The Influence of the El Niño-Southern Oscillation on Cloud-to-Ground Lightning Activity along the Gulf Coast of the United States

This study investigates the response of lightning to the El Niño Southern Oscillation (ENSO) in the vicinity of the U.S. Gulf Coast region and nearby adjacent waters of the Gulf of Mexico, for the years 1995-2002. The Gulf Coast region was selected for this study because of its high flash density (Orville and Huffines, 2001) and because it is an area where the ENSO fingerprint is very clearly demonstrated on both temperature and precipitation patterns (CPC, 2002). Additionally, this geographic domain roughly matches the only known study on this topic (Goodman et al., 2000). Winter is the season of greatest response to ENSO (CPC, 2004), and past studies show that summer has the most lightning activity (e.g., Orville and Huffines, 2001). The temporal domain of the study is restricted to 1995 and beyond, as this follows a system-wide upgrade of the National Lightning Detection Network (NLDN) that improved overall flash detection efficiency (Cummins, et. al.1998; Wacker and Orville, 1999). Both qualitative and quantitative methods were employed to explore the lightning data for ENSO teleconnections. Mean flash density maps were constructed for the complete period of record, individual months and the winter and summer seasons. Maps were visually examined for qualitative comparison with past climatologies and the Goodman et al., (2002) ENSO study. Additionally, monthly flash deviations are computed, visualized and correlated with the Niño 3.4 SST anomaly for all months in the study, seeking out variations in both the amount of flash deviation and spatial properties. Abundant literature exists on both ENSO and lightning individually. This study offers an insight into their intersection