Analysis of the Equatorial Lower Stratosphere Quasi-Biennial Oscillation (QBO) Using ECMWF-Interim Reanalysis Data Set

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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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

<p>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.</p>

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Differences between the QBO in the first and in the second half of the ERA-40 reanalysis

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-9259-2006 ◽

2006 ◽

Vol 6 (5) ◽

pp. 9259-9271 ◽

Cited By ~ 1

Author(s):

H. J. Punge ◽

M. A. Giorgetta

Keyword(s):

Zonal Wind ◽

Lower Stratosphere ◽

Wind Data ◽

Part Versus ◽

Quasi Biennial Oscillation ◽

Data Set ◽

Wind Profiles ◽

Biennial Oscillation ◽

Good Number ◽

Over Time

Abstract. The representation of the quasi-biennial oscillation (QBO) is investigated in the ERA-40 reanalysis. In the lower stratosphere, where there is a good number of observations, the representation of the QBO is equally well throughout the record. However, strong differences between the first and the second half of the zonal wind data set are found in the upper stratosphere, with a typical offset of −10 m/s in the equatorial zonal wind in the earlier part versus the later part of the ERA-40 data set. The strength of the QBO is also affected. Possible explanations are discussed. The identified change of the assimilated wind profiles over time in ERA-40 requires a careful use of equatorial upper stratospheric winds from the reanalysis for validation purposes.

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Differences between the QBO in the first and in the second half of the ERA-40 reanalysis

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-599-2007 ◽

2007 ◽

Vol 7 (3) ◽

pp. 599-608 ◽

Cited By ~ 10

Author(s):

H. J. Punge ◽

M. A. Giorgetta

Keyword(s):

Zonal Wind ◽

Wind Shear ◽

Lower Stratosphere ◽

Part Versus ◽

Quasi Biennial Oscillation ◽

Data Set ◽

Wind Profiles ◽

In The Beginning ◽

Biennial Oscillation ◽

Over Time

Abstract. The representation of the quasi-biennial oscillation (QBO) is investigated in the ERA-40 reanalysis. In the lower stratosphere, where there are a reasonable number of observations, the representation of the QBO is equally good throughout the record. However, strong differences between the first and the second half of the zonal wind data set are found in the upper stratosphere, with a typical offset of –10 m/s in the equatorial zonal wind in the earlier part versus the later part of the ERA-40 record. At the same time, the strength of the QBO is similar. The 7-year running means of zonal wind, wind shear and temperature reveal interesting structures with major changes occuring in the beginning and the middle of the 1980s. Possible explanations are discussed. The identified change of the reanalysed wind profiles over time in ERA-40 demands for a careful use of equatorial upper stratospheric winds from the reanalysis e.g.~for model validation purposes.

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Tropical Waves and the Quasi-Biennial Oscillation in the Lower Stratosphere

Journal of the Atmospheric Sciences ◽

10.1175/1520-0469(1976)033<0430:twatqb>2.0.co;2 ◽

1976 ◽

Vol 33 (3) ◽

pp. 430-435 ◽

Cited By ~ 7

Author(s):

A. J. Miller ◽

J. K. Angell ◽

J. Korshover

Keyword(s):

Lower Stratosphere ◽

Quasi Biennial Oscillation ◽

Tropical Waves ◽

Biennial Oscillation

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Analysis of Arctic Spring Ozone Anomaly in the Phases of QBO and 11-year Solar Cycle for 1979–2011

10.20944/preprints202104.0057.v1 ◽

2021 ◽

Author(s):

Yousuke Yamashita ◽

Hideharu Akiyoshi ◽

Masaaki Takahashi

Keyword(s):

Solar Cycle ◽

Climate Model ◽

Polar Vortex ◽

Reanalysis Data ◽

Early Spring ◽

The Arctic ◽

Negative Anomaly ◽

Late Winter ◽

Quasi Biennial Oscillation ◽

Biennial Oscillation

Arctic ozone amount in winter to spring shows large year-to-year variation. This study investigates Arctic spring ozone in relation to the phase of quasi-biennial oscillation (QBO)/the 11-year solar cycle, using satellite observations, reanalysis data, and outputs of a chemistry climate model (CCM) during the period of 1979–2011. For this duration, we found that the composite mean of the Northern Hemisphere high-latitude total ozone in the QBO-westerly (QBO-W)/solar minimum (Smin) phase is slightly smaller than those averaged for the QBO-W/Smax and QBO-E/Smax years in March. An analysis of a passive ozone tracer in the CCM simulation indicates that this negative anomaly is primarily caused by transport. The negative anomaly is consistent with a weakening of the residual mean downward motion in the polar lower stratosphere. The contribution of chemical processes estimated using the column amount difference between ozone and the passive ozone tracer is between 10–20% of the total anomaly in March. The lower ozone levels in the Arctic spring during the QBO-W/Smin years are associated with a stronger Arctic polar vortex from late winter to early spring, which is linked to the reduced occurrence of sudden stratospheric warming in the winter during the QBO-W/Smin years.

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Tropical troposphere to stratosphere transport of carbon monoxide and long-lived trace species in the Chemical Lagrangian Model of the Stratosphere (CLaMS)

Geoscientific Model Development Discussions ◽

10.5194/gmdd-7-5087-2014 ◽

2014 ◽

Vol 7 (4) ◽

pp. 5087-5139 ◽

Cited By ~ 6

Author(s):

R. Pommrich ◽

R. Müller ◽

J.-U. Grooß ◽

P. Konopka ◽

F. Ploeger ◽

...

Keyword(s):

Carbon Monoxide ◽

Large Scale ◽

Lower Stratosphere ◽

Lagrangian Model ◽

Quasi Biennial Oscillation ◽

Data Set ◽

Model Version ◽

The Tropics ◽

The Impact ◽

Good Agreement

Abstract. Variations in the mixing ratio of trace gases of tropospheric origin entering the stratosphere in the tropics are of interest for assessing both troposphere to stratosphere transport fluxes in the tropics and the impact of these transport fluxes on the composition of the tropical lower stratosphere. Anomaly patterns of carbon monoxide (CO) and long-lived tracers in the lower tropical stratosphere allow conclusions about the rate and the variability of tropical upwelling to be drawn. Here, we present a simplified chemistry scheme for the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the simulation, at comparatively low numerical cost, of CO, ozone, and long-lived trace substances (CH4, N2O, CCl3F (CFC-11), CCl2F2 (CFC-12), and CO2) in the lower tropical stratosphere. For the long-lived trace substances, the boundary conditions at the surface are prescribed based on ground-based measurements in the lowest model level. The boundary condition for CO in the free troposphere is deduced from MOPITT measurements (at &approx; 700–200 hPa). Due to the lack of a specific representation of mixing and convective uplift in the troposphere in this model version, enhanced CO values, in particular those resulting from convective outflow are underestimated. However, in the tropical tropopause layer and the lower tropical stratosphere, there is relatively good agreement of simulated CO with in-situ measurements (with the exception of the TROCCINOX campaign, where CO in the simulation is biased low &approx; 10–20 ppbv). Further, the model results are of sufficient quality to describe large scale anomaly patterns of CO in the lower stratosphere. In particular, the zonally averaged tropical CO anomaly patterns (the so called "tape recorder" patterns) simulated by this model version of CLaMS are in good agreement with observations. The simulations show a too rapid upwelling compared to observations as a consequence of the overestimated vertical velocities in the ERA-interim reanalysis data set. Moreover, the simulated tropical anomaly patterns of N2O are in good agreement with observations. In the simulations, anomaly patterns for CH4 and CFC-11 were found to be consistent with those of N2O; for all long-lived tracers, positive anomalies are simulated because of the enhanced tropical upwelling in the easterly phase of the quasi-biennial oscillation.

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Variability in the speed of the Brewer–Dobson circulation as observed by Aura/MLS

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-4563-2013 ◽

2013 ◽

Vol 13 (9) ◽

pp. 4563-4575 ◽

Cited By ~ 34

Author(s):

T. Flury ◽

D. L. Wu ◽

W. G. Read

Keyword(s):

Time Series ◽

Interannual Variability ◽

Lower Stratosphere ◽

Meridional Circulation ◽

Time Lag ◽

Quasi Biennial Oscillation ◽

One Year ◽

The Tropics ◽

Biennial Oscillation ◽

Stratospheric Water Vapour

Abstract. We use Aura/MLS stratospheric water vapour (H2O) measurements as tracer for dynamics and infer interannual variations in the speed of the Brewer–Dobson circulation (BDC) from 2004 to 2011. We correlate one-year time series of H2O in the lower stratosphere at two subsequent pressure levels (68 hPa, ~18.8 km and 56 hPa, ~19.9 km at the Equator) and determine the time lag for best correlation. The same calculation is made on the horizontal on the 100 hPa (~16.6 km) level by correlating the H2O time series at the Equator with the ones at 40° N and 40° S. From these lag coefficients we derive the vertical and horizontal speeds of the BDC in the tropics and extra-tropics, respectively. We observe a clear interannual variability of the vertical and horizontal branch. The variability reflects signatures of the Quasi Biennial Oscillation (QBO). Our measurements confirm the QBO meridional circulation anomalies and show that the speed variations in the two branches of the BDC are out of phase and fairly well anti-correlated. Maximum ascent rates are found during the QBO easterly phase. We also find that transport of H2O towards the Northern Hemisphere (NH) is on the average two times faster than to the Southern Hemisphere (SH) with a mean speed of 1.15 m s−1 at 100 hPa. Furthermore, the speed towards the NH shows much more interannual variability with an amplitude of about 21% whilst the speed towards the SH varies by only 10%. An amplitude of 21% is also observed in the variability of the ascent rate at the Equator which is on the average 0.2 mm s−1.

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Response of trace gases to the disrupted 2015–2016 quasi-biennial oscillation

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-6813-2017 ◽

2017 ◽

Vol 17 (11) ◽

pp. 6813-6823 ◽

Cited By ~ 22

Author(s):

Olga V. Tweedy ◽

Natalya A. Kramarova ◽

Susan E. Strahan ◽

Paul A. Newman ◽

Lawrence Coy ◽

...

Keyword(s):

Water Vapor ◽

Chemical Constituents ◽

Trace Gases ◽

Quasi Biennial Oscillation ◽

Data Set ◽

Uv Index ◽

Stratospheric Water Vapor ◽

Northern Summer ◽

Tropical Tropopause ◽

Biennial Oscillation

Abstract. The quasi-biennial oscillation (QBO) is a quasiperiodic alternation between easterly and westerly zonal winds in the tropical stratosphere, propagating downward from the middle stratosphere to the tropopause with a period that varies from 24 to 32 months ( ∼  28 months on average). The QBO wind oscillations affect the distribution of chemical constituents, such as ozone (O3), water vapor (H2O), nitrous oxide (N2O), and hydrochloric acid (HCl), through the QBO-induced meridional circulation. In the 2015–2016 winter, radiosonde observations revealed an anomaly in the downward propagation of the westerly phase, which was disrupted by the upward displacement of the westerly phase from ∼  30 hPa up to 15 hPa and the sudden appearance of easterlies at 40 hPa. Such a disruption is unprecedented in the observational record from 1953 to the present. In this study we show the response of trace gases to this QBO disruption using O3, HCl, H2O, and temperature from the Aura Microwave Limb Sounder (MLS) and total ozone measurements from the Solar Backscatter Ultraviolet (SBUV) Merged Ozone Data Set (MOD). Results reveal the development of positive anomalies in stratospheric equatorial O3 and HCl over ∼  50–30 hPa in May–September of 2016 and a substantial decrease in O3 in the subtropics of both hemispheres. The SBUV observations show near-record low levels of column ozone in the subtropics in 2016, resulting in an increase in the surface UV index during northern summer. Furthermore, cold temperature anomalies near the tropical tropopause result in a global decrease in stratospheric water vapor.

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Dynamics of the Disrupted 2015/16 Quasi-Biennial Oscillation

Journal of Climate ◽

10.1175/jcli-d-16-0663.1 ◽

2017 ◽

Vol 30 (15) ◽

pp. 5661-5674 ◽

Cited By ~ 29

Author(s):

Lawrence Coy ◽

Paul A. Newman ◽

Steven Pawson ◽

Leslie R. Lait

Keyword(s):

Lower Stratosphere ◽

Global Climate ◽

Quasi Biennial Oscillation ◽

Wave Forcing ◽

Wind Variability ◽

Momentum Fluxes ◽

Horizontal Momentum ◽

The Tropics ◽

Global Reanalysis ◽

Biennial Oscillation

A significant disruption of the quasi-biennial oscillation (QBO) occurred during the Northern Hemisphere (NH) winter of 2015/16. Since the QBO is the major wind variability source in the tropical lower stratosphere and influences the rate of ascent of air entering the stratosphere, understanding the cause of this singular disruption may provide new insights into the variability and sensitivity of the global climate system. Here this disruptive event is examined using global reanalysis winds and temperatures from 1980 to 2016. Results reveal record maxima in tropical horizontal momentum fluxes and wave forcing of the tropical zonal mean zonal wind over the NH 2015/16 winter. The Rossby waves responsible for these record tropical values appear to originate in the NH and were focused strongly into the tropics at the 40-hPa level. Two additional NH winters, 1987/88 and 2010/11, were also found to have large tropical lower-stratospheric momentum flux divergences; however, the QBO westerlies did not change to easterlies in those cases.

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