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

2010 ◽  
Vol 67 (5) ◽  
pp. 1402-1419 ◽  
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.

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

2011 ◽  
Vol 68 (6) ◽  
pp. 1273-1289 ◽  
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).

scholarly journals A tropospheric pathway of the stratospheric quasi-biennial oscillation (QBO) impact on the boreal winter polar vortex

2020 ◽  
Author(s):  
Koji Yamazaki ◽  
Tetsu Nakamura ◽  
Jinro Ukita ◽  
Kazuhira Hoshi
Keyword(s):  
General Circulation ◽  
Wave Train ◽  
Polar Vortex ◽  
Circulation Model ◽  
Periodic Oscillation ◽  
Boreal Winter ◽  
Stationary Waves ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Biennial Oscillation

Abstract. The quasi-biennial oscillation (QBO) is quasi-periodic oscillation of the tropical zonal wind in the stratosphere. When the tropical lower stratospheric wind is easterly (westerly), the winter Northern Hemisphere (NH) stratospheric polar vortex tends to be weak (strong). This relation is known as Holton–Tan relationship. Several mechanisms for this relationship have been proposed, especially linking the tropics with high-latitudes through stratospheric pathway. Although QBO impacts on the troposphere have been extensively discussed, a tropospheric pathway of the Holton–Tan relationship has not been explored previously. We here propose a tropospheric pathway of the QBO impact, which may partly account for the Holton–Tan relationship in early winter, especially in the November–December period. The study is based on analyses on observational data and results from a simple linear model and atmospheric general circulation model (AGCM) simulations. The mechanism is summarized as follows: the easterly phase of the QBO is accompanied with colder temperature in the tropical tropopause layer, which enhances convective activity over the tropical western Pacific and suppresses over the Indian Ocean, thus enhancing the Walker circulation. This convection anomaly generates Rossby wave train, propagating into the mid-latitude troposphere, which constructively interferences with the climatological stationary waves, especially in wavenumber 1, resulting in enhanced upward propagation of the planetary wave and a weakened polar vortex.

scholarly journals A tropospheric pathway of the stratospheric quasi-biennial oscillation (QBO) impact on the boreal winter polar vortex

2020 ◽  
Vol 20 (8) ◽  
pp. 5111-5127
Author(s):  
Koji Yamazaki ◽  
Tetsu Nakamura ◽  
Jinro Ukita ◽  
Kazuhira Hoshi
Keyword(s):  
General Circulation ◽  
Wave Train ◽  
Polar Vortex ◽  
Circulation Model ◽  
Periodic Oscillation ◽  
Boreal Winter ◽  
Stationary Waves ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Biennial Oscillation

Abstract. The quasi-biennial oscillation (QBO) is quasi-periodic oscillation of the tropical zonal wind in the stratosphere. When the tropical lower stratospheric wind is easterly (westerly), the winter Northern Hemisphere (NH) stratospheric polar vortex tends to be weak (strong). This relation is known as the Holton–Tan relationship. Several mechanisms for this relationship have been proposed, especially linking the tropics with high latitudes through stratospheric pathway. Although QBO impacts on the troposphere have been extensively discussed, a tropospheric pathway of the Holton–Tan relationship has not been explored previously. Here, we propose a tropospheric pathway of the QBO impact, which may partly account for the Holton–Tan relationship in early winter, especially in the November–December period. The study is based on analyses of observational data and results from a simple linear model and atmospheric general circulation model (AGCM) simulations. The mechanism is summarized as follows: the easterly phase of the QBO is accompanied with colder temperature in the tropical tropopause layer, which enhances convective activity over the tropical western Pacific and suppresses it over the Indian Ocean, thus enhancing the Walker circulation. This convection anomaly generates a Rossby wave train, propagating into the midlatitude troposphere, which constructively interferences with the climatological stationary waves, especially in wavenumber 1, resulting in enhanced upward propagation of the planetary wave and a weakened polar vortex.

scholarly journals How Does the Quasi-Biennial Oscillation Affect the Stratospheric Polar Vortex?

2013 ◽  
Vol 71 (1) ◽  
pp. 391-409 ◽  
Author(s):  
Peter A. G. Watson ◽  
Lesley J. Gray
Keyword(s):  
Time Scales ◽  
Transient Response ◽  
General Circulation ◽  
Polar Vortex ◽  
Circulation Model ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Novel Approach ◽  
Dynamical Time ◽  
Biennial Oscillation

Abstract The stratospheric polar vortex is weaker in the easterly phase of the quasi-biennial oscillation (QBO-E) than in the westerly phase (QBO-W), but the mechanism behind the QBO's influence is not well understood. The composite difference of the atmospheric state between QBO-E and QBO-W is found to closely resemble the structure of the northern annular mode, the leading empirical orthogonal function of stratospheric variability, including its wave components. Studies of dynamical systems indicate that many different forcings could give rise to this response, and therefore this composite difference does not provide much information about the forcing mechanism. It is argued that the full transient response of a system to an applied forcing is likely to be much more informative about the dynamics of the forcing mechanism, especially the response on time scales shorter than the dynamical time scale, which is about a week for vortex variability. It is shown that the transient response of the vortex to forcing by the QBO in a general circulation model is consistent with the proposed mechanism of Holton and Tan, indicating that this mechanism has a role in the QBO modulation of vortex strength, in contrast to the conclusions of several recent studies. This novel approach of examining the transient response to a forcing on short time scales may be useful in various other outstanding problems.

scholarly journals Does the Holton–Tan Mechanism Explain How the Quasi-Biennial Oscillation Modulates the Arctic Polar Vortex?

2012 ◽  
Vol 69 (5) ◽  
pp. 1713-1733 ◽  
Author(s):  
Chaim I. Garfinkel ◽  
Tiffany A. Shaw ◽  
Dennis L. Hartmann ◽  
Darryn W. Waugh
Keyword(s):  
Zonal Wind ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
Critical Line ◽  
Polar Vortex ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Mean Meridional Circulation ◽  
The Mean ◽  
Biennial Oscillation

Abstract Idealized experiments with the Whole Atmosphere Community Climate Model (WACCM) are used to explore the mechanism(s) whereby the stratospheric quasi-biennial oscillation (QBO) modulates the Northern Hemisphere wintertime stratospheric polar vortex. Overall, the effect of the critical line emphasized in the Holton–Tan mechanism is less important than the effect of the mean meridional circulation associated with QBO winds for the polar response to the QBO. More specifically, the introduction of easterly winds at the equator near 50 hPa 1) causes enhanced synoptic-scale Eliassen–Palm flux (EPF) convergence in the subtropics from 150 to 50 hPa, which leads to the subtropical critical line moving poleward in the lower stratosphere, and 2) creates a barrier to planetary wave propagation from subpolar latitudes to midlatitudes in the middle and upper stratosphere (e.g., less equatorward EPF near 50°N), which leads to enhanced planetary wave convergence in the polar vortex region. These two effects are mechanistically distinct; while the former is related to the subtropical critical line, the latter is due to the mean meridional circulation of the QBO. All of these effects are consistent with linear theory, although the evolution of the entire wind distribution is only quasi-linear because induced zonal wind changes cause the wave driving to shift and thereby positively feed back on the zonal wind changes. Finally, downward propagation of the QBO in the equatorial stratosphere, upper stratospheric equatorial zonal wind, and changes in the tropospheric circulation appear to be less important than lower stratospheric easterlies for the polar stratospheric response. Overall, an easterly QBO wind anomaly in the lower stratosphere leads to a weakened stratospheric polar vortex, in agreement with previous studies, although not because of changes in the subtropical critical line.

The Influence of the Quasi-Biennial Oscillation on the Troposphere in Winter in a Hierarchy of Models. Part II: Perpetual Winter WACCM Runs

2011 ◽  
Vol 68 (9) ◽  
pp. 2026-2041 ◽  
Author(s):  
Chaim I. Garfinkel ◽  
Dennis L. Hartmann
Keyword(s):  
Climate Model ◽  
Deep Convection ◽  
Polar Vortex ◽  
Reanalysis Data ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Thermal Wind ◽  
The North ◽  
Tropical Deep Convection ◽  
Biennial Oscillation

Abstract Experiments with the Whole Atmosphere Community Climate Model (WACCM) are used to understand the influence of the stratospheric tropical quasi-biennial oscillation (QBO) in the troposphere. The zonally symmetric circulation in thermal wind balance with the QBO affects high-frequency eddies throughout the extratropical troposphere. The influence of the QBO is strongest and most robust in the North Pacific near the jet exit region, in agreement with observations. Variability of the stratospheric polar vortex does not appear to explain the effect of the QBO in the troposphere in the model, although it does contribute to the response in the North Atlantic. Anomalies in tropical deep convection associated with the QBO appear to damp, rather than drive, the effect of the QBO in the extratropical troposphere. Rather, the crucial mechanism whereby the QBO modulates the extratropical troposphere appears to be the interaction of tropospheric transient waves with the axisymmetric circulation in thermal wind balance with the QBO. The response to QBO winds of realistic amplitude is stronger for perpetual February radiative conditions and sea surface temperatures than perpetual January conditions, consistent with the observed response in reanalysis data, in a coupled seasonal WACCM integration, and in dry model experiments described in Part I.

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

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.

Impact of the Quasi-Biennial Oscillation on the boreal winter tropospheric circulation in CMIP5/6 models

2020 ◽  
Author(s):  
Jian Rao ◽  
Chaim Garfinkel ◽  
Ian White ◽  
Chen Schwartz
Keyword(s):  
Pacific Ocean ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Buoyancy Frequency ◽  
Maritime Continent ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Enso Events ◽  
The Pacific ◽  
Biennial Oscillation

<p>Using 17 CMIP5/6 models with a spontaneously-generated quasi-biennial oscillation (QBO)-like phenomenon, this study explores and evaluates three dynamical pathways for impacts of the QBO on the troposphere: (i) the Holtan-Tan (HT) effect on the stratospheric polar vortex and the northern annular mode (NAM), (ii) the subtropical zonal wind downward arching over the Pacific, and (iii) changes in local convection over the Maritime Continent and Indo-Pacific Ocean. More than half of the models can reproduce at least one of the three pathways, but few models can reproduce all of the three routes. Firstly, most models are able to simulate a weakened polar vortex during easterly QBO (EQBO) winters, in agreement with the observed HT effect. However, the weakened polar vortex response during EQBO winters is underestimated or not present at all in other models, and hence the QBO → vortex → tropospheric NAM/AO chain is not simulated. For the second pathway associated with the downward arching of the QBO winds, seven models incorrectly or poorly simulate the extratropical easterly anomaly center over 20–40°N in the Pacific sector during EQBO, and hence the negative relative vorticity anomalies poleward of the easterly center is not resolved in those models, leading to an underestimated or incorrectly modelled height response over North Pacific. However the other ten do capture this effect. The third pathway is only observed in the Indo-Pacific Ocean, where the strong climatological deep convection and the warm pool are situated. Nine models can simulate the convection anomalies associated with the QBO over the Maritime Continent, which is likely caused by the near-tropopause low buoyancy frequency anomalies. No robust relationship between the QBO and El Niño–Southern Oscillation (ENSO) events can be established using the ERA-Interim reanalysis, and nine models consistently confirm little modulation of the ocean basin-wide Walker circulation and ENSO events by the QBO.</p>

scholarly journals Variability of the Stratospheric Quasi-Biennial Oscillation and Its Wave Forcing Simulated in the Beijing Climate Center Atmospheric General Circulation Model

2019 ◽  
Vol 77 (1) ◽  
pp. 149-165 ◽  
Author(s):  
Yixiong Lu ◽  
Tongwen Wu ◽  
Weihua Jie ◽  
Adam A. Scaife ◽  
Martin B. Andrews ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
General Circulation Models ◽  
Kelvin Waves ◽  
Quasi Biennial Oscillation ◽  
Wave Forcing ◽  
Atmospheric General Circulation ◽  
Biennial Oscillation

Abstract It is well known that the stratospheric quasi-biennial oscillation (QBO) is forced by equatorial waves with different horizontal/vertical scales, including Kelvin waves, mixed Rossby–gravity (MRG) waves, inertial gravity waves (GWs), and mesoscale GWs, but the relative contribution of each wave is currently not very clear. Proper representation of these waves is critical to the simulation of the QBO in general circulation models (GCMs). In this study, the vertical resolution in the Beijing Climate Center Atmospheric General Circulation Model (BCC-AGCM) is increased to better represent large-scale waves, and a mesoscale GW parameterization scheme, which is coupled to the convective sources, is implemented to provide unresolved wave forcing of the QBO. Results show that BCC-AGCM can spontaneously generate the QBO with realistic periods, amplitudes, and asymmetric features between westerly and easterly phases. There are significant spatiotemporal variations of parameterized convective GWs, largely contributing to a great degree of variability in the simulated QBO. In the eastward wind shear of the QBO at 20 hPa, forcing provided by resolved waves is 0.1–0.2 m s−1 day−1 and forcing provided by parameterized GWs is ~0.15 m s−1 day−1. On the other hand, westward forcings by resolved waves and parameterized GWs are ~0.1 and 0.4–0.5 m s−1 day−1, respectively. It is inferred that the eastward forcing of the QBO is provided by both Kelvin waves and mesoscale convective GWs, whereas the westward forcing is largely provided by mesoscale GWs. MRG waves barely contribute to the formation of the QBO in the model.

scholarly journals Surface impacts of the Quasi Biennial Oscillation

2017 ◽  
Author(s):  
Lesley J. Gray ◽  
James A. Anstey ◽  
Yoshio Kawatani ◽  
Hua Lu ◽  
Scott Osprey ◽  
...  
Keyword(s):  
North Pacific ◽  
Polar Vortex ◽  
Late Winter ◽  
Early Winter ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Tropical Precipitation ◽  
The North ◽  
Biennial Oscillation ◽  
The North Pacific

Abstract. Teleconnections between the Quasi Biennial Oscillation (QBO) and the Northern Hemisphere zonally-averaged zonal winds, mean sea level pressure (mslp) and tropical precipitation are explored using regression analysis. A novel technique is introduced to separate responses associated with the stratospheric polar vortex from other underlying mechanisms. A previously reported mslp response in January, with a pattern that resembles the positive phase of the North Atlantic Oscillation (NAO) under QBO westerly conditions, is confirmed and found to be primarily associated with a QBO modulation of the stratospheric polar vortex. This mid-winter response is relatively insensitive to the exact height of the maximum QBO westerlies and a maximum response occurs with westerlies over a relatively deep range between 10–70 hPa. Two additional mslp responses are reported, in early winter (December) and late winter (February/March). In contrast to the January response the early and late winter responses show maximum sensitivity to the QBO winds at ~ 20 hPa and ~ 70 hPa but are relatively insensitive to the QBO winds in between (~ 50 hPa). The late winter response is centred over the North Pacific and is associated with QBO influence from the lowermost stratosphere at tropical/subtropical latitudes. The early winter response consists of anomalies over both the North Pacific and Europe, but the mechanism is unclear and requires further investigation. QBO anomalies are found in tropical precipitation amounts and a southward shift of the Inter-tropical Convergence Zone under westerly QBO conditions is also evident.

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