lightning Activity in Greece during the Warm Periods of 2003-06

Lightning activity over Greece during the warm season (May-September) of the years 2003-06 is investigated in relation to the synoptic meteorological conditions that prevailed in the region. The study is based on the use of cloud-to-ground lightning activity data from the Met Office Arrival Time Difference system and upper-air analyses from the European Centre for Medium-Range Weather Forecasts. Analysis of the spatial variability of lightning shows that the highest "relative" flash densities are observed in northern and western Greece and in central and western Peloponnissos. The relative flash density is correlated with elevation: it increases with elevation along the slopes of terrain features. The study of the synoptic patterns related to lightning is based on the analysis of 60 active days and 60 inactive days in terms of lightning activity over Greece. The days with high lightning activity are characterized by a short-wave trough at the 500-hPa level over the Ionian Sea. On the other hand, during the days with no lightning, a northwest flow prevails over Greece. It was also found that high lightning activity is related to high values of absolute vorticity, equivalent potential temperature, and convective available potential energy.