New Insights on the Impact of Ozone‐Depleting Substances on the Brewer‐Dobson Circulation

Ábalos, Marta; Polvani, Lorenzo M.; Calvo, Natalia; Kinnison, Douglas E.; Ploeger, Felix; Randel, William J.; Solomon, Susan

doi:10.1029/2018jd029301

Cited by 43 publications

(51 citation statements)

References 68 publications

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“…However, as originally noted in Polvani et al (), and as we will show below for the CCMI models, the effects of ODS on BDC trends exhibit clear seasonal and hemispheric asymmetries that are aligned with ozone changes, indicating that the direct radiative forcing of ODS is relatively unimportant for BDC trends. We have recently confirmed this fact using the Whole Atmosphere Community Climate Model (WACCM), as detailed in Abalos et al ().…”

Section: Methodssupporting

confidence: 74%

Large Impacts, Past and Future, of Ozone‐Depleting Substances on Brewer‐Dobson Circulation Trends: A Multimodel Assessment

et al. 2019

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Substantial increases in the atmospheric concentration of well‐mixed greenhouse gases (notably CO2), such as those projected to occur by the end of the 21st century under large radiative forcing scenarios, have long been known to cause an acceleration of the Brewer‐Dobson circulation (BDC) in climate models. More recently, however, several single‐model studies have proposed that ozone‐depleting substances might also be important drivers of BDC trends. As these studies were conducted with different forcings over different periods, it is difficult to combine them to obtain a robust quantitative picture of the relative importance of ozone‐depleting substances as drivers of BDC trends. To this end, we here analyze—over identical past and future periods—the output from 20 similarly forced models, gathered from two recent chemistry‐climate modeling intercomparison projects. Our multimodel analysis reveals that ozone‐depleting substances are responsible for more than half of the modeled BDC trends in the two decades 1980–2000. We also find that, as a consequence of the Montreal Protocol, decreasing concentrations of ozone‐depleting substances in coming decades will strongly decelerate the BDC until the year 2080, reducing the age‐of‐air trends by more than half, and will thus substantially mitigate the impact of increasing CO2. As ozone‐depleting substances impact BDC trends, primarily, via the depletion/recovery of stratospheric ozone over the South Pole, they impart seasonal and hemispheric asymmetries to the trends which may offer opportunities for detection in coming decades.

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Section: Methodssupporting

confidence: 74%

Large Impacts, Past and Future, of Ozone‐Depleting Substances on Brewer‐Dobson Circulation Trends: A Multimodel Assessment

et al. 2019

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“…This resulted in stronger wave dissipation in the upper stratosphere in November and in the middle stratosphere in December, leading to the concomitant intensification of the residual circulation, in agreement with the findings of previous studies that used CCMs (Li et al, 2008;McLandress et al, 2010;Li et al, 2010;Keeble et al, 2014;Oberländer-Hayn et al, 2015;Polvani et al, 2018;Abalos et al, 2019). A new result of this study is that the intensification of the residual circulation is weaker when the CMIP6 ozone field is prescribed and, furthermore, it extends farther down in the lower stratosphere in November.…”

Section: Discussionsupporting

confidence: 91%

Effects of prescribed CMIP6 ozone on simulating the Southern Hemisphere atmospheric circulation response to ozone depletion

Ivanciu¹,

Matthes²,

Wahl³

et al. 2020

Preprint

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Abstract. The Antarctic ozone hole has led to substantial changes in the Southern Hemisphere atmospheric circulation, such as the strengthening and poleward shift of the mid-latitude westerly jet. Ozone recovery during the twenty-first century is expected to continue to affect the jet's strength and position, leading to changes in the opposite direction compared to the twentieth century and competing with the effect of increasing greenhouse gases. Simulations of the Earth's past and future climate, such as those performed for the Coupled Model Intercomparison Project Phase 6 (CMIP6), require an accurate representation of these ozone effects. Climate models that use prescribed ozone fields lack the important feedbacks between ozone chemistry, radiative heating, dynamics, as well as transport. These limitations ultimately affect their climate response to ozone depletion. This study investigates the impact of prescribing the ozone field recommended for CMIP6 on the simulated effects of ozone depletion in the Southern Hemisphere. We employ a new, state-of the-art coupled climate model, FOCI, to compare simulations in which the CMIP6 ozone is prescribed with simulations in which the ozone chemistry is calculated interactively. At the same time, we compare the roles played by ozone depletion and by increasing concentrations of greenhouse gases in driving changes in the Southern Hemisphere atmospheric circulation, using a series of historical sensitivity simulations. FOCI reliably captures the known effects of ozone depletion, simulating an austral spring and summer intensification of the mid-latitude westerly winds and of the Brewer-Dobson circulation in the Southern Hemisphere. Ozone depletion is the primary driver of these historical circulation changes in FOCI. These changes are weaker in the simulations that prescribe the CMIP6 ozone field. We attribute this weaker response to the missing ozone-radiative-dynamical feedbacks and to a prescribed ozone hole that is displaced compared to the simulated polar vortex, altering the propagation of planetary wave activity. As a result, the dynamical contribution to the ozone-induced austral spring lower stratospheric cooling is suppressed, leading to a weaker cooling trend. Consequently, the intensification of the polar night jet is also weaker in the simulations with prescribed CMIP6 ozone. In addition, the persistence of the Southern Annular Mode is shorter in the prescribed ozone chemistry simulations. These results suggest that climate models which prescribe the CMIP6 ozone field still underestimate the historical ozone-induced dynamical changes in the Southern Hemisphere, while models that calculate the ozone chemistry interactively simulate an improved response to ozone depletion.

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“…The full age spectrum allows for a clearer interpretation, but its deduction from observations is much more challenging and usually hinges on simplifying assumptions like the stationarity of the flow or a specific parameterization of the age spectrum shape (e.g. Andrews et al, 1999;Schoeberl et al, 2005). Ongoing modelling studies suggest promising new methods for deducing the age spectrum based on either an improved parametric approach (Hauck et al, 2019) or an inversion approach (Podglajen and Ploeger, 2019).…”

Section: Introductionmentioning

confidence: 99%

How robust are stratospheric age of air trends from different reanalyses?

et al. 2019

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Abstract. An accelerating Brewer–Dobson circulation (BDC) is a robust signal of climate change in model predictions but has been questioned by trace gas observations. We analyse the stratospheric mean age of air and the full age spectrum as measures for the BDC and its trend. Age of air is calculated using the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by ERA-Interim, JRA-55 and MERRA-2 reanalysis data to assess the robustness of the representation of the BDC in current generation meteorological reanalyses. We find that the climatological mean age significantly depends on the reanalysis, with JRA-55 showing the youngest and MERRA-2 the oldest mean age. Consideration of the age spectrum indicates that the older air for MERRA-2 is related to a stronger spectrum tail, which is likely associated with weaker tropical upwelling and stronger recirculation. Seasonality of stratospheric transport is robustly represented in reanalyses, with similar mean age variations and age spectrum peaks. Long-term changes from 1989 to 2015 turn out to be similar for the reanalyses with mainly decreasing mean age accompanied by a shift of the age spectrum peak towards shorter transit times, resembling the forced response in climate model simulations to increasing greenhouse gas concentrations. For the shorter periods, 1989–2001 and 2002–2015, the age of air changes are less robust. Only ERA-Interim shows the hemispheric dipole pattern in age changes from 2002 to 2015 as viewed by recent satellite observations. Consequently, the representation of decadal variability of the BDC in current generation reanalyses appears less robust and is a major uncertainty of modelling the BDC.

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New Insights on the Impact of Ozone‐Depleting Substances on the Brewer‐Dobson Circulation

Cited by 43 publications

References 68 publications

Large Impacts, Past and Future, of Ozone‐Depleting Substances on Brewer‐Dobson Circulation Trends: A Multimodel Assessment

Large Impacts, Past and Future, of Ozone‐Depleting Substances on Brewer‐Dobson Circulation Trends: A Multimodel Assessment

Effects of prescribed CMIP6 ozone on simulating the Southern Hemisphere atmospheric circulation response to ozone depletion

How robust are stratospheric age of air trends from different reanalyses?

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