Uncertainties in modelling heterogeneous chemistry and Arctic ozone depletion in the winter 2009/2010

Wohltmann, Ingo; Wegner, Tobias; Müller, Rolf; Lehmann, Ralph; Rex, Markus; Manney, G. L.; Santee, M. L.; Bernath, Peter F.; Suminska-Ebersoldt, O.; Stroh, F.; Hobe, Marc von; Volk, C. M.; Hösen, E.; Ravegnani, F.; Ulanovsky, A.; Yushkov, V.

doi:10.5194/acp-13-3909-2013

Cited by 62 publications

(89 citation statements)

References 58 publications

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“…As commonly applied for simulating PSCs in atmospheric models (e.g. Wohltmann et al, 2013), NAT formation in EMAC is initiated at T NAT -3 K. This results in NAT clouds being formed before STS clouds, and thus NAT formation occurs at the expense of STS since the NAT clouds consume all the available HNO 3 . This therefore results in an overestimation of NAT since in reality STS and NAT clouds are often observed at the same time (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…However, this approach is commonly applied for simulating PSCs in atmospheric models (e.g. Wohltmann et al, 2013). As was discussed by Wohltmann et al (2013), this approach technically results in NAT clouds being formed before STS clouds, and thus NAT formation occurs at the expense of STS since the NAT clouds consume all the available HNO 3 .…”

Section: Model-measurement Comparisonsmentioning

confidence: 99%

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Comparison of ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations of the Arctic winter 2009/2010 and 2010/2011 with Envisat/MIPAS and Aura/MLS observations

et al. 2018

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Abstract. We present model simulations with the atmospheric chemistry-climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) nudged toward European Centre for Medium-Range Weather Forecasts (ECMWF) ERAInterim reanalyses for the Arctic winters 2009/2010 and 2010/2011. This study is the first to perform an extensive assessment of the performance of the EMAC model for Arctic winters as previous studies have only made limited evaluations of EMAC simulations which also were mainly focused on the Antarctic winter stratosphere. We have chosen the two extreme Arctic winters 2009/2010 and 2010/2011 to evaluate the formation of polar stratospheric clouds (PSCs) and the representation of the chemistry and dynamics of the polar winter stratosphere in EMAC. The EMAC simulations are compared to observations by the Michelson Interferometer for Passive Atmospheric Soundings (Envisat/MIPAS) and the observations from the Aura Microwave Limb Sounder (Aura/MLS). The Arctic winter 2010/2011 was one of the coldest stratospheric winters on record, leading to the strongest depletion of ozone measured in the Arctic. The Arctic winter 2009/2010 was, from the climatological perspective, one of the warmest stratospheric winters on record. However, it was distinguished by an exceptionally cold stratosphere (colder than the climatological mean) from mid-December 2009 to mid-January 2010, leading to prolonged PSC formation and existence. Significant denitrification, the removal of HNO 3 from the stratosphere by sedimentation of HNO 3 -containing polar stratospheric cloud particles, occurred in that winter. In our comparison, we focus on PSC formation and denitrification. The comparisons between EMAC simulations and satellite observations show that model and measurements compare well for these two Arctic winters (differences for HNO 3 generally within ±20 %) and thus that EMAC nudged toward ECMWF ERA-Interim reanalyses is capable of giving a realistic representation of the evolution of PSCs and associated sequestration of gas-phase HNO 3 in the polar winter stratosphere. However, simulated PSC volume densities are smaller than the ones derived from Envisat/MIPAS observations by a factor of 3-7. Further, PSCs in EMAC are not simulated as high up (in altitude) as they are observed. This underestimation of PSC volume density and vertical extension of the PSCs results in an underestimation of the vertical redistribution of HNO 3 due to denitrification/re-nitrification. The differences found here between model simulations and observations stipulate further improvements in the EMAC set-up for simulating PSCs.

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Section: Discussionmentioning

confidence: 99%

Section: Model-measurement Comparisonsmentioning

confidence: 99%

Comparison of ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations of the Arctic winter 2009/2010 and 2010/2011 with Envisat/MIPAS and Aura/MLS observations

et al. 2018

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“…Although some recent studies have suggested that liquid PSCs play a dominant role in activating chlorine (e.g., Wegner et al, 2012;Wohltmann et al, 2013), the formation temperatures of solid nitric acid trihydrate (NAT, Hanson and Mauersberger, 1988) and ice particles remain convenient thresholds for the initiation of chlorine activation processes. In this study, we examine daily 12:00 UT minimum temperatures and calculations of area with temperatures below PSC thresholds (henceforth T min and A PSC , respectively).…”

Section: Temperature and Vortex Diagnosticsmentioning

confidence: 99%

Comparisons of polar processing diagnostics from 34 years of the ERA-Interim and MERRA reanalyses

et al. 2015

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Abstract. We present a comprehensive comparison of polar processing diagnostics derived from the National Aeronautics and Space Administration (NASA) Modern Era Retrospective-analysis for Research and Applications (MERRA) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERAInterim). We use diagnostics that focus on meteorological conditions related to stratospheric chemical ozone loss based on temperatures, polar vortex dynamics, and air parcel trajectories to evaluate the effects these reanalyses might have on polar processing studies. Our results show that the agreement between MERRA and ERA-Interim changes significantly over the 34 years from 1979 to 2013 in both hemispheres and in many cases improves. By comparing our diagnostics during five time periods when an increasing number of higher-quality observations were brought into these reanalyses, we show how changes in the data assimilation systems (DAS) of MERRA and ERA-Interim affected their meteorological data. Many of our stratospheric temperature diagnostics show a convergence toward significantly better agreement, in both hemispheres, after 2001 when Aqua and GOES (Geostationary Operational Environmental Satellite) radiances were introduced into the DAS. Other diagnostics, such as the winter mean volume of air with temperatures below polar stratospheric cloud formation thresholds (V PSC ) and some diagnostics of polar vortex size and strength, do not show improved agreement between the two reanalyses in recent years when data inputs into the DAS were more comprehensive. The polar processing diagnostics calculated from MERRA and ERA-Interim agree much better than those calculated from earlier reanalysis data sets. We still, however, see fairly large differences in many of the diagnostics in years prior to 2002, raising the possibility that the choice of one reanalysis over another could significantly influence the results of polar processing studies. After 2002, we see overall good agreement among the diagnostics, which demonstrates that the ERA-Interim and MERRA reanalyses are equally appropriate choices for polar processing studies of recent Arctic and Antarctic winters.

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“…The relative roles and temperature dependencies of surface reactions on and in water ice, nitric acid trihydrate ice, and supercooled liquid sulfuric acid−water−nitric acid and binary sulfuric acid−water particles at background levels have been research topics since the late 1980s, and some important questions have recently reemerged. Some recent studies have suggested that heterogeneous chemistry taking place on background particles of sulfuric acid and water is sufficient to explain nearly all of the chlorine activation (17)(18)(19) and ozone losses in both the Arctic and Antarctic (17) without any need for temperatures below −78°C or formation of polar stratospheric clouds, which would represent a major change in understanding. The potential for liquid binary aerosols to play some role in ozone loss under cold conditions was first identified decades ago (20,21).…”

Section: Lower Stratospheric Chemistrymentioning

confidence: 99%

Fundamental differences between Arctic and Antarctic ozone depletion

Solomon

Haskins

Ivy

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Antarctic ozone depletion is associated with enhanced chlorine from anthropogenic chlorofluorocarbons and heterogeneous chemistry under cold conditions. The deep Antarctic "hole" contrasts with the generally weaker depletions observed in the warmer Arctic. An unusually cold Arctic stratospheric season occurred in 2011, raising the question of how the Arctic ozone chemistry in that year compares with others. We show that the averaged depletions near 20 km across the cold part of each pole are deeper in Antarctica than in the Arctic for all years, although 2011 Arctic values do rival those seen in less-depleted years in Antarctica. We focus not only on averages but also on extremes, to address whether or not Arctic ozone depletion can be as extreme as that observed in the Antarctic. This information provides unique insights into the contrasts between Arctic and Antarctic ozone chemistry. We show that extreme Antarctic ozone minima fall to or below 0.1 parts per million by volume (ppmv) at 18 and 20 km (about 70 and 50 mbar) whereas the lowest Arctic ozone values are about 0.5 ppmv at these altitudes. At a higher altitude of 24 km (30-mbar level), no Arctic data below about 2 ppmv have been observed, including in 2011, in contrast to values more than an order of magnitude lower in Antarctica. The data show that the lowest ozone values are associated with temperatures below −80°C to −85°C depending upon altitude, and are closely associated with reduced gaseous nitric acid concentrations due to uptake and/or sedimentation in polar stratospheric cloud particles.stratosphere | atmospheric chemistry T he extensive springtime depletion of Antarctic ozone has attracted both public and scientific interest since its discovery (1) and explanation in the 1980s. The ozone hole has been linked to the coupling of human-made chlorofluorocarbons with surface chemistry on and in polar stratospheric clouds (PSCs) that form during extreme cold conditions (2). Polar stratospheric clouds are composed of nitric acid hydrates, liquid solutions of sulfuric acid, water, and nitric acid, and (under very cold conditions) water ice (e.g., ref. 3 and citations therein). Some of the key reactions are photochemical, so that the ozone hole does not form during midwinter when the polar cap is dark, but rather in late winter/spring as sunlight returns, provided that temperatures remain low. Although the same basic chemical mechanisms operate in both hemispheres, the Arctic winter stratosphere is generally warmer than the Antarctic, and it warms up earlier in the spring. These two factors taken together explain why ozone depletion in the Arctic is generally much smaller than in the Antarctic. A particularly cold Arctic stratospheric winter and spring in 2010/2011 displayed much larger ozone depletion than typical years, as highlighted by Manney et al. (4). This noteworthy geophysical event has intrigued scientists and raised several important questions: Could this be the first Arctic ozone hole? Are Arctic ozone losses ever observed to be as extreme...

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Uncertainties in modelling heterogeneous chemistry and Arctic ozone depletion in the winter 2009/2010

Cited by 62 publications

References 58 publications

Comparison of ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations of the Arctic winter 2009/2010 and 2010/2011 with Envisat/MIPAS and Aura/MLS observations

Comparison of ECHAM5/MESSy Atmospheric Chemistry (EMAC) simulations of the Arctic winter 2009/2010 and 2010/2011 with Envisat/MIPAS and Aura/MLS observations

Comparisons of polar processing diagnostics from 34 years of the ERA-Interim and MERRA reanalyses

Fundamental differences between Arctic and Antarctic ozone depletion

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