How Can Increasing Temperatures In Polar Regions Affect Climate All Across Earth?

Weather events 10–l kilometers above Globe's surface, in the atmospheric layer called the stratosphere, bear upon weather on the ground as well as atmospheric condition hundreds of kilometers in a higher place. Experiments demonstrate that resolving stratospheric dynamics enables forecasters to predict surface weather condition farther into the future, particularly during winter in the Northern Hemisphere [Tripathi et al., 2022]. Thus, meteorologists looking to better their curt- and long-term weather condition forecasts are seeking authentic models representing the mode stratospheric disturbances propagate downward into the troposphere, the atmospheric layer closest to Earth's surface.

Chief among these disturbances are common events called sudden stratospheric warmings (SSWs). During SSWs, stratospheric temperatures can fluctuate by more than 50°C over a thing of days.

Coupling processes and atmospheric variability that occur during sudden stratospheric warming events. — Fig. 1. Schematic of the coupling processes and atmospheric variability that occur during sudden stratospheric warming events. Cerise and blue circles denote regions of warming and cooling, respectively.

Contempo research has conclusively shown the being of a strong connection betwixt SSWs and extensive changes throughout Earth'due south atmosphere. These changes can impact atmospheric chemical science, temperatures, winds, neutral (nonionized particle) and electron densities, and electric fields (Effigy 1), and they extend from the surface to the thermosphere (Figure 2) and across both hemispheres. These changes span regions that scientists had not previously considered to exist continued.

Fig. 2. Vertical contour of atmospheric temperature indicating the different layers of the atmosphere.

Agreement these coupling mechanisms has practical importance: SSWs open the door for improved tropospheric and space weather forecasting capabilities. The implications extend non merely to weather forecasting hither on the surface but also to greater agreement of chemical processes in the temper, the sources of adverse effects on satellite navigation systems (eastward.grand., GPS) and telecommunication, and possibly even the study of atmospheres on other planets.

How Sudden Stratospheric Warmings Brainstorm

SSWs were first detected in the 1950s, when observations using balloon-borne instruments called radiosondes revealed that temperatures in the Northern Hemisphere wintertime stratosphere go through periods of rapid increase [Scherhag, 1952]. These periods spanned several days and were followed by a decrease toward typical climatological values over the next 1–3 weeks.

Farther enquiry showed that despite their name, SSWs actually beginning in the troposphere. Matsuno [1971] proposed a mechanism for the occurrence of SSWs that is still considered largely valid today: At altitudes of less than x kilometers above Earth'southward surface, planetary-scale waves form and propagate upward into the stratosphere, where they dissipate. This leads to a weakening of the polar vortex, a confined region of potent due east winds that form during winter at high latitudes. As the polar vortex weakens, polar stratospheric temperatures increase.

SSW Patterns

The planetary waves that bulldoze the formation of SSWs tend to have larger amplitudes in the Northern Hemisphere compared with the Southern Hemisphere. This is partly considering of differences in the distributions of mountains, country, and sea in the hemispheres—tropospheric planetary waves are fed past temperature contrasts between state and body of water as well every bit mountains that channel wind menstruum, factors more than prevalent in the north. Thus, SSWs occur primarily in the Northern Hemisphere, although a single strong SSW in the Southern Hemisphere was observed in September 2002.

Although the magnitude of SSWs can vary, scientists are particularly keen to understand very strong midwinter warmings, referred to as "major" warmings. A variety of definitions exist, but the criteria for what constitutes a major warming in the Northern Hemisphere oft include the reversal from eastward to west of the longitudinal mean winds at 60°N latitude and about 30 kilometers in altitude.

Major SSWs occur in the Northern Hemisphere winter about 6 times per decade [Charlton and Polvani, 2007], depending upon the long-term variations in tropospheric and stratospheric winds, such as those driven by the El Niño–Southern Oscillation, quasi-biennial oscillation, and solar activity [Labitzke, 1987].

Surface Effects and Weather Prediction

Hemisphere-calibration weather patterns in the wintertime Northern Hemisphere troposphere and stratosphere are associated with changes in an index called the Northern Annular Style (NAM) [Thompson and Wallace, 1998]. In the troposphere, the NAM is characterized by a pressure anomaly over the polar region, with an contrary-signed anomaly most fifty°–55°N. That is, high-pressure anomalies over the North Pole are coupled with low-pressure anomalies farther south and vice versa. This pattern is related to stronger eastward winds during positive NAM phases (i.eastward., for a negative polar pressure anomaly) and westward wind anomalies during negative NAM phases. In the stratosphere, the NAM describes the force of the polar vortex. Negative NAM phases are associated with weak stratospheric polar vortices, like those that occur during SSWs.

NAM anomalies often move downward from the stratosphere to the tropopause (the boundary between the troposphere and the stratosphere) over the course of about 10 days and can then significantly alter extratropical weather patterns during the following 2 months. Knowledge of this downwards movement can extend the range of weather forecasts.

SSWs tin can increase the probability of record-breaking cold temperatures and snow in eastern North America.

Outside the tropics, an SSW tin can displace extratropical cyclonic storm tracks toward the equator, among other consequences. This displacement increases the probability that storms will pass over the United Kingdom and southern Europe, and information technology increases the probability of record-breaking common cold temperatures and snowfall in eastern North America [Kidston et al., 2022]. Although atmospheric reanalyses and climate model simulations clearly illustrate the downward propagation of the NAM anomalies, nosotros do non yet fully sympathize the mechanism responsible for the stratospheric control of tropospheric conditions patterns.

The downwards influence of SSWs extends even to the ocean by providing a persistent forcing to surface winds, which modulate large-scale ocean circulation [Reichler et al., 2022]. Still, unlike the relatively short term atmospheric furnishings, SSWs contribute to variability in the ocean on timescales of 5–10 years. Such variability on longer timescales arises considering of the clustering of SSW occurrences, leading to a consistent, multiyear forcing at the ocean surface.

Upwardly and Outward

Stratospheric wind changes during SSWs kicking off a chain of events that pb to anomalies in the stratosphere and up into the next layer, the mesosphere, in both hemispheres. The stratospheric circulation changes during SSWs modulate the spectrum of atmospheric waves that propagate upwardly into the mesosphere, leading to changes in the daily average wind speeds and temperatures in the upper mesosphere and lower thermosphere (80–120 kilometers in a higher place the surface).

The mesospheric wind changes are related to the ways that winds in the stratosphere influence the filtering of atmospheric gravity waves. The mesospheric anomalies oftentimes, although not always, initially appear a week or more prior to the peak stratospheric disturbances. This timing gives the advent that the SSW anomalies propagate downward all the way from the mesosphere to the troposphere, although nosotros do not presently know whether the mesosphere has whatever control over stratospheric variability.

Warming of the Southern Hemisphere (summer) polar mesosphere as well occurs during SSWs. This warming is related to wave-driven circulation changes in the Northern Hemisphere, which atomic number 82 to a warming of the tropical mesosphere. The contradistinct temperature slope between the tropics and the southern pole alters the midlatitude summer circulation, changing the filtering of atmospheric gravity waves. With a different gravity wave spectrum reaching the mesosphere, polar summertime mesosphere temperatures increase [Körnich and Becker, 2010]. This, in turn, modulates the germination of polar mesospheric, or noctilucent, clouds [Karlsson et al., 2007].

Much of the high-altitude variability is driven past a phenomenon called atmospheric tides. Like body of water tides, these are periodic, global-calibration oscillations in the temper based on the 24-hour solar day and the furnishings of the Lord's day and the Moon on the temper. Changes in stratosphere–mesosphere winds during SSWs pb to a change in atmospheric tides in both the Northern and Southern Hemispheres, demonstrating the global influence of SSWs on the mesosphere.

We as well see surprisingly big changes in modes of the gravitationally driven lunar tide. Although generally relatively pocket-sized, during SSWs the lunar tide meets or even exceeds the aamplitude of the usually much larger thermally driven solar atmospheric tides [Pedatella et al., 2022].

Chemistry Effects

Effects from SSWs are not limited to warming and cooling mechanisms. The variability in the stratosphere and mesosphere likewise modifies the atmospheric chemistry in these regions. This variability includes altering the distribution of atmospheric trace gases, including stratospheric ozone.

In the stratosphere, the descending motility of air within the polar vortex leads to a sharp slope in trace gas concentrations across the vortex edge: The vortex border is essentially a barrier between large trace gas concentrations inside the vortex and small concentrations outside the vortex or vice versa. The vortex breakdown during SSWs removes this bulwark, increasing the mixing of air between midlatitudes and the polar region. This leads to more homogeneous concentrations throughout the Northern Hemisphere stratosphere during and after SSWs. In addition, SSW-induced temperature changes tin can change chemic reaction rates, which is particularly important for upper stratospheric ozone.

The send of gases to a lower location in the atmosphere can increase the destruction of ozone.

Following certain SSW events, the polar stratopause (the boundary between the stratosphere and the mesosphere) re-forms at an distance of 70–80 kilometers, which is approximately twenty kilometers higher than its usual position. Interaction between the wave forcing and mean winds causes the stratopause and potent moving ridge forcing to descend in altitude. These changes cause chemical species that typically reside in the upper mesosphere to be transported downward into the lower mesosphere and upper stratosphere during the weeks following an SSW. This downwardly transport results in anomalously big concentrations of, for instance, nitrogen oxides (NO _x ) and carbon monoxide (CO) in the lower mesosphere and upper stratosphere. The transport of these gases to a lower location in the temper has implications for the chemical science in the polar winter stratosphere, including enhanced levels of NO _x that increment the destruction of ozone.

The Space Weather Connexion

Space weather condition—which describes conditions in the area between the Globe and the Sun—isn't determined by the Sun alone, despite popular impressions. SSWs are a considerable source of variability in Earth'southward thermosphere and ionosphere and are thus an of import component of nearly-Earth space atmospheric condition.

This is especially true in the equatorial and depression-latitude ionosphere, where loftier ionospheric conductivity in the low-latitude equatorial region causes the most significant SSW-induced variability. SSW events modify large-scale electron density structures within about 20° of the geomagnetic equator in a phenomenon known as the equatorial ionization bibelot [Chau et al., 2022]. The electron density variability during SSWs is of a magnitude like to that of a moderate geomagnetic storm [Goncharenko et al., 2010], demonstrating that SSWs are a potentially of import contributor to adverse space weather condition.

The tidal changes during SSWs additionally change the equatorial electrojet, a narrow band of electric current along the geomagnetic equator at an altitude of about 100 kilometers, as well as the global solar repose current organization. Researchers take yet to determine the event that the variability of the electrical field and vertical plasma move has on the day-to-mean solar day occurrence of equatorial postsunset ionosphere irregularities. These irregularities affect advice and navigation signals, so understanding how SSWs induce electric field variability, which would enable us to better our predictions of these events, is of considerable importance.

SSWs also bulldoze variations in the composition, density, temperature, and winds of the upper thermosphere (well-nigh 400 kilometers above Globe'due south surface). On global scales, satellite elevate observations have revealed a reduction in the thermosphere density and temperature during SSWs [Yamazaki et al., 2022]. The roughly five% reduction in neutral density can accept an appreciable bear on on satellite drag and orbital debris.

Future Opportunities

The big atmospheric anomalies during SSW episodes allow a improve understanding of whole-atmosphere coupling processes. This coupling presents a practical opportunity to meliorate both atmospheric and space weather forecasting. Detailed noesis of how stratospheric anomalies influence tropospheric conditions will open the door to improved forecasts. The furnishings of SSWs on the upper atmosphere will enable scientists to ameliorate infinite weather forecasting, peculiarly for determining the day-to-day variability in the ionosphere.

Information gained from the study of coupling between Earth's atmospheric layers is potentially applicable to atmospheres of other planets.

The physical processes that contribute to the variability of the Earth's atmospheric layers likewise operate in other planetary atmospheres and define their dynamics and energy budgets. Information gained from the written report of coupling betwixt Earth's atmospheric layers is potentially applicable to atmospheres of other planets.

It is unclear what, if any, effect climate change has on the frequency of occurrence and characteristics of SSWs. Moreover, electric current definitions of SSW events may non exist appropriate in a drastically different climate [Butler et al., 2022]. But information technology is crucial to sympathise that in a complex and evolving Earth system, whatever modify in SSWs will invariably involve changes throughout the whole atmosphere.

Acknowledgments

Ideas for this article were developed during international team meetings supported past the International Infinite Science Plant (ISSI; Bern, Switzerland). The National Center for Atmospheric Research is supported by the U.S. National Science Foundation. J.50.C., C.S., and T.A.S. are partly supported past the German language Research Foundation'due south Priority Program 1788 "DynamicEarth." L.P.G. is supported past NASA through LWS grant NNX13AI62G and by U.South. NSF grant AGS-1343056. H.Southward. is partly supported by the German Research Foundation (DFG) under FOR 1898 (MS-GWaves), project SCHM 2158/5-ane (GWING). V.L.H. is supported by U.South. NSF AGS-1343031, NASA LWS NNX14AH54G, and NASA HGI NNX17AB80G. B.F. is supported past the Spanish MCINN nether grant ESP2014-54362-P and EC FEDER funds.

References

Butler, A. H., et al. (2015), Defining sudden stratospheric warmings, Bull. Am. Meteorol. Soc., 96, one,913–ane,928, https://doi.org/10.1175/BAMS-D-xiii-00173.1.

Charlton, A. J., and L. Chiliad. Polvani (2007), A new look at stratospheric sudden warmings: Part I. Climatology and modeling benchmarks, J. Clim., 20, 449–469, https://doi.org/10.1175/JCLI3996.ane.

Chau, J. 50., et al. (2012), Equatorial and low latitude ionospheric effects during sudden stratospheric warming events, Space Sci. Rev., 168, 385–417, https://doi.org/ten.1007/s11214-011-9797-5.

Goncharenko, L. P., et al. (2010), Impact of sudden stratospheric warmings on equatorial ionization anomaly, J. Geophys. Res., 115, A00G07, https://doi.org/ten.1029/2010JA015400.

Karlsson, B., H. Körnich, and J. Gumbel (2007), Show for interhemispheric stratosphere-mesosphere coupling derived from noctilucent cloud properties, Geophys. Res. Lett., 34, L16806, https://doi.org/x.1029/2007GL030282.

Kidston, J., et al. (2015), Stratospheric influence on tropospheric jet streams, storm tracks and surface atmospheric condition, Nat. Geosci., 8, 433–440, https://doi.org/ten.1038/ngeo2424.

Körnich, H., and E. Becker (2010), A simple model for the interhemispheric coupling of the middle atmosphere circulation, Adv. Infinite Res., 45, 661–668, https://doi.org/ten.1016/j.asr.2009.11.001.

Labitzke, K. (1987), Sunspots, the QBO, and the stratospheric temperature in the due north polar region, Geophys. Res. Lett., 14, 535–537, https://doi.org/10.1029/GL014i005p00535.

Matsuno, T. (1971), A dynamical model of the stratospheric sudden warming, J. Atmos. Sci., 28, ane,479–1,494, https://doi.org/10.1002/2014JA019849.

Reichler, T., et al. (2012), A stratospheric connectedness to Atlantic climate variability, Nat. Geosci., 5, 783–787, https://doi.org/x.1038/ngeo1586.

Scherhag, R. (1952), Die explosionsartige Stratosphärenerwarmung des Spätwinters 1951/52, Ber. Dtsch. Wetterdienstes, half-dozen, 51–63.

Thompson, D. Due west. J., and J. M. Wallace (1998), The Arctic oscillation signature in the winter geopotential peak and temperature fields, Geophys. Res. Lett., 25, 1,297–ane,300, https://doi.org/x.1029/98GL00950.

Tripathi, O. P., et al. (2015), The predictability of the extratropical stratosphere on monthly fourth dimension-scales and its impact on the skill of tropospheric forecasts, Q. J. R. Meteorol. Soc., 141, 987–1,003, https://doi.org/x.1002/qj.2432.

Yamazaki, Y., M. J. Kosch, and J. T. Emmert (2015), Evidence for stratospheric sudden warming furnishings on the upper thermosphere derived from satellite orbital disuse information during 1967–2013, Geophys. Res. Lett., 42, 6,180–6,188, https://doi.org/ten.1002/2015GL065395.

Author Data

N. Grand. Pedatella (electronic mail: nickp@ucar.edu), High Altitude Observatory, National Middle for Atmospheric Enquiry, Boulder, Colo.; besides at COSMIC Program Office, Academy Corporation for Atmospheric Enquiry, Boulder, Colo.; J. Fifty. Chau, Leibniz-Institute of Atmospheric Physics, University of Rostock, Kühlungsborn, Deutschland; H. Schmidt, Max Planck Institute for Meteorology, Hamburg, Germany; Fifty. P. Goncharenko, Haystack Observatory, Massachusetts Institute of Technology, Westford; C. Stolle, GFZ German Inquiry Middle for Geosciences, Potsdam; K. Hocke, University of Bern, Switzerland; V. L. Harvey, Laboratory for Atmospheric and Space Physics, Academy of Colorado Boulder; B. Funke, Instituto de Astrofísica de Andalucía, Consejo Superior de Investigaciones Científicas, Granada, Spain; and T. A. Siddiqui, GFZ German Research Heart for Geosciences, Potsdam

Citation:

Pedatella, Due north. M.,Chau, J. L.,Schmidt, H.,Goncharenko, L. P.,Stolle, C.,Hocke, K.,Harvey, 5. L.,Funke, B., and Siddiqui, T. A. (2018), How sudden stratospheric warming affects the whole temper, Eos, 99, https://doi.org/10.1029/2018EO092441. Published on 20 March 2022.

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