The driving of baroclinic anomalies at different timescales

Blanco-Fuentes, Javier; Zurita‐Gotor, Pablo

doi:10.1029/2011gl049785

Cited by 13 publications

(17 citation statements)

References 22 publications

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“…The role played by the low-phase-speed eddies in our model in maintaining the lower-level baroclinicity in the annular modes is consistent with the very recent observational study by Blanco-Fuentes and Zurita-Gotor (2011), in which they also found that the low-frequency eddies, in contrast to the synoptic eddies, contribute to the low-frequency latitudinal shift of the zonal flow baroclinicity along with the SAM. When the surface friction on baroclinic eddies is increased, the leading mode of the zonal wind variability can shift from a latitudinal fluctuation of the jet position to a pulsing of the jet intensity.…”

Section: Summary and Discussionsupporting

confidence: 91%

Annular Mode–Like Variation in a Multilayer Quasigeostrophic Model

Zhang

Yang

Nie

et al. 2012

Journal of the Atmospheric Sciences

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Eddy-zonal flow interactions in the annular modes are investigated in this study using a modified beta-plane multilayer quasigeostrophic (QG) channel model. This study shows the different response of high-and lowphase-speed (frequency) eddies to the zonal wind anomalies and suggests a baroclinic mechanism through which the two eddies work symbiotically maintaining the positive eddy feedback in the annular modes. Analysis also indicates that the different roles played by these two eddies in the annular modes are related to the differences in their critical line distributions. Eddies with higher phase speeds experience a low-level critical layer at the center of the jet. They drive the zonal wind anomalies associated with the annular mode but weaken the baroclinicity of the jet in the process. Lower-phase-speed eddies encounter low-level critical lines on the jet flanks. While their momentum fluxes are not as important for the jet shift, they play an important role by restoring the lower-level baroclinicity at the jet center, creating a positive feedback loop with the fast eddies that extends the persistence of the jet shift.The importance of the lower-level baroclinicity restoration by the low-phase-speed eddies in the annular modes is further demonstrated in sensitivity runs, in which surface friction on eddies is increased to selectively damp the low-phase-speed eddies. For simulations in which the low-phase-speed eddies become inactive, the leading mode of the zonal wind variability shifts from the position fluctuation to a pulsing of the jet intensity. Further studies indicate that the response of the lower-level baroclinicity to the zonal wind anomalies caused by the low-phase-speed eddies can be crucial in maintaining the annular mode-like variations.

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Section: Summary and Discussionsupporting

confidence: 91%

Annular Mode–Like Variation in a Multilayer Quasigeostrophic Model

Zhang

Yang

Nie

et al. 2012

Journal of the Atmospheric Sciences

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“…Following Blanco‐Fuentes and Zurita‐Gotor [], we investigate the driving of low‐frequency baroclinicity variability by analyzing the relations between baroclinicity and its forcing terms in the vertically integrated thermodynamic equation (vertical integrals are denoted with angle brackets ⟨⟩):

\frac{\partial (⟨⟩, \overset{true¯}{θ_{y}})}{\partial t} = prefix- \frac{\partial}{a \partial φ} ((), \frac{1}{normalcos φ} \frac{\partial (⟨⟩, \overset{true¯}{v^{'} θ^{'}}) normalcos φ}{a \partial φ}) - \frac{\partial}{a \partial φ} (⟨⟩, \overset{ω}{true} Θ_{p}) + other terms

…”

Section: Resultssupporting

confidence: 88%

“…We group all other terms together with the diabatic heating and any discretization errors into a residue. Blanco‐Fuentes and Zurita‐Gotor [] project spatially all the above terms on the leading EOF of baroclinicity variability, which has dipolar structure and is highly correlated with SAM. Here we project instead on the baroclinicity pattern congruent with the heat flux variability, obtained regressing

(⟨⟩, \overset{true¯}{θ_{y}}) ((),, y, t)

on BAM.…”

Section: Resultssupporting

confidence: 88%

Low‐frequency suppression of Southern Hemisphere tropospheric eddy heat flux

Zurita‐Gotor

2017

Geophysical Research Letters

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This paper analyzes the variability of the zonal cospectrum of Southern Hemisphere tropospheric eddy heat flux in reanalysis data. It is shown that the reduced spectral power of low‐frequency eddy heat flux variability largely arises from the anticorrelation in the eddy heat transports by different zonal wave numbers. Although the most plausible mechanism for this relation invokes baroclinicity as a mediating agent, this hypothesis does not seem to be supported by the observed variability of baroclinicity. Low‐frequency baroclinicity variability is primarily driven by the mean meridional circulation, with only a minor role for the eddy heat flux.

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“…They found evidence of baroclinicity driving the barotropic flow and very large coherence between the eddy heat and momentum fluxes at low frequency, with the momentum fluxes leading the variability, see Figure e. The covariability between the barotropic and baroclinic components of the wind is also a robust result in observations (Blanco‐Fuentes & Zurita‐Gotor, ) and comprehensive climate models. In Figure d the large correlation between the long‐lag decay rates of (barotropic) jet anomalies and baroclinicity is shown for a selection of CMIP5 models, so that models with more persistent jet variability also tend to have more persistent baroclinicity.…”

Section: The Midlatitude Circulationmentioning

confidence: 73%

Model Hierarchies for Understanding Atmospheric Circulation

Maher

Gerber

Medeiros

et al. 2019

Reviews of Geophysics

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In this review, we highlight the complementary relationship between simple and comprehensive models in addressing key scientific questions to describe Earth's atmospheric circulation. The systematic representation of models in steps, or hierarchies, connects our understanding from idealized systems to comprehensive models and ultimately the observed atmosphere. We define three interconnected principles that can be used to characterize the model hierarchies of the atmosphere. We explore the rich diversity within the governing equations in the dynamical hierarchy, the ability to isolate and understand atmospheric processes in the process hierarchy, and the importance of the physical domain and resolution in the hierarchy of scale. We center our discussion on the large‐scale circulation of the atmosphere and its interaction with clouds and convection, focusing on areas where simple models have had a significant impact. Our confidence in climate model projections of the future is based on our efforts to ground the climate predictions in fundamental physical understanding. This understanding is, in part, possible due to the hierarchies of idealized models that afford the simplicity required for understanding complex systems.

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The driving of baroclinic anomalies at different timescales

Cited by 13 publications

References 22 publications

Annular Mode–Like Variation in a Multilayer Quasigeostrophic Model

Annular Mode–Like Variation in a Multilayer Quasigeostrophic Model

Low‐frequency suppression of Southern Hemisphere tropospheric eddy heat flux

Model Hierarchies for Understanding Atmospheric Circulation

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