ENSO Modulation of U.S. Cloud-to-ground Lightning Activity

Cloud-to-ground (CG) lightning has substantial impacts on human health and property. However, the link between U.S. lightning activity and the El Niño-Southern Oscillation (ENSO), a dominant driver of global climate variability, has not been thoroughly investigated, in part because most lightning datasets sample only a handful of ENSO events. To overcome this limitation, we developed an empirical model of 6-hourly lightning flash count over the U.S. using environmental variables (e.g. convective available potential energy and precipitation) and National Lightning Detection Network data for 2003-2016. This model reproduces the observed interannual variability of lightning over most of the U.S. Then, we used the empirical model to construct a proxy lightning dataset for the period 1979-2021 and investigate the spatial and seasonal patterns of the ENSO-lightning relationship. El Niño is associated with increased lightning activity over the Coastal Southeast U.S. during early winter, the Northwest in the midsummer, and the Southwest during late winter and early spring, whereas La Niña is associated with increased lightning activity over the Tennessee River Valley during February-March.