The relevance of reactions of the methyl peroxy radical
                        (CH&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;) and methylhypochlorite
                        (CH&lt;sub&gt;3&lt;/sub&gt;OCl) for Antarctic chlorine activation and ozone
                        loss

Zafar, Abdul Mannan; Müller, Rolf; Grooß, Jens‐Uwe; Robrecht, Sabine; Vogel, Bärbel; Lehmann, Ralph

doi:10.1080/16000889.2018.1507391

Cited by 3 publications

(17 citation statements)

References 88 publications

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“…The simulations presented here were performed with the boxmodel version of CLaMS (McKenna et al, 2002a, b). Stratospheric chemistry is simulated based on a set-up used in previous studies (Grooß et al, 2011;Müller et al, 2018;Zafar et al, 2018) for single air parcels along trajectories including diabatic descent and neglecting mixing between neighbouring air masses. A full chemical reaction scheme comprising gas phase and heterogeneous chemistry is applied using the SVODE solver (Brown et al, 1989).…”

Section: Model Set-upmentioning

confidence: 99%

“…Particle size and surface area density are calculated based on the density of liquid particles, the aerosol number density, and the standard deviation. In contrast to the set-ups in Grooß et al (2011), Müller et al (2018) and Zafar et al (2018), only formation of liquid particles (both binary H 2 O/H 2 SO 4 and ternary HNO 3 /H 2 O/H 2 SO 4 solutions) is allowed (i.e. no NAT or ice particles are formed in this model set-up) to enable a better comparability with the studies of Anderson et al (2012Anderson et al ( , 2017 and Anderson and Clapp (2018).…”

Section: Model Set-upmentioning

confidence: 99%

“…The γ value describes the uptake of ClONO 2 into liquid particles due to the decomposition of ClONO 2 during Reaction (R1) and is thus a measure of the probability of the occurrence of this heterogeneous reaction (Shi et al, 2001). Laboratory studies showed a dependence of γ R1 on the solubility of HCl in the droplet, which generally increases for a lower H 2 SO 4 fraction in the particle (H 2 SO 4 wt %) (Elrod et al, 1995;Hanson, 1998;Zhang et al, 1994;Hanson and Ravishankara, 1994). From Eq.…”

Section: Explanation Of the Water Vapour Thresholdmentioning

confidence: 99%

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Mechanism of ozone loss under enhanced water vapour conditions in the mid-latitude lower stratosphere in summer

et al. 2019

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Abstract. Water vapour convectively injected into the mid-latitude lowermost stratosphere could affect stratospheric ozone. The associated potential ozone loss process requires low temperatures together with elevated water vapour mixing ratios. Since this ozone loss is initiated by heterogeneous chlorine activation on liquid aerosols, an increase in sulfate aerosol surface area due to a volcanic eruption or geoengineering could increase the likelihood of its occurrence. However, the chemical mechanism of this ozone loss process has not yet been analysed in sufficient detail and its sensitivity to various conditions is not yet clear. Under conditions of climate change associated with an increase in greenhouse gases, both a stratospheric cooling and an increase in water vapour convectively injected into the stratosphere are expected. Understanding the influence of low temperatures, elevated water vapour and enhanced sulfate particles on this ozone loss mechanism is a key step in estimating the impact of climate change and potential sulfate geoengineering on mid-latitude ozone. Here, we analyse the ozone loss mechanism and its sensitivity to various stratospheric conditions in detail. By conducting a box-model study with the Chemical Lagrangian Model of the Stratosphere (CLaMS), chemistry was simulated along a 7 d backward trajectory. This trajectory was calculated neglecting mixing of neighbouring air masses. Chemical simulations were initialized using measurements taken during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) aircraft campaign (2013, Texas), which encountered an elevated water vapour mixing ratio of 10.6 ppmv at a pressure level around 100 hPa. We present a detailed analysis of the ozone loss mechanism, including the chlorine activation, chlorine-catalysed ozone loss cycles, maintenance of activated chlorine and the role of active nitrogen oxide radicals (NOx). Focussing on a realistic trajectory in a temperature range from 197 to 202 K, a threshold in water vapour of 10.6 ppmv has to be exceeded and maintained for stratospheric ozone loss to occur. We investigated the sensitivity of the water vapour threshold to temperature, sulfate content, inorganic chlorine (Cly), inorganic nitrogen (NOy) and inorganic bromine (Bry). The water vapour threshold is mainly determined by the temperature and sulfate content. However, the amount of ozone loss depends on Cly, Bry and the duration of the time period over which chlorine activation can be maintained. NOy affects both the potential of ozone formation and the balance between reactions yielding chlorine activation and deactivation, which determines the water vapour threshold. Our results show that in order to deplete ozone, a chlorine activation time of 24 to 36 h for conditions of the water vapour threshold with low temperatures must be maintained. A maximum ozone loss of 9 % was found for a 20 ppmv water vapour mixing ratio using North American Monsoon (NAM) tropopause standard conditions with a chemical box-model simulation along a realistic trajectory. For the same trajectory, using observed conditions (of 10.6 ppmv H2O), the occurrence of simulated ozone loss was dependent on the sulfate amount assumed. Detailed analysis of current and future possibilities is needed to assess whether enhanced water vapour conditions in the summertime mid-latitude lower stratosphere lead to significant ozone loss.

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Section: Model Set-upmentioning

confidence: 99%

Section: Model Set-upmentioning

confidence: 99%

Section: Explanation Of the Water Vapour Thresholdmentioning

confidence: 99%

See 1 more Smart Citation

Mechanism of ozone loss under enhanced water vapour conditions in the mid-latitude lower stratosphere in summer

et al. 2019

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show abstract

“…The simulations presented here were performed with the box-model version of CLaMS (McKenna et al, 2002a, b). Stratospheric chemistry is simulated based on a setup used in previous studies (Grooß et al, 2011;Müller et al, 2018;Zafar et al, 2018) for single air parcels along trajectories including diabatic descent and neglecting mixing between neighbouring air masses. A full chemical reaction scheme comprising gas phase and heterogeneous chemistry is applied using the SVODEsolver (Brown et al, 1989).…”

Section: Model Setupmentioning

confidence: 99%

“…Chemical reaction kinetics are taken from Sander et al (2011), heterogeneous reaction rates for R1-R3 were calculated based on the the study of Shi et al (2001), and photolysis rates are calculated for spherical geometry (Becker et al, 2000). In contrast to the setup in Grooß et al (2011), Müller et al (2018) and Zafar et al (2018), only formation of liquid particles (both binary H 2 O/H 2 SO 4 and ternary HNO 3 /H 2 O/H 2 SO 4 solutions) is allowed (i.e. no NAT or ice particles Atmos.…”

Section: Model Setupmentioning

confidence: 99%

Mechanism of ozone loss under enhanced water vapour conditions in the mid-latitude lower stratosphere in summer

Robrecht¹,

Vogel²,

Grooß³

et al. 2018

Preprint

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Abstract. Water vapour convectively injected into the mid-latitude lowermost stratosphere could affect stratospheric ozone. The associated potential ozone loss process requires low temperatures and an elevated water vapour mixing ratio. An increase in sulphate aerosol surface area due to a volcanic eruption or geoengineering could increase the likelihood of occurrence of this process. However, the chemical mechanism of this ozone loss process has not yet been analysed in sufficient detail and its sensitivity to various conditions is not yet clear. Under conditions of climate change associated with an increase in greenhouse gases, both a stratospheric cooling and an increase in water vapour convectively injected into the stratosphere is expected. Understanding the influence of low temperatures, elevated water vapour and enhanced sulphate particles on this ozone loss mechanism is a key step in estimating the impact of climate change and potential sulphate geoengineering on mid-latitude ozone. Here, we analyse the ozone loss mechanism and its sensitivity to various stratospheric conditions in detail. Conducting a box-model study with the Chemical Lagrangian Model of the Stratosphere (CLaMS), chemistry was simulated along a 7-day backward trajectory. This trajectory was calculated neglecting mixing of neighbouring air masses. Chemical simulations were initialized using measurements taken during the Study of Emissions and atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) aircraft campaign (2013, Texas), which encountered an elevated water vapour mixing ratio at a pressure level around 100&#8201;hPa. We present a detailed analysis of the ozone loss mechanism, including the chlorine activation, chlorine catalysed ozone loss cycles, maintenance of activated chlorine and the role of active nitrogen oxide radicals (NOx). Focussing on a realistic trajectory in a temperature range from 197&#8211;203&#8201;K, a threshold in water vapour of 11.0&#8211;11.6&#8201;ppmv has to be exceeded and maintained for stratospheric ozone loss to occur. We investigated the sensitivity of the water vapour threshold to temperature, sulphate content, inorganic chlorine (Cly), inorganic nitrogen (NOy) and inorganic bromine (Bry). The water vapour threshold is mainly determined by the temperature and sulphate content. However, the amount of ozone loss depends on Cly, NOy, Bry and the duration of the time period over which chlorine activation can be maintained. Our results show that to deplete ozone, a chlorine activation time of 24 to 36 hours for conditions of the water vapour threshold with low temperatures and high water vapour mixing ratios must be maintained. A maximum ozone loss of 9&#8201;% was found for a 20&#8201;ppmv water vapour mixing ratio at North American Monsoon (NAM) tropopause standard conditions with the model run along a realistic trajectory. For the same trajectory, using observed conditions (of 10.6&#8201;ppmv), whether ozone loss occurs was simulated dependent on the sulphate amount assumed. Detailed analysis of current and future possibilities is needed to assess whether enhanced water vapour conditions in the summertime mid-latitude lower stratosphere leads to significant ozone loss.

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The impact of dehydration and extremely low HCl values in the Antarctic stratospheric vortex in mid-winter on ozone loss in spring

Zhang-Liu,

Müller,

Grooß

et al. 2024

Preprint

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Abstract. Simulations of Antarctic chlorine and ozone chemistry show that in the core of the Antarctic vortex (16–18 km, 85–55 hPa, 390–430 K) HCl null cycles (initiated by reactions CH4 + Cl and CH2O + Cl) are effective. These HCl null cycles allow HCl mixing ratios to remain very low throughout Antarctic winter and ozone destroying chlorine (ClOx) to remain enhanced, so that rapid ozone depletion proceeds. Sensitivity studies show that the reaction CH3O2 + ClO is important for the efficacy of the HCl null cycle initiated by the reaction CH4 + Cl and that using the current kinetic recommendations instead of earlier ones has little impact on the simulations. Dehydration in Antarctica strongly reduces ice formation and the uptake of HNO3 from the gas phase; however the efficacy of HCl null cycles is not affected. Further, the effect of the observed very low HCl mixing ratios in Antarctic winter are considered; HCl null cycles are efficient in maintaining low HCl (and high ClOx) throughout Antarctic winter. All simulations presented here for the core of the Antarctic vortex show extremely low minimum ozone values (below 50 ppb) in late September/early October in agreement with observations.

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The relevance of reactions of the methyl peroxy radical (CH<sub>3</sub>O<sub>2</sub>) and methylhypochlorite (CH<sub>3</sub>OCl) for Antarctic chlorine activation and ozone loss

Abstract: Lehmann (2018) The relevance of reactions of the methyl peroxy radical (CH 3 O 2) and methylhypochlorite (CH 3 OCl) for Antarctic chlorine activation and ozone loss, Tellus B:

Cited by 3 publications

References 88 publications

Mechanism of ozone loss under enhanced water vapour conditions in the mid-latitude lower stratosphere in summer

Mechanism of ozone loss under enhanced water vapour conditions in the mid-latitude lower stratosphere in summer

Mechanism of ozone loss under enhanced water vapour conditions in the mid-latitude lower stratosphere in summer

The impact of dehydration and extremely low HCl values in the Antarctic stratospheric vortex in mid-winter on ozone loss in spring

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