The Combined Influence of the Stratospheric Polar Vortex and ENSO on Zonal Asymmetries in the Southern Hemisphere Upper Tropospheric Circulation during Austral Spring and Summer

2021 ◽  
Author(s):  
Marisol Osman ◽  
Theodore Shepherd ◽  
Carolina Vera
Keyword(s):  
Southern Hemisphere ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Austral Spring ◽  
Stratospheric Polar Vortex ◽  
Wave Source ◽  
Weather Forecasts ◽  
Rossby Wave Source ◽  
Enso Teleconnections ◽  
Tropospheric Circulation

<p>The influence of El Niño Southern Oscillation (ENSO) and the Stratospheric Polar Vortex (SPV) on the zonal asymmetries in the Southern Hemisphere atmospheric circulation during spring and summer is examined. The main objective is to explore if the SPV can modulate the ENSO teleconnections in the extratropics. We use a large ensemble of seasonal hindcasts from the European Centre for Medium-Range Weather Forecasts Integrated Forecast System to provide a much larger sample size than is possible from the observations alone.</p><p>We find a small but statistically significant relationship between ENSO and the SPV, with El Niño events occurring with weak SPV and La Niña events occurring with strong SPV more often than expected by chance, in agreement with previous works. We show that the zonally asymmetric response to ENSO and SPV can be mainly explained by a linear combination of the response to both forcings, and that they can combine constructively or destructively. From this perspective, we find that the tropospheric asymmetries in response to ENSO are more intense when El Niño events occur with weak SPV and La Niña events occur with strong SPV, at least from September through December. In the stratosphere, the ENSO teleconnections are mostly confounded by the SPV signal. The analysis of Rossby Wave Source and of wave activity shows that both are stronger when El Niño events occur together with weak SPV, and when La Niña events occur together with strong SPV.</p>

scholarly journals Arctic Oscillation impact on thermal regime in the Eastern part of the Baltic region

2016 ◽  
Vol 2 (1) ◽  
pp. 89-96
Author(s):  
Индре Гечайте ◽  
Indre Gecaite ◽  
Александр Погорельцев ◽  
Aleksandr Pogoreltsev ◽  
Александр Угрюмов ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Geomagnetic Activity ◽  
Large Scale ◽  
Arctic Oscillation ◽  
Polar Vortex ◽  
Baltic Region ◽  
Stratospheric Polar Vortex ◽  
Weather Forecasts ◽  
Tropospheric Circulation ◽  
The Baltic

The paper presents statistical estimations of Arctic Oscillation (AO) impact on air temperature regime in the eastern part of the Baltic region. The region is characterized by high inter-annual and inter-seasonal variability. It is important to note that in the region of global warming extremely low winter temperatures can be observed on the European territory of Russia. AO is one of the large-scale global patterns of atmospheric circulation closely associated with weather variability in northern Europe. AО anomalies occur in the upper atmosphere (stratosphere) and only then are transferred to tropospheric lower layers. The anomalies can persist over a long period of time (up to two months); so they can serve as precursors in long-range weather forecasts. In turn, changes in stratospheric polar vortex and sudden stratospheric warmings can be related to geomagnetic activity. Perhaps geomagnetic activity influences the meridional temperature gradient and then changes the structure of the stratospheric zonal wind. These changes have an effect on the tropospheric circulation. The stratosphere–troposphere coupling takes place during winter months. Therefore, the paper deals with extremely cold winter anomalies in the eastern part of the Baltic Sea region. At the same time, we examine atmospheric circulation peculiarities associated with AO phase change. We analyze data for 1951–2014.

scholarly journals Evolution of the stratospheric polar vortex edge intensity and duration in the Southern hemisphere over the 1979–2020 period

2021 ◽  
Author(s):  
Audrey Lecouffe ◽  
Sophie Godin-Beekmann ◽  
Andrea Pazmiño ◽  
Alain Hauchecorne
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Onset Date ◽  
Late Winter ◽  
Stratospheric Polar Vortex ◽  
The Difference ◽  
Lower Variability

Abstract. The intensity and position of the Southern Hemisphere stratospheric polar vortex edge is evaluated as a function of equivalent latitude over the 1979–2020 period on three isentropic levels (475 K, 550 K and 675 K) from ECMWF ERA-Interim reanalysis. The study also includes an analysis of the onset and breakup dates of the polar vortex, which are determined from wind thresholds (e.g. 15.2 m.s−1, 20 m.s−1and 25 m.s−1) along the vortex edge. The vortex edge is stronger in late winter, over September–October – November with the period of strongest intensity occurring later at the lowermost level. A lower variability of the edge position is observed during the same period. Long-term increase of the vortex edge intensity and break-up date is observed over the 1979–1999 period, linked to the increase of the ozone hole. Long-term decrease of the vortex onset date related to the 25 m.s−1wind threshold is also observed at 475 K during this period. The solar cycle and to a lower extent the quasi-biennal oscillation (QBO) and El Niño Southern Oscillation (ENSO) modulate the inter-annual evolution of the strength of the vortex edge and the vortex breakup dates. Stronger vortex edge and longer vortex duration is observed in solar minimum (minSC) years, with the QBO and ENSO further modulating the solar cycle influence, especially at 475 K and 550 K: during West QBO (wQBO) phases, the difference between vortex edge intensity for minSC and maxSC years is smaller than during East QBO (eQBO) phases. The polar vortex edge is stronger and lasts longer for maxSC/wQBO years than for maxSC/eQBO years. ENSO has a weaker impact but the vortex edge is somewhat stronger during cold ENSO phases for both minSC and maxSC years.

scholarly journals Evolution of the stratospheric polar vortex in the Southern and Northern Hemispheres over the period 1979 – 2020

2021 ◽  
Author(s):  
Audrey Lecouffe ◽  
Sophie Godin-Beekmann ◽  
Andrea Pazmiño ◽  
Alain Hauchecorne
Keyword(s):  
Southern Hemisphere ◽  
Potential Vorticity ◽  
Southern Oscillation ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Geophysical Research ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Antarctic Polar Vortex ◽  
The Antarctic

<p>The stratospheric polar vortex in the Southern Hemisphere plays an important role in the intensity of the stratospheric ozone destruction during austral spring, which started in the late 1970s. The so-called ozone hole has in turn influenced the evolution of weather patterns in the Southern Hemisphere in the last decades (WMO, 2018). The Northern Hemisphere polar vortex is less stable because of larger dynamical activity in winter. It is thus less cold and polar arctic ozone losses are less important. The seasonal and interannual evolution of the polar vortex in both hemispheres has been analyzed using meteorological fields from the European Center for Meteorology Weather Forecasts ERA-Interim reanalyses and the MIMOSA model (Modélisation Isentrope du transport Méso-échelle de l’Ozone Stratosphérique par Advection, Hauchecorne et al., 2002). This model provides high spatial resolution potential vorticity (PV) and equivalent latitude fields at several isentropic levels (675K, 550K and 475K) that are used to evaluate the temporal evolution of the polar vortex edge. The edge of the vortex is computed on isentropic surfaces from the wind and gradient of PV as a function of equivalent latitude (e.g. Nash et al, 1996; Godin et al., 2001). On an interannual scale, the signature of some typical forcings driving stratospheric natural variability such as the 11-year solar cycle, the quasi-biennial oscillation (QBO), and El Niño Southern Oscillation (ENSO) is evaluated. The study includes analysis of the onset and breakup dates of the polar vortex, which are determined from the wind field along the vortex edge. Several threshold values, such as 15.2m/s, 20m/s and 25m/s following Akiyoshi et al. (2009) are used. Results on the seasonal and interannual evolution of the intensity and position of the vortex edge, as well as the onset and breakup dates of the Southern and Northern polar vortex edge over the 1979 – 2020 period will be shown.</p><p><strong>References:</strong></p><ul><li>Akiyoshi, H., Zhou, L., Yamashita, Y., Sakamoto, K., Yoshiki, M., Nagashima, T., Takahashi, M., Kurokawa, J., Takigawa, M., and Imamura, T. A CCM simulation of the breakup of the Antarctic polar vortex in the years 1980–2004 under the CCMVal scenarios, Journal ofGeophysical Research: Atmospheres, 114, 2009.</li> <li>Godin S., V. Bergeret, S. Bekki, C. David, G. Mégie, Study of the interannual ozone loss and the permeability of the Antarctic Polar Vortex from long-term aerosol and ozone lidar measurements in Dumont d’Urville (66.4◦S, 140◦E), J. Geophys. Res., 106, 1311-1330, 2001.</li> <li>Hauchecorne, A., S. Godin, M. Marchand, B. Hesse, and C. Souprayen, Quantification of the transport of chemical constituents from the polar vortex to midlatitudes in the lower stratosphere using the high-resolution advection model MIMOSA and effective diffusivity, J. Geophys. Res., 107 (D20), 8289, doi:10.1029/2001JD000491, 2002.</li> <li>Nash, E. R., Newman, P. A., Rosenfield, J. E., and Schoeberl, M. R. (1996), An objective determination of the polar vortex using Ertel’s potential vorticity, Journal of geophysical research, VOL.101(D5), 9471- 9478</li> <li>World Meteorological Organization, Global Ozone Research and Monitoring Project – Report No. 58, 2018.</li> </ul>

On the Southern Hemisphere stratospheric response to ENSO and its impacts on tropospheric circulation

2021 ◽  
pp. 1-51
Keyword(s):  
Southern Hemisphere ◽  
Southern Oscillation ◽  
Enso Cycle ◽  
Austral Spring ◽  
Enso Events ◽  
Separate Model ◽  
Tropospheric Circulation ◽  
Hemisphere Surface ◽  
Leading Mode ◽  
Model Ensembles

Abstract As the leading mode of Pacific variability, the El Niño-Southern Oscillation (ENSO) causes vast and wide-spread climatic impacts, including in the stratosphere. Following discovery of a stratospheric pathway of ENSO to the Northern Hemisphere surface, here we aim to investigate if there is a substantial Southern Hemisphere (SH) stratospheric pathway in relation to austral winter ENSO events. Large stratospheric anomalies connected to ENSO occur on average at high SH latitudes as early as August, peaking at around 10 hPa. An overall colder austral spring Antarctic stratosphere is generally associated with the warm phase of the ENSO cycle, and vice versa. This behavior is robust among reanalysis and six separate model ensembles encompassing two different model frameworks. A stratospheric pathway is identified by separating ENSO events that exhibit a stratospheric anomaly from those that don’t and comparing to stratospheric extremes that occur during neutral-ENSO years. The tropospheric eddy-driven jet response to the stratospheric ENSO pathway is the most robust in the spring following a La Niña, but extends into summer, and is more zonally-symmetric compared to the tropospheric ENSO teleconnection. The magnitude of the stratospheric pathway is weaker compared to the tropospheric pathway and therefore when it is present, has a secondary role. For context, the magnitude is approximately half that of the eddy-driven jet modulation due to austral spring ozone depletion in the model simulations. This work establishes that the stratospheric circulation acts as an intermediary in coupling ENSO variability to variations in the austral spring and summer tropospheric circulation.

Baroclinic-to-Barotropic Pathway in El Niño–Southern Oscillation Teleconnections from the Viewpoint of a Barotropic Rossby Wave Source

2016 ◽  
Vol 73 (12) ◽  
pp. 4989-5002 ◽  
Author(s):  
Xuan Ji ◽  
J. David Neelin ◽  
C. Roberto Mechoso
Keyword(s):  
Flow Pattern ◽  
Rossby Wave ◽  
Zonal Wind ◽  
Southern Oscillation ◽  
Atmospheric Model ◽  
Surface Drag ◽  
Wave Source ◽  
Vertical Advection ◽  
Rossby Wave Source ◽  
Enso Teleconnections

Abstract The baroclinic-to-barotropic pathway in ENSO teleconnections is examined from the viewpoint of a barotropic Rossby wave source that results from decomposition into barotropic and baroclinic components. Diagnoses using the NCEP–NCAR reanalysis are supplemented by analysis of the response of a tropical atmospheric model of intermediate complexity to the NCEP–NCAR barotropic Rossby wave source. Among the three barotropic Rossby wave source contributions (shear advection, vertical advection, and surface drag), the leading contribution is from shear advection and, more specifically, the mean baroclinic zonal wind advecting the anomalous baroclinic zonal wind. Vertical advection is the smallest term, while surface drag tends to cancel and reinforce the shear advection in different regions through damping on the baroclinic mode, which spins up a barotropic response. There are also nontrivial impacts of transients in the barotropic wind response to ENSO. Both tropical and subtropical baroclinic vorticity advection contribute to the barotropic component of the Pacific subtropical jet near the coast of North America, where the resulting barotropic wind contribution approximately doubles the zonal jet anomaly at upper levels, relative to the baroclinic anomalies alone. In this view, the barotropic Rossby wave source in the subtropics simply arises from the basic-state baroclinic flow acting on the well-known baroclinic ENSO flow pattern that spreads from the deep tropics into the subtropics over a scale of equatorial radius of deformation. This is inseparably connected to the leading deep tropical Rossby wave source that arises from eastern Pacific climatological baroclinic winds advecting the tropical portion of the same ENSO flow pattern.

scholarly journals Southern Hemisphere Summer Mesopause Responses to El Niño–Southern Oscillation

2016 ◽  
Vol 29 (17) ◽  
pp. 6319-6328 ◽  
Author(s):  
Tao Li ◽  
Natalia Calvo ◽  
Jia Yue ◽  
James M. Russell ◽  
Anne K. Smith ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Zonal Wind ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Onset Time ◽  
Polar Vortex ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Enso Events

Abstract In the Southern Hemisphere (SH) polar region, satellite observations reveal a significant upper-mesosphere cooling and a lower-thermosphere warming during warm ENSO events in December. An opposite pattern is observed in the tropical mesopause region. The observed upper-mesosphere cooling agrees with a climate model simulation. Analysis of the simulation suggests that enhanced planetary wave (PW) dissipation in the Northern Hemisphere (NH) high-latitude stratosphere during El Niño strengthens the Brewer–Dobson circulation and cools the equatorial stratosphere. This increases the magnitude of the SH stratosphere meridional temperature gradient and thus causes the anomalous stratospheric easterly zonal wind and early breakdown of the SH stratospheric polar vortex. The resulting perturbation to gravity wave (GW) filtering causes anomalous SH mesospheric eastward GW forcing and polar upwelling and cooling. In addition, constructive inference of ENSO and quasi-biennial oscillation (QBO) could lead to stronger stratospheric easterly zonal wind anomalies at the SH high latitudes in November and December and early breakdown of the SH stratospheric polar vortex during warm ENSO events in the easterly QBO phase (defined by the equatorial zonal wind at ~25 hPa). This would in turn cause much more SH mesospheric eastward GW forcing and much colder polar temperatures, and hence it would induce an early onset time of SH summer polar mesospheric clouds (PMCs). The opposite mechanism occurs during cold ENSO events in the westerly QBO phase. This implies that ENSO together with QBO could significantly modulate the breakdown time of SH stratospheric polar vortex and the onset time of SH PMC.

scholarly journals Stratosphere–Troposphere Coupling in the Southern Hemisphere

2005 ◽  
Vol 62 (3) ◽  
pp. 708-715 ◽  
Author(s):  
David W. J. Thompson ◽  
Mark P. Baldwin ◽  
Susan Solomon
Keyword(s):  
Climate Variability ◽  
Southern Hemisphere ◽  
Large Scale ◽  
Temporal Evolution ◽  
Polar Vortex ◽  
Climate Impacts ◽  
Sudden Stratospheric Warming ◽  
Stratospheric Polar Vortex ◽  
Tropospheric Circulation ◽  
Stratospheric Variability

Abstract This study examines the temporal evolution of the tropospheric circulation following large-amplitude variations in the strength of the Southern Hemisphere (SH) stratospheric polar vortex in data from 1979 to 2001 and following the SH sudden stratospheric warming of 2002. In both cases, anomalies in the strength of the SH stratospheric polar vortex precede similarly signed anomalies in the tropospheric circulation that persist for more than 2 months. The SH tropospheric circulation anomalies reflect a bias in the polarity of the SH annular mode (SAM), a large-scale pattern of climate variability characterized by fluctuations in the strength of the SH circumpolar flow. Consistent with the climate impacts of the SAM, variations in the stratospheric polar vortex are also followed by coherent changes in surface temperatures throughout much of Antarctica. The results add to a growing body of evidence that suggests that stratospheric variability plays an important role in driving climate variability at Earth’s surface on a range of time scales.

scholarly journals The wave geometry of final stratospheric warming events

2021 ◽  
Vol 2 (2) ◽  
pp. 453-474
Author(s):  
Amy H. Butler ◽  
Daniela I. V. Domeisen
Keyword(s):  
Southern Hemisphere ◽  
Polar Vortex ◽  
Stratospheric Warming ◽  
Stratospheric Polar Vortex ◽  
Total Column Ozone ◽  
Planetary Scale ◽  
Tropospheric Circulation ◽  
Column Ozone ◽  
Total Column

Abstract. Every spring, the stratospheric polar vortex transitions from its westerly wintertime state to its easterly summertime state due to seasonal changes in incoming solar radiation, an event known as the “final stratospheric warming” (FSW). While FSWs tend to be less abrupt than reversals of the boreal polar vortex in midwinter, known as sudden stratospheric warming (SSW) events, their timing and characteristics can be significantly modulated by atmospheric planetary-scale waves. While SSWs are commonly classified according to their wave geometry, either by how the vortex evolves (whether the vortex displaces off the pole or splits into two vortices) or by the dominant wavenumber of the vortex just prior to the SSW (wave-1 vs. wave-2), little is known about the wave geometry of FSW events. We here show that FSW events for both hemispheres in most cases exhibit a clear wave geometry. Most FSWs can be classified into wave-1 or wave-2 events, but wave-3 also plays a significant role in both hemispheres. The timing and classification of the FSW are sensitive to which pressure level the FSW central date is defined, particularly in the Southern Hemisphere (SH) where trends in the FSW dates associated with ozone depletion and recovery are more evident at 50 than 10 hPa. However, regardless of which FSW definition is selected, we find the wave geometry of the FSW affects total column ozone anomalies in both hemispheres and tropospheric circulation over North America. In the Southern Hemisphere, the timing of the FSW is strongly linked to both total column ozone before the event and the tropospheric circulation after the event.

scholarly journals The 2019 Southern Hemisphere stratospheric polar vortex weakening and its impacts

2021 ◽  
pp. 1-50
Author(s):  
Eun-Pa Lim ◽  
Harry H. Hendon ◽  
Amy H. Butler ◽  
David W. J. Thompson ◽  
Zachary Lawrence ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Polar Vortex ◽  
Austral Spring ◽  
Stratospheric Polar Vortex ◽  
Climate Conditions ◽  
Extreme Climate ◽  
The Antarctic

Capsule SummaryDuring austral spring 2019 the Antarctic stratosphere experienced record-breaking warming and a near-record polar vortex weakening, resulting in predictable extreme climate conditions throughout the Southern Hemisphere through December 2019.

scholarly journals Seasonal prediction of the boreal winter stratosphere

2021 ◽  
Author(s):  
Alice Portal ◽  
Paolo Ruggieri ◽  
Froila M. Palmeiro ◽  
Javier García-Serrano ◽  
Daniela I. V. Domeisen ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Polar Vortex ◽  
Seasonal Prediction ◽  
Wave Activity ◽  
Boreal Winter ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Eddy Heat Flux ◽  
Prediction Systems ◽  
Model Database

AbstractThe predictability of the Northern Hemisphere stratosphere and its underlying dynamics are investigated in five state-of-the-art seasonal prediction systems from the Copernicus Climate Change Service (C3S) multi-model database. Special attention is devoted to the connection between the stratospheric polar vortex (SPV) and lower-stratosphere wave activity (LSWA). We find that in winter (December to February) dynamical forecasts initialised on the first of November are considerably more skilful than empirical forecasts based on October anomalies. Moreover, the coupling of the SPV with mid-latitude LSWA (i.e., meridional eddy heat flux) is generally well reproduced by the forecast systems, allowing for the identification of a robust link between the predictability of wave activity above the tropopause and the SPV skill. Our results highlight the importance of November-to-February LSWA, in particular in the Eurasian sector, for forecasts of the winter stratosphere. Finally, the role of potential sources of seasonal stratospheric predictability is considered: we find that the C3S multi-model overestimates the stratospheric response to El Niño–Southern Oscillation (ENSO) and underestimates the influence of the Quasi–Biennial Oscillation (QBO).

Sign in / Sign up

Export Citation Format

Share Document