Type Classification of Sudden Stratospheric Warming Based on Pre- and Postwarming Periods

Abstract In existing literature, sudden stratospheric warming (SSW) events have been typically defined as displacement or split types. Detailed reexamination of SSW evolution has revealed that an SSW event often alters its type before and after the central day of the warming event. On the basis of this observation, we objectively define three types of SSW using wave amplitude: displacement–displacement (DD) type, displacement–split (DS) type, and split–split (SS) type. The geopotential height (GPH) amplitude of zonal wavenumbers 1 and 2 averaged over 55°–65°N at 10 hPa was used as a criterion for the classification. If the amplitude of zonal wavenumber 1 is larger (smaller) than that of wavenumber 2 before and after the central day of SSW, the event is regarded as a DD (SS) type. If the amplitude of zonal wavenumber 1 is larger than that of wavenumber 2 before the central day but is smaller after that day, the event is regarded as a DS type. The above classification algorithm has been applied to both reanalysis data and model results. We observe that conventional split-type SSW events identified by previous studies can be categorized as either DS- or SS-type events, each type of which exhibits different evolution characteristics. In particular, they are distinctively different during the prewarming period. In the SS type, the characteristics of the conventional split type are more obvious, and the features that differ from those of the DD type are the most robust. The model results generally resemble the reanalysis data, particularly in the DD cases.

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Composite analysis of a major sudden stratospheric warming

Annales Geophysicae ◽

10.5194/angeo-33-783-2015 ◽

2015 ◽

Vol 33 (6) ◽

pp. 783-788 ◽

Cited By ~ 5

Author(s):

K. Hocke ◽

M. Lainer ◽

A. Schanz

Keyword(s):

Geopotential Height ◽

Reanalysis Data ◽

Composite Analysis ◽

Stratospheric Warming ◽

Analysis Method ◽

Sudden Stratospheric Warming ◽

Reliable Prediction ◽

The Mean ◽

The Individual ◽

Ozone Column

Abstract. We present the characteristics of a major sudden stratospheric warming (SSW) by using the composite analysis method and ERA Interim reanalysis data from 1979 to 2014. The anomalies of the parameters total ozone column density (TOC), temperature (T), potential vorticity (PV), eastward wind (u), northward wind (v), vertical wind (w), and geopotential height (z) are derived with respect to the ERA Interim climatology (mean seasonal behaviour 1979 to 2014). The composites are calculated by using the time series of the anomalies and the central dates of 20 major SSWs. Increases of up to 90 Dobson units are found for polar TOC after the SSW. Polar TOC remains enhanced until the summer after the major SSW. Precursors of the SSW are a negative TOC anomaly 3 months before the SSW and enhanced temperature at 10 hPa at mid-latitudes about 1 month before the SSW. Eastward wind at 1 hPa is decreased at mid-latitudes about 1 month before the SSW. The 1 hPa geopotential height level is increased by about 500 m during the month before the SSW. These features are significant at the 2σ level for the mean behaviour of the ensemble of the major SSWs. However, knowledge of these precursors may not lead to a reliable prediction of an individual SSW since the variability of the individual SSWs and the polar winter stratosphere is large.

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Comparing Sudden Stratospheric Warming Definitions in Reanalysis Data*

Journal of Climate ◽

10.1175/jcli-d-15-0004.1 ◽

2015 ◽

Vol 28 (17) ◽

pp. 6823-6840 ◽

Cited By ~ 25

Author(s):

Froila M. Palmeiro ◽

David Barriopedro ◽

Ricardo García-Herrera ◽

Natalia Calvo

Keyword(s):

Seasonal Cycle ◽

Winter Season ◽

Reanalysis Data ◽

Sudden Stratospheric Warming ◽

Pronounced Increase ◽

Future Studies ◽

Common Peak ◽

Before And After ◽

The Mean ◽

Large Case

Abstract Sudden stratospheric warmings (SSWs) are characterized by a pronounced increase of the stratospheric polar temperature during the winter season. Different definitions have been used in the literature to diagnose the occurrence of SSWs, yielding discrepancies in the detected events. The aim of this paper is to compare the SSW climatologies obtained by different methods using reanalysis data. The occurrences of Northern Hemisphere SSWs during the extended-winter season and the 1958–2014 period have been identified for a suite of eight representative definitions and three different reanalyses. Overall, and despite the differences in the number and exact dates of occurrence of SSWs, the main climatological signatures of SSWs are not sensitive to the considered reanalysis. The mean frequency of SSWs is 6.7 events decade−1, but it ranges from 4 to 10 events, depending on the method. The seasonal cycle of events is statistically indistinguishable across definitions, with a common peak in January. However, the multidecadal variability is method dependent, with only two definitions displaying minimum frequencies in the 1990s. An analysis of the mean signatures of SSWs in the stratosphere revealed negligible differences among methods compared to the large case-to-case variability within a given definition. The stronger and more coherent tropospheric signals before and after SSWs are associated with major events, which are detected by most methods. The tropospheric signals of minor SSWs are less robust, representing the largest source of discrepancy across definitions. Therefore, to obtain robust results, future studies on stratosphere–troposphere coupling should aim to minimize the detection of minor warmings.

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Winter 2018 major sudden stratospheric warming impact on midlatitude mesosphere from microwave radiometer measurements

10.5194/acp-2018-1361 ◽

2019 ◽

Cited By ~ 2

Author(s):

Yuke Wang ◽

Valery Shulga ◽

Gennadi Milinevsky ◽

Aleksey Patoka ◽

Oleksandr Evtushevsky ◽

...

Keyword(s):

Zonal Wind ◽

Geopotential Height ◽

Microwave Radiometer ◽

Recovery Phase ◽

The Arctic ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Easterly Wind ◽

The Impact ◽

Midlatitude Mesosphere

Abstract. The impact of a major sudden stratospheric warming (SSW) in the Arctic in February 2018 on the mid-latitude mesosphere was investigated by performing microwave radiometer measurements of carbon monoxide (CO) and zonal wind above Kharkiv, Ukraine (50.0° N, 36.3° E). The mesospheric peculiarities of this SSW event were observed using recently designed and installed microwave radiometer in East Europe for the first time. The data from the ERA-Interim and NCEP–NCAR reanalyses, as well as the Aura Microwave Limb Sounder measurements, have been also used. Microwave observations of the daily CO profiles in January–March 2018 allowed retrieving mesospheric zonal wind at 70–85 km (below the winter mesopause) over the Kharkiv site. The reverse of the mesospheric westerly from about 10 m s−1 to the easterly wind of about −10 m s−1 around 10 February has been registered. Local microwave observations in the NH midlatitudes combined with reanalysis data show wide ranges of daily variability in CO, zonal wind, temperature and geopotential height in the mesosphere and stratosphere during the SSW 2018. Oscillations in the vertical CO profile, zonal wind, and geopotential height during the SSW, stratopause disappearance after the SSW onset and strong CO and westerly wind peaks at the start of the SSW recovery phase have been observed. The observed CO variability can be explained by vertical and horizontal air mass redistribution due to planetary wave activity with the replacement of the CO-rich air by CO-poor air and vice versa, in agreement with other studies. The results of microwave measurements of CO and zonal wind in the midlatitude mesosphere at 70–85 km altitudes, which still is not adequately covered by ground-based observations, are useful for improving our understanding of the SSW impacts in this region.

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Dynamical evolution of a minor sudden stratospheric warming in the Southern Hemisphere in 2019

10.5194/acp-2021-444 ◽

2021 ◽

Author(s):

Guangyu Liu ◽

Toshihiko Hirooka ◽

Nawo Eguchi ◽

Kirstin Krüger

Keyword(s):

Southern Hemisphere ◽

Vertical Component ◽

Polar Vortex ◽

Planetary Waves ◽

High Latitudes ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Zonal Wavenumber ◽

Westerly Winds ◽

A Minor

Abstract. This study analyzes the Japanese 55-year Reanalysis (JRA-55) dataset from 2002 to 2019 to examine the sudden stratospheric warming event that occurred in the Southern Hemisphere (SH) in 2019 (hereafter referred to as SSW2019). Strong warming at the polar cap and decelerated westerly winds were observed, but since there was no reversal of westerly winds to easterly winds at 60° S in the middle to lower stratosphere, the SSW2019 is classified as a minor warming event. The results show that quasi-stationary planetary waves of zonal wavenumber 1 developed during the SSW2019. The strong vertical component of the Eliassen–Palm flux with zonal wavenumber 1 is indicative of pronounced propagation of planetary waves to the stratosphere. The wave driving in September 2019 shows that the values are larger than those of the major SSW event in 2002 (hereafter referred to as SSW2002). Since there was no pronounced preconditioning (as in SSW2002) and the polar vortex was already strong before the SSW2019 occurred, a major disturbance of the polar vortex was unlikely to have taken place. The strong wave driving in SSW2019 occurred in high latitudes. Waveguides (i.e., positive values of the refractive index) are found at high latitudes in the upper stratosphere during the warming period, which provided favorable conditions for quasi-stationary planetary waves to propagate upward and poleward.

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Does the coupling of the mesospheric semiannual oscillation with the quasi-biennial oscillation provide predictability of Antarctic sudden stratospheric warmings?

10.5194/acp-2020-1237 ◽

2021 ◽

Author(s):

Viktoria J. Nordström ◽

Annika Seppälä

Keyword(s):

Lower Stratosphere ◽

Reanalysis Data ◽

Stratospheric Warming ◽

Early Winter ◽

Sudden Stratospheric Warming ◽

Quasi Biennial Oscillation ◽

Westerly Winds ◽

Low Latitudes ◽

Biennial Oscillation ◽

Semiannual Oscillation

Abstract. During September 2019 there was a sudden stratospheric warming over Antarctica, which brought disruption to the usually stable winter vortex. The mesospheric winds reversed and temperatures in the stratosphere rose by over 50 K. Whilst this was only the second SSW in the Southern Hemisphere (SH), the other having occurred in 2002, its Northern counterpart experiences about six per decade. Currently, an amplification of atmospheric waves during winter is thought to trigger SSWs. However, our understanding remains incomplete, especially in regards to its occurrence in the SH. Here, we investigate the interaction of two equatorial atmospheric modes, the Quasi Biennial Oscillation (QBO) and the Semiannual Oscillation (SAO) during the SH winters of 2019 and 2002. Using MERRA-2 reanalysis data we find that the two modes interact at low latitudes during their easterly phases in the early winter, forming a zero wind line that stretches from the lower stratosphere into the mesosphere. This influences the meridional wave guide, resulting in easterly momentum being deposited in the mesosphere throughout the polar winter, reducing the magnitude of the westerly winds. As the winter progresses these features descend into the stratosphere, until SSW conditions are reached. We find similar behaviour in two other years leading to delayed dynamical disruptions later in the spring. The timing and magnitude of the SAO and the extent of the upper stratospheric easterly QBO signal, that results in the SAO-QBO interaction, was found to be unique in these years, when compared to the years with a similar QBO phase. We propose that this early winter behaviour may be a key physical process in decelerating the mesospheric winds which may precondition the Southern atmosphere for a SSW. Thus the early winter equatorial upper stratosphere-mesosphere together with the polar mesosphere may provide critical early clues to an imminent SH SSW.

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Whole Atmosphere Coupling during the September 2019 Antarctic Sudden Stratospheric Warming

10.5194/egusphere-egu21-8857 ◽

2021 ◽

Author(s):

Yosuke Yamazaki ◽

Yasunobu Miyoshi

Keyword(s):

Large Scale ◽

Lower Thermosphere ◽

Upper Atmosphere ◽

The Arctic ◽

Electron Content ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Total Electron ◽

Total Electron Content Data ◽

Zonal Wavenumber

A sudden stratospheric warming (SSW) is a large-scale meteorological phenomenon, which is most commonly observed in the Arctic region during winter months. In September 2019, a rare SSW occurred in the Antarctic region, providing a unique opportunity to study its impact on the middle and upper atmosphere. Geopotential height measurements by the Microwave Limb Sounder aboard NASA's Aura satellite reveal a burst of westward-propagating quasi-6-day wave (Q6DW) with zonal wavenumber 1 in the mesosphere and lower thermosphere following the SSW. At this time, ionospheric data from ESA's Swarm satellite constellation mission show prominent 6-day variations in the daytime equatorial electrojet intensity and low-latitude plasma densities. The whole atmosphere model GAIA reproduces salient features of the middle and upper atmosphere response to the SSW. GAIA results suggest that the observed ionospheric 6-day variations are not directly driven by the Q6DW but driven indirectly through tidal modulations by the Q6DW. An analysis of global total electron content data reveals signatures of secondary waves arising from the nonlinear interaction between the Q6DW and tides.

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SAO-QBO Coupling before the 2019 and 2002 Southern Sudden Stratospheric Warmings

10.5194/egusphere-egu21-9318 ◽

2021 ◽

Author(s):

Viktoria Nordström ◽

Annika Seppälä

Keyword(s):

Lower Stratosphere ◽

Reanalysis Data ◽

Stratospheric Warming ◽

Early Winter ◽

Sudden Stratospheric Warming ◽

Quasi Biennial Oscillation ◽

Westerly Winds ◽

Low Latitudes ◽

Biennial Oscillation ◽

Semiannual Oscillation

During September 2019 there was a sudden stratospheric warming over Antarctica, which brought disruption to the usually stable winter vortex. The mesospheric winds reversed and temperatures in the stratosphere rose by over 50~K. Whilst this was only the second SSW in the Southern Hemisphere (SH), the other having occurred in 2002, its Northern counterpart experiences about six per decade. Currently, an amplification of atmospheric waves during winter is thought to trigger SSWs. Our understanding, however, remains incomplete, especially with regards to its occurrence in the SH.&#160;Here, we investigate the interaction of two equatorial atmospheric modes, the Quasi Biennial Oscillation (QBO) and the Semiannual Oscillation (SAO) during the SH winters of 2019 and 2002. Using MERRA-2 reanalysis data we find that the two modes interact at low latitudes during their easterly phases in the early winter, forming a zero wind line that stretches from the lower stratosphere into the mesosphere. This influences the meridional wave guide, resulting in easterly momentum being deposited in the mesosphere throughout the polar winter, reducing the magnitude of the westerly winds. As the winter progresses these features descend into the stratosphere, until SSW conditions are reached. We find similar behaviour in two other years leading to delayed dynamical disruptions later in the spring. The timing and magnitude of the SAO and the extent of the upper stratospheric easterly QBO signal, that results in the SAO-QBO interaction, was found to be unique in these years, when compared to the years with a similar QBO phase.&#160;We propose that this early winter behaviour may be a key physical process in decelerating the mesospheric winds which may precondition the Southern atmosphere for a SSW. Thus the early winter equatorial upper stratosphere-mesosphere together with the polar mesosphere may provide critical early clues to an imminent SH SSW.

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Nonmigrating tidal activity related to the sudden stratospheric warming in the Arctic winter of 2003/2004

Annales Geophysicae ◽

10.5194/angeo-27-975-2009 ◽

2009 ◽

Vol 27 (3) ◽

pp. 975-987 ◽

Cited By ~ 24

Author(s):

D. Pancheva ◽

P. Mukhtarov ◽

B. Andonov

Keyword(s):

Middle Atmosphere ◽

Detailed Comparison ◽

The Arctic ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Double Peak ◽

Zonal Wavenumber ◽

Nonmigrating Tides ◽

Tide Interaction ◽

Diurnal Tides

Abstract. This paper is focused on the nonmigrating tidal activity seen in the SABER/TIMED temperatures that is related to the major sudden stratospheric warming (SSW) taking place in the Arctic winter of 2003/2004. The emphasis is on the nonmigrating diurnal tides observed in the stratosphere and lower mesosphere which is usually accepted to be insignificant in comparison with that in the upper mesosphere and thermosphere. By using different independent spectral methods we found a significant amplification in December–January of the following nonmigrating 24-h tides: zonally symmetric (s=0), eastward propagating with zonal wavenumber 1 (E1), and westward propagating with zonal wavenumbers 2 and 3 (W2 and W3) tides. It has been found that the double peak nonmigrating tidal amplifications located in the stratosphere (~40 km) and in the lower mesosphere (~70 km) are a consequence of the maintained hydrostatic relation. By detailed comparison of the evolution and spatial structure of the nonmigrating diurnal tides with those of the migrating diurnal tide and stationary planetary waves (SPWs) evidence for a SPW-migrating tide interaction as a source of nonmigrating tides has been presented. Therefore, the nonmigrating 24-h tides turn out to be an important component of the middle atmosphere dynamics during the major SSW in the Arctic winter of 2003/2004.

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Defining Sudden Stratospheric Warming in Climate Models: Accounting for Biases in Model Climatologies

Journal of Climate ◽

10.1175/jcli-d-16-0465.1 ◽

2017 ◽

Vol 30 (14) ◽

pp. 5529-5546 ◽

Cited By ~ 17

Author(s):

Junsu Kim ◽

Seok-Woo Son ◽

Edwin P. Gerber ◽

Hyo-Seok Park

Keyword(s):

Climate Models ◽

Climate Model ◽

Coupled Model ◽

Polar Vortex ◽

Reanalysis Data ◽

Cmip5 Models ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Intercomparison Project ◽

Wave Flux

A sudden stratospheric warming (SSW) is often defined as zonal-mean zonal wind reversal at 10 hPa and 60°N. This simple definition has been applied not only to the reanalysis data but also to climate model output. In the present study, it is shown that the application of this definition to models can be significantly influenced by model mean biases (i.e., more frequent SSWs appear to occur in models with a weaker climatological polar vortex). To overcome this deficiency, a tendency-based definition is proposed and applied to the multimodel datasets archived for phase 5 of the Coupled Model Intercomparison Project (CMIP5). In this definition, SSW-like events are defined by sufficiently strong vortex deceleration. This approach removes a linear relationship between SSW frequency and intensity of the climatological polar vortex in the CMIP5 models. The models’ SSW frequency instead becomes significantly correlated with the climatological upward wave flux at 100 hPa, a measure of interaction between the troposphere and stratosphere. Lower stratospheric wave activity and downward propagation of stratospheric anomalies to the troposphere are also reasonably well captured. However, in both definitions, the high-top models generally exhibit more frequent SSWs than the low-top models. Moreover, a hint of more frequent SSWs in a warm climate is found in both definitions.

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Propagation of gravity waves and its effects on pseudomomentum flux in a sudden stratospheric warming event

10.5194/egusphere-egu21-1909 ◽

2021 ◽

Author(s):

In-Sun Song ◽

Changsup Lee ◽

Hye-Yeong Chun ◽

Jeong-Han Kim ◽

Geonhwa Jee ◽

...

Keyword(s):

Ray Tracing ◽

Gravity Waves ◽

Lower Thermosphere ◽

Upper Atmosphere ◽

Lower Atmosphere ◽

Horizontal Wind ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Curvature Effects ◽

Zonal Wavenumber

Effects of realistic propagation of gravity waves (GWs) on distribution of GW pseudomomentum fluxes are explored using a global ray-tracing model for the 2009 sudden stratospheric warming (SSW) event. Four-dimensional (4D;&#160;x&#8211;z&#160;and&#160;t) and two-dimensional (2D;&#160;z&#160;and&#160;t) results are compared for various parameterized pseudomomentum fluxes. In ray-tracing equations, refraction due to horizontal wind shear and curvature effects are found important and comparable to one another in magnitude. In the 4D, westward pseudomomentum fluxes are enhanced in the upper troposphere and northern stratosphere due to refraction and curvature effects around fluctuating jet flows. In the northern polar upper mesosphere and lower thermosphere, eastward pseudomomentum fluxes are increased in the 4D. GWs are found to propagate more to the upper atmosphere in the 4D, since horizontal propagation and change in wave numbers due to refraction and curvature effects can make it more possible that GWs elude critical level filtering and saturation in the lower atmosphere. GW focusing effects occur around jet cores, and ray-tube effects appear where the polar stratospheric jets vary substantially in space and time. Enhancement of the structure of zonal wavenumber 2 in pseudomomentum fluxes in the middle stratosphere begins from the early stage of the SSW evolution. An increase in pseudomomentum fluxes in the upper atmosphere is present even after the onset in the 4D. Significantly enhanced pseudomomentum fluxes, when the polar vortex is disturbed, are related to GWs with small intrinsic group velocity (wave capture), and they would change nonlocally nearby large-scale vortex structures without substantially changing local mean flows.

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