Quasi-Biennial Oscillation in Stratospheric Zonal Wind and Indian Summer Monsoon

Abstract In the past the stratospheric quasi-biennial oscillation (QBO) has sometimes been proposed to explain the tendency for the Indian summer monsoon (ISM) to alternate between strong and weak years. In this study, NCEP Reanalysis-2 (R-2) and Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) fields are statistically analyzed to assess the relationship between equatorial zonal winds in the stratosphere and ISM. In a first step, it is shown that zonal winds at 15 hPa during the preceding winter (January–February) are the best stratospheric predictor of the summer rainfall over the Indian subcontinent as a whole. This relationship mainly holds for August and September, or the late ISM. Surprisingly, the QBO pattern is not significantly associated with the rainfall variability during June–July or the early ISM. CMAP and NCEP R-2 fields corroborate these findings and show that westerly QBO years are associated with a deepening of the monsoon trough over the Gangetic plains and decreased convective activity in the eastern equatorial Indian region. However, further statistical analysis shows that the QBO–ISM link is complex since a westerly QBO phase at 15 hPa in boreal winter leads to a weaker monsoon surface circulation with, in particular, a weakening of the Somali jet at the beginning of the monsoon, but a much stronger circulation in September. At that time, the Tibetan high is reinforced, the tropical easterly jet at 200 hPa is stronger over India, and the local reversed Hadley circulation is also strengthened north of the equator. The mechanisms by which the QBO may affect ISM have been explored through, in particular, correlations between stratospheric winds and tropopause temperature and pressure fields. The results provide support for an out-of-phase behavior of convective activity between the Indian subcontinent and the equatorial Indian Ocean induced by the QBO phase, especially during the late ISM. During a westerly QBO phase, convective activity is, in September, enhanced over India, which brings higher precipitation, compared to the east phase. This work also suggests that the winter QBO at 15 hPa could have some skill in foreshadowing the late ISM.

Download Full-text

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

Journal of Climate ◽

10.1175/jcli-d-16-0464.1 ◽

2017 ◽

Vol 30 (17) ◽

pp. 6977-6997 ◽

Cited By ~ 4

Author(s):

Hiroaki Naoe ◽

Makoto Deushi ◽

Kohei Yoshida ◽

Kiyotaka Shibata

Keyword(s):

Zonal Wind ◽

Climate Model ◽

Vertical Shear ◽

Quasi Biennial Oscillation ◽

The Past ◽

Meteorological Research Institute ◽

Climate Simulations ◽

The Future ◽

Ozone Depleting Substances ◽

Biennial Oscillation

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.

Download Full-text

The Influence of the Quasi-Biennial Oscillation on the Troposphere in Winter in a Hierarchy of Models. Part I: Simplified Dry GCMs

Journal of the Atmospheric Sciences ◽

10.1175/2011jas3665.1 ◽

2011 ◽

Vol 68 (6) ◽

pp. 1273-1289 ◽

Cited By ~ 50

Author(s):

Chaim I. Garfinkel ◽

Dennis L. Hartmann

Keyword(s):

Zonal Wind ◽

Climate Model ◽

Polar Vortex ◽

Equation Model ◽

Quasi Biennial Oscillation ◽

Stratospheric Polar Vortex ◽

The North ◽

Subtropical Jet ◽

Long Time ◽

Biennial Oscillation

Abstract A dry primitive equation model is used to explain how the quasi-biennial oscillation (QBO) of the tropical stratosphere can influence the troposphere, even in the absence of tropical convection anomalies and a variable stratospheric polar vortex. QBO momentum anomalies induce a meridional circulation to maintain thermal wind balance. This circulation includes zonal wind anomalies that extend from the equatorial stratosphere into the subtropical troposphere. In the presence of extratropical eddies, the zonal wind anomalies are intensified and extend downward to the surface. The tropospheric response differs qualitatively between integrations in which the subtropical jet is strong and integrations in which the subtropical jet is weak. While fluctuation–dissipation theory provides a guide to predicting the response in some cases, significant nonlinearity in others, particularly those designed to model the midwinter subtropical jet of the North Pacific, prevents its universal application. When the extratropical circulation is made zonally asymmetric, the response to the QBO is greatest in the exit region of the subtropical jet. The dry model is able to simulate much of the Northern Hemisphere wintertime tropospheric response to the QBO observed in reanalysis datasets and in long time integrations of the Whole Atmosphere Community Climate Model (WACCM).

Download Full-text

Observational evidences of the influences of tropospheric subtropical and midlatitude stratospheric westerly jets on the equatorial stratospheric intraseasonal oscillations

10.5194/acp-2016-118 ◽

2016 ◽

Author(s):

G. Karthick Kumar Reddy ◽

T. K. Ramkumar ◽

S. Venkatramana Reddy

Keyword(s):

Zonal Wind ◽

Lower Atmosphere ◽

Theoretical Modelling ◽

Quasi Biennial Oscillation ◽

Medium Range Weather Forecast ◽

Westerly Jet ◽

Longitudinal Sector ◽

Vertical Propagation ◽

Biennial Oscillation ◽

Subtropical Westerly Jet

Abstract. Using six Global Positioning System (GPS) Radio Occultation (RO) satellites (SAC-C, METOP-A and COSMIC/FORMOSAT-3, CNOFS, GRACE and TerraSAR-X) determined height profiles (1–40 km) of atmospheric temperature over the Indian tropical station of Gadanki and the European Center for Medium Range Weather Forecast (ECMWF) Interim Reanalyses (ERA-Interim) zonal wind and temperature data for four years (2009–2012), the present work reports that the tropospheric Subtropical Westerly Jet (SWJ) and the Midlatitude Stratospheric Westerly Jet (MStWJ) play important roles in controlling differently the vertical propagation of tropical Intra Seasonal Oscillations (ISO) with different period bands from the troposphere up to the stratosphere during Northern winters. In the months of December–May (Northern winter to summer, NWTS) of all these years, there is significant 10–20 day and 20–40 day oscillations in the troposphere up to the height of 13 km and above this it reappears at all heights above 21 km. The 40–80 day oscillation also shows similar characteristics except that it almost disappeared during NWTS months of the year 2010–2011 in the stratosphere. The absence of these signals in the intervening heights of ~ 17–20 km is explained on the basis that these two bands actually propagate from the tropical to subtropical region near the tropopause and then reappears in the tropical stratosphere after refracted by the subtropical westerly jet. The poleward and equatorward propagation of these bands in the troposphere and stratosphere respectively are found using the ERA-interim data. Further the two longer period bands of ISO show strong quasi-biennial oscillation in the lower atmosphere with opposite phases (when one band shows maximum the other one shows minimum in a particular year) between these two bands. It is also observed that the phase of the tropical stratospheric Quasi Biennial Oscillation (QBO) has significant control on the strength of the Mid latitude stratospheric westerly jet (MStWJ) that in turn controls the refraction of the tropical tropospheric longer (40–80 days, Longer period ISO; LISO) but not the smaller periods of ISO (SISO) back to the tropical stratosphere. In accordance with earlier theoretical modelling studies, the westerly phase of the lower stratospheric QBO occurred during NWTS months of 2010–2011 over the Indian longitudinal sector causes severe disruption of the MStWJ at 30 km height. This disruption caused the prevention of refraction back again to the tropical stratosphere of significant tropospheric LISO that arrived from the tropics through the tropopause. Further, in these four years, it is observed no direct vertical propagation of tropical tropospheric ISO to the stratosphere. The interannual variations in the tropical stratospheric LISO are related strongly to the phase of the equatorial lower stratospheric QBO in zonal wind and the strength of the MStWJ.

Download Full-text

Influence of the Quasi-Biennial Oscillation on the Extratropical Winter Stratosphere in an Atmospheric General Circulation Model and in Reanalysis Data

Journal of the Atmospheric Sciences ◽

10.1175/2009jas3292.1 ◽

2010 ◽

Vol 67 (5) ◽

pp. 1402-1419 ◽

Cited By ~ 31

Author(s):

James A. Anstey ◽

Theodore G. Shepherd ◽

John F. Scinocca

Keyword(s):

Zonal Wind ◽

General Circulation ◽

Polar Vortex ◽

Reanalysis Data ◽

Empirical Orthogonal Functions ◽

Vertical Profiles ◽

Quasi Biennial Oscillation ◽

Stratospheric Polar Vortex ◽

Atmospheric General Circulation ◽

Biennial Oscillation

Abstract The interannual variability of the stratospheric polar vortex during winter in both hemispheres is observed to correlate strongly with the phase of the quasi-biennial oscillation (QBO) in tropical stratospheric winds. It follows that the lack of a spontaneously generated QBO in most atmospheric general circulation models (AGCMs) adversely affects the nature of polar variability in such models. This study examines QBO–vortex coupling in an AGCM in which a QBO is spontaneously induced by resolved and parameterized waves. The QBO–vortex coupling in the AGCM compares favorably to that seen in reanalysis data [from the 40-yr ECMWF Re-Analysis (ERA-40)], provided that careful attention is given to the definition of QBO phase. A phase angle representation of the QBO is employed that is based on the two leading empirical orthogonal functions of equatorial zonal wind vertical profiles. This yields a QBO phase that serves as a proxy for the vertical structure of equatorial winds over the whole depth of the stratosphere and thus provides a means of subsampling the data to select QBO phases with similar vertical profiles of equatorial zonal wind. Using this subsampling, it is found that the QBO phase that induces the strongest polar vortex response in early winter differs from that which induces the strongest late-winter vortex response. This is true in both hemispheres and for both the AGCM and ERA-40. It follows that the strength and timing of QBO influence on the vortex may be affected by the partial seasonal synchronization of QBO phase transitions that occurs both in observations and in the model. This provides a mechanism by which changes in the strength of QBO–vortex correlations may exhibit variability on decadal time scales. In the model, such behavior occurs in the absence of external forcings or interannual variations in sea surface temperatures.

Download Full-text

Influence of the Equatorial QBO on the Extratropical Stratosphere

Journal of the Atmospheric Sciences ◽

10.1175/jas3657.1 ◽

2006 ◽

Vol 63 (3) ◽

pp. 936-951 ◽

Cited By ~ 18

Author(s):

John Hampson ◽

Peter Haynes

Keyword(s):

Correlation Coefficient ◽

Zonal Wind ◽

Potential Temperature ◽

Lower Boundary ◽

Quasi Biennial Oscillation ◽

Wave Forcing ◽

Least Squares Fit ◽

Phase Alignment ◽

Biennial Oscillation ◽

Extratropical Circulation

Abstract The work described here examines the influence of the equatorial quasi-biennial oscillation (QBO) on the extratropics in a zonally truncated 3D mechanistic stratospheric model. Model results show that the extratropical response to the QBO depends critically on the phase alignment of the QBO with the annual cycle: the signal of extratropical response varies by a factor of 8 between the phase alignment that gives minimum response and that which gives maximum response. Model simulations in which the time and height structure of the QBO are varied suggest that, in this zonally truncated model, the equatorial height of 21–23 km is most influential for the extratropical response and that late autumn/early winter is the time at which the QBO has the most influence over the extratropical circulation. The correlation coefficient between the QBO (measured by zonal wind) and the extratropics (measured by zonal wind or potential temperature) is as high as 0.95. The correlation coefficient is largest for simulations with lower boundary wave forcing weaker than that which gives largest extratropical interannual variability. For stronger extratropical wave forcing, the correlation coefficient is slightly smaller, but the regression coefficient of the linear term in a least squares fit is significantly larger.

Download Full-text

Global Balanced Wind Derived from SABER Temperature and Pressure Observations and its Validations

10.5194/essd-2021-192 ◽

2021 ◽

Author(s):

Xiao Liu ◽

Jiyao Xu ◽

Jia Yue ◽

You Yu ◽

Paulo P. Batista ◽

...

Keyword(s):

Zonal Wind ◽

Meteor Radar ◽

Quasi Biennial Oscillation ◽

Height Range ◽

Zonal Winds ◽

Wind Theory ◽

Temperature And Pressure ◽

Identical Zero ◽

Biennial Oscillation ◽

Good Agreement

Abstract. Zonal winds in the stratosphere and mesosphere play important roles in the atmospheric dynamics and aeronomy. However, the direct measurement of winds in this height range is difficult. We present a dataset of the monthly mean zonal wind in the height range of 18–100 km and at latitudes of 50° S–50° N from 2002 to 2019, which is derived by the gradient balance wind theory and the temperature and pressure observed by the SABER instrument. The tide alias above 80 km at the equator is replaced by the monthly mean zonal wind measured by a meteor radar at 0.2° S. The dataset (named as BU) is validated by comparing with the zonal wind from MERRA2 (MerU), UARP (UraU), HWM14 empirical model (HwmU), meteor radar (MetU) and lidar (LidU) at seven stations from 53.5° N to 29.7° S. At 18–70 km, BU and MerU have (1) nearly identical zero wind lines, (2) year-to-year variations of the eastward/westward wind jets at middle and high latitudes, (3) the quasi-biennial oscillation (QBO) and semi-annual oscillation (SAO), especially the anormal QBO in early 2016. The comparisons among BU, UraU and HwmU show good agreement in general below 80 km. Above 80 km, the agreements among BU, UraU, HwmU, MetU and LidU are good in general, except some discrepancies at limited heights and months. The BU data are archived as netCDF files and can be available at https://dx.doi.org/10.12176/01.99.00574 (Liu et al., 2021).

Download Full-text

Representation of the Equatorial Stratopause Semiannual Oscillation in Global Atmospheric Reanalyses

10.5194/acp-2020-73 ◽

2020 ◽

Author(s):

Yoshio Kawatani ◽

Toshihiko Hirooka ◽

Kevin Hamilton ◽

Anne K. Smith ◽

Masatomo Fujiwara

Keyword(s):

Zonal Wind ◽

Good Representation ◽

Polar Regions ◽

Quasi Biennial Oscillation ◽

Amplitude Maximum ◽

Systematic Improvement ◽

Stratospheric Circulation ◽

Biennial Oscillation ◽

Semiannual Oscillation

Abstract. This paper reports on a project to compare the representation of the semiannual oscillation (SAO) in the equatorial stratosphere and lower mesosphere among six major global atmospheric reanalysis datasets and with recent satellite SABER and MLS observations. All reanalyses have a good representation of the quasi-biennial oscillation (QBO) in the equatorial lower and middle stratosphere and each displays a clear SAO centered near the stratopause. However, the differences among reanalyses are much more substantial in the SAO region than in the QBO dominated region. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly-mean zonal wind and temperature; this depends on latitude, longitude, height, and time. The zonal wind SD displays a prominent equatorial maximum that increases with height, while the temperature SD is minimum near the equator and largest in the polar regions. Along the equator the zonal wind SD is smallest around the longitude of Singapore where consistently high-quality near-equatorial radiosonde observations are available. Interestingly the near-Singapore minimum in SD is evident to at least ~ 3 hPa, i.e. considerably higher than the usual ~ 10 hPa ceiling for in situ radiosonde observations. Our measurement of the agreement among the reanalyses shows systematic improvement over the period considered (1980–2016), up to near the stratopause. Characteristics of the SAO at 1 hPa, such as its detailed time variation and the displacement off the equator of the zonal wind SAO amplitude maximum, differ significantly among the reanalyses. Disagreement among the reanalyses becomes still greater above 1 hPa. One of the reanalyses in our study also has a version produced without assimilating satellite observations and a comparison of the SAO in these two versions demonstrates the very great importance of satellite derived temperatures in the realistic analysis of the tropical upper stratospheric circulation.

Download Full-text

Equatorial annual oscillation with QBO-driven 5-year modulation in NCEP data

Annales Geophysicae ◽

10.5194/angeo-25-37-2007 ◽

2007 ◽

Vol 25 (1) ◽

pp. 37-45 ◽

Cited By ~ 11

Author(s):

H. G. Mayr ◽

J. G. Mengel ◽

F. T. Huang ◽

E. R. Nash

Keyword(s):

Spectral Analysis ◽

Zonal Wind ◽

Lower Stratosphere ◽

Circumstantial Evidence ◽

High Latitudes ◽

Time Intervals ◽

Quasi Biennial Oscillation ◽

Temperature Variations ◽

Environmental Prediction ◽

Biennial Oscillation

Abstract. An analysis is presented of the stratospheric zonal wind and temperature variations supplied by the National Center for Environmental Prediction (NCEP). The derived zonal-mean variations are employed. Stimulated by modeling studies, the data are separated into the hemispherically symmetric and anti-symmetric components, and spectral analysis is applied to study the 12-month annual oscillation (AO) and the quasi-biennial oscillation (QBO). For data samples that cover as much as 40 years, the zonal wind results reveal a pronounced 5-year modulation of the symmetric AO in the lower stratosphere, which is confined to equatorial latitudes. This modulation is also seen in the temperature variations but extends to high latitudes, qualitatively consistent with published model results. A comparison between different time intervals of the data indicates that the signature of the 5-year oscillation is larger when the QBO of 30 months is more pronounced. Thus there is circumstantial evidence that this particular QBO period is involved in generating the oscillation as was shown in a modeling study (Mayr et al., 2000). In agreement with the model, the spectral analysis also reveals a weak anti-symmetric 5-year oscillation in the zonal wind data, which could interact with the strong anti-symmetric AO to produce the modulation of the symmetric AO. The 30-month QBO is well suited to be synchronized by, and phase-locked to, the equatorial semi-annual oscillation (SAO), and this may explain why this QBO periodicity and its 5-year spin-off are observed to persist for many cycles.

Download Full-text