The variability of the El Nino southern oscillation and Modoki mode and their impacts on New York state climate

Abstract

The El Nino Southern Oscillation (ENSO) has long been an influential climate and weather driver for many regions. Many studies have examined the variability of the phases of ENSO, leading to discovery of a separate mode of El Nino dubbed the El Nino Modoki, featuring a tripole Walker circulation. However, few studies have examined the variability of El Nino with Modoki separated from regular El Nino events. The goals of this study were to demonstrate that the El Nino signal was stronger separate from Modoki (thus leading to higher predictability), and to examine the effect of the Modoki on both a national and regional level, showing the connection between other teleconnections such as the Pacific North American teleconnection (PNA), the Arctic Oscillation (AO), and the North American Oscillation teleconnection (NAO). Using NCEP/NCAR composites, conventional El Nino events were found to have a stronger signal, with persistent features being easier to identify. Similarly, the Modoki showed a pattern thatmilar but different to the regular El Nino. Using New York State for the area of regional analysis, all ENSO phases were found to modify the effect of the PNA, but the effect was different depending on location. Both of these results indicate that it is possible to generate a clearer picture of the impacts of ENSO by properly classifying these events