The Impacts of El Nino Diversity on Northern Hemisphere Atmospheric Blocking

Atmospheric blocking events are persistent quasi-stationary geopotential height anomalies that divert the jet stream from its climatological path in the mid- to high-latitudes. Previous studies have found that different phases of the El Nino-Southern Oscillation (ENSO) influence the characteristics of blocking, but none have considered the spatial diversity of El Nino. In this study, we examine Northern Hemisphere blocking events with respect to the "Central Pacific" (CP) and "Eastern Pacific" (EP) flavors of El Nino in 83 years of ERA5 reanalysis. The two El Nino flavors have dissimilar patterns of forcing on atmospheric circulation that impact the strength and placement of the upper-level jet stream, thus affecting blocking event frequency and duration. Significant contrasts in blocking characteristics between CP and EP years are disregarded when a single ENSO index is used, and we emphasize that El Nino flavors should be considered in future investigations of blocking and ENSO-related variability.