Global lightning and climate variability inferred from ELF magnetic field variations

We report characteristics of global lightning activity on a seasonal time scale as inferred from two independently operating instruments measuring magnetic field variations in the lower ELF range. In this picture, the strongest source. of lightning activity is centered on the North American continent. We reduce the source proximity effect to the observing sites experimentally with a simple. differential technique and reconfirm the conclusion of Holzer and Deal (1956) that wave propagation conditions in the lower ELF range are of minor importance. The. resulting mean seasonal variations of continental lightning in mid-and tropical latitudes are found to be related to surface temperature variations in moderate-and tropical rain forest climates and they support the view of Williams (1992) that monitoring of global lightning activity may provide a thermometer-independent measure of temperature changes associated with climate variability.