Linking midlatitudes eddy heat flux trends and polar amplification

Chemke, Rei; Polvani, Lorenzo M.

doi:10.1038/s41612-020-0111-7

Cited by 34 publications

(36 citation statements)

References 69 publications

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“…TOMS, OMI, and OMPS. Furthermore, both de Laat et al (2017) and Tully et al (2019) appear not to have homogenized the different data sets used and did not infer missing measurements during the polar night and elsewhere.…”

Section: Introductionmentioning

confidence: 99%

“…Interannual variability in Antarctic stratospheric dynamics, manifest most obviously in interannual variability in Antarctic stratospheric temperatures, drives significant interannual variability in the severity of Antarctic ozone depletion (Schoeberl et al, 1996;Newman and Nash , 2000;Newman et al, 2004Newman et al, , 2006. Using TCO measurements from multiple satellite-based instruments, and after accounting for interannual variability in stratospheric temperatures, de Laat et al (2017) found that ozone mass deficit decreased by 0.77 ± 0.17 Mt yr −1 (2σ ) between 2000 and 2015. More recently, Tully et al (2019) analysed linear trends in several Antarctic ozone hole metrics over the periods 1979 to 2001 and 2001 to 2017.…”

Section: Introductionmentioning

confidence: 99%

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Indicators of Antarctic ozone depletion: 1979 to 2019

Bodeker

Kremser

2021

Atmos. Chem. Phys.

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Abstract. The National Institute of Water and Atmospheric Research/Bodeker Scientific (NIWA–BS) total column ozone (TCO) database and the associated BS-filled TCO database have been updated to cover the period 1979 to 2019, bringing both to version 3.5.1 (V3.5.1). The BS-filled database builds on the NIWA–BS database by using a machine-learning algorithm to fill spatial and temporal data gaps to provide gap-free TCO fields over Antarctica. These filled TCO fields then provide a more complete picture of wintertime changes in the ozone layer over Antarctica. The BS-filled database has been used to calculate continuous, homogeneous time series of indicators of Antarctic ozone depletion from 1979 to 2019, including (i) daily values of the ozone mass deficit based on TCO below a 220 DU threshold; (ii) daily measures of the area over Antarctica where TCO levels are below 150 DU, below 220 DU, more than 30 % below 1979 to 1981 climatological means, and more than 50 % below 1979 to 1981 climatological means; (iii) the date of disappearance of 150 DU TCO values, 220 DU TCO values, values 30 % or more below 1979 to 1981 climatological means, and values 50 % or more below 1979 to 1981 climatological means, for each year; and (iv) daily minimum TCO values over the range 75 to 90∘ S equivalent latitude. Since both the NIWA–BS and BS-filled databases provide uncertainties on every TCO value, the Antarctic ozone depletion metrics are provided, for the first time, with fully traceable uncertainties. To gain insight into how the vertical distribution of ozone over Antarctica has changed over the past 36 years, ozone concentrations, combined and homogenized from several satellite-based ozone monitoring instruments as well as the global ozonesonde network, were also analysed. A robust attribution to changes in the drivers of long-term secular variability in these metrics has not been performed in this analysis. As a result, statements about the recovery of Antarctic TCO from the effects of ozone-depleting substances cannot be made. That said, there are clear indications of a change in trend in many of the metrics reported on here around the turn of the century, close to when Antarctic stratospheric concentrations of chlorine and bromine peaked.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Indicators of Antarctic ozone depletion: 1979 to 2019

Bodeker

Kremser

2021

Atmos. Chem. Phys.

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“…Furthermore, the attendant stratospheric circulation anomalies can propagate downward to the tropopause, with the stratospheric forcing subsequently able to alter tropospheric SAM by changing the synoptic-scale eddy feedbacks that maintain variations in the polar front jet (Christiansen, 1999(Christiansen, , 2001Kodera and Kuroda, 2002;Limpasuvan et al, 2004;Song and Robinson, 2004;Smith and Scott, 2016). Consequently, a number of studies have suggested that the circulation changes induced by the ozone hole involve alterations to these dynamical processes, although the exact mechanisms remain uncertain (e.g., Hartmann et al, 2000;Chen and Held, 2007;McLandress et al, 2010McLandress et al, , 2011Harnik et al, 2011;Orr et al, 2012Orr et al, , 2013Hu et al, 2015). Orr et al (2012) performed a model-based study focused on a momentum budget analysis within the transformed Eulerian mean (TEM) framework.…”

Section: Introductionmentioning

confidence: 99%

“…Atmospheric reanalysis datasets combine observations with a fixed weather forecast model in an optimal way to construct a best estimate of the state of the atmosphere. They have previously been used to investigate the circulation trends in the stratosphere and troposphere that occur in response to the ozone hole (e.g., Chen and Held, 2007;Harnik et al, 2011;Shaw et al, 2011;Orr et al, 2012Orr et al, , 2013Banerjee et al, 2020). These studies tend to be based on a single reanalysis dataset, despite many others being available .…”

Section: Introductionmentioning

confidence: 99%

Is our dynamical understanding of the circulation changes associated with the Antarctic ozone hole sensitive to the choice of reanalysis dataset?

Orr

Martineau

et al. 2021

Atmos. Chem. Phys.

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Abstract. This study quantifies differences among four widely used atmospheric reanalysis datasets (ERA5, JRA-55, MERRA-2, and CFSR) in their representation of the dynamical changes induced by springtime polar stratospheric ozone depletion in the Southern Hemisphere from 1980 to 2001. The intercomparison is undertaken as part of the SPARC (Stratosphere–troposphere Processes and their Role in Climate) Reanalysis Intercomparison Project (S-RIP). The reanalyses are generally in good agreement in their representation of the strengthening of the lower stratospheric polar vortex during the austral spring–summer season, associated with reduced radiative heating due to ozone loss, as well as the descent of anomalously strong westerly winds into the troposphere during summer and the subsequent poleward displacement and intensification of the polar front jet. Differences in the trends in zonal wind between the reanalyses are generally small compared to the mean trends. The exception is CFSR, which exhibits greater disagreement compared to the other three reanalysis datasets, with stronger westerly winds in the lower stratosphere in spring and a larger poleward displacement of the tropospheric westerly jet in summer. The dynamical changes associated with the ozone hole are examined by investigating the momentum budget and then the eddy heat and momentum fluxes in terms of planetary- and synoptic-scale Rossby wave contributions. The dynamical changes are consistently represented across the reanalyses and support our dynamical understanding of the response of the coupled stratosphere–troposphere system to the ozone hole. Although our results suggest a high degree of consistency across the four reanalysis datasets in the representation of these dynamical changes, there are larger differences in the wave forcing, residual circulation, and eddy propagation changes compared to the zonal wind trends. In particular, there is a noticeable disparity in these trends in CFSR compared to the other three reanalyses, while the best agreement is found between ERA5 and JRA-55. Greater uncertainty in the components of the momentum budget, as opposed to mean circulation, suggests that the zonal wind is better constrained by the assimilation of observations compared to the wave forcing, residual circulation, and eddy momentum and heat fluxes, which are more dependent on the model-based forecasts that can differ between reanalyses. Looking forward, however, these findings give us confidence that reanalysis datasets can be used to assess changes associated with the ongoing recovery of stratospheric ozone.

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“…This is perhaps especially an issue in the stratosphere, as compared to the troposphere this region is characterised by smaller volumes of observational data available for assimilation and larger biases in observational data , implying a greater reliance on the performance of the forecast model and its representation of dynamical processes (e.g., Orr et al, 2010). The representation of the underlying dynamics in reanalyses is therefore an additional concern, which has not been examined for the SH despite showing nonnegligible differences for some diagnostics in the Northern Hemisphere (e.g., Bengtsson et al, 2006;Lu et al, 2015;Martineau et al, 2016Martineau et al, , 2018bChemke and Polvani, 2020).…”

Section: Introductionmentioning

confidence: 99%

Is our dynamical understanding of the circulation changes associated with the Antarctic ozone hole sensitive to the choice of reanalysis dataset?

Orr¹,

Lu²,

Martineau³

et al. 2020

Preprint

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Abstract. This study quantifies differences among four widely used atmospheric reanalysis datasets (ERA5, JRA-55, MERRA-2, and CSFR) in their representation of the dynamical changes induced by severe springtime polar stratospheric ozone depletion in the Southern Hemisphere during 1980–2001. The intercomparison is undertaken as part of the SPARC (Stratosphere–troposphere Processes and their Role in Climate) Reanalysis Intercomparison Project (S-RIP). The dynamical changes associated with the ozone hole are examined by investigating the eddy heat and momentum fluxes and wave forcing. The reanalyses are generally in good agreement in their representation of the expected strengthening of the lower stratospheric polar vortex during the austral spring-summer season, as well as the descent of anomalously strong winds to the surface during summer and the subsequent poleward displacement and intensification of the polar front jet. Differences in the trends in zonal wind are generally small compared to the mean trends. The exception is CSFR, which shows greater disagreement compared to the other three reanalysis datasets, with stronger westerly winds in the lower stratosphere in spring and a larger poleward displacement of the tropospheric westerly jet in summer. Although our results suggest a high degree of consistency across the four reanalysis datasets in the representation of the dynamical changes associated with the ozone hole, there are larger differences in the wave forcing and eddy propagation changes compared to the similarities in the circulation trends. There is a large amount of disagreement in CFSR wave forcing/propagation trends compared to the other three reanalyses, while the best agreement is found between ERA5 and JRA-55. The underlying causes of these differences are consistent with the wind response being more constrained by the assimilation of observations compared to the wave forcing, which is more dependent on the model-based forecasts that can differ between reanalyses. Looking forward, these findings give us confidence that reanalysis datasets can be used to assess changes associated with the ongoing recovery of stratospheric ozone.

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Linking midlatitudes eddy heat flux trends and polar amplification

Cited by 34 publications

References 69 publications

Indicators of Antarctic ozone depletion: 1979 to 2019

Indicators of Antarctic ozone depletion: 1979 to 2019

Is our dynamical understanding of the circulation changes associated with the Antarctic ozone hole sensitive to the choice of reanalysis dataset?

Is our dynamical understanding of the circulation changes associated with the Antarctic ozone hole sensitive to the choice of reanalysis dataset?

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