How Well do we Understand the Dynamics of Stratospheric Warmings?

McIntyre, Michael E.

doi:10.2151/jmsj1965.60.1_37

Cited by 282 publications

(218 citation statements)

References 95 publications

Supporting

Mentioning

200

Contrasting

Order By: Relevance

“…The boundary between polar vortex and midlatitude air is indicated by the position of the strong horizontal gradient of Epv on an isentropic surface [Mcintyre, 1982;Palmer, 1983, 1984] We view the Epv data in an alternative way, as first presented by Mcintyre and Palmer [1984] and Butchart and Remsberg [1986]. We began by contouring the Epv values on an equivalent area map projection.…”

Section: Methodology Determining the Vortex Boundary Region And Vortementioning

confidence: 99%

An objective determination of the polar vortex using Ertel's potential vorticity

Nash¹,

Newman²,

Rosenfield³

et al. 1996

J. Geophys. Res.

565

746

View full text Add to dashboard Cite

Abstract. We have developed objective criteria for choosing the location of the northern hemisphere polar vortex boundary region and the onset and breakup dates of the vortex. By determining the distribution of Ertel's potential vorticity (Epv) on equivalent latitudes, we define the vortex edge as the location of maximum gradient of Epv constrained by the location of the maximum wind jet calculated along Epv isolines. We define the vortex boundary region to be at the local maximum convex and concave curvature in the Epv distribution surrounding the edge. We have determined that the onset and breakup dates of the vortex on the 450 K isentropic surface occur when the maximum wind speed calculated along Epv isolines rises above and falls below approximately 15.2 m s-•. We use 1992-1993 as a test case to study the onset and breakup periods, and we find that the increase of polar vortex Epv values is associated with the dominance of the term in the potential vorticity equation involving the movement of air through the surface due to the diabatic circulation. We also find that the decrease is associated with the dominance of the term involving radiatively induced changes in the stability of the atmosphere.

show abstract

Section: Methodology Determining the Vortex Boundary Region And Vortementioning

confidence: 99%

An objective determination of the polar vortex using Ertel's potential vorticity

Nash¹,

Newman²,

Rosenfield³

et al. 1996

J. Geophys. Res.

565

746

View full text Add to dashboard Cite

show abstract

“…Owing to the constraints of strong stable stratification and rapid rotation, the largescale motions of planetary atmospheres and oceans may, to a first approximation, be characterized by their quasi-two-dimensional motion. Zonal jets arise inevitably when potential vorticity is mixed horizontally over limited latitudinal regions, regardless of the form of the mixing (McIntyre 1982;Dritschel & McIntyre 2008;Dunkerton & Scott 2008;McIntyre 2008;Scott 2010). Potential vorticity mixing by planetary-scale Rossby waves in the polar winter stratosphere has already been discussed by McIntyre (1982), who noted the tendency for mixing to weaken potential vorticity gradients in a 'surf zone', while intensifying them on either side, resulting in an intensification of the polar night jet.…”

Section: Introductionmentioning

confidence: 91%

The structure of zonal jets in geostrophic turbulence

2012

View full text Add to dashboard Cite

The structure of zonal jets arising in forced-dissipative, two-dimensional turbulent flow on the β-plane is investigated using high-resolution, long-time numerical integrations, with particular emphasis on the late-time distribution of potential vorticity. The structure of the jets is found to depend in a simple way on a single nondimensional parameter, which may be conveniently expressed as the ratio L Rh /L ε , where L Rh = √ U/β and L ε = (ε/β 3 ) 1/5 are two natural length scales arising in the problem; here U may be taken as the r.m.s. velocity, β is the background gradient of potential vorticity in the north-south direction, and ε is the rate of energy input by the forcing. It is shown that jet strength increases with L Rh /L ε , with the limiting case of the potential vorticity staircase, comprising a monotonic, piecewise-constant profile in the north-south direction, being approached for L Rh /L ε ∼ O(10). At lower values, eddies created by the forcing become sufficiently intense to continually disrupt the steepening of potential vorticity gradients in the jet cores, preventing strong jets from developing. Although detailed features such as the regularity of jet spacing and intensity are found to depend on the spectral distribution of the forcing, the approach of the staircase limit with increasing L Rh /L ε is robust across a variety of different forcing types considered.

show abstract

“…For La Nina winters during the easterly QBO (EQBO) phase, an anomalous stratospheric temperature increase is observed in early winter, while a nonrobust signal is observed during La Nina winters under westerly QBO (WQBO) condi tions (Garfinkel and Hartmann 2007). Likewise, the occurrence of SSWs can also be modulated by the QBO, as SSW occurrence could be favored during EQBO winters (McIntyre 1982), and delayed to mid-and late winter under WQBO conditions (Lu et al 2008). Therefore, within a short record and by using a low threshold, the interference with the SSWs and QBO signals could lead to an uncertain La Nina response.…”

Section: Introductionmentioning

confidence: 99%

The Stratospheric Pathway of La Niña

2016

View full text Add to dashboard Cite

A Northern Hemisphere (NH) polar stratospheric pathway for La Nina events is established during win tertime based on reanalysis data for the 1958-2012 period. A robust polar stratospheric response is observed in the NH during strong La Nina events, characterized by a significantly stronger and cooler polar vortex. Significant wind anomalies reach the surface, and a robust impact on the North Atlantic-European (NAE) region is observed. A dynamical analysis reveals that the stronger polar stratospheric winds during La Nina winters are due to reduced upward planetary wave activity into the stratosphere. This finding is the result of destructive interference between the climatological and the anomalous La Nina tropospheric stationary eddies over the Pacific-North American region.In addition, the lack of a robust stratospheric signature during La Nina winters reported in previous studies is investigated. It is found that this is related to the lower threshold used to detect the events, which signature is consequently more prone to be obscured by the influence of other sources of variability. In particular, the occurrence of stratospheric sudden warmings (SSWs), partly linked to the phase of the quasi-biennial oscil lation, modulates the observed stratospheric signal. In the case of La Nina winters defined by a lower threshold, a robust stratospheric cooling is found only in the absence of SSWs. Therefore, these results highlight the importance of using a relatively restrictive threshold to define La Nina events in order to obtain a robust surface response in the NAE region through the stratosphere.

show abstract

How Well do we Understand the Dynamics of Stratospheric Warmings?

Cited by 282 publications

References 95 publications

An objective determination of the polar vortex using Ertel's potential vorticity

An objective determination of the polar vortex using Ertel's potential vorticity

The structure of zonal jets in geostrophic turbulence

The Stratospheric Pathway of La Niña

Contact Info

Product

Resources

About