Suppressed eddy driving during southward excursions of the North Atlantic jet on synoptic to seasonal time scales

Madonna, Erica; Li, Camille; Wettstein, J. J.

doi:10.1002/asl.937

Cited by 13 publications

(11 citation statements)

References 88 publications

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“…For example, in the North Atlantic sector one may expect the climatological co-existence of an eddydriven jet and a subtropical jet to correspond to high d and θ states and the rarer merged jet conditions (e.g. Harnik et al, 2014;Madonna et al, 2019) to correspond to lower d and θ values. However, zonal asymmetries linked to land-sea contrast and orography are more prominent than in the SH (e.g.…”

Section: Discussionmentioning

confidence: 99%

A dynamical systems characterization of atmospheric jet regimes

et al. 2021

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Abstract. Atmospheric jet streams are typically separated into primarily “eddy-driven” (or polar-front) jets and primarily “thermally driven” (or subtropical) jets. Some regions also display “merged” jets, resulting from the (quasi-)collocation of the regions of eddy generation with the subtropical jet. The different locations and driving mechanisms of these jets arise from very different underlying mechanisms and result in very different jet characteristics. Here, we link the current understanding of dynamical jet maintenance mechanisms, mostly arising from conceptual or idealized models, to the phenomena observed in reanalysis data. We specifically focus on developing a unitary analysis framework grounded in dynamical systems theory, which may be applied to both idealized models and reanalysis, as well as allowing for direct intercomparison. Our results illustrate the effectiveness of dynamical systems indicators to diagnose jet regimes.

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Section: Discussionmentioning

confidence: 99%

A dynamical systems characterization of atmospheric jet regimes

et al. 2021

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“…In addition, earlier studies suggest that there is further intra-seasonal structure in jet variability, such as preferred transitions (Franzke et al 2011;Novak et al 2015), which are only indirectly represented in the Markov model. There is also evidence that thermal processes can play a crucial role in driving jet transitions (Novak et al 2015), particularly for the southern regime (Madonna et al 2019). As these are effectively distinct from the eddy-driven processes associated with higher levels of persistence, it is possible that this is a source of IFS jet latitude skill not represented in the Markov model.…”

Section: Discussionmentioning

confidence: 99%

Jet latitude regimes and the predictability of the North Atlantic Oscillation

Strommen

2020

Quart J Royal Meteoro Soc

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In recent years, numerical weather prediction models have begun to show notable levels of skill at predicting the average winter North Atlantic Oscillation (NAO) when initialised one month ahead. At the same time, these model predictions exhibit unusually low signal-to-noise ratios, in what has been dubbed a 'signal-to-noise paradox'. We analyse both the skill and signal-to-noise ratio of the Integrated Forecast System (IFS), the European Center for Medium-range Weather Forecasts (ECMWF) model, in an ensemble hindcast experiment. Specifically, we examine the contribution to both from the regime dynamics of the North Atlantic eddy-driven jet. This is done by constructing a statistical model which captures the predictability inherent to to the trimodal jet latitude system, and fitting its parameters to reanalysis and IFS data. Predictability in this regime system is driven by interannual variations in the persistence of the jet latitude regimes, which determine the preferred state of the jet. We show that the IFS has skill at predicting such variations in persistence: because the position of the jet strongly influences the NAO, this automatically generates skill at predicting the NAO. We show that all of the skill the IFS has at predicting the winter NAO over the period 1980-2010 can be attributed to its skill at predicting regime persistence in this way. Similarly, the tendency of the IFS to underestimate regime persistence can account for the low signal-to-noise ratio, giving a possible explanation for the signal-to-noise paradox. Finally, we examine how external forcing drives variability in jet persistence, as well as highlight the role played by transient baroclinic eddy feedbacks to modulate regime persistence.

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“…ENSO impacts the winter Arctic stratosphere, with a generally weaker (stronger) polar vortex during EN (LN) (e.g., Sassi et al, 2004;García-Herrera et al, 2006;Manzini et al, 2006;Manzini, 2009;Bell et al, 2009;Cagnazzo and Manzini, 2009;Garfinkel and Hartmann, 2008;Iza et al, 2016); for an overview see Domeisen et al (2019). While observations and models generally agree on the sign of the winter mean stratospheric response, changes in the frequency of sudden stratospheric warmings (SSWs) are less robust (e.g., Butler and Polvani, 2011;Garfinkel et al, 2012;Polvani et al, 2017;Domeisen et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Nonlinearity in the tropospheric pathway of ENSO to the North Atlantic

Jiménez‐Esteve

Domeisen

2020

Weather Clim. Dynam.

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Abstract. The El Niño–Southern Oscillation (ENSO) can exert a remote impact on North Atlantic and European (NAE) winter climate. This teleconnection is driven by the superposition and interaction of different influences, which are generally grouped into two main pathways, namely the tropospheric and stratospheric pathways. In this study, we focus on the tropospheric pathway through the North Pacific and across the North American continent. Due to the possible nonstationary behavior and the limited time period covered by reanalysis datasets, the potential nonlinearity of this pathway remains unclear. In order to address this question, we use a simplified physics atmospheric model forced with seasonally varying prescribed sea surface temperatures (SST) following the evolution of different ENSO phases with linearly varying strength at a fixed location. To isolate the tropospheric pathway the zonal mean stratospheric winds are nudged towards the model climatology. The model experiments indicate that the tropospheric pathway of ENSO to the North Atlantic exhibits significant nonlinearity with respect to the tropical SST forcing, both in terms of the location and amplitude of the impacts. For example, strong El Niño leads to a significantly stronger impact on the North Atlantic Oscillation (NAO) than a La Niña forcing of the same amplitude. For La Niña forcings, there is a saturation in the response, with no further increase in the NAO impact even when doubling the SST forcing, while this is not the case for El Niño. These findings may have important consequences for long-range prediction of the North Atlantic and Europe.

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Suppressed eddy driving during southward excursions of the North Atlantic jet on synoptic to seasonal time scales

Cited by 13 publications

References 88 publications

A dynamical systems characterization of atmospheric jet regimes

A dynamical systems characterization of atmospheric jet regimes

Jet latitude regimes and the predictability of the North Atlantic Oscillation

Nonlinearity in the tropospheric pathway of ENSO to the North Atlantic

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