Variability of global lightning activity on the ENSO time scale

Global lightning activity has been studied on the ENSO (El Nino Southern Oscillation) time scale based on recordings of the Earth's Schumann resonances at Nagycenk (NCK), Hungary as well as observations from the OTD (Optical Transient Detector) and the LIS (Lightning Imaging Sensor) satellites in space. Both the intensity and position of lightning activity vary on the ENSO time scale. The magnitude of the global variation in lightning flash rate is similar to 10% from La Nina to El Nino. In general, more lightning is observed in the tropical-extratropical land regions during warm, El Nino episodes, especially in Southeast Asia. Although oceanic lightning activity is a minor contributor to global lightning, an opposite behavior is observed in the Pacific and other oceanic regions. More lightning is present during cold, La Nina conditions than during the warm, El Nifto episodes. The annual distribution of global lightning is slightly offset from the equator into the Northern Hemisphere due to the north-south asymmetry of the land/ocean area ratio. Schumann resonance intensity variations suggest a southward (equator-ward) shift and satellite observations support this and show in addition an eastward shift in the global position during warm, El Nino episodes. The greatest lightning contrast between warm El Nino and cold La Nina episodes has been identified at the latitudes of descending dry air in the Hadley circulation. (C) 2008 Elsevier B.V. All rights reserved.