scholarly journals Coupling in the middle atmosphere related to the 2013 major sudden stratospheric warming

2015 ◽  
Vol 33 (3) ◽  
pp. 309-319 ◽  
Author(s):  
R. J. de Wit ◽  
R. E. Hibbins ◽  
P. J. Espy ◽  
E. A. Hennum
Keyword(s):  
Gravity Wave ◽  
Global Perspective ◽  
Coupling Mechanism ◽  
Temperature Structure ◽  
Stratospheric Warming ◽  
Mean Flow ◽  
Sudden Stratospheric Warming ◽  
High Northern Latitude ◽  
Wave Forcing ◽  
Summer Hemisphere

Abstract. The previously reported observation of anomalous eastward gravity wave forcing at mesopause heights around the onset of the January 2013 major sudden stratospheric warming (SSW) over Trondheim, Norway (63° N, 10° E), is placed in a global perspective using Microwave Limb Sounder (MLS) temperature observations from the Aura satellite. It is shown that this anomalous forcing results in a clear cooling over Trondheim about 10 km below mesopause heights. Conversely, near the mesopause itself, where the gravity wave forcing was measured, observations with meteor radar, OH airglow and MLS show no distinct cooling. Polar cap zonal mean temperatures show a similar vertical profile. Longitudinal variability in the high northern-latitude mesosphere and lower thermosphere (MLT) is characterized by a quasi-stationary wave-1 structure, which reverses phase at altitudes below ~ 0.1 hPa. This wave-1 develops prior to the SSW onset, and starts to propagate westward at the SSW onset. The latitudinal pole-to-pole temperature structure associated with the major SSW shows a warming (cooling) in the winter stratosphere (mesosphere) which extends to about 40° N. In the stratosphere, a cooling extending over the equator and far into the summer hemisphere is observed, whereas in the mesosphere an equatorial warming is noted. In the Southern Hemisphere mesosphere, a warm anomaly overlaying a cold anomaly is present, which is shown to propagate downward in time. This observed structure is in accordance with the temperature perturbations predicted by the proposed interhemispheric coupling mechanism for cases of increased winter stratospheric planetary wave activity, of which major SSWs are an extreme case. These results provide observational evidence for the interhemispheric coupling mechanism, and for the wave-mean flow interaction believed to be responsible for the establishment of the anomalies in the summer hemisphere.

scholarly journals Observations of gravity wave forcing of the mesopause region during the January 2013 major Sudden Stratospheric Warming

2014 ◽  
Vol 41 (13) ◽  
pp. 4745-4752 ◽  
Author(s):  
R. J. Wit ◽  
R. E. Hibbins ◽  
P. J. Espy ◽  
Y. J. Orsolini ◽  
V. Limpasuvan ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Mesopause Region ◽  
Wave Forcing

scholarly journals Optimizing the Definition of a Sudden Stratospheric Warming

2018 ◽  
Vol 31 (6) ◽  
pp. 2337-2344 ◽  
Author(s):  
Amy H. Butler ◽  
Edwin P. Gerber
Keyword(s):  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Systematic Analysis ◽  
Wave Forcing ◽  
Zonal Winds ◽  
Stratospheric Temperature ◽  
Stratospheric Wind ◽  
Definition Of ◽  
Access To Data ◽  
The Continuum

Various criteria exist for determining the occurrence of a major sudden stratospheric warming (SSW), but the most common is based on the reversal of the climatological westerly zonal-mean zonal winds at 60° latitude and 10 hPa in the winter stratosphere. This definition was established at a time when observations of the stratosphere were sparse. Given greater access to data in the satellite era, a systematic analysis of the optimal parameters of latitude, altitude, and threshold for the wind reversal is now possible. Here, the frequency of SSWs, the strength of the wave forcing associated with the events, changes in stratospheric temperature and zonal winds, and surface impacts are examined as a function of the stratospheric wind reversal parameters. The results provide a methodical assessment of how to best define a standard metric for major SSWs. While the continuum nature of stratospheric variability makes it difficult to identify a decisively optimal threshold, there is a relatively narrow envelope of thresholds that work well—and the original focus at 60° latitude and 10 hPa lies within this window.

scholarly journals Understanding of European Cold Extremes, Sudden Stratospheric Warming, and Siberian Snow Accumulation in the Winter of 2017/18

2020 ◽  
Vol 33 (2) ◽  
pp. 527-545 ◽  
Author(s):  
Zhuozhuo Lü ◽  
Fei Li ◽  
Yvan J. Orsolini ◽  
Yongqi Gao ◽  
Shengping He
Keyword(s):  
Snow Depth ◽  
Time Lag ◽  
Snow Accumulation ◽  
Arctic Sea Ice ◽  
Planetary Waves ◽  
Stratospheric Warming ◽  
Mean Flow ◽  
Sudden Stratospheric Warming ◽  
Cold Extremes

AbstractIt is unclear whether the Eurasian snow plays a role in the tropospheric driving of sudden stratospheric warming (SSW). The major SSW event of February 2018 is analyzed using reanalysis datasets. Characterized by predominant planetary waves of zonal wave 2, the SSW developed into a vortex split via wave–mean flow interaction. In the following two weeks, the downward migration of zonal-mean zonal wind anomalies was accompanied by a significant transition to the negative phase of the North Atlantic Oscillation, leading to extensive cold extremes across Europe. Here, we demonstrate that anomalous Siberian snow accumulation could have played an important role in the 2018 SSW occurrence. In the 2017/18 winter, snow depths over Siberia were much higher than normal. A lead–lag correlation analysis shows that the positive fluctuating snow depth anomalies, leading to intensified “cold domes” over eastern Siberia (i.e., in a region where the climatological upward planetary waves maximize), precede enhanced wave-2 pulses of meridional heat fluxes (100 hPa) by 7–8 days. The snow–SSW linkage over 2003–19 is further investigated, and some common traits among three split events are found. These include a time lag of about one week between the maximum anomalies of snow depth and wave-2 pulses (100 hPa), high sea level pressure favored by anomalous snowpack, and a ridge anchoring over Siberia as precursor of the splits. The role of tropospheric ridges over Alaska and the Urals in the wave-2 enhancement and the role of Arctic sea ice loss in Siberian snow accumulation are also discussed.

scholarly journals Investigation on the abnormal quasi-two day wave activities during sudden stratospheric warming period of January 2006

2017 ◽  
Author(s):  
Sheng-Yang Gu ◽  
Xiankang Dou ◽  
Dora Pancheva
Keyword(s):  
Planetary Wave ◽  
Phase Speed ◽  
Dominant Mode ◽  
Wave Number ◽  
Stratospheric Warming ◽  
Mean Flow ◽  
Sudden Stratospheric Warming ◽  
Reanalysis Dataset ◽  
Short Period ◽  
Zonal Wave Number

Abstract. The quasi-two day wave (QTDW) during austral summer period usually coincides with sudden stratospheric warming (SSW) event in the winter hemisphere, while the influences of SSW on QTDW are not totally understood. In this work, the anomalous QTDW activities during the major SSW period of January 2006 are further investigated on the basis of hourly Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) reanalysis dataset. Strong westward QTDW with zonal wave number 2 (W2) is identified besides the conventionally dominant mode of zonal wave number 3 (W3). Meanwhile, the W3 peaks with an extremely short period of ~ 42 hours. Compared with January 2005 with no evident SSW, we found that the zonal mean zonal wind in the summer mesosphere is enhanced during 2006. The enhanced summer easterly sustains critical layers for W2 and short-period W3 QTDWs with larger phase speed, which facilitate their amplification through wave-mean flow interaction. The stronger summer easterly also provides stronger barotropic/baroclinic instabilities and thus larger forcing for the amplification of QTDW. The inter-hemispheric coupling induced by strong winter stratospheric planetary wave activities during SSW period is most likely responsible for the enhancement of summer easterly. Besides, we found that the nonlinear interaction between W3 QTDW and the wave number 1 stationary planetary wave (SPW1) may also contribute to the source of W2 at middle and low latitudes in the mesosphere.

scholarly journals Tropospheric circulation response to sudden stratospheric warming observed in January 2013

2020 ◽  
pp. 241-254
Author(s):  
A.I. Pogoreltsev ◽  
O.G. Aniskina ◽  
A.Y. Kanukhina ◽  
T.S. Ermakova ◽  
A.I. Ugryumov ◽  
...  
Keyword(s):  
Winter Season ◽  
Wave Activity ◽  
Cold Weather ◽  
Synoptic Situation ◽  
Dynamical Regime ◽  
Stratospheric Warming ◽  
Mean Flow ◽  
Sudden Stratospheric Warming ◽  
Middle Latitudes ◽  
Tropospheric Circulation

Analysis of the dynamical regime changes in the stratosphere during different phases of the Sudden Stratospheric Warming (SSW) that has been observed in January 2013 is presented. The different mechanisms of SSW influence on the tropospheric circulation through the stationary planetary waves (SPWs) reflection and/or increase in SPWs activity due to nonlinear interaction with the mean flow and their subsequent propagation into the troposphere are discussed. Three-dimensional wave activity flux and its divergence are determined using the UK Met Office data; the synoptic situation and its changes during the SSW events are analyzed. The wave activity penetrates downward from stratosphere into the troposphere and can affect weather processes during the SSW and right afterwards. It is this time that polar anticyclones can be formed at high latitudes, which quickly go southward along meridional directions and then deviate to the East at middle latitudes. Interestingly, the locations of polar anticyclone formations and subsequent displacements correspond to the regions of maximal horizontal wave activity fluxes connected with stratospheric processes. The results obtained allow us to suggest that accounting of stratospheric processes and their influence on the troposphere in winter season can improve the middle-range forecast of anticyclone formation and cold weather events at middle latitudes.

scholarly journals Strengthening of the Tropopause Inversion Layer during the 2009 Sudden Stratospheric Warming: A MERRA-2 Study

2016 ◽  
Vol 73 (5) ◽  
pp. 1871-1887 ◽  
Author(s):  
Krzysztof Wargan ◽  
Lawrence Coy
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Inversion Layer ◽  
Vertical Component ◽  
Circulation Model ◽  
Static Stability ◽  
Stratospheric Warming ◽  
Residual Circulation ◽  
Sudden Stratospheric Warming ◽  
Wave Forcing

Abstract The behavior of the tropopause inversion layer (TIL) during the 2009 sudden stratospheric warming (SSW) is analyzed using NASA’s Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), and short-term simulations with the MERRA-2 general circulation model. Consistent with previous studies, it is found that static stability in a shallow layer above the polar tropopause sharply increases following the SSW, leading to a strengthening of the high-latitude TIL. Simultaneously, the height of the thermal tropopause decreases by around 1 km. Similar behavior is also detected during other major SSW events between the years 2004 and 2013. Using an ensemble of general circulation model forecasts initialized from MERRA-2, it is demonstrated that the primary cause of the strengthening of the TIL is an increased convergence of the vertical component of the stratospheric residual circulation in response to an SSW-induced acceleration of the mean downward motion between 75° and 90°N. In addition, ~6% of the strengthening in 2009 is attributed to an enhanced anticyclonic circulation at the tropopause. A preliminary analysis indicates that during other recent SSW events there was a significant increase in the convergence of the vertical residual wind velocity throughout the middle and lower stratosphere. The static stability increase simulated by the model during the 2009 SSW is 60%–80% of that seen in MERRA-2. The underestimate is traced back to a tendency for the forecasts to underestimate the resolved planetary wave forcing on the stratosphere compared to the reanalysis.

scholarly journals The Role of Eddy-Eddy Interactions in Sudden Stratospheric Warming Formation

2019 ◽  
Author(s):  
Erik Anders Lindgren ◽  
Aditi Sheshadri
Keyword(s):  
General Circulation ◽  
Lower Stratosphere ◽  
Circulation Model ◽  
Wave Number ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Wave Forcing ◽  
Wave Numbers ◽  
Tropospheric Heating ◽  
Wave Flux

Abstract. The effects of eddy-eddy interactions on sudden stratospheric warming formation are investigated using an idealized atmospheric general circulation model, in which tropospheric heating perturbations of zonal wave numbers 1 and 2 are used to produce planetary scale wave activity. Eddy-eddy interactions are removed at different vertical extents of the atmosphere in order to examine the sensitivity of stratospheric circulation to local changes in eddy-eddy interactions. We show that the effects of eddy-eddy interactions on sudden warming formation, including sudden warming frequencies, are strongly dependent on the wave number of the tropospheric forcing and the vertical levels where eddy-eddy interactions are removed. Significant changes in sudden warming frequencies are evident when eddy-eddy interactions are removed even when the lower stratospheric wave forcing does not change, highlighting the fact that the upper stratosphere is not a passive recipient of wave forcing from below. We find that while eddy-eddy interactions are required in the troposphere and lower stratosphere to produce displacements when wave number 2 heating is used, both splits and displacements can be produced without eddy-eddy interactions in the troposphere and lower stratosphere when the model is forced by wave number 1 heating. We suggest that the relative strengths of wave numbers 1 and 2 vertical wave flux entering the stratosphere largely determine the split and displacement ratios when wave number 2 forcing is used, but not wave number 1.

scholarly journals Sensitivity of middle atmospheric temperature and circulation in the UIUC GCM to the treatment of subgrid-scale gravity-wave breaking

2006 ◽  
Vol 6 (5) ◽  
pp. 9085-9121 ◽  
Author(s):  
F. Yang ◽  
M. E. Schlesinger ◽  
E. V. Rozanov ◽  
N. Andronova ◽  
V. A. Zubov ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
General Circulation ◽  
Lower Thermosphere ◽  
Atmospheric Temperature ◽  
Mean Flow ◽  
Quasi Biennial Oscillation ◽  
Warm Bias ◽  
Wave Forcing ◽  
Budget Analysis

Abstract. The sensitivity of the middle atmospheric temperature and circulation to the treatment of mean-flow forcing due to breaking gravity waves at the sub-grid scale was investigated using the University of Illinois at Urbana-Champaign 40-layer General Circulation Model (GCM). The gravity-wave forcing was represented either by Rayleigh friction or by a detailed parameterization scheme with different sets of parameters. The modeled middle atmospheric temperature and circulation exhibit large sensitivity to the parameterized sub-grid gravity-wave forcing. A large warm bias of up to 50°C was found in the model's summer upper mesosphere and lower thermosphere. This warm bias was caused by the inability of the GCM to simulate the reversal of the zonal winds from easterly to westerly crossing the mesopause in the summer hemisphere. Attempts were made to slow down the easterly winds near the mesopause and to reduce the warm bias. The GCM was able to realistically simulate the semi-annual oscillation in the upper stratosphere and lower mesosphere with observational constraints on certain parameter values, but failed to simulate the quasi-biennial oscillation in any of the experiments. Budget analysis indicates that in the middle atmosphere the forces that act to maintain a steady zonal-mean zonal wind are primarily those associated with the meridional transport circulation and breaking gravity waves. Contributions from the interaction of the model-resolved eddies with the mean flow are secondary.

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