On the peak amplitude of lightning return stroke currents striking the sea

Data gathered from the US National Lightning Detection Network (TM) (NLDN) show that the peak currents of lightning flashes striking the sea are significantly higher than those of lightning flashes striking the land. We suggest that the unfavorable conditions for the formation of positive charge pockets in maritime clouds lead to lightning initiation at higher cloud potentials compared to their land counterparts, resulting in larger peak currents in negative lightning flashes striking the sea. As the positive charge pocket does not promote positive ground strokes, no such discontinuity should be expected in positive first return strokes to ground between land and sea.