Climatology of the Stratospheric Polar Vortex and Planetary Wave Breaking

Abstract The major stratospheric sudden warming (SSW) of January 2006 is examined using meteorological fields from Goddard Earth Observing System version 4 (GEOS-4) analyses and forecast fields from the Navy Operational Global Atmospheric Prediction System–Advanced Level Physics, High Altitude (NOGAPS-ALPHA). The study focuses on the upper tropospheric forcing that led to the major SSW and the vertical structure of the subtropic wave breaking near 10 hPa that moved low tropical values of potential vorticity (PV) to the pole. Results show that an eastward-propagating upper tropospheric ridge over the North Atlantic with its associated cold temperature perturbations (as manifested by high 360-K potential temperature surface perturbations) and large positive local values of meridional heat flux directly forced a change in the stratospheric polar vortex, leading to the stratospheric subtropical wave breaking and warming. Results also show that the anticyclonic development, initiated by the subtropical wave breaking and associated with the poleward advection of the low PV values, occurred over a limited altitude range of approximately 6–10 km. The authors also show that the poleward advection of this localized low-PV anomaly was associated with changes in the Eliassen–Palm (EP) flux from equatorward to poleward, suggesting an important role for Rossby wave reflection in the SSW of January 2006. Similar upper tropospheric forcing and subtropical wave breaking were found to occur prior to the major SSW of January 2003.

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Quantifying Asymmetric Wave Breaking and Two-Way Transport

Journal of the Atmospheric Sciences ◽

10.1175/jas3296.1 ◽

2004 ◽

Vol 61 (22) ◽

pp. 2735-2748 ◽

Cited By ~ 6

Author(s):

Noboru Nakamura

Keyword(s):

Wave Breaking ◽

Polar Vortex ◽

Effective Diffusivity ◽

The Other ◽

Stratospheric Polar Vortex ◽

Air Masses ◽

Rossby Wave Breaking ◽

Advection Diffusion Equation ◽

Extratropical Tropopause ◽

Asymmetric Wave

Abstract Effective diffusivity calculated from a scalar field that obeys the advection–diffusion equation has proved useful for estimating the permeability of unsteady boundaries of air masses such as the edge of the stratospheric polar vortex and the extratropical tropopause. However, the method does not discriminate the direction of transport—whereas some material crosses the boundary from one side to the other, some material does so in the other direction—yet the extant method concerns only the net transport. In this paper, the diagnostic is extended to allow partitioning of fluxes of mass and tracer into opposing directions. This is accomplished by discriminating the regions of “inward” and “outward” wave breaking with the local curvature of the tracer field. The utility of the new method is demonstrated for nonlinear Kelvin– Helmholtz instability and Rossby wave breaking in the stratosphere using a numerically generated tracer. The method successfully quantifies two-way transport and hence the direction of wave breaking—the predominantly equatorward breaking of Rossby waves in the extratropical middle stratosphere, for example. Isolated episodes of mixing are identified well, particularly by the mass flux that primarily arises from the tracer filaments. Comparison of different transport schemes suggests that the results are reasonably robust under a varying subgrid representation of the model.

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The Generic Nature of the Tropospheric Response to Sudden Stratospheric Warmings

Journal of Climate ◽

10.1175/jcli-d-19-0697.1 ◽

2020 ◽

Vol 33 (13) ◽

pp. 5589-5610 ◽

Cited By ~ 1

Author(s):

Ian P. White ◽

Chaim I. Garfinkel ◽

Edwin P. Gerber ◽

Martin Jucker ◽

Peter Hitchcock ◽

...

Keyword(s):

High Latitude ◽

Planetary Wave ◽

Polar Vortex ◽

Stratospheric Polar Vortex ◽

Near Surface ◽

Momentum Budget ◽

Free Running ◽

Eddy Fluxes ◽

Surface Jet ◽

Thermally Triggered

AbstractThe tropospheric response to midwinter sudden stratospheric warmings (SSWs) is examined using an idealized model. SSW events are triggered by imposing high-latitude stratospheric heating perturbations of varying magnitude for only a few days, spun off from a free-running control integration (CTRL). The evolution of the thermally triggered SSWs is then compared with naturally occurring SSWs identified in CTRL. By applying a heating perturbation, with no modification to the momentum budget, it is possible to isolate the tropospheric response directly attributable to a change in the stratospheric polar vortex, independent of any planetary wave momentum torques involved in the initiation of an SSW. Zonal-wind anomalies associated with the thermally triggered SSWs first propagate downward to the high-latitude troposphere after ~2 weeks, before migrating equatorward and stalling at midlatitudes, where they straddle the near-surface jet. After ~3 weeks, the circulation and eddy fluxes associated with thermally triggered SSWs evolve very similarly to SSWs in CTRL, despite the lack of initial planetary wave driving. This suggests that at longer lags, the tropospheric response to SSWs is generic and it is found to be linearly governed by the strength of the lower-stratospheric warming, whereas at shorter lags, the initial formation of the SSW potentially plays a large role in the downward coupling. In agreement with previous studies, synoptic waves are found to play a key role in the persistent tropospheric jet shift at long lags. Synoptic waves appear to respond to the enhanced midlatitude baroclinicity associated with the tropospheric jet shift, and preferentially propagate poleward in an apparent positive feedback with changes in the high-latitude refractive index.

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Synoptic–Dynamic Climatology of the Aleutian High

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0215.1 ◽

2018 ◽

Vol 75 (4) ◽

pp. 1271-1283 ◽

Cited By ~ 4

Author(s):

Stephen J. Colucci ◽

Thomas S. Ehrmann

Keyword(s):

Wave Breaking ◽

Geopotential Height ◽

Polar Vortex ◽

Heat Fluxes ◽

Aleutian Islands ◽

Height Anomaly ◽

Reanalysis Dataset ◽

Stratospheric Polar Vortex ◽

Geometric Moments ◽

Almost All

Abstract A climatology of the anticyclone that commonly appears over the Aleutian Islands in the wintertime Northern Hemisphere stratosphere is presented. Applying a geometric moments technique to a reanalysis dataset and updating a previously published definition, 68 Aleutian high (AH) events have been identified during 35 winter (October–March) seasons (1979/80–2013/14), or about 2 events per season. The events lasted an average of approximately 33 days. Thirteen of the 68 AH events each temporally and spatially coincided with tropospheric blocking identified with a wave-breaking definition, while 41 of the AH onsets each coincided with a persistently positive geopotential height anomaly in the troposphere. Also, 41 of the 68 AH events each coincided with or were followed by an objectively defined disturbance (split or displacement) to the stratospheric polar vortex. Finally, 47 of these disturbance events were each preceded by an AH onset, such that in almost all winters (33 out of 35), an early season AH was followed by a later-season polar vortex disturbance (PVD). Potential vorticity (PV) inversion revealed that the geopotential height rises associated with composite AH onset were forced primarily by anticyclonic PV increases in the stratosphere, with the troposphere providing a lesser contribution. Poleward eddy heat fluxes in the stratosphere preceded and especially followed composite AH onset, consistent with the findings that composite AH onset was forced primarily by anticyclonic PV increases in the stratosphere and that many AH onsets were each followed by a PVD onset.

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Wave breaking along the stratospheric polar vortex as seen in ERA-40 data

Geophysical Research Letters ◽

10.1029/2007gl029509 ◽

2007 ◽

Vol 34 (8) ◽

Cited By ~ 9

Author(s):

John T. Abatzoglou ◽

Gudrun Magnusdottir

Keyword(s):

Wave Breaking ◽

Polar Vortex ◽

Stratospheric Polar Vortex

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Preconditioning of Arctic Stratospheric Polar Vortex Shift Events

Journal of Climate ◽

10.1175/jcli-d-17-0695.1 ◽

2018 ◽

Vol 31 (14) ◽

pp. 5417-5436 ◽

Cited By ~ 11

Author(s):

Jinlong Huang ◽

Wenshou Tian ◽

Lesley J. Gray ◽

Jiankai Zhang ◽

Yan Li ◽

...

Keyword(s):

North America ◽

North Atlantic ◽

Planetary Wave ◽

Polar Vortex ◽

The Arctic ◽

Bering Strait ◽

Surface Cooling ◽

Stratospheric Polar Vortex ◽

Significant Difference ◽

Eastern North Atlantic

Abstract This study examines the preconditioning of events in which the Arctic stratospheric polar vortex shifts toward Eurasia (EUR events), North America (NA events), and the Atlantic (ATL events) using composite analysis. An increase in blocking days over northern Europe and a decrease in blocking days over the Bering Strait favor the movement of the vortex toward Eurasia, while the opposite changes in blocking days over those regions favor the movement of the vortex toward North America. An increase in blocking days over the eastern North Atlantic and a decrease in blocking days over the Bering Strait are conducive to movement of the stratospheric polar vortex toward the Atlantic. These anomalous precursor blocking patterns are interpreted in terms of the anomalous zonal wave-1 or wave-2 planetary wave fluxes into the stratosphere that are known to influence the vortex position and strength. In addition, the polar vortex shift events are further classified into events with small and large polar vortex deformation, since the two types of events are likely to have a different impact at the surface. A significant difference in the zonal wave-2 heat flux into the lower stratosphere exists prior to the two types of events and this is linked to anomalous blocking patterns. This study further defines three types of tropospheric blocking events in which the spatial patterns of blocking frequency anomalies are similar to the blocking patterns prior to EUR, NA, and ATL events, respectively, and our reanalysis reveals that the polar vortex is indeed more likely to shift toward Eurasia, North America, and the Atlantic in the presence of the above three defined tropospheric blocking events. These shifts of the polar vortex toward Eurasia, North America, and the Atlantic lead to statistically significant negative height anomalies near the tropopause and corresponding surface cooling anomalies over these three regions.

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On the role of Rossby wave breaking in the quasi‐biennial modulation of the stratospheric polar vortex during boreal winter

Quarterly Journal of the Royal Meteorological Society ◽

10.1002/qj.3775 ◽

2020 ◽

Vol 146 (729) ◽

pp. 1939-1959

Author(s):

Hua Lu ◽

Matthew H. Hitchman ◽

Lesley J. Gray ◽

James A. Anstey ◽

Scott M. Osprey

Keyword(s):

Rossby Wave ◽

Wave Breaking ◽

Polar Vortex ◽

Boreal Winter ◽

Stratospheric Polar Vortex ◽

Rossby Wave Breaking

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Intraseasonal Variability of the Zonal-Mean Extratropical Tropopause: The Role of Changes in Polar Vortex Strength and Upper-Troposphere Wave Breaking

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-15-0177.1 ◽

2016 ◽

Vol 73 (3) ◽

pp. 1383-1399 ◽

Cited By ~ 2

Author(s):

Jesús Á. Barroso ◽

Pablo Zurita-Gotor

Keyword(s):

Time Scales ◽

Wave Breaking ◽

Intraseasonal Variability ◽

Dynamical Evolution ◽

Polar Vortex ◽

Principal Component ◽

Qualitative Behavior ◽

Stratospheric Polar Vortex ◽

Anomalous Wave ◽

The Impact

Abstract A principal component analysis of the Northern Hemisphere extratropical zonal-mean tropopause variability at intraseasonal time scales is presented in this work. Wavy deformations of the tropopause dominate this variability and explain significantly more variance than changes in the extratropical-mean tropopause height. The first mode is well correlated with the zonal index. Analysis of the dynamical evolution of the modes shows that tropopause deformations are caused by anomalous wave breaking at the tropopause level occurring in a preexisting anomalous stratospheric polar vortex. Specifically, an intense (weak) polar vortex is associated with a rising (sinking) of the polar tropopause, while anomalous wave breaking in the midlatitudes produces a dipolar tropopause change that is consistent with the anomalous meridional eddy flux of quasigeostrophic potential vorticity. These two forcings operate on different time scales and can be separated when the data are filtered at high or low frequency. Baroclinic equilibration seems to play a small role in the extratropical internal tropopause variability and the impact of tropospheric and stratospheric dynamics is quantitatively similar. A similar analysis for the Southern Hemisphere extratropics displays the same qualitative behavior.

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Impact of Synoptic-Scale Wave Breaking on the NAO and Its Connection with the Stratosphere in ERA-40

Journal of Climate ◽

10.1175/2009jcli2750.1 ◽

2009 ◽

Vol 22 (20) ◽

pp. 5464-5480 ◽

Cited By ~ 19

Author(s):

Torben Kunz ◽

Klaus Fraedrich ◽

Frank Lunkeit

Keyword(s):

North Atlantic ◽

Wave Breaking ◽

Large Scale ◽

Polar Vortex ◽

Synoptic Scale ◽

Stratospheric Polar Vortex ◽

Close Link ◽

The North ◽

The North Atlantic ◽

The Impact

Abstract This observational study investigates the impact of North Atlantic synoptic-scale wave breaking on the North Atlantic Oscillation (NAO) and its connection with the stratosphere in winter, as derived from the 40-yr ECMWF Re-Analysis (ERA-40). Anticyclonic (AB) and cyclonic wave breaking (CB) composites are compiled of the temporal and spatial components of the large-scale circulation using a method for the detection of AB and CB events from daily maps of potential vorticity on an isentropic surface. From this analysis a close link between wave breaking, the NAO, and the stratosphere is found: 1) a positive feedback between the occurrence of AB (CB) events and the positive (negative) phase of the NAO is suggested, whereas wave breaking in general without any reference to AB- or CB-like behavior does not affect the NAO, though it preferably emerges from its positive phase. 2) AB strengthens the North Atlantic eddy-driven jet and acts to separate it from the subtropical jet, while CB weakens the eddy-driven jet and tends to merge both jets. 3) AB (CB) events are associated with a stronger (weaker) lower-stratospheric polar vortex, characterized by the 50-hPa northern annular mode. During persistent weak vortex episodes, significantly more frequent CB than AB events are observed concurrently with a significant negative NAO response up to 55 days after the onset of the stratospheric perturbation. Finally, tropospheric wave breaking is related to nonannular stratospheric variability, suggesting an additional sensitivity of wave breaking and, thus, the NAO to specific distortions of the stratospheric polar vortex, rather than solely its strength.

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Compensation between Resolved and Unresolved Wave Drag in the Stratospheric Final Warmings of the Southern Hemisphere

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0270.1 ◽

2015 ◽

Vol 72 (11) ◽

pp. 4393-4411 ◽

Cited By ~ 11

Author(s):

Guillermo Scheffler ◽

Manuel Pulido

Keyword(s):

Gravity Wave ◽

Southern Hemisphere ◽

Momentum Flux ◽

General Circulation ◽

Planetary Wave ◽

Polar Vortex ◽

General Circulation Models ◽

Wave Drag ◽

Stratospheric Polar Vortex ◽

Sensitivity Experiments

Abstract The role of planetary wave drag and gravity wave drag in the breakdown of the stratospheric polar vortex and its associated final warming in the Southern Hemisphere is examined using reanalyses from MERRA and a middle-atmosphere dynamical model. The focus of this work is on identifying the causes of the delay in the final breakdown of the stratospheric polar vortex found in current general circulation models. Sensitivity experiments were conducted by changing the launched momentum flux in the gravity wave drag parameterization. Increasing the launched momentum flux produces a delay of the final warming date with respect to the control integration of more than 2 weeks. The sensitivity experiments show significant interactions between planetary waves and unresolved gravity waves. The increase of gravity wave drag in the model is compensated by a strong decrease of Eliassen–Palm flux divergence (i.e., planetary wave drag). This concomitant decrease of planetary wave drag is at least partially responsible for the delay of the final warming in the model. Experiments that change the resolved planetary wave activity entering the stratosphere through artificially changing the bottom boundary flux of the model also show an interaction mechanism. Gravity wave drag responds via critical-level filtering to planetary wave drag perturbations by partially compensating them. Therefore, there is a feedback cycle that leads to a partial compensation between gravity wave and planetary wave drag.

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