The impact of baroclinic eddy feedback on the persistence of jet variability in the two-layer model

Pablo Zurita-Gotor, Javier Blanco-Fuentes, Edwin Gerber

Research output: Contribution to journalArticle

Abstract

Although it is well known that the persistence of extratropical jet shifts is enhanced by a positive eddy feedback, the dynamics of this feedback is still debated. Two types of mechanisms have been proposed: barotropic mechanisms rely on changes in upper-level propagation and baroclinic mechanisms rely on the coupling between barotropic and baroclinic flow. Recent studies have suggested that barotropic models can capture key aspects of the observed jet variability but the role of baroclinic dynamics has been less explored. This study investigates the temporal relations between barotropic and baroclinic anomalies and their eddy forcings during the internal variability of the simple two-layer quasigeostrophic model. A large correlation is found between barotropic and baroclinic anomalies and between the meridional and vertical components of the Eliassen-Palm divergence, especially at low frequency. The low-frequency variability is consistent with the baroclinic mechanism: persistent upper-level eddy momentum convergence is associated with (and precedes) persistent anomalies in the poleward eddy heat flux. In contrast, at high frequency, poleward heat flux anomalies are associated with eddy momentum divergence aloft and both eddy forcings have same-sign contributions to the upper-level eddy potential vorticity (PV) flux. In this limit the eddy PV flux is associated with wave activity transience as effective diffusivity is too small to dissipate the wave-mean flow interaction term. The large correlation between barotropic and baroclinic anomalies implies that the low-frequency variability of barotropic flow may be affected by thermal damping when this damping is sufficiently strong. For example, zonal index persistence drops drastically in our model when baroclinicity shifts are prevented by strong thermal restoration.

Original languageEnglish (US)
Pages (from-to)410-429
Number of pages20
JournalJournal of the Atmospheric Sciences
Volume71
Issue number1
DOIs
StatePublished - Jan 2014

Fingerprint

eddy
persistence
anomaly
barotropic motion
potential vorticity
damping
heat flux
momentum
divergence
baroclinic motion
diffusivity

Keywords

  • Annular mode
  • Atmospheric circulation
  • Baroclinic flows
  • Climate variability
  • Eddies
  • Quasigeostrophic models

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

The impact of baroclinic eddy feedback on the persistence of jet variability in the two-layer model. / Zurita-Gotor, Pablo; Blanco-Fuentes, Javier; Gerber, Edwin.

In: Journal of the Atmospheric Sciences, Vol. 71, No. 1, 01.2014, p. 410-429.

Research output: Contribution to journalArticle

@article{299c2a22912540f280d99dae8b83d43f,
title = "The impact of baroclinic eddy feedback on the persistence of jet variability in the two-layer model",
abstract = "Although it is well known that the persistence of extratropical jet shifts is enhanced by a positive eddy feedback, the dynamics of this feedback is still debated. Two types of mechanisms have been proposed: barotropic mechanisms rely on changes in upper-level propagation and baroclinic mechanisms rely on the coupling between barotropic and baroclinic flow. Recent studies have suggested that barotropic models can capture key aspects of the observed jet variability but the role of baroclinic dynamics has been less explored. This study investigates the temporal relations between barotropic and baroclinic anomalies and their eddy forcings during the internal variability of the simple two-layer quasigeostrophic model. A large correlation is found between barotropic and baroclinic anomalies and between the meridional and vertical components of the Eliassen-Palm divergence, especially at low frequency. The low-frequency variability is consistent with the baroclinic mechanism: persistent upper-level eddy momentum convergence is associated with (and precedes) persistent anomalies in the poleward eddy heat flux. In contrast, at high frequency, poleward heat flux anomalies are associated with eddy momentum divergence aloft and both eddy forcings have same-sign contributions to the upper-level eddy potential vorticity (PV) flux. In this limit the eddy PV flux is associated with wave activity transience as effective diffusivity is too small to dissipate the wave-mean flow interaction term. The large correlation between barotropic and baroclinic anomalies implies that the low-frequency variability of barotropic flow may be affected by thermal damping when this damping is sufficiently strong. For example, zonal index persistence drops drastically in our model when baroclinicity shifts are prevented by strong thermal restoration.",
keywords = "Annular mode, Atmospheric circulation, Baroclinic flows, Climate variability, Eddies, Quasigeostrophic models",
author = "Pablo Zurita-Gotor and Javier Blanco-Fuentes and Edwin Gerber",
year = "2014",
month = "1",
doi = "10.1175/JAS-D-13-0102.1",
language = "English (US)",
volume = "71",
pages = "410--429",
journal = "Journals of the Atmospheric Sciences",
issn = "0022-4928",
publisher = "American Meteorological Society",
number = "1",

}

TY - JOUR

T1 - The impact of baroclinic eddy feedback on the persistence of jet variability in the two-layer model

AU - Zurita-Gotor, Pablo

AU - Blanco-Fuentes, Javier

AU - Gerber, Edwin

PY - 2014/1

Y1 - 2014/1

N2 - Although it is well known that the persistence of extratropical jet shifts is enhanced by a positive eddy feedback, the dynamics of this feedback is still debated. Two types of mechanisms have been proposed: barotropic mechanisms rely on changes in upper-level propagation and baroclinic mechanisms rely on the coupling between barotropic and baroclinic flow. Recent studies have suggested that barotropic models can capture key aspects of the observed jet variability but the role of baroclinic dynamics has been less explored. This study investigates the temporal relations between barotropic and baroclinic anomalies and their eddy forcings during the internal variability of the simple two-layer quasigeostrophic model. A large correlation is found between barotropic and baroclinic anomalies and between the meridional and vertical components of the Eliassen-Palm divergence, especially at low frequency. The low-frequency variability is consistent with the baroclinic mechanism: persistent upper-level eddy momentum convergence is associated with (and precedes) persistent anomalies in the poleward eddy heat flux. In contrast, at high frequency, poleward heat flux anomalies are associated with eddy momentum divergence aloft and both eddy forcings have same-sign contributions to the upper-level eddy potential vorticity (PV) flux. In this limit the eddy PV flux is associated with wave activity transience as effective diffusivity is too small to dissipate the wave-mean flow interaction term. The large correlation between barotropic and baroclinic anomalies implies that the low-frequency variability of barotropic flow may be affected by thermal damping when this damping is sufficiently strong. For example, zonal index persistence drops drastically in our model when baroclinicity shifts are prevented by strong thermal restoration.

AB - Although it is well known that the persistence of extratropical jet shifts is enhanced by a positive eddy feedback, the dynamics of this feedback is still debated. Two types of mechanisms have been proposed: barotropic mechanisms rely on changes in upper-level propagation and baroclinic mechanisms rely on the coupling between barotropic and baroclinic flow. Recent studies have suggested that barotropic models can capture key aspects of the observed jet variability but the role of baroclinic dynamics has been less explored. This study investigates the temporal relations between barotropic and baroclinic anomalies and their eddy forcings during the internal variability of the simple two-layer quasigeostrophic model. A large correlation is found between barotropic and baroclinic anomalies and between the meridional and vertical components of the Eliassen-Palm divergence, especially at low frequency. The low-frequency variability is consistent with the baroclinic mechanism: persistent upper-level eddy momentum convergence is associated with (and precedes) persistent anomalies in the poleward eddy heat flux. In contrast, at high frequency, poleward heat flux anomalies are associated with eddy momentum divergence aloft and both eddy forcings have same-sign contributions to the upper-level eddy potential vorticity (PV) flux. In this limit the eddy PV flux is associated with wave activity transience as effective diffusivity is too small to dissipate the wave-mean flow interaction term. The large correlation between barotropic and baroclinic anomalies implies that the low-frequency variability of barotropic flow may be affected by thermal damping when this damping is sufficiently strong. For example, zonal index persistence drops drastically in our model when baroclinicity shifts are prevented by strong thermal restoration.

KW - Annular mode

KW - Atmospheric circulation

KW - Baroclinic flows

KW - Climate variability

KW - Eddies

KW - Quasigeostrophic models

UR - http://www.scopus.com/inward/record.url?scp=84891650768&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84891650768&partnerID=8YFLogxK

U2 - 10.1175/JAS-D-13-0102.1

DO - 10.1175/JAS-D-13-0102.1

M3 - Article

AN - SCOPUS:84891650768

VL - 71

SP - 410

EP - 429

JO - Journals of the Atmospheric Sciences

JF - Journals of the Atmospheric Sciences

SN - 0022-4928

IS - 1

ER -