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Abstract In around 1990, significant shifts occurred in the spatial pattern and temporal evolution of the El Niño‐Southern Oscillation (ENSO), with these shifts showing asymmetry between El Niño and La Niña phases. El Niño transitioned from the Eastern Pacific (EP) to the Central Pacific (CP) type, while La Niña's multi‐year (MY) events increased. These changes correlated with shifts in ENSO dynamics. Before 1990, El Niño was influenced by the Tropical Pacific (TP) ENSO dynamic, shifting to the Subtropical Pacific (SP) ENSO dynamic afterward, altering its spatial pattern. La Niña was influenced by the SP ENSO dynamic both before and after 1990 and has maintained the CP type. The strengthened SP ENSO dynamic since 1990, accompanied by enhanced precipitation efficiency during La Niña, make it easier for La Niña to transition into MY events. In contrast, there is no observed increase in precipitation efficiency during El Niño.
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The Impacts of El Niño Diversity on Northern Hemisphere Atmospheric Blocking
Abstract 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 Niño–Southern Oscillation (ENSO) influence the characteristics of blocking, but none have considered the spatial diversity of El Niño. In this study, we examine Northern Hemisphere blocking events with respect to the “Central Pacific” (CP) and “Eastern Pacific” (EP) flavors of El Niño in 83 years of ERA5 reanalysis. The two El Niño 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 Niño flavors should be considered in future investigations of blocking and ENSO‐related variability.
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- Award ID(s):
- 2202663
- PAR ID:
- 10429634
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 50
- Issue:
- 13
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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