Weakening of the Teleconnection From El Nino-Southern Oscillation to the Arctic Stratosphere Over the Past Few Decades: What Can Be Learned From Subseasonal Forecast Models?

While a connection between the El Nino-Southern Oscillation (ENSO) and the Northern Hemisphere wintertime stratospheric polar vortex appears robust in observational studies focusing on the period before 1979 and in many modeling studies, this connection is not evident over the past few decades. In t...

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Bibliographic Details
Published in:Journal of Geophysical Research: Atmospheres
Main Authors: Garfinkel, Chaim, I, Schwartz, Chen, Butler, Amy H., Domeisen, Daniela I., V, Son, Seok-Woo, White, Ian P.
Format: Article in Journal/Newspaper
Language:unknown
Published: American Geophysical Union 2020
Subjects:
WAVE-ACTIVITY FLUX
SURFACE-TEMPERATURE
SUDDEN WARMINGS
NORTH-ATLANTIC
ENSO
VARIABILITY
PATTERNS
PATHWAY
IMPACT
MJO
El Nino
Arctic vortex
subseasonal forecasting
North Atlantic
Online Access:https://hdl.handle.net/10371/206182
https://doi.org/10.1029/2018JD029961
Description
Summary:While a connection between the El Nino-Southern Oscillation (ENSO) and the Northern Hemisphere wintertime stratospheric polar vortex appears robust in observational studies focusing on the period before 1979 and in many modeling studies, this connection is not evident over the past few decades. In this study, the factors that have led to the disappearance of the ENSO-vortex relationship are assessed by comparing this relationship in observational data and in operational subseasonal forecasting models over the past few decades. For reforecasts initialized in December, the models simulate a significantly weaker vortex during El Nino than La Nina (LN) as occurred before 1979, but no such effect was observed to have occurred. The apparent cause of this is the eastern European and western Siberian height anomalies present during ENSO. The observed LN events were associated with persistent ridging over eastern Europe as compared to El Nino. Although the Subseasonal-to-Seasonal models are initialized with this ridge, the ridge quickly dissipates. As ridging over this region enhances wave flux entering the stratosphere, the net effect is no robust stratospheric response to ENSO in the observations despite a North Pacific teleconnection that would, in isolation, lead to less wave flux for LN. The anomalies in the eastern European sector in response to ENSO likely reflect unforced internal atmospheric variability. Y 1

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