Zonal Wind Quasi-biennial Oscillation Research Articles

Seasonality of the QBO Impact on Equatorial Clouds

AbstractThe Quasi‐Biennial Oscillation (QBO) dominates the interannual variability in the tropical lower stratosphere and is characterized by the descent of alternating easterly and westerly zonal winds. The QBO impact on tropical clouds and convection has received great attention in recent years due to its implications for weather and climate. In this study, a 15‐year record of high vertical resolution cloud observations from CALIPSO and a 50 hPa zonal wind QBO index from ERA5 are used to document the QBO impact on equatorial (10°S–10°N) clouds. Observations from radio occultations, the CERES instrument, and the ERA5 reanalysis are also used to document the QBO impact on temperature, cloud radiative effect (CRE), and zonal wind, respectively. It is shown that the QBO impact on zonal mean equatorial cloud fraction has a strong seasonality. The strongest cloud fraction response to the QBO occurs in boreal spring and early summer, which extends from above the mean tropopause to ∼12.5 km and results in a significant longwave CRE anomaly of 1 W/m2. The seasonality of the QBO impact on cloud fraction is synchronized with the QBO impacts on temperature and zonal wind in the tropical upper troposphere.

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.

Correlations of latitudinal dynamics of atmospheric moisture content with quasi-biennial oscillations of zonal wind in the equatorial stratosphere and solar activity over the north-east of Eurasia during 1979-2015

Correlations of latitudinal dynamics of atmospheric moisture content with quasi-biennial oscillations of zonal wind in the equatorial stratosphere and solar activity over the north-east of Eurasia during 1979-2015

Low‐frequency oscillations of the gravity wave energy density in the lower atmosphere at low latitudes revealed by U.S. radiosonde data

AbstractWe adopted 14 year (from 1998 to 2011) radiosonde data from 16 stations at latitudes between 14.33°S to 29.37°N to investigate the low‐frequency oscillations of inertial gravity wave energy densities (including kinetic energy density, potential energy density, and total energy density) in the lower atmosphere from 2 km to 30 km. Apparent signatures of 11 year solar cycle and quasi‐biennial oscillation (QBO) were found in the gravity wave energy densities in the troposphere and lower stratosphere, respectively. Detailed analyses suggested that the 11 year oscillation and QBO of gravity wave activity might be due to the 11 year oscillation of convection activity and zonal wind QBO modulation, respectively. Besides, the gravity wave energy also showed a 35.2 month oscillation in the lower stratosphere, which might be generated by the interaction between the QBO (with the period of 26.7 months), and the 11 year solar cycle, while more possible causes are the direct modulation from the background zonal wind. Our results showed that the QBO signature in gravity wave total energy density could extend northward to over 20°N in the Northern Hemisphere, while the 11 year solar cycle in gravity wave activity could only extend to lower than 7.5°N. The oscillation with the period of 35.2 months may be a prolonged QBO in both gravity wave activity and background zonal wind.

Total ozone variations and trends during the period 1979–2014

Variations and trends in the total ozone (TO) content over the period 1979–2014 are studied using monthly mean data from ERA-Interim reanalysis database in different latitudinal belts and TOMS/SBUV/OMI satellite data. We estimated how TO variations, averaged over different latitudinal belts and globally, are modulated by Arctic and Antarctic oscillations, quasi-biennial oscillations of zonal wind in the equatorial stratosphere, El Nino–Southern Oscillation, zonal average meridional heat flux in the lower stratosphere, solar activity (SA), stratospheric content of ozone-depleting substances (ODS), and volcanic aerosol particles. Variations in global TO can be described well using regression dependence on ODS and SA; and certain of the above-mentioned factors should be additionally taken into consideration for a more accurate quantitative description of TO time behavior in certain latitudinal belts.

Weakened stratospheric quasibiennial oscillation driven by increased tropical mean upwelling

The zonal wind in the tropical stratosphere switches between prevailing easterlies and westerlies with a period of about 28 months. In the lowermost stratosphere, the vertical structure of this quasibiennial oscillation (QBO) is linked to the mean upwelling, which itself is a key factor in determining stratospheric composition. Evidence for changes in the QBO have until now been equivocal, raising questions as to the extent of stratospheric circulation changes in a global warming context. Here we report an analysis of near-equatorial radiosonde observations for 1953-2012, and reveal a long-term trend of weakening amplitude in the zonal wind QBO in the tropical lower stratosphere. The trend is particularly notable at the 70-hectopascal pressure level (an altitude of about 19 kilometres), where the QBO amplitudes dropped by roughly one-third over the period. This trend is also apparent in the global warming simulations of the four models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) that realistically simulate the QBO. The weakening is most reasonably explained as resulting from a trend of increased mean tropical upwelling in the lower stratosphere. Almost all comprehensive climate models have projected an intensifying tropical upwelling in global warming scenarios, but attempts to estimate changes in the upwelling by using observational data have yielded ambiguous, inconclusive or contradictory results. Our discovery of a weakening trend in the lower-stratosphere QBO amplitude provides strong support for the existence of a long-term trend of enhanced upwelling near the tropical tropopause.

Variability in background stratospheric aerosols over the tropics and its association with atmospheric dynamics

[1] Spatiotemporal variability of background stratospheric aerosols over the tropics (30°S–30°N) and its association with atmospheric dynamics are studied using the zonal-averaged Stratospheric Aerosol and Gas Experiment II (SAGE-II) derived aerosol extinction at 525 nm along with lidar data at 532 nm from Gadanki (13.5°N, 79.2°E) during the period 1998–2005. In general, a pronounced increase in aerosol loading is observed in the spatial distribution of aerosols over the equatorial region compared to the off-equatorial regions. The particulate optical depth (τP) in the lower stratospheric region showed an increasing trend particularly after 2002 in both these regions. This increase could partly be attributed to a corresponding increase in the number of feeble/minor volcanic eruptions. Over and above this steady increase, the τP also showed significant periodic variations. In addition to the prominent short-period variations, the stratospheric τP showed a significant biennial variation (with a period of ∼30 months) in association with stratospheric quasi-biennial oscillation in zonal wind (QBOU). During the westerly phase of stratospheric QBOU, the mean particulate optical depth decreases rapidly with increase in latitude on either side of equator in both the hemispheres, while it remains fairly steady around the equator up to 15° in latitude on either side with a small bite-out around the equator during the easterly phase, particularly during the very quiet period of 1998–2002. During the latter half (after 2002), when the stratosphere was mildly disturbed, the latitudinal variation of τP was fairly similar in both phases of QBOU with a higher value of τP near the equator during the westerly phase. The QBO signal in aerosol extinction around 25 km is found to be in opposite phase with that observed in the upper regime (28–32 km) and lower regime (18–22 km), depicting the influence of the secondary meridional circulation produced owing to vertical shear of QBOU in the equatorial region.

The Influence of the 11‐year Sunspot Cycle on the Atmospheric Circulation During Winter

AbstractBased on reanalysis data of the meteorological field and sunspot cycle index, the influences of the 11‐year sunspot cycle (SSC) on stratospheric and tropospheric circulation during winter (November to March) in the northern hemisphere are investigated by using statistical analysis and dynamical diagnosis. According to the east or west phase of stratospheric equatorial zonal wind quasi biennial oscillation (QBO), we have analyzed the solar effects in different situations. In east QBO phases, the solar effects focus on the equatorial upper stratosphere and southern hemispheric stratosphere, where enhanced solar ultraviolet radiations heat up the stratospheric ozone layer, leading to increase of the temperature apparently. The solar maxima events reinforce the southern stratospheric Brewer‐Dobson circulation, and result in warming of the southern polar areas. The planetary wave plays a significant role in high latitudes regions of the northern hemisphere, hence the solar cycle signals could be nearly neglected. In west QBO phases, solar effects are more important in north hemisphere. In early winter, solar maxima effects are not only warming the equatorial stratospheric ozone, but also restraining the northern atmospheric B‐D circulation, leading to increase of the equatorial stratospheric temperature and zonal wind gradient change, hence the two waveguides of planetary wave are altered after those processes. In late winter, the polar waveguide of planetary wave is enhanced by solar effects and the B‐D circulation is recovered gradually. After these procedures the temperature of northern polar stratosphere starts to increase conspicuously, accompanied by the decrease of equatorial zonal temperature.

Trends in total ozone and the effect of the equatorial zonal wind QBO

Trends in total column ozone have been analyzed in terms of the equatorial zonal wind. We used zonal monthly mean total ozone from Total Ozone Mapping Spectrometer (TOMS) and monthly mean zonal wind in the equatorial stratosphere at 30 hPa to define the phases of the quasi-biennial oscillation (QBO). Total column ozone trends have been assessed during the period 1979–2004, for both Hemispheres, and for each month, under three conditions considering, all the ozone dataset, ozone values during easterly phase and ozone values during westerly phase of the QBO. When the whole dataset is considered, negative trends are observed. From low to midlatitudes a zonal pattern is noticed with increasing negative values toward higher latitudes. When the data is filtered according to the QBO phase, statistically significant positive trends appear in the westerly case during January to May at low latitudes .The trend pattern in the case of the easterly phase presents more negative values.

Structural stability of quasi-biennial oscillations of zonal wind in the equatorial stratosphere

Structural stability of quasi-biennial oscillations of zonal wind in the equatorial stratosphere

An investigation of long-term variability of ozone 3-dimensional fields in the tropics connected with the 11-year solar cycle and peculiarities of the general atmospheric circulation

In this study, the long-term features of 3-dimensional ozone fields in the tropics (30° S– 30° N) over the 25-year period (1979–2003) based on the solar backscatter ultraviolet (SBUV) version 8 satellite observations were analysed. The application of the Empirical Orthogonal Function (EOF) decomposition allows characteristic spatial and temporal patterns to be identified in fields of partial ozone pressure anomalies, which are closely related to the natural causes such as the 11-year solar cycle, the Quasi Biennial Oscillation (QBO) and the Quasi Biennial Oscillation and an Annual Beat (QBO-AB). Also the vertical structure of the ozone QBO at the equator was investigated in comparison with the vertical structure of the zonal wind QBO. The analysis of the SBUV ozone data showed that the phase of the ozone QBO at the equator remains constant within the layer 10–50 hPa.

Simulation of the quasi-biennial oscillations of the zonal wind in the equatorial stratosphere: Part II. Atmospheric general circulation models

The problem of simulating quasi-biennial oscillations (QBOs) of zonal velocity in the equatorial stratosphere in atmospheric general circulation models is considered. In accordance with the results from Part I of this study on the basis of the models developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences (INM RAS), the possibility of implementing (in these models) mechanisms of QBO excitation through both the interaction of planetary waves with the mean flow and breaking of short gravity waves is investigated. A new high-resolution 2° × 2.5° × 80 version of the INM RAS model is designed, a climate simulation with the two 2° × 2.5° × 39 and 2° × 2.5° × 80 versions of the INM RAS model is briefly described, results of spectral analysis of equatorial wave activity are presented, and the QBO formation processes in these models are considered in detail. For the new 2° × 2.5° × 80 model, realistic QBOs of zonal wind are obtained as the result of the action of both mechanisms.

Integral microphysical parameters of stratospheric background aerosol for 2002–2005 (the SAGE III satellite experiment)

The surface area and volume densities (S and V) of the particles of stratospheric background aerosol in the 15–20 km and 20–25 km layers for 2002–2005 were obtained from measurements of the aerosol extinction coefficient with the SAGE III instrument by using the linear-regression method of solving the inverse problem. The measurements were taken within the latitudinal belts 43°–80°N and 34°–58°S. The spatial and temporal dependences of S and V demonstrate homogeneous distribution fields in summer, whereas noticeable inhomogeneities are observed in winter and early spring. In all years of the measurements, an increase in the integral characteristics of stratospheric background aerosol was observed during the fall-to-winter transition period. Longitudinal variations in S and V can be both slight and significant (50–70%). Analysis of the interannual variability of the mean areas and volumes of aerosol particles shows that their minima (as a rule) were observed in 2002 and their maxima were observed in 2005. In most of the cases, no monotonic annual variations in the aerosol characteristics are noted. The dependence of the aerosol parameters on the phase of the quasi-biennial oscillations of zonal wind in the stratosphere is observed. The data obtained for 2002–2005 are, on the whole, in good agreement with the climatological data obtained for 1996–1999.

Solar‐QBO interaction and its impact on stratospheric ozone in a zonally averaged photochemical transport model of the middle atmosphere

We investigate the solar cycle modulation of the quasi‐biennial oscillation (QBO) in stratospheric zonal winds and its impact on stratospheric ozone with an updated version of the zonally averaged CHEM2D middle atmosphere model. We find that the duration of the westerly QBO phase at solar maximum is 3 months shorter than at solar minimum, a more robust result than in an earlier CHEM2D study due to reduced Rayleigh friction drag in the present version of the model. The modeled solar cycle ozone response, determined via multiple linear regression, is compared with observational estimates from the combined Solar Backscattered Ultraviolet (SBUV/2) data set for the period 1979–2003. We find that a model simulation including imposed solar UV variations, the zonal wind QBO, and an imposed 11‐year variation in planetary wave 1 amplitude produces a lower stratospheric ozone response of ∼2.5% between 0 and 20°S and an upper stratospheric ozone response of ∼1% between 45 and 55 km, in good agreement with the SBUV‐derived ozone response. This simulation also produces an (enhancement/reduction) in the (lower/upper) stratospheric temperature response at low latitudes compared to the effects of solar UV variations alone, which are consistent with model vertical velocity anomalies produced by the solar‐modulated QBO and imposed changes in planetary wave forcing.

Periodic behavior of groundwater level fluctuations in residential areas

For residential cities and their suburbs the continuous increase in groundwater level constitutes a common problem that can threaten the buried pipeline systems and structures, as well as road pavements. In this paper, the periodic pattern of groundwater level fluctuations is investigated for six monitoring wells located in residential areas in Kuwait. Monthly water level measurements obtained from the monitoring wells for periods varying from 8 to 10 years are employed to examine the relationship with monthly-averaged temperature and -totaled rainfall. The periodograms of the water level, rainfall, and temperature data are also determined. The results reveal that the annual periodicity typically observed in the last two climatological data sets can significantly be identified in all the series of subsurface water level examined here. Other periodicities of 27 and 18 months existing in the periodogram of rainfall are identified in two and four water level series, respectively. It is advocated here that the 27-month period present in the rainfall data of Kuwait is attributed to the well-known Quasi-Biennial Oscillation in zonal wind, which has been reported by many researchers for areas near the equator such as India and Indonesia. A time series model that triggers the influence of the detected periodicities is developed for the water level data to show an example of exploiting the fluctuation pattern for providing forecasts of groundwater table changes. The model can possibly be used to set a time plan for starting a continuous dewatering process to avoid problems related to groundwater level rise in residential areas.

Abnormal behavior of total ozone over Indian region during 1991-98

The total column ozone variation over India has been studied using monthly mean ozone for the period of 18 years from 1981 to 1998, which were collected with Dobson Spectrophotometer at four Indian stations, New Delhi (28° N), Varanasi (24° N), Pune (18° N), and Kodaikanal (10° N). The effect of atmospheric phenomena like Quasi Biennial Oscillation (QBO), solar cycle and volcanic eruptions (El Chichon of 1982, Mt. Pinatubo of 1991) on ozone variations has also been explored in this paper. The results of the analysis has shown that the ozone variations in the tropical region seem to have mostly caused by the equatorial QBO in zonal wind at lower stratosphere and solar cycle. During the period 1981-90, there is no much year to year variability in total ozone, whereas during the period 1991-98, much variability is observed between year to year. The total ozone is decreased from 1991 to 1993 and later started recovering. The ozone anomalies calculated for the period 1981-98 showed positive anomaly for the period 1981-90 and negative anomaly for the period 1991-98. Though the contribution of QBO and solar cycle to total ozone for the two different periods of 1981-90 and 1991-98 is almost same, the total ozone amounts for the later period are lower. These lower ozone amounts may be attributed to the Mt. Pinatubo volcanic eruption.

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.

The features of ozone quasi—biennial oscillation in tropical stratosphere and its numerical simulation

The inlcrunnual variation of the vertical distribution of ozone in the tropical stratosphere and its quasi—biennial oscillation (QBO) is analyzed using HALOE data. The results are compared with the wind QBO. A numerical experiment is carried out to study the effects of wind QBO on the distribution, and variation of ozone in the stratosphere by using (he NCAR interactive chemical, dynamical, and radiative two—dimensional model (SOCRATES). Data analysis shows that the location of the maximum ozone mixing ratio in the stratosphere changes in the meridional and vertical directions, and assumes a quasi—biennial period. The meridional and vertical motion of the maximum mixing ratio leads to a QBO of column ozone and its hemispheric asymmetry. The QBO of the location of the maximum is closely connected with the zonal wind QBO. The data analysis also shows that in the tropical region, the phase of the QBO for ozone density changes many times with height. Numerical simulation shows that the meridional circulation induced by the wind QBO includes three pairs of cells in the stratosphere, which have hemispheric symmetry. The transport of ozone by the induced meridional circulation in various latitudes and heights is the main dynamic cause for the ozone QBO. Cells of the induced circulation in the middle stratosphere (25-35 km) play an important role in producing the ozone QBO.

Quasi‐biennial oscillation in vertical velocity inferred from trace gas data in the equatorial lower stratosphere

Vertical velocity variations associated with the quasi‐biennial oscillation (QBO) in the equatorial lower stratosphere are investigated with the Halogen Occultation Experiment (HALOE) data from 1993 to 1998. The vertical velocity is inferred from ascent rates of an annual cycle in total water ([H2O] + 2[CH4]) profiles around the 20–60 hPa layer over the equator. The zonally averaged ascent rates of total water anomalies exhibit QBO‐related variations with anomalies of 0.10–0.15 mm s−1 between 20 and 40 hPa at the equator, whereas there scarcely exists an annual cycle in the ascent rates. The QBO variation of the ascent rates shows that its positive anomalies precede negative anomalies of temperature and ozone variations by about 2–3 months at the equator and 30–60 hPa. This phase relationship is in conflict with former results from several two‐dimensional model studies, which have reported that vertical velocity variations are almost out of phase with temperature anomalies preceding ozone anomalies by a few months. It is supposed that these differences could be caused by the observed large tendency of temperature anomalies, which is related to the observed rapid acceleration of the QBO westerly. An estimate of vertical advection of zonal momentum expected from the ascent rates suggests that the asymmetric acceleration of the zonal wind QBO can be explained by the QBO‐induced vertical velocity being asymmetric between the easterly and the westerly shear zones.