Stratosphere–Troposphere Coupling and Links with Eurasian Land Surface Variability

Abstract A diagnostic of Northern Hemisphere winter extratropical stratosphere–troposphere interactions is presented to facilitate the study of stratosphere–troposphere coupling and to examine what might influence these interactions. The diagnostic is a multivariate EOF combining lower-stratospheric planetary wave activity flux in December with sea level pressure in January. This EOF analysis captures a strong linkage between the vertical component of lower-stratospheric wave activity over Eurasia and the subsequent development of hemisphere-wide surface circulation anomalies, which are strongly related to the Arctic Oscillation. Wintertime stratosphere–troposphere events picked out by this diagnostic often have a precursor in autumn: years with large October snow extent over Eurasia feature strong wintertime upward-propagating planetary wave pulses, a weaker wintertime polar vortex, and high geopotential heights in the wintertime polar troposphere. This provides further evidence for predictability of wintertime circulation based on autumnal snow extent over Eurasia. These results also raise the question of how the atmosphere will respond to a modified snow cover in a changing climate.

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Tropospheric forcing of the boreal polar vortex splitting in January 2003

Annales Geophysicae ◽

10.5194/angeo-28-2133-2010 ◽

2010 ◽

Vol 28 (11) ◽

pp. 2133-2148 ◽

Cited By ~ 9

Author(s):

D. H. W. Peters ◽

P. Vargin ◽

A. Gabriel ◽

N. Tsvetkova ◽

V. Yushkov

Keyword(s):

Rossby Wave ◽

Planetary Wave ◽

Winter Season ◽

Polar Vortex ◽

Wave Activity ◽

The Arctic ◽

Stratospheric Warming ◽

Sudden Stratospheric Warming ◽

Stratospheric Polar Vortex ◽

Wave Trains

Abstract. The dynamical evolution of the relatively warm stratospheric winter season 2002–2003 in the Northern Hemisphere was studied and compared with the cold winter 2004–2005 based on NCEP-Reanalyses. Record low temperatures were observed in the lower and middle stratosphere over the Arctic region only at the beginning of the 2002–2003 winter. Six sudden stratospheric warming events, including the major warming event with a splitting of the polar vortex in mid-January 2003, have been identified. This led to a very high vacillation of the zonal mean circulation and a weakening of the stratospheric polar vortex over the whole winter season. An estimate of the mean chemical ozone destruction inside the polar vortex showed a total ozone loss of about 45 DU in winter 2002–2003; that is about 2.5 times smaller than in winter 2004–2005. Embedded in a winter with high wave activity, we found two subtropical Rossby wave trains in the troposphere before the major sudden stratospheric warming event in January 2003. These Rossby waves propagated north-eastwards and maintained two upper tropospheric anticyclones. At the same time, the amplification of an upward propagating planetary wave 2 in the upper troposphere and lower stratosphere was observed, which could be caused primarily by those two wave trains. Furthermore, two extratropical Rossby wave trains over the North Pacific Ocean and North America were identified a couple of days later, which contribute mainly to the vertical planetary wave activity flux just before and during the major warming event. It is shown that these different tropospheric forcing processes caused the major warming event and contributed to the splitting of the polar vortex.

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Volcanic activity sparks the Arctic Oscillation

Scientific Reports ◽

10.1038/s41598-021-94935-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Weizheng Qu ◽

Fei Huang ◽

Jinping Zhao ◽

Ling Du ◽

Yong Cao

Keyword(s):

Volcanic Activity ◽

Volcanic Eruption ◽

Arctic Oscillation ◽

Polar Vortex ◽

Volcanic Eruptions ◽

The Arctic ◽

Vortex System ◽

Significant Fluctuation ◽

The Arctic Oscillation

AbstractThe parasol effect of volcanic dust and aerosol caused by volcanic eruption results in the deepening and strengthening of the Arctic vortex system, thus stimulating or strengthening the Arctic Oscillation (AO). Three of the strongest AOs in more than a century have been linked to volcanic eruptions. Every significant fluctuation of the AO index (AOI = ΔH_middle latitudes − ΔH_Arctic) for many years has been associated with a volcanic eruption. Volcanic activity occurring at different locations in the Arctic vortex circulation will exert different effects on the polar vortex.

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Final Sudden Stratospheric Warmings and the memory of the stratosphere

10.5194/egusphere-egu21-9970 ◽

2021 ◽

Author(s):

Alain Hauchecorne ◽

Chantal Claud ◽

Philippe Keckhut

Keyword(s):

Zonal Wind ◽

Planetary Wave ◽

Middle Atmosphere ◽

Temperature Anomaly ◽

Polar Vortex ◽

Wave Activity ◽

Late Winter ◽

Easterly Wind ◽

Weather Forecasts ◽

Stratospheric Circulation

Sudden Stratospheric Warming (SSW) is the most spectacular dynamic event occurring in the middle atmosphere. It can lead to a warming of the winter polar stratosphere by a few tens of K in one to two weeks and a reversal of the stratospheric circulation from wintertime prevailing westerly winds to easterly winds similar to summer conditions. This strong modification of the stratospheric circulation has consequences for several applications, including the modification of the stratospheric infrasound guide. Depending on the date of the SSW, the westerly circulation can be re-established if the SSW occurs in mid-winter or the summer easterly circulation can be definitively established if the SSW occurs in late winter. In the latter case it is called Final Warming (FW). Each year, it is possible to define the date of the FW as the date of the final inversion of the zonal wind at 60&#176;N - 10 hPa . If the FW is associated with a strong peak of planetary wave activity and a rapid increase in polar temperature, it is classified as dynamic FW. If the transition to the easterly wind is smooth without planetary wave activity, the FW is classified as radiative.The analysis of the ERA5 database, which has recently been extended to 1950 (71 years of data), allowed a statistical analysis of the evolution of the stratosphere in winter. The main conclusions of this study will be presented :- the state of the polar vortex in a given month is anticorrelated with its state 2 to 3 months earlier. The beginning of winter is anticorrelated with mid-winter and mid-winter is anticorrelated with the end of winter;- dynamic FWs occur early in the season (March - early April) and are associated with a strong positive polar temperature anomaly, while radiative FWs occur later (late April - early May) without a polar temperature anomaly;- the summer stratosphere (polar temperature and zonal wind) keeps the memory of its state in April-May at the time of FW at least until July .These results could help to improve medium-range weather forecasts in the Northern Hemisphere due to the strong dynamic coupling between the troposphere and stratosphere during SSW events.

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Precursory Changes in Planetary Wave Activity for Midwinter Surface Pressure Anomalies over the Arctic

Journal of the Meteorological Society of Japan Ser II ◽

10.2151/jmsj.86.415 ◽

2008 ◽

Vol 86 (3) ◽

pp. 415-427 ◽

Cited By ~ 13

Author(s):

Koutarou TAKAYA ◽

Hisashi NAKAMURA

Keyword(s):

Surface Pressure ◽

Planetary Wave ◽

Wave Activity ◽

The Arctic

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Dynamics and Geometry of Extratropical Cyclones in the Upper Troposphere by a Neighbor Enclosed Area Tracking Algorithm

Journal of Climate ◽

10.1175/jcli-d-12-00379.1 ◽

2013 ◽

Vol 26 (21) ◽

pp. 8641-8653 ◽

Cited By ~ 4

Author(s):

Masaru Inatsu ◽

Shotaro Amada

Keyword(s):

Morphological Characteristics ◽

Major Axis ◽

Relative Vorticity ◽

Tracking Algorithm ◽

The Arctic ◽

Extratropical Cyclones ◽

Background Flow ◽

Upper Troposphere ◽

The Arctic Oscillation ◽

Hemisphere Winter

Abstract This study shows that the morphological characteristics of upper-tropospheric extratropical eddies are closely related to the background flow in the Northern Hemisphere winter. Enclosed surfaces of 300-hPa relative vorticity are identified by using the neighbor enclosed area tracking algorithm, and the periphery of these surfaces are approximated by ellipses. Eddies are classified into five categories according to the approximate ellipse. Eddies having an oblateness of less than 0.6 are classified as near circle, or are otherwise classified as northeast–southwest (NE–SW), northwest–southeast (NW–SE), north–south, or west–east, according to the direction of the major axis. In the wintertime climatology, NE–SW-oriented cyclones are collocated with the jet stream, while NW–SE-oriented cyclones mostly reside north of the jet. In interannual variability, moreover, the frequency of NE–SW cyclones is slightly correlated with the Arctic Oscillation (AO) index, while the frequency of NW–SE cyclones is highly anticorrelated with the AO index. This is consistent with positive feedback between horizontally slanted eddies and background flow, as has been shown in many previous studies.

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Role of the Polar-night Jet Oscillation on the formation of the Arctic Oscillation in the Northern Hemisphere winter

Journal of Geophysical Research Atmospheres ◽

10.1029/2003jd004123 ◽

2004 ◽

Vol 109 (D11) ◽

Cited By ~ 49

Author(s):

Yuhji Kuroda

Keyword(s):

Northern Hemisphere ◽

Arctic Oscillation ◽

The Arctic ◽

Polar Night ◽

The Arctic Oscillation ◽

Hemisphere Winter ◽

Jet Oscillation ◽

Northern Hemisphere Winter

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Improvement in Prediction of the Arctic Oscillation with a Realistic Ocean Initial Condition in a CGCM

Journal of Climate ◽

10.1175/jcli-d-14-00457.1 ◽

2015 ◽

Vol 28 (22) ◽

pp. 8951-8967 ◽

Cited By ~ 9

Author(s):

Hae-Jeong Kim ◽

Joong-Bae Ahn

Keyword(s):

Arctic Oscillation ◽

Polar Vortex ◽

Polar Front ◽

Forecast Skill ◽

Sea Surface ◽

The Arctic ◽

Initial Condition ◽

Stratospheric Polar Vortex ◽

The Arctic Oscillation ◽

Polar Front Jet

Abstract This study verifies the impact of improved ocean initial conditions on the Arctic Oscillation (AO) forecast skill by assessing the one-month lead predictability of boreal winter AO using the Pusan National University (PNU) coupled general circulation model (CGCM). Hindcast experiments were performed on two versions of the model, one does not use assimilated ocean initial data (V1.0) and one does (V1.1), and the results were comparatively analyzed. The forecast skill of V1.1 was superior to that of V1.0 in terms of the correlation coefficient between the predicted and observed AO indices. In the regression analysis, V1.1 showed more realistic spatial similarities than V1.0 did in predicted sea surface temperature and atmospheric circulation fields. The authors suggest the relative importance of the contribution of the ocean initial condition to the AO forecast skill was because the ocean data assimilation increased the predictability of the AO, to some extent, through the improved interaction between tropical forcing induced by realistic sea surface temperature (SST) and atmospheric circulation. In V1.1, as in the observation, the cold equatorial Pacific SST anomalies generated the weakened tropical convection and Hadley circulation over the Pacific, resulting in a decelerated subtropical jet and accelerated polar front jet in the extratropics. The intensified polar front jet implies a stronger stratospheric polar vortex relevant to the positive AO phase; hence, surface manifestations of the reflected positive AO phase were then induced through the downward propagation of the stratospheric polar vortex. The results suggest that properly assimilated initial ocean conditions might contribute to improve the predictability of global oscillations, such as the AO, through large-scale tropical ocean–atmosphere interaction.

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How does downward planetary wave coupling affect polar stratospheric ozone in the Arctic winter stratosphere?

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-2437-2017 ◽

2017 ◽

Vol 17 (3) ◽

pp. 2437-2458 ◽

Cited By ~ 11

Author(s):

Sandro W. Lubis ◽

Vered Silverman ◽

Katja Matthes ◽

Nili Harnik ◽

Nour-Eddine Omrani ◽

...

Keyword(s):

Ozone Concentration ◽

Planetary Wave ◽

Wave Reflection ◽

Stratospheric Ozone ◽

Polar Vortex ◽

The Arctic ◽

Climate Simulation ◽

Residual Circulation ◽

Wave Flux ◽

The Impact

Abstract. It is well established that variable wintertime planetary wave forcing in the stratosphere controls the variability of Arctic stratospheric ozone through changes in the strength of the polar vortex and the residual circulation. While previous studies focused on the variations in upward wave flux entering the lower stratosphere, here the impact of downward planetary wave reflection on ozone is investigated for the first time. Utilizing the MERRA2 reanalysis and a fully coupled chemistry–climate simulation with the Community Earth System Model (CESM1(WACCM)) of the National Center for Atmospheric Research (NCAR), we find two downward wave reflection effects on ozone: (1) the direct effect in which the residual circulation is weakened during winter, reducing the typical increase of ozone due to upward planetary wave events and (2) the indirect effect in which the modification of polar temperature during winter affects the amount of ozone destruction in spring. Winter seasons dominated by downward wave reflection events (i.e., reflective winters) are characterized by lower Arctic ozone concentration, while seasons dominated by increased upward wave events (i.e., absorptive winters) are characterized by relatively higher ozone concentration. This behavior is consistent with the cumulative effects of downward and upward planetary wave events on polar stratospheric ozone via the residual circulation and the polar temperature in winter. The results establish a new perspective on dynamical processes controlling stratospheric ozone variability in the Arctic by highlighting the key role of wave reflection.

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