Temperature Quasi-biennial Oscillation Research Articles

Anomalous changes of temperature and ozone QBOs in 2015−2017 from radiosonde observation and MERRA-2 reanalysis

Anomalous changes of zonal wind quasi-biennial oscillation (QBO) in winter 2015−2016 have received close attention. Combining radiosonde and satellite observations and reanalysis data, we investigate anomalous changes in temperature and ozone QBOs from the lower to middle stratosphere. As wind shear direction is reversed due to unexpected changes of zonal wind QBO at about 24−30 km, the shortest cold phase at 21−27 km appears in temperature QBO. This is different from the completely interrupted westward phase in zonal wind QBO, while the longest cold phase above almost 27 km lasts for 2−3 years from 2015 to 2017, owing to the absence of corresponding warm phase. Meridional scale reduction of temperature QBO causes a small temperature anomaly, thus the thermal wind relationship looks seemingly different from that in the other regular QBO cycles. QBO in the ozone mixing ratio anomaly shows a double-peak with inverse phase, and its phase below (above) 30 km is in agreement with (opposite to) the phase of temperature QBO because of different control mechanisms of ozone. Following temperature QBO variation, QBO in the ozone mixing ratio anomaly exhibits a less positive phase at 20−30 km in 2016−2017, and a very long positive phase above 30 km from 2015 to 2017. QBO in total column ozone shows a small peak in winter 2016−2017 since ozone is mainly concentrated at 20 to 30 km. Anomalous changes of temperature and ozone QBOs due to unexpected QBO zonal wind variation can be well-explained according to thermal wind balance and thermodynamic balance.

Future Changes in the Ozone Quasi-Biennial Oscillation with Increasing GHGs and Ozone Recovery in CCMI Simulations

The future quasi-biennial oscillation (QBO) in ozone in the equatorial stratosphere is examined by analyzing transient climate simulations due to increasing greenhouse gases (GHGs) and decreasing ozone-depleting substances under the auspices of the Chemistry–Climate Model Initiative. The future (1960–2100) and historical (1979–2010) simulations are conducted with the Meteorological Research Institute Earth System Model. Three climate periods, 1960–85 (past), 1990–2020 (present), and 2040–70 (future) are selected, corresponding to the periods before, during, and after ozone depletion. The future ozone QBO is characterized by increases in amplitude by 15%–30% at 5–10 hPa and decreases by 20%–30% at 40 hPa, compared with the past and present climates; the future and present ozone QBOs increase in amplitude by up to 60% at 70 hPa, compared with the past climate. The increased amplitude at 5–10 hPa suggests that the temperature-dependent photochemistry plays an important role in the enhanced future ozone QBO. The weakening of vertical shear in the zonal wind QBO is responsible for the decreased amplitude at 40 hPa in the future ozone QBO. An interesting finding is that the weakened zonal wind QBO in the lowermost tropical stratosphere is accompanied by amplified QBOs in ozone, vertical velocity, and temperature. Further study is needed to elucidate the causality of amplification about the ozone and temperature QBOs under climate change in conditions of zonal wind QBO weakening.

Quasi-biennial oscillation in ozone and temperature over tropics

Spatiotemporal variations of the quasi-biennial oscillation (QBO) in temperature and ozone over the tropical–subtropical belts (40°N–40°S) have been studied using Microwave Limb Sounder data for the period 1992–1999. Wavelet analysis has been performed to study inter-annual variations in amplitude and phases of the QBO. Latitude-height cross-sections of the amplitudes of temperature and ozone QBO exhibit a double-peak structure near the equator. Phase structure reveals that the temperature QBO descended faster than the ozone QBO. Cross-wavelet analysis shows an anti-phase relation between the amplitudes of the temperature and ozone QBO in the upper stratospheric region, whereas in-phase relation exists in the middle stratospheric region.

QBO effects manifesting in ozone, temperature, and wind profiles

Abstract. On the basis of ozonesonde records up to 1998 the responses on the equatorial quasi-biennial oscillation (QBO), manifesting in ozone, temperature, and wind (QBO effects) were isolated in the region from the ground to altitudes as high as 35km at 22 stations located in Europe (7), North America (7), Japan (4), Hawaii (1), Australia (2), and Antarctic (1). The vertical structures of the QBO effects of ozone are represented as an alternation of layers of well-developed quasi-biennial signals, whose phases gradually change with height and thin transitional layers of ill-developed signals, whose phases change abruptly with height. The amplitudes of the effects depend on height and reach the maxima of 3–6nbar in the lower stratosphere. At the majority of sites the effects are found to be approximately in phase between 20 and 23km. Two types of the vertical structures of the temperature QBO effects are found. At most of the sites located equatorward of about 50° the stratospheric temperature anomalies are characterized by downward propagation, whereas at sites situated poleward of about 50° they look as column-like structures. Near the tropopause the effects frequently reveal dipole-like structure, when the stratospheric and tropospheric anomalies are of opposite signs. The amplitudes of the effects are in the range of 0.5–1°C. The vertical structures of the QBO effects of horizontal wind components reveal a diversity of patterns. The amplitudes of the QBO effects of the meridional and zonal winds are comparable and lie in the range of 0.5–2m s–1. As a rule, the maxima of the effects are noticed slightly below the tropopause, as well as in the middle stratosphere. In general, a statistical assurance of the obtained QBO effects is rather poor. However, a considerable part of them reveal similarity, which can be hardly explained by chance. Furthermore, the results agree with possible physical mechanisms of off-equatorial influence of the QBO, as well as with results of other observational studies. Differences between the QBO effects obtained at different sites can be induced by peculiarities of corresponding ozonesonde records, differing by periods, gaps, number of sondes, errors of measurements, etc. Also, the differences can be associated with an inconstancy of characteristics of the equatorial QBO itself, as well as with an interdependency of the QBO and the annual cycle. Finally, the differences can reflect real regional characteristics of the QBO effects associated with local peculiarities of the large-scale circulation. Key words. Meteorology and atmospheric dynamics (climatology; general circulation; middle atmosphere dynamics)

The 1978 shift in the NCEP reanalysis stratospheric quasi‐biennial oscillation

The National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP) reanalysis exhibits interdecadal changes in the structure of the quasi‐biennial oscillation (QBO) and annual mean fields in the tropical stratosphere during 1958–2001. A sudden temperature increase occurred around 1978, with equatorial maxima of ∼3 K at 10 hPa and near the tropopause. When this 1978 jump is removed, a moderate cooling trend is found throughout the tropical lower stratosphere, with an equatorial maximum cooling of 3 K over 40 years near 30 hPa. While the QBO in zonal wind is similar in both the 1958–1978 and 1979–2001 periods, the QBO in temperature is significantly reduced in amplitude and latitudinally contracted after 1978, and the QBO meridional circulation is stronger. Vertical temperature variations in the annual mean and QBO have been underestimated since the introduction of nadir‐sounding satellites. A mechanism is suggested for how this may affect meridional circulations in data assimilation models.

Two‐dimensional model simulations of the QBO in ozone and tracers in the tropical stratosphere

Meteorological data from the United Kingdom Meteorological Office (UKMO) and constituent data from the Upper Atmospheric Research Satellite (UARS) are used to construct yearly zonal mean dynamical fields for the 1990s for use in the NASA/Goddard Space Flight Center (GSFC) two‐dimensional (2‐D) chemistry and transport model. This allows for interannual dynamical variability to be included in the model constituent simulations. In this study, we focus on the tropical stratosphere. We find that the phase of quasi‐biennial oscillation (QBO) signals in equatorial CH4 and profile and total column O3 data are resolved quite well using this empirically based 2‐D model transport framework. However, the QBO amplitudes in the model constituents are systematically underestimated relative to the observations at most levels. This deficiency is probably due in part to the limited vertical resolutions of the 2‐D model and the UKMO and UARS input data sets. We find that using different heating rate calculations in the model affects the interannual and QBO amplitudes in the constituent fields, but has little impact on the phase. Sensitivity tests reveal that the QBO in transport dominates the ozone interannual variability in the lower stratosphere, with the effect of the temperature QBO being dominant in the upper stratosphere via the strong temperature dependence of the ozone loss reaction rates. We also find that the QBO in odd nitrogen radicals, which is caused by the QBO modulated transport of NOy, plays a significant but not dominant role in determining the ozone QBO variability in the middle stratosphere. The model mean age of air is in good overall agreement with that determined from tropical lower‐middle stratospheric OMS balloon observations of SF6 and CO2. The interannual variability of the equatorial mean age in the model increases with altitude and maximizes near 40 km, with a range of 4–5 years over the 1993–2000 time period.

The Influence of Wave– and Zonal Mean–Ozone Feedbacks on the Quasi-biennial Oscillation

The effects of wave and zonal mean ozone heating on the evolution of the quasi-biennial oscillation (QBO) are examined using a two-dimensional mechanistic model of the equatorial stratosphere. The model atmosphere is governed by coupled equations for the zonal mean and (linear) wave fields of ozone, temperature, and wind, and is driven by specifying the amplitudes of a Kelvin wave and a Rossby‐gravity wave at the lower boundary. Wave‐mean flow interactions are accounted for in the model, but not wave‐wave interactions. A reference simulation (RS) of the QBO, in which ozone feedbacks are neglected, is carried out and the results compared with Upper Atmosphere Research Satelliteobservations. The RS is then compared with three model experiments, which examine separately and in combination the effects of wave ozone and zonal mean ozone feedbacks. Wave‐ozone feedbacks alone increase the driving by the Kelvin and Rossby‐gravity waves by up to 10%, producing stronger zonal wind shear zones and a stronger meridional circulation. Zonal mean‐ ozone feedbacks (ozone QBO) alone decrease the magnitude of the temperature QBO by up to 15%, which in turn affects the momentum deposition by the wave fields. Overall, the zonal mean‐ozone feedbacks increase the magnitude of the meridional circulation by up to 30%. The combined effects of wave‐ozone and ozone QBO feedbacks generally produce a larger response then either process alone. Moreover, these combined ozone feedbacks produce a temperature QBO amplitude that is up to 30% larger than simulations without the feedbacks. Correspondingly, significant changes are also observed in the zonal wind and ozone QBOs. When ozone feedbacks are included in the model, the Kelvin and Rossby‐gravity wave amplitudes can be reduced by ;10% and still produce a QBO similar to simulations without ozone.

Vertical structure of the extratropical quasi‐biennial oscillation in ozone, temperature, and wind derived from ozonesonde data

An analysis of the extratropical ozone sounding data shows that ozone, temperature, and wind as well as tropopause height reveal interannual variability with timescales in the range 24–30 months. This quasi‐biennial variability is noticed, as a rule, in a whole range of ozone sounding heights (0–35 km) and connected with the equatorial quasi‐biennial oscillation (QBO). The QBOs in ozone and temperature are revealed differently in the middle and lower stratosphere as well as in the troposphere. In the middle stratosphere a downward phase progression of the ozone QBO is noticed similar to that of the equatorial dynamical QBOs. The rate of the phase descent of the QBO depends on the geographical region and varies from 0.5 km/month to 1 km/month. In the northern hemisphere the rate is greatest in the polar region but lowest in the subtropics. Local maxima are noticed in the vertical structures of the ozone QBOs. In the northern midlatitudes these maxima are centered at heights of about 12, 20, and 30 km. In the lower stratosphere the QBO in ozone is in phase with that in temperature. Mean amplitudes of the temperature QBO in the troposphere are close to those in the stratosphere. The downward phase progression of the temperature QBO is noticed in the northern midlatitude stratosphere. There is an abrupt phase shift between the QBOs in ozone and temperature in the lower stratosphere and those in the middle troposphere. Over the North American stations the phase shift is that the temperature QBOs in the troposphere are in opposite phase with those in the stratosphere. In zonal and meridional winds the QBO are revealed in the northern midlatitudes. In contrast with the QBOs in ozone and temperature, the wind QBOs reveal the small rate of the phase changing with height. There are no significant phase shifts between the wind QBO in the lower stratosphere and that in the troposphere. The maximum amplitudes of the wind QBO are noticed in the vicinity of the tropopause position and at heights of 25–30 km. Amplitudes of the QBO in zonal wind are close to those in meridional wind. The QBO of tropopause height exposed in the northern hemisphere has the greatest amplitude over Japan. The tropopause height QBO is in opposite phase (in phase) with the QBOs in ozone and temperature in the lower stratosphere (troposphere). Vertical structures of the QBOs obtained for ozone, temperature, and wind in the stratosphere as well as the corresponding QBO of tropopause height support a hypothesis that the extratropical QBO is caused by quasi‐biennial forcing of the mean diabatic meridional circulation by planetary‐scale waves with the resulting modulation of vertical advection.

Quasi-Biennial Oscillations of Ozone and Diabatic Circulation in the Equatorial Stratosphere

The quasi-biennial oscillation (QBO) in ozone in the equatorial stratosphere is obtained by analyzing the Stratospheric Aerosol and Gas Experiment (SAGE) data from 1984 to 1989. The phase of the ozone QBO in the lower stratosphere is found to precede the zonal wind QBO by several months as opposed to the theoretically expected in-phase relationship between the two. A mechanistic model is developed to explore possible reasons for this disagreement. The model is capable of simulating the actual time evolution of the ozone QBO by introducing the observed zonal wind profile as input. The modeled results confirm the conventional view that the ozone QBO is generated by the vertical ozone advection that is driven to maintain the temperature structure against radiative damping. However, a series of experiments emphasizes the importance of the feedback of the ozone QBO to the diabatic heating through the absorption of solar radiation. Due to this effect, the phase of the ozone QBO shifts up to a quarter cycle ahead and approaches that of the temperature QBO. Because of this inphase relationship, the feedback of the ozone QBO to the diabatic heating acts to compensate for the radiative damping of the temperature structure, thus reducing the magnitude of the induced diabatic circulation. Because the reduction of the magnitude of the vertical motion facilitates downward transport of easterly momentum by the mean flow, this feedback process can help to resolve the insufficiency of the easterly momentum in driving the dynamical QBO in general circulation models (GCMs). It should be emphasized that more sophisticated models that allow for full interaction between the chemical species and radiative and dynamical processes should be developed to improve our understanding of both dynamical and ozone QBOs.

Two‐dimensional model studies of the interannual variability of trace gases in the middle atmosphere

A parameterization of the mechanisms believed to be responsible for the quasi‐biennial oscillation (QBO) in the zonal winds of the equatorial lower stratosphere has been included in an interactive dynamical‐radiative‐photochemical model of the atmosphere. As well as a QBO signal in the zonal wind, temperature, and ozone there are QBO signals in a range of other chemical species contained in the model. In the case of long‐lived tracers the QBO signal results from the direct effect of the QBO‐induced modification to the model circulation. The sign and magnitude of these QBO signals depend on the sign and strength of the vertical gradient of these long‐lived tracers in the lower stratosphere. For shorter‐lived species a QBO signal can result from the QBO in temperature or in trace gases controlling the species' production and loss. In many cases, much larger interannual variability is predicted for these short er‐lived species. Notably, NO2 and N2O5, whose chemistry is very temperature dependent, show very strong QBO signals. In the case of ozone the transition from dynamical control in the lower stratosphere to photochemical control at higher altitudes can be seen in its QBO signal. These predictions of interannual variability of trace species should be considered when analyzing and interpreting observational data, particularly when calculating year‐to‐year trends.

Influence of the Annual Cycle in Meridional Transport on the Quasi-biennial Oscillation in Total Ozone

The equatorial stratospheric quasi-biennial oscillation (QBO) in zonal wind and temperature is observed to be symmetric about the equator. The QBO in column ozone, although it is believed to be caused primarily by vertical displacements due to the meridional circulation associated with the equatorial temperature QBO, is asymmetric with respect to the equator, and is strongly linked to the phase of the annual cycle. In this note a simple one-layer model is used to demonstrate that the gross features of the observed QBO in total ozone can be attributed to meridional advection of the ozone perturbation by the annually reversing mean meridional Hadley circulation. This advection causes a displacement of the equatorial ozone anomaly towards the winter hemisphere, and thus products an asymmetry with respect to the equator. It also modulates the amplitude of the ozone QBO, since the phase of the equatorial wind QBO with respect to the annual cycle may produce either constructive or destructive interference between the effects of the annually reversing meridional transport and the vertical advection by the equatorial wind QBO.

Recent Rocketsonde-Derived Temperature Variations in the Western Hemisphere

Rocketsonde-derived temperature variations within north polar, north subtropical and equatorial zones of the western hemisphere are examined for height layers of 26–35, 36–45 and 46–55 km for the years 1965–76, inclusive. As a comparison, radiosonde-derived temperature variations are examined for the surface to 16 km and 16–24 km layers for the same hemisphere and zones. The rocketsonde data suggest, in general, a warming in middle and upper stratosphere prior to 1970, and a somewhat larger (up to 5°C) cooling thereafter, yielding a temperature variation basically in phase with sunspot number, but the radiosonde data for the low stratosphere do not indicate such a variation. While this discrepancy raises questions concerning the representativeness of either or both sets of data, model findings do suggest that any warming resulting from enhanced ultraviolet radiation at sunspot maximum would be an order of magnitude greater in the middle and high stratosphere than in the low stratosphere. A quasi-biennial oscillation in temperature clearly extends at least up to the stratopause (50 km) in equatorial and subtropical zones, with a maximum amplitude (with the given smoothing) of about 1°C near 30 or 40 km, and a phase shift with height twice as large in the equatorial zone as in the subtropics.