What's in a Name? On the Use and Significance of the Term â•œPolar Vortexâ•š

1. The Stratospheric Polar Vortex, Tropospheric Jet Streams, and Cold Air

Outbreaks

This commentary appears in the Special Collection focusing on the Arctic stratospheric “polar vortex” in

2019/2020. But how clear are we about what constitutes a “polar vortex”? Confusion persists in the popular press

about what a polar vortex is and how polar vortices relate to extreme weather events. This confusion stems in part

from imprecise descriptions by the scientific community.

In January 2014, a cold air outbreak (CAO) set record-low minimum temperatures throughout the south central

and eastern US (e.g., Screen etal.,2015). Headlines hailed it as “the polar vortex,” and this language became

commonplace in news and popular science media. At the time, the term “polar vortex” in scientific literature

typically described the stratospheric polar vortex (see, e.g., Lillo etal.,2021; Waugh etal.,2017, for discussion

of this), but some studies used the term to describe the “tropospheric polar vortex” (e.g., Wallace etal.,2014; Yu

& Zhang,2015), in both cases often without further qualification. Waugh etal.(2017) sought to dispel confusion,

describing the stratospheric and tropospheric “circumpolar” vortices as these terms had been commonly used

in scientific literature, highlighting their differences and relationships to extreme weather events, and providing

recommendations for describing them. While this work is widely cited, the two concepts are still often confused,

including on educational websites and in climate change communication studies (e.g., Lyons etal.,2018; Shep-

herd,2016; UCAR,2021; UCDavis,2019). Even recent papers within the atmospheric science community are

Abstract Mainstream and popular science media are rife with misunderstandings about what a “polar

vortex” is. The term most aptly describes the stratospheric polar vortex, a single feature dominating the cool-

season circulation from ∼15–50km. Regional jet stream variations dominate the tropospheric circulation,

which is not well-described as a polar vortex; indeed, there is no single consistent definition of a tropospheric

polar vortex in the literature. Stratospheric polar vortex disturbances profoundly influence extreme weather

events, including cold air outbreaks (CAOs). How the stratospheric polar vortex affects tropospheric jets,

whose local excursions drive CAOs, is not fully understood. Public-facing parts of publications describing

research on this topic are not always clear about how the “polar vortex” is defined; greater clarity could improve

communications both within the community and with non-specialist audiences.

Plain Language Summary What is a “polar vortex”? The atmospheric science community most

commonly uses this term to describe the stratospheric polar vortex, a band of winds extending from about

15–50km altitude that flows around the pole of each hemisphere during their respective fall through spring

seasons. However, the term “polar vortex” has been used in mainstream media and popular science platforms to

instead describe local variations in the upper tropospheric jet streams (winds that blow most strongly between

about 8 and 13km altitude) and even individual extreme cold weather events. We argue that the term should

be used only in reference to the stratospheric polar vortex, which is a single feature that predominantly controls

dynamical and chemical variability in the winter polar stratosphere. The stratospheric polar vortex is related to

but distinct from more regional jet stream excursions and associated weather extremes; further study is needed

to fully understand these relationships.

MANNEY ET AL.

This is an open access article under

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distribution in any medium, provided the

original work is properly cited, the use is

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What's in a Name? On the Use and Significance of the Term

“Polar Vortex”

Gloria L. Manney

1,2

 , Amy H. Butler

 , Zachary D. Lawrence

4,5,6

 , Krzysztof Wargan

7,8

 , and

Michelle L. Santee



NorthWest Research Associates, Socorro, NM, USA,

New Mexico Institute of Mining and Technology, Socorro, NM,

USA,

NOAA Chemical Sciences Laboratory, Boulder, CO, USA,

Cooperative Institute for Research in Environmental

Sciences, University of Colorado, Boulder, CO, USA,

NOAA Physical Sciences Laboratory, Boulder, CO, USA,

NorthWest

Research Associates, Boulder, CO, USA,

NASA Goddard Space Flight Center, Greenbelt, MD, USA,

Science Systems and

Applications, Inc., Lanham, MD, USA,

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

Key Points:

• The stratospheric polar vortex is

a well-defined feature dominating

the cool-season circulation in each

hemisphere from ∼15–50km altitude

• The tropospheric circulation does not

constitute a single coherent structure

and is most aptly described by

regional jet stream variations

• Accuracy in defining and describing

the “polar vortex” and its effects is

key to improving understanding by

non-specialist audiences

Correspondence to:

G. L. Manney,

manney@nwra.com

Citation:

Manney, G. L., Butler, A. H., Lawrence,

Z. D., Wargan, K., & Santee, M. L.

(2022). What's in a name? On the use

and significance of the term “polar

vortex”. Geophysical Research Letters,

49, e2021GL097617. https://doi.

org/10.1029/2021GL097617

Received 7 JAN 2022

Accepted 12 MAY 2022

Author Contributions:

Conceptualization: Gloria L. Manney,

Amy H. Butler, Zachary D. Lawrence,

Krzysztof Wargan, Michelle L. Santee

Methodology: Gloria L. Manney,

Amy H. Butler, Zachary D. Lawrence,

Krzysztof Wargan, Michelle L. Santee

Software: Gloria L. Manney

Visualization: Gloria L. Manney

Writing – original draft: Gloria L.

Manney

10.1029/2021GL097617

Special Section:

The Exceptional Arctic Polar

Vortex in 2019/2020: Causes

and Consequences

COMMENTARY

1 of 7

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not always clear about which circulation feature(s) they are discussing, and some use the term “polar vortex”

to describe synoptic-scale disturbances associated with CAOs, echoing the inaccurate usage in popular media

(e.g., Bushra & Rohli,2019,2021; Dai etal.,2021; Jiang,2021; Juzbašić etal.,2021; Kömüşcü & Oğuz,2021;

Nielsen-Gammon etal.,2021; Overland,2021; Overland & Wang,2019; Xiong etal.,2021; Zhang etal.,2021).

Sometimes the most public-facing parts of research papers (abstracts, plain language summaries, key points) do

not clearly define how the term “polar vortex” is used.

Figure1 shows characteristics of the stratospheric and tropospheric circulation on two occasions the popular

press described CAOs as a polar vortex “outbreak” or “attack,” but which were associated with very different

stratospheric polar vortex conditions. This figure shows the stratospheric polar vortex, upper tropospheric jet

streams, and the circulation that is sometimes described as a “tropospheric polar vortex” (i.e., the 2 and 3 PVU

potential vorticity (PV) contours on the 330-K isentropic surface, one possible definition discussed by Waugh

etal.,2017).

The stratospheric polar vortex is bounded by the polar night jet, a band of strong eastward winds throughout the

stratosphere that forms in fall in each hemisphere and vanishes in spring. Different diagnostics of the stratospheric

polar vortex edge (e.g., Lawrence & Manney,2018) select similar physically meaningful boundaries (Figure1a,

left, defined using a PV contour coincident with the strongest PV gradients, as in Lawrence etal.(2018)). The

stratospheric polar vortex constitutes a single feature that dominates the circulation and transport throughout the

polar stratosphere from fall through spring.

The so-called “tropospheric polar vortex,” as most often defined, exists year-round, but no single definition

uniquely identifies it or the altitude(s) at which it exists (the characteristics described herein do not depend

substantially on which of numerous definitions is used). We show one common definition (Waugh etal.,2017,

and references therein) whereby its edge follows the axis of an upper tropospheric jet on an isentropic surface in

the middle to upper troposphere. The maximum winds of these jets are very localized in altitude compared to the

stratospheric polar night jet, and they vary strongly with longitude (e.g., Manney, Hegglin, etal.,2011; Manney

etal.,2014, Figure1a). Because regional variability of discontinuous jet streams governs the extratropical trop-

ospheric circulation, “tropospheric polar vortex” definitions do not describe a single dominant circumpolar

circulation. Further confusion arises from the distinction between tropospheric “polar” (primarily eddy driven)

and “subtropical” (largely radiatively driven) jets. While some recent papers and popular science pieces identify

the “tropospheric polar vortex” with the tropospheric polar jet (e.g., Bushra & Rohli,2021; UCAR,2021; Waugh

etal.,2017), numerous studies show that tropospheric jets are not well-represented by this simplified conceptual

division but rather form a seasonally and regionally varying complex with hybrid radiatively and eddy-driven

features that is rarely continuous around the globe (S. Lee & Kim,2003; Manney etal.,2014; Spensberger &

Spengler,2020, and references therein).

These differences are reflected in windspeeds (Figures1a and1b), which peak sharply along the stratospheric

polar vortex edge; in contrast, a “tropospheric polar vortex” defined as noted above meanders through regions

of weak and strong winds, leading to a broad, flat distribution of “vortex-edge” windspeeds. Potential vorticity

gradients (indicating polar vortex strength) are consistently strong along the circumference of the stratospheric

polar vortex but have many localized maxima in small portions of the “tropospheric vortex” edge and elsewhere

in the extratropics (Figure 1c). This results in relatively stronger mean PV gradients along the stratospheric

vortex edge, versus weaker mean PV gradients and most frequent values near zero in the troposphere (Figure1d).

Further, tropospheric windspeeds (Figure1a) often show a single jet (or no strong jet) because separate tropo-

spheric polar and subtropical jets do not always exist. A “tropospheric polar vortex” might therefore follow the

polar jet in one region but the subtropical jet in another, thus traversing regimes controlled by different dynamical

processes.

The stratospheric polar vortex is critical for transport, chemical processing, confinement of processed air, and

ozone loss. Processes promoting ozone depletion are commonly analyzed from a vortex-centered perspective

because the stratospheric vortex represents a strong transport barrier, isolating air primed for ozone destruction

(e.g., Manney etal.,2020; Manney, Santee, etal.,2011; Schoeberl etal.,1992); the amount of polar ozone loss

in a given spring depends critically on the strength and coldness of the winter/spring stratospheric polar vortex.

In contrast, upper tropospheric ozone variability is dominated by regional variations in stratosphere-troposphere

exchange and the amount of lower stratospheric ozone available for transport into the troposphere (e.g., Albers

Writing – review & editing: Amy H.

Butler, Zachary D. Lawrence, Krzysztof

Wargan, Michelle L. Santee

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Figure 1.

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et al.,2018; Breeden et al., 2021; Olsen etal.,2019). Figures 1e and 1f illustrate these differences: Ozone

gradi ents change abruptly across the stratospheric polar vortex edge but are quite uniform within it. In contrast,

ozone gradients are strong in many localized regions within the “tropospheric polar vortex,” with highly varia-

ble gradients often appearing well poleward of the “vortex” edge. These characteristics are reflected in sharply

peaked ozone distributions along the stratospheric polar vortex edge and large variability in ozone along the

“tropospheric vortex” edge (Figure1f). Note that the broad change from uniform gradients to highly variable

gradients across the “tropospheric vortex edge” as defined here is a reflection of vertical ozone gradients and the

tilt of the 330-K isentropic surface in the subtropics.

Stratosphere-troposphere coupling (e.g., Baldwin & Dunkerton,2001; Kidston etal.,2015) dynamically links

variability of the polar vortex to extremes at the surface (e.g., Domeisen & Butler,2020). For example, extreme

stratospheric polar vortex disruptions (sudden stratospheric warmings, SSWs) are associated with increased risk

of mid-latitude CAOs (e.g., Baldwin etal.,2021; Butler etal.,2017; Huang etal.,2021; King etal.,2019), and

unusually strong stratospheric polar vortices are associated with anomalously high extratropical surface tempera-

tures (including heat waves and destructive wildfires) (Lawrence etal.,2020; Limpasuvan etal.,2005; Overland

& Wang,2021). Because radiative timescales are longer in the lower stratosphere, disruptions to the circulation

can persist there for weeks to months, potentially providing subseasonal-to-seasonal forecast skill for extremes

like CAOs (e.g., Domeisen etal.,2019). Using information about the stratospheric polar vortex to predict CAOs

is, however, complicated because the timing and location of individual CAOs varies significantly following

polar vortex disruptions, perhaps related to details of the stratospheric polar vortex characteristics and evolution.

Recent work suggests that Eurasian CAOs are more closely linked to SSWs, while North American CAOs are

more strongly associated with stratospheric polar vortex elongation that might or might not accompany an SSW

(e.g., Cohen, Agel, Barlow, Garfinkel, & White,2021; Kretschmer etal.,2018; S. H. Lee etal.,2019). It is worth

emphasizing that CAOs can occur during both strong and weak stratospheric polar vortex conditions (e.g., Cohen,

Agel, Barlow, Furtado, etal.,2021; S. H. Lee etal.,2019): Figure1 shows a CAO (January 2014) linked to a

strong (but distorted) stratospheric vortex and one (February 2021) following an SSW.

CAOs are often termed “polar vortex events” in the news, popular science media, and less specialized peer-re-

viewed papers (e.g., Lyons etal.,2018, on communication of climate change risks), but the dynamical processes

involved argue that they are best described as equatorward excursions of the tropospheric jets and southward

advection of cold Arctic air. These features are not generally correlated with the strength of any globally defined

“tropospheric polar vortex” (e.g., Bushra & Rohli,2021; Cellitti etal.,2006; Waugh etal.,2017), so the utility

of the latter concept in relation to CAOs is questionable. CAOs in some regions are indeed more likely, and more

likely to be severe, following SSWs (e.g., Huang etal.,2021; King etal.,2019; S. H. Lee etal.,2019), explaining

why the media often hails reports of an SSW with “the polar vortex is coming” even though an SSW actually

represents a rapid deceleration, or disappearance, of the stratospheric polar vortex winds. While the relationship

to stratospheric polar vortex disturbances can improve lead times for probabilistic forecasts of CAO occurrence,

more extensive mechanistic understanding of how stratospheric polar vortex anomalies affect regional excursions

of tropospheric jet streams is needed to further improve prediction of when and where CAOs will occur.

The term “polar vortex” is used in another way that is not directly related to any planetary-scale circumpolar

vortex, but is related to many CAOs (e.g., Lillo etal.,2021). A “tropopause polar vortex” (TPV) is a sub-synop-

tic-scale feature characterized by a deep depression of the tropopause (sometimes to near the surface) bounded by

an “Arctic jet stream” poleward of and below the tropospheric polar jet (Shapiro etal.,1987). Lillo etal.(2021)

showed that the North American CAO in late January 2019 resulted directly from a TPV moving southward from

its high-latitude origins; TPVs play a role in many (but by no means all) CAOs (e.g., Biernat etal.,2021; Papritz

etal.,2019). While the existence of yet another feature termed a “polar vortex” may engender confusion, the

direct link of these localized vortices to CAOs emphasizes the importance of local/regional circulation anomalies

(and associated jet stream excursions) to extreme weather events.

Figure 1. Characteristics of (left to right) 6 January 2014 and 16 February 2021 stratospheric and upper tropospheric circulations: (a) Windspeeds (colorfill) and two

potential vorticity (PV) contours representing the stratospheric polar vortex edge (green) and boundary of tropospheric “global” circulation (orange). (b) Windspeed

histograms along the “vortex edge” (most equatorward PV contour shown in panel (a)); vertical lines show mean around that PV contour. (c) Normalized PV gradient

magnitudes. (d) Normalized PV gradient magnitude along the “vortex edge” (hemispheric mean is 1 by definition; vertical lines as in panel (b)). (e) Normalized ozone

gradient magnitudes. (f) Normalized ozone mixing ratios along the “vortex edge” (vertical lines as in panel (b)). Cyan contours in panels (c and e) show “vortex edge”

PV. 600-K (330-K) fields are shown for stratosphere (troposphere), except windspeeds are at 345K (near level of maximum tropospheric jet stream winds). Data are

from MERRA-2 (Gelaro etal.,2017).

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Points such as those above regarding the stratospheric polar vortex have been highlighted in studies using theoret-

ical fluid-dynamical or dynamical systems approaches (e.g., Mester & Esler,2020; Scott & Dritschel,2006; Serra

etal.,2017). It is not clear that similar approaches could usefully describe what some have termed a “tropospheric

polar vortex.”

2. Best Practices for Describing the Polar Vortex

It is clearly appropriate and useful to describe the stratospheric polar vortex as dominating stratospheric cool-sea-

son variability and exerting influence on the surface on sub-seasonal to seasonal timescales, including prob-

abilistic links to extreme weather events. Jet stream excursions and related troughs and ridges are suitable for

describing the genesis and evolution of CAOs, whereas the concept of a “tropospheric polar vortex” is typically

not helpful in describing extreme weather events or elucidating their causes. We conclude:

1. The term “polar vortex” is most appropriate for describing the stratospheric polar vortex, but given its broad

use and misuse, “stratospheric” should be specified explicitly.

2. The stratospheric polar vortex is a climatological feature that exists throughout the cool seasons (though

sometimes temporarily disrupted) and thus should not be described as an “event” with a sub-seasonal time

scale.

3. The tropospheric circulation, especially in relation to extreme weather events, can most clearly be described in

relation to the tropospheric jet streams, without invoking the term “tropospheric polar vortex.” More accurate

and appropriate terminology for referring to such events would be “Arctic CAO” (or more simply a CAO) or

a “polar front.”

4. While the term “tropopause polar vortex” has been used to describe sub-synoptic scale vortices that are

sometimes linked to CAOs, local features might be more clearly described in relation to their provenance, for

example, a “Canadian tropopause vortex.”

5. Scientists should be careful in the public-facing parts of our communications (e.g., titles, abstracts, plain

language summaries, web sites) to be clear and precise about what we mean by the term “polar vortex.”

6. In communications with the media, atmospheric scientists should emphasize that stratospheric polar vortex

variability is indeed helpful in predicting CAOs and other extreme weather events, but stratospheric influence

is exerted via regional jet stream variations that cannot in themselves be called a “polar vortex.”

Further study is needed to elucidate the relationship of stratospheric polar vortex variations to underlying regional

tropospheric jet stream variations and ultimately to extreme weather events. The stratospheric polar vortex and

tropospheric jet streams play important, but distinct, roles in understanding and forecasting extreme weather

events. Accurate description of these features is thus critical to improving communication, both within the scien-

tific community and with the public, regarding events that can have profound human impacts.

Data Availability Statement

The MERRA-2 data set used here is publicly available: https://disc.gsfc.nasa.gov/datasets?project=MERRA-2

(Global Modeling and Assimilation Office (GMAO),2015).

References

Albers, J. R., Perlwitz, J., Butler, A. H., Birner, T., Kiladis, G. N., Lawrence, Z. D., etal. (2018). Mechanisms governing interannual vari-

ability of stratosphere-to-troposphere ozone transport. Journal of Geophysical Research: Atmospheres, 123(1), 234–260. https://doi.

org/10.1002/2017JD026890

Baldwin, M. P., Ayarzagüena, B., Birner, T., Butchart, N., Butler, A. H., Charlton-Perez, A. J., etal. (2021). Sudden stratospheric warmings.

Reviews of Geophysics, 59(1), e2020RG000708. https://doi.org/10.1029/2020RG000708

Baldwin, M. P., & Dunkerton, T. J. (2001). Stratospheric harbingers of anomalous weather regimes. Science, 294(5542), 581–584. https://doi.

org/10.1126/science.1063315

Biernat, K. A., Bosart, L. F., & Keyser, D. (2021). A climatological analysis of the linkages between tropopause polar vortices, cold pools,

and cold air outbreaks over the central and eastern United States. Monthly Weather Review, 149(1), 189–206. https://doi.org/10.1175/

MWR-D-20-0191.1

Breeden, M. L., Butler, A. H., Albers, J. R., Sprenger, M., & Langford, A. O. (2021). The spring transition of the North Pacific jet and its relation

to deep stratosphere-to-troposphere mass transport over western North America. Atmospheric Chemistry and Physics, 21(4), 2781–2794.

https://doi.org/10.5194/acp-21-2781-2021

Acknowledgments

We thank the Microwave Limb Sounder

team at JPL, especially Brian Knosp, Luis

Millán, and Ryan Fuller, for data manage-

ment, processing, and analysis support;

NASA's GMAO for the MERRA-2 data

set; Ken Minschwaner, Jessica George,

and Kody Gray for helpful discussions;

and two anonymous reviewers for their

insightful comments. We are grateful to

B. J. Hoskins, M. E. McIntyre, and A.

W. Robertson (Hoskins etal.,1985) for

inspiring the title of this commentary.

G. L. Manney was partially supported

by the JPL Microwave Limb Sounder

team under a JPL subcontract to NWRA.

Z. D. Lawrence was partially supported

under a NWS OSTI Weeks 3–4 Project

(NA20NWS4680051). G. L. Manney and

Z. D. Lawrence were partially supported

by NSF Climate and Large-scale

Dynamics Grant #2015906. K. Wargan

was supported by NASA's GMAO core

funding. Work at the Jet Propulsion Labo-

ratory, California Institute of Technology,

was carried out under a contract with the

National Aeronautics and Space Adminis-

tration (80NM0018D0004).

Geophysical Research Letters

MANNEY ET AL.

10.1029/2021GL097617

6 of 7

Bushra, N., & Rohli, R. V. (2019). An objective procedure for delineating the circumpolar vortex. Earth and Space Science, 6(5), 774–783. https://

doi.org/10.1029/2019EA000590

Bushra, N., & Rohli, R. V. (2021). Relationship between atmospheric teleconnections and the Northern Hemisphere's circumpolar vortex. Earth

and Space Science, 8(9), e2021EA001802. https://doi.org/10.1029/2021EA001802

Butler, A. H., Sjoberg, J. P., Seidel, D. J., & Rosenlof, K. H. (2017). A sudden stratospheric warming compendium. Earth System Science Data,

9(1), 63–76. https://doi.org/10.5194/essd-9-63-2017

Cellitti, M. P., Walsh, J. E., Rauber, R. M., & Portis, D. H. (2006). Extreme cold air outbreaks over the United States, the polar vortex, and the

large-scale circulation. Journal of Geophysical Research, 111(D2), D02114. https://doi.org/10.1029/2005JD006273

Cohen, J. L., Agel, L., Barlow, M., Garfinkel, C. I., & White, I. (2021). Linking Arctic variability and change with extreme winter weather in the

United States. Science, 373(6559), 1116–1121. https://doi.org/10.1126/science.abi9167

Cohen, J. L., Agel, L. A., Barlow, M. A., Furtado, J. C., Kretschmer, M., & Matthias, V. (2021). The “polar vortex” winter of 2013/14. AGU

Fall Meeting.

Dai, G., Li, C., Han, Z., Luo, D., & Yao, Y. (2021). The nature and predictability of the East Asian extreme cold events of 2020/21. Advances in

Atmospheric Sciences. https://doi.org/10.1007/s00376-021-1057-3

Domeisen, D. I., & Butler, A. H. (2020). Stratospheric drivers of extreme events at the Earth's surface. Communications Earth & Environment,

1(1), 59. https://doi.org/10.1038/s43247-020-00060-z

Domeisen, D. I., Butler, A. H., Charlton-Perez, A. J., Ayarzagüena, B., Baldwin, M. P., Dunn-Sigouin, E., etal. (2019). The role of the strato-

sphere in subseasonal to seasonal prediction Part II: Predictability arising from stratosphere - troposphere coupling. Journal of Geophysical

Research: Atmospheres, 125(2), e2019JD030923. https://doi.org/10.1029/2019JD030923

Gelaro, R., McCarty, W., Suárez, M. J., Todling, R., Molod, A., Takacs, L., etal. (2017). The Modern-Era Retrospective analysis for Research and

Applications, version-2 (MERRA-2). Journal of Climate, 30(14), 5419–5454. https://doi.org/10.1175/JCLI-D-16-0758.1

Global Modeling and Assimilation Office (GMAO). (2015). MERRA-2 inst3_3d_asm_nv: 3d, 3-hourly,instantaneous, model-level, assimilation,

assimilated meteorological fields v5.12.4, Greenbelt, MD, USA. Goddard Earth Sciences Data and Information Services Center (GES DISC).

https://doi.org/10.5067/WWQSXQ8IVFW8

Hoskins, B. J., McIntyre, M. E., & Robertson, A. W. (1985). On the use and significance of isentropic potential vorticity maps. Quarterly Journal

of the Royal Meteorological Society, 111(470), 877–946. https://doi.org/10.1002/qj.49711147002

Huang, J., Hitchcock, P., Maycock, A. C., McKenna, C. M., & Tian, W. (2021). Northern hemisphere cold air outbreaks are more likely to be

severe during weak polar vortex conditions. Communications Earth & Environment, 2(1), 147. https://doi.org/10.1038/s43247-021-00215-6

Jiang, J. H. (2021). Polar vortex linked to atmospheric circulation at daily scale. Retrieved from https://eos.org/editor-highlights/

polar-vortex-linked-to-atmospheric-circulation-at-daily-scale?utm_campaign=ealert

Juzbašić, A., Kryjov, V. N., & Ahn, J. B. (2021). On the anomalous development of the extremely intense positive Arctic Oscillation of the

2019–2020 winter. Environmental Research Letters, 16(5), 055008. https://doi.org/10.1088/1748-9326/abe434

Kidston, J., Scaife, A. A., Hardiman, S. C., Mitchell, D. M., Butchart, N., Baldwin, M. P., & Gray, L. J. (2015). Stratospheric influence on tropo-

spheric jet streams, storm tracks and surface weather. Nature Geoscience, 8(6), 433–440. https://doi.org/10.1038/ngeo2424

King, A. D., Butler, A. H., Jucker, M., Earl, N. O., & Rudeva, I. (2019). Observed relationships between sudden stratospheric warmings and

European climate extremes. Journal of Geophysical Research: Atmospheres, 124(24), 13943–13961. https://doi.org/10.1029/2019JD030480

Kömüşcü, A. Ü., & Oğuz, K. (2021). Analysis of cold anomalies observed over Turkey during the 2018/2019 winter in relation to polar vortex and

other atmospheric patterns. Meteorology and Atmospheric Physics, 133(4), 1327–1354. https://doi.org/10.1007/s00703-021-00806-0

Kretschmer, M., Cohen, J., Mattias, V., Runge, J., & Coumou, D. (2018). The different stratospheric influence on cold-extremes in Eurasia and

North America. npj Climate and Atmospheric Science, 1, 44. https://doi.org/10.1038/s41612-018-0054-4

Lawrence, Z. D., & Manney, G. L. (2018). Characterizing stratospheric polar vortex variability with computer vision techniques. Journal of

Geophysical Research: Atmospheres, 123(3), 1510–1535. https://doi.org/10.1002/2017JD027556

Lawrence, Z. D., Manney, G. L., & Wargan, K. (2018). Reanalysis intercomparisons of stratospheric polar processing diagnostics. Atmospheric

Chemistry and Physics, 18, 13547–13579. https://doi.org/10.5194/acp-18-13547-2018

Lawrence, Z. D., Perlwitz, J., Butler, A. H., Manney, G. L., Newman, P.A., Lee, S. H., & Nash, E. R. (2020). The remarkably strong Arctic

stratospheric polar vortex of winter 2020: Links to record-breaking Arctic oscillation and ozone loss. Journal of Geophysical Research: Atmos-

pheres, 125(22). e2020JD033271. https://doi.org/10.1029/2020JD033271

Lee, S., & Kim, H.-K. (2003). The dynamical relationship between subtropical and eddy-driven jets. Journal of the Atmospheric Sciences, 60(12),

1490–1503. https://doi.org/10.1175/1520-0469(2003)060<1490:tdrbsa>2.0.co;2

Lee, S. H., Furtado, J. C., & Charlton-Perez, A. J. (2019). Wintertime North American weather regimes and the Arctic stratospheric polar vortex.

Geophysical Research Letters, 46(24), 14892–14900. https://doi.org/10.1029/2019GL085592

Lillo, S. P., Cavallo, S. M., Parsons, D. B., & Riedel, C. (2021). The role of a tropopause polar vortex in the generation of the January 2019

extreme Arctic outbreak. Journal of the Atmospheric Sciences, 78(9), 2801–2821. https://doi.org/10.1175/JAS-D-20-0285.1

Limpasuvan, V., Hartmann, D. L., Thompson, D. W. J., Jeev, K., & Yung, Y. L. (2005). Stratosphere-troposphere evolution during polar vortex

intensification. Journal of Geophysical Research: Atmospheres, 110(D24), D24101. https://doi.org/10.1029/2005JD006302

Lyons, B. A., Hasell, A., & Stroud, N. J. (2018). Enduring extremes? Polar vortex, drought, and climate change beliefs. Environmental Commu-

nication, 12(7), 876–894. https://doi.org/10.1080/17524032.2018.1520735

Manney, G. L., Hegglin, M. I., Daffer, W. H., Santee, M. L., Ray, E. A., Pawson, S., etal. (2011). Jet characterization in the upper troposphere/

lower stratosphere (UTLS): Applications to climatology and transport studies. Atmospheric Chemistry and Physics, 11(12), 6115–6137.

https://doi.org/10.5194/acp-11-6115-2011

Manney, G. L., Hegglin, M. I., Daffer, W. H., Schwartz, M. J., Santee, M. L., & Pawson, S. (2014). Climatology of upper tropospheric/lower

stratospheric (UTLS) jets and tropopauses in MERRA. Journal of Climate, 27(9), 3248–3271. https://doi.org/10.1175/jcli-d-13-00243.1

Manney, G. L., Livesey, N. J., Santee, M. L., Froidevaux, L., Lambert, A., Lawrence, Z. D., etal. (2020). Record-low Arctic stratospheric ozone

in 2020: MLS observations of chemical processes and comparisons with previous extreme winters. Geophysical Research Letters, 47(16),

e2020GL089063. https://doi.org/10.1029/2020GL089063

Manney, G. L., Santee, M. L., Rex, M., Livesey, N. J., Pitts, M. C., Veefkind, P., etal. (2011). Unprecedented Arctic ozone loss in 2011. Nature,

478(7370), 469–475. https://doi.org/10.1038/nature10556

Mester, M., & Esler, J. G. (2020). Dynamical elliptical diagnostics of the Antarctic polar vortex. Journal of the Atmospheric Sciences, 77(3),

1167–1180. https://doi.org/10.1175/JAS-D-19-0232.1

Nielsen-Gammon, J., Bolinger, R., Attard, H., Bentley, A., Brown, V., Fuhrmann, C., etal. (2021). Evaluation of the February 2021 south-central

big freeze. AGU Fall Meeting.

Geophysical Research Letters

MANNEY ET AL.

10.1029/2021GL097617

7 of 7

Olsen, M. A., Manney, G. L., & Liu, J. (2019). The ENSO and QBO impact on ozone variability and stratosphere-troposphere exchange relative

to the subtropical jets. Journal of Geophysical Research: Atmospheres, 124(13), 7379–7392. https://doi.org/10.1029/2019JD030435

Overland, J. E. (2021). Rare events in the Arctic. Climatic Change, 168(3), 27. https://doi.org/10.1007/s10584-021-03238-2

Overland, J. E., & Wang, M. (2019). Impact of the winter polar vortex on greater North America. International Journal of Climatology, 39(15),

5815–5821. https://doi.org/10.1002/joc.6174

Overland, J. E., & Wang, M. (2021). The 2020 Siberian heat wave. International Journal of Climatology, 41(S1), E2341–E2346. https://doi.

org/10.1002/joc.6850

Papritz, L., Rouges, E., Aemisegger, F., & Wernli, H. (2019). On the thermodynamic preconditioning of Arctic air masses and the role of tropo-

pause polar vortices for cold air outbreaks from Fram Strait. Journal of Geophysical Research: Atmospheres, 124(21), 11033–11050. https://

doi.org/10.1029/2019JD030570

Schoeberl, M. R., Lait, L. R., Newman, P.A., & Rosenfield, J. E. (1992). The structure of the polar vortex. Journal of Geophysical Research,

97(D8), 7859–7882. https://doi.org/10.1029/91jd02168

Scott, R. K., & Dritschel, D. G. (2006). Vortex–vortex interactions in the winter stratosphere. Journal of the Atmospheric Sciences, 63(2),

726–740. https://doi.org/10.1175/JAS3632.1

Screen, J. A., Deser, C., & Sun, L. (2015). Reduced risk of North American cold extremes due to continued Arctic sea ice loss. Bulletin of the

American Meteorological Society, 96(9), 1489–1503. https://doi.org/10.1175/BAMS-D-14-00185.1

Serra, M., Sathe, P., Beron-Vera, F., & Haller, G. (2017). Uncovering the edge of the polar vortex. Journal of the Atmospheric Sciences, 74(11),

3871–3885. https://doi.org/10.1175/JAS-D-17-0052.1

Shapiro, M. A., Hampel, T., & Krueger, A. J. (1987). The Arctic tropopause fold. Monthly Weather Review, 1152(2), 444–454. https://doi.

org/10.1175/1520-0493(1987)115<0444:TAFF>2.0.CO;2

Shepherd, M. (2016). 12 weather and climate concepts that confuse the public. Retrieved from https://www.forbes.com/sites/

marshallshepherd/2016/12/13/12-weather-and-climate-concepts-that-confuse-the-public/?sh=2943e192350b

Spensberger, C., & Spengler, T. (2020). Feature-based jet variability in the upper troposphere. Journal of Climate, 33(16), 6849–6871. https://

doi.org/10.1175/JCLI-D-19-0715.1

UCAR. (2021). Why the polar vortex keeps breaking out of the Arctic. Retrieved from https://scied.ucar.edu/learning-zone/climate-change-impacts/

why-polar-vortex-keeps-breaking-out-arctic

UCDavis. (2019). What is the polar vortex? Retrieved from https://climatechange.ucdavis.edu/climate-change-definitions/what-is-the-polar-vortex/

Wallace, J. M., Held, I. M., Thompson, D. W., Trenberth, K. E., & Walsh, J. E. (2014). Global warming and winter weather. Science, 343(6172),

729–730. https://doi.org/10.1126/science.343.6172.729

Waugh, D. W., Sobel, A. H., & Polvani, L. M. (2017). What is the polar vortex and how does it influence weather? Bulletin of the American

Meteorological Society, 98(1), 37–441. https://doi.org/10.1175/BAMS-D-15-00212.1

Xiong, X., Liu, X., Wu, W., Yang, Q., & Zhou, D. K. (2021). Polar vortex outbreak air transport: Observation using satellite IR sounder derived

ozone product and comparison with model. AGU Meeting Fall.

Yu, B., & Zhang, X. (2015). A physical analysis of the severe 2013/2014 cold winter in North America. Journal of Geophysical Research: Atmos-

pheres, 120(19), 10149–10165. https://doi.org/10.1002/2015JD023116

Zhang, X., Fu, Y., Han, Z., Overland, J. E., Rinke, A., Tang, H., etal. (2021). Extreme cold events from East Asia to North America in winter

2020/21: Comparisons, causes, and future implications. Advances in Atmospheric Sciences. https://doi.org/10.1007/s00376-021-1229-1