Role of the quasi-biennial oscillation in the downward extension of stratospheric northern annular mode anomalies

Zhang, Ruhua; Tian, Wenshou; Wang, Tao

doi:10.1007/s00382-020-05285-4

Cited by 19 publications

(9 citation statements)

References 110 publications

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“…The periodicity of about two years we found in the stratospheric S-SAM is consistent with the possible link between the SAM and the Quasi Biennial Oscillation as proposed by (Vasconcellos et al 2020). There is evidence of influence between the QBO and the Northern Annular Mode (e.g., Holton and Tan 1980;Watson and Gray 2014;Zhang et al 2020), so it is not unlikely that the SAM would be similarly affected. Establishing this link would require further research.…”

Section: Discussionsupporting

confidence: 88%

Assessment of zonally symmetric and asymmetric components of the Southern Annular Mode using a novel approach

2021

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The Southern Annular Mode (SAM) is the main mode of variability in the Southern Hemisphere extra-tropical circulation and it is so called because of its zonally symmetric ring-like shape. However, the SAM pattern actually contains noticeable deviations from zonal symmetry. Thus, the purpose of this study is to describe the zonally asymmetric and symmetric components of the SAM variability and their impacts. We regress monthly geopotential height fields at each level onto the asymmetric and symmetric component of the SAM to create two new indices: Asymmetric SAM (A-SAM) and Symmetric SAM (S-SAM). In the troposphere, the A-SAM is associated with a zonal wave 3 which is rotated a quarter wavelength with respect to the climatological zonal wave 3, is much stronger in the Pacific ocean, where it extends vertically to the stratosphere with an equivalent barotropic structure. On the other hand, the S-SAM is associated with negative geopotential height anomalies over Antarctica surrounded by a zonally symmetric ring of positive geopotential height anomalies. The observed relationship between the El Niño Southern Oscillation and the SAM is fully explained by the A-SAM index. The positive trend of the SAM is present only in its symmetric component. Despite this, the SAM is becoming more zonally asymmetric. The regional impacts of the SAM in temperature and precipitation are strongly affected by its asymmetric component. We show that the asymmetric component of the SAM has its own unique variability, trends and impacts, some of these signals are only evident when the two SAM components are separated.

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Section: Discussionsupporting

confidence: 88%

Assessment of zonally symmetric and asymmetric components of the Southern Annular Mode using a novel approach

2021

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“…Zhang et al . (2020) recently showed that, compared with that in the WQBO, the probability of a negative Northern Annular Mode (NAM) extending downward into the troposphere is significantly higher in the EQBO, resulting in colder temperatures over northern Eurasia. The variations in planetary wavenumber 1 (WN 1) and in the residual circulation associated with the EQBO are responsible for this increase in the negative NAM downward extension.…”

Section: Introductionmentioning

confidence: 99%

The observed influence of the Quasi‐Biennial Oscillation in the lower equatorial stratosphere on the East Asian winter monsoon during early boreal winter

Chen

Huangfu

et al. 2021

Intl Journal of Climatology

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This study examines the relationship between the Quasi‐Biennial Oscillation (QBO) and the variability of the East Asian winter monsoon (EAWM) in the Northern Hemisphere (NH) winter. Here, we consider the effects of QBO winds in the lower stratosphere at 70 hPa. It is found that during the period of 1958–2019, the EAWM in the early winter months (November–December) is weaker in the easterly phase of the QBO (EQBO) than in the westerly phase of the QBO (WQBO). During EQBO, the northerly monsoon flow is weakened, and anomalous warm temperatures occur over East Asia. Moreover, components of the EAWM circulation system, including the Siberian High, Aleutian Low, East Asian trough, and East Asian jet stream, are all weakened. Our further analysis suggests that the QBO may influence the EAWM directly via a subtropical pathway. The EQBO tends to weaken the East Asian jet stream and shift it poleward, and the changes in the East Asian jet stream lead to a weakened EAWM. The activities of planetary waves are also changed in association with the QBO. Examinations of individual zonal wavenumbers (WNs) of planetary waves in the SLP field reveal that WN 1 is strengthened while WNs 2 and 3 are weakened during EQBO. Specifically, the anomalous WN 2 leads to weakening of the Siberian High, Aleutian Low, and East Asian trough, and the anomalous WN 3 reduces the pressure gradient between the East Asia landmass and the western Pacific. The changes in WNs 2 and 3 associated with the QBO play a dominant role in anomalous EAWM.

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“…Understanding the processes that drive the QBO and are responsible for its variability is important not just for its own sake but also for assessing the influence of the QBO in the transport of chemical species, the interpretation of apparent changes in the strength of the BDC, and the tele-connections to the extratropical stratosphere and troposphere. [109][110][111][112][113][114][115]…”

Section: Summary and Discussionmentioning

confidence: 99%

On the response of the middle atmosphere to anthropogenic forcing

García

2021

Annals of the New York Academy of Sciences

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Anthropogenic forcing of the atmosphere by greenhouse gases (GHG) and ozone-depleting substances has provided an unintended test of the robustness of current understanding of the physics and chemistry of the middle atmosphere, that is, the stratosphere and mesosphere. We explore this topic by examining how well anthropogenic changes can be simulated by modern, comprehensive numerical models. Specifically, we discuss the simulations of trends in global mean temperature; the development of the ozone hole and its impact on the dynamics of the Southern Hemisphere, both in the stratosphere and troposphere; trends in the stratospheric Brewer-Dobson circulation; and the response of the quasi-biennial oscillation (QBO) to increasing burdens of CO 2 . We find that, in most of these cases, numerical simulation is able to reproduce observed changes and provide physical insights into the relevant mechanisms. Simulation of the QBO is on a less firm footing. Although many numerical models can now generate realistic QBOs, future projections of its behavior under the increasing burdens of GHG are inconsistent and even contradictory.

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Role of the quasi-biennial oscillation in the downward extension of stratospheric northern annular mode anomalies

Cited by 19 publications

References 110 publications

Assessment of zonally symmetric and asymmetric components of the Southern Annular Mode using a novel approach

Assessment of zonally symmetric and asymmetric components of the Southern Annular Mode using a novel approach

The observed influence of the Quasi‐Biennial Oscillation in the lower equatorial stratosphere on the East Asian winter monsoon during early boreal winter

On the response of the middle atmosphere to anthropogenic forcing

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