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

Polvani, Lorenzo M.; Wang, Lei; Ábalos, Marta; Butchart, Neal; Chipperfield, Martyn P.; Dameris, Martin; Deushi, Makoto; Dhomse, Sandip; Jöckel, Patrick; Kinnison, Douglas E.; Michou, Martine; Morgenstern, Olaf; Oman, Luke D.; Plummer, David A.; Stone, Kane

doi:10.1029/2018jd029516

Cited by 38 publications

(46 citation statements)

References 42 publications

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“…An unusual sudden stratospheric warming occurred in Antarctica in 2002, which would lead to a spurious dynamical cooling trend in the SH high latitudes for 2000-2018. We repeat the analyses by removing Noting the opposite signs of radiative components in the SH during August-December for the first versus second periods and their magnitudes with a factor of ∼4 difference (figures 5 and 6), the changes of the BDC SH cell appear to be at least partly linked to ozone depletion and healing (see the modeling studies of Polvani et al 2018, Polvani et al 2019). It is also worth noting that by removing 2002, the SH radiative warming in September for 2000-2018 becomes significant at the 90% confidence level (figure 6).…”

Section: Resultsmentioning

confidence: 99%

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Observed changes in Brewer–Dobson circulation for 1980–2018

Solomon

Pahlavan

et al. 2019

Environ. Res. Lett.

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Previous work has examined the Brewer-Dobson circulation (BDC) changes for 1980-2009 based on satellite Microwave Sounding Unit (MSU/AMSU) lower-stratospheric temperature (T LS ) observations and ERA-Interim reanalysis data. Here we examine the BDC changes for the longer period now available , which also allows analysis of both the ozone depletion (1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999) and ozone healing (2000-2018) periods. We provide observational evidence that the annual mean BDC accelerated for 1980-1999 but decelerated for 2000-2018, with the changes largely driven by the Southern Hemisphere (SH), which might be partly contributed by the effects of ozone depletion and healing. We also show that the annual mean BDC has accelerated in the last 40 years (at the 90% confidence level) with a relative strengthening of ∼1.7% per decade. This overall acceleration was driven by both Northern Hemisphere (40%) and SH (60%) cells. Significant SH radiative warming is also identified in September for 2000-2018 after excluding the year 2002 when a very rare SH stratospheric sudden warming occurred, supporting the view that healing of the Antarctic ozone layer has now begun to occur during the month of September.

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Section: Resultsmentioning

confidence: 99%

“…Several modeling studies also find that the BDC becomes stronger (weaker) in response to the ozone depletion (recovery) (e.g. Shindell and Schmidt 2004, Li et al 2008, Oman et al 2009, McLandress et al 2010, Polvani et al 2011, Lin and Fu 2013, Polvani et al 2018, Polvani et al 2019.…”

Section: Introductionmentioning

confidence: 99%

Observed changes in Brewer–Dobson circulation for 1980–2018

Solomon

Pahlavan

et al. 2019

Environ. Res. Lett.

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“…Ozone is most abundant in the stratosphere, and its presence is crucial for protecting life on Earth from harmful solar ultraviolet radiation. In the troposphere, ozone acts as a greenhouse gas, and near the surface acts as a toxic pollutant (e.g., Ramaswamy et al, 2001;World Health Organization, 2003). Because the stratosphere can be regarded as a reser-voir of ozone, changes in stratosphere-to-troposphere transport (STT) play a very important role in determining the evolution of tropospheric ozone (Zeng and Pyle, 2003;Collins, 2003;Sudo et al, 2003;Zeng et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Future trends in stratosphere-to-troposphere transport in CCMI models

et al. 2020

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Abstract. One of the key questions in the air quality and climate sciences is how tropospheric ozone concentrations will change in the future. This will depend on two factors: changes in stratosphere-to-troposphere transport (STT) and changes in tropospheric chemistry. Here we aim to identify robust changes in STT using simulations from the Chemistry Climate Model Initiative (CCMI) under a common climate change scenario (RCP6.0). We use two idealized stratospheric tracers to isolate changes in transport: stratospheric ozone (O3S), which is exactly like ozone but has no chemical sources in the troposphere, and st80, a passive tracer with fixed volume mixing ratio in the stratosphere. We find a robust increase in the tropospheric columns of these two tracers across the models. In particular, stratospheric ozone in the troposphere is projected to increase 10 %–16 % by the end of the 21st century in the RCP6.0 scenario. Future STT is enhanced in the subtropics due to the strengthening of the shallow branch of the Brewer–Dobson circulation (BDC) in the lower stratosphere and of the upper part of the Hadley cell in the upper troposphere. The acceleration of the deep branch of the BDC in the Northern Hemisphere (NH) and changes in eddy transport contribute to increased STT at high latitudes. These STT trends are caused by greenhouse gas (GHG) increases, while phasing out of ozone-depleting substances (ODS) does not lead to robust transport changes. Nevertheless, the decline of ODS increases the reservoir of ozone in the lower stratosphere, which results in enhanced STT of O3S at middle and high latitudes. A higher emission scenario (RCP8.5) produces stronger STT trends, with increases in tropospheric column O3S more than 3 times larger than those in the RCP6.0 scenario by the end of the 21st century.

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“…It also determines stratosphere-to-troposphere exchange of ozone (Hegglin and Shepherd, 2009), which is important for the tropospheric ozone budget (Wild, 2007). In the tropical lower stratosphere, where the photochemical lifetime of ozone is long, variations and trends in the strength of the BDC are the main drivers of ozone within the annual cycle (Weber et al, 2011) for inter-annual and longer-term variability (Randel and Thompson, 2011) and in response to climate change (e.g. Keeble et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

The effect of atmospheric nudging on the stratospheric residual circulation in chemistry–climate models

et al. 2019

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Abstract. We perform the first multi-model intercomparison of the impact of nudged meteorology on the stratospheric residual circulation using hindcast simulations from the Chemistry–Climate Model Initiative (CCMI). We examine simulations over the period 1980–2009 from seven models in which the meteorological fields are nudged towards a reanalysis dataset and compare these with their equivalent free-running simulations and the reanalyses themselves. We show that for the current implementations, nudging meteorology does not constrain the mean strength of the stratospheric residual circulation and that the inter-model spread is similar, or even larger, than in the free-running simulations. The nudged models generally show slightly stronger upwelling in the tropical lower stratosphere compared to the free-running versions and exhibit marked differences compared to the directly estimated residual circulation from the reanalysis dataset they are nudged towards. Downward control calculations applied to the nudged simulations reveal substantial differences between the climatological lower-stratospheric tropical upward mass flux (TUMF) computed from the modelled wave forcing and that calculated directly from the residual circulation. This explicitly shows that nudging decouples the wave forcing and the residual circulation so that the divergence of the angular momentum flux due to the mean motion is not balanced by eddy motions, as would typically be expected in the time mean. Overall, nudging meteorological fields leads to increased inter-model spread for most of the measures of the mean climatological stratospheric residual circulation assessed in this study. In contrast, the nudged simulations show a high degree of consistency in the inter-annual variability in the TUMF in the lower stratosphere, which is primarily related to the contribution to variability from the resolved wave forcing. The more consistent inter-annual variability in TUMF in the nudged models also compares more closely with the variability found in the reanalyses, particularly in boreal winter. We apply a multiple linear regression (MLR) model to separate the drivers of inter-annual and long-term variations in the simulated TUMF; this explains up to ∼75 % of the variance in TUMF in the nudged simulations. The MLR model reveals a statistically significant positive trend in TUMF for most models over the period 1980–2009. The TUMF trend magnitude is generally larger in the nudged models compared to their free-running counterparts, but the intermodel range of trends doubles from around a factor of 2 to a factor of 4 due to nudging. Furthermore, the nudged models generally do not match the TUMF trends in the reanalysis they are nudged towards for trends over different periods in the interval 1980–2009. Hence, we conclude that nudging does not strongly constrain long-term trends simulated by the chemistry–climate model (CCM) in the residual circulation. Our findings show that while nudged simulations may, by construction, produce accurate temperatures and realistic representations of fast horizontal transport, this is not typically the case for the slower zonal mean vertical transport in the stratosphere. Consequently, caution is required when using nudged simulations to interpret the behaviour of stratospheric tracers that are affected by the residual circulation.

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

Cited by 38 publications

References 42 publications

Observed changes in Brewer–Dobson circulation for 1980–2018

Observed changes in Brewer–Dobson circulation for 1980–2018

Future trends in stratosphere-to-troposphere transport in CCMI models

The effect of atmospheric nudging on the stratospheric residual circulation in chemistry–climate models

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