Summer-time lightning activity and its relation with precipitation: Diurnal variation over maritime, coastal and continental areas

The lightning activity and precipitation at 3-hour time intervals in grid boxes of 0.25 × 0.25° over East and Central Mediterranean during the summer of 2005 and 2006 are analyzed. The results show that i) the peak of flash density over the continental and coastal areas is in the afternoon hours, while over the maritime areas the peak is in the morning hours; ii) the number of cases with 3-hour accumulated precipitation when lightning flashes are detected is smaller than the number of no-flash cases over all three types of areas - maritime, coastal and continental; iii) the frequency distribution of the precipitation amount is shifted towards larger values for the cases with flashes as compared to the cases without flashes. The analysis also reveals that the average precipitation amount per case is larger when lightning occurred than when it was absent. However the area-average precipitation amount is not always larger for the cases with flashes than the no-flash cases: It depends on the type of the surface (maritime, coastal and continental) and on the period of the day: morning or afternoon. Area-average precipitation amount is smaller when lightning occurred than when it was absent for the afternoon hours over the maritime area and for the morning hours over the continental area. High correlation coefficients R (between 0.70 and 0.98) are found between rain rate and average flash density when flash density is averaged in logarithmic bins of rain-rate.