Toward a more physical representation of precipitation scavenging in global chemistry models: cloud overlap and ice physics and their impact on tropospheric ozone

Neu, J. L.; Prather, Michael J.

doi:10.5194/acp-12-3289-2012

Cited by 108 publications

(95 citation statements)

References 67 publications

(89 reference statements)

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“…The wet deposition of Hg species has been implemented by adding the Hg compounds to the scheme in WRF-Chem for gas and particulate convective transport and wet deposition. In-cloud and below-cloud scavenging of Hg species has been treated in accordance with the approach described by Neu and Prather (2012), with Hg species scavenging rate assumed to be the same as that for HNO 3 (g). The model domain covers Europe and the Mediterranean Sea, including part of the western North Atlantic Ocean, North Africa, and the Middle East with a horizontal resolution of 24 × 24 km, and 30 vertical levels from soil to 50 hPa.…”

Section: Wrf-chemmentioning

confidence: 99%

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

et al. 2017

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Abstract. Atmospheric chemistry and transport of mercury play a key role in the global mercury cycle. However, there are still considerable knowledge gaps concerning the fate of mercury in the atmosphere. This is the second part of a model intercomparison study investigating the impact of atmospheric chemistry and emissions on mercury in the atmosphere. While the first study focused on ground-based observations of mercury concentration and deposition, here we investigate the vertical and interhemispheric distribution and speciation of mercury from the planetary boundary layer to the lower stratosphere. So far, there have been few model studies investigating the vertical distribution of mercury, mostly focusing on single aircraft campaigns. Here, we present a first comprehensive analysis based on various aircraft observations in Europe, North America, and on intercontinental flights.The investigated models proved to be able to reproduce the distribution of total and elemental mercury concentrations in the troposphere including interhemispheric trends. One key aspect of the study is the investigation of mercury oxidation in the troposphere. We found that different chemistry schemes were better at reproducing observed oxidized mercury patterns depending on altitude. High concentrations of oxidized mercury in the upper troposphere could be reproduced with oxidation by bromine while elevated concentrations in the lower troposphere were better reproduced by OH and ozone chemistry. However, the results were not always conclusive as the physical and chemical parameterizations in the chemistry transport models also proved to have a substantial impact on model results.

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Section: Wrf-chemmentioning

confidence: 99%

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

et al. 2017

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“…For all simulations, model configurations simulate wet deposition of gas species using the Neu and Prather (2012) scheme, including a bug fix to CESM1.2, where the SO 2 Henry's law coefficient has been updated, resulting in reduced washout rates. This fix resulted in an increased burden of SO 4 in CAM4-chem, which has been adjusted by increasing the in-and below-cloud solubility factor of SO 4 from 0.3 to 0.4.…”

Section: S Tilmes Et Al: Evaluation Of Tropospheric Chemistry and Amentioning

confidence: 99%

Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

et al. 2015

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Abstract. The Community Atmosphere Model (CAM), version 5, is now coupled to extensive tropospheric and stratospheric chemistry, called CAM5-chem, and is available in addition to CAM4-chem in the Community Earth System Model (CESM) version 1.2. The main focus of this paper is to compare the performance of configurations with internally derived "free running" (FR) meteorology and "specified dynamics" (SD) against observations from surface, aircraft, and satellite, as well as understand the origin of the identified differences. We focus on the representation of aerosols and chemistry. All model configurations reproduce tropospheric ozone for most regions based on in situ and satellite observations. However, shortcomings exist in the representation of ozone precursors and aerosols. Tropospheric ozone in all model configurations agrees for the most part with ozonesondes and satellite observations in the tropics and the Northern Hemisphere within the variability of the observations. Southern hemispheric tropospheric ozone is consistently underestimated by up to 25 %. Differences in convection and stratosphere to troposphere exchange processes are mostly responsible for differences in ozone in the different model configurations. Carbon monoxide (CO) and other volatile organic compounds are largely underestimated in Northern Hemisphere mid-latitudes based on satellite and aircraft observations. Nitrogen oxides (NO x ) are biased low in the free tropical troposphere, whereas peroxyacetyl nitrate (PAN) is overestimated in particular in high northern latitudes. The present-day methane lifetime estimates are compared among the different model configurations. These range between 7.8 years in the SD configuration of CAM5-chem and 8.8 years in the FR configuration of CAM4-chem and are therefore underestimated compared to observational estimations. We find that differences in tropospheric aerosol surface area between CAM4 and CAM5 play an important role in controlling the burden of the tropical tropospheric hydroxyl radical (OH), which causes differences in tropical methane lifetime of about half a year between CAM4-chem and CAM5-chem. In addition, different distributions of NO x from lightning explain about half of the difference between SD and FR model versions in both CAM4-chem and CAM5-chem. Remaining differences in the tropical OH burden are due to enhanced tropical ozone burden in SD configurations compared to the FR versions, which are not only caused by differences in chemical production or loss but also by transport and mixing. For future studies, we recommend the use of CAM5-chem configurations, due to improved aerosol description and inclusion of aerosol-cloud interactions. However, smaller tropospheric surface area density in the current version of CAM5-chem compared to CAM4-chem results in Published by Copernicus Publications on behalf of the European Geosciences Union. S. Tilmes et al.: Evaluation of tropospheric chemistry and aerosols in CESM1.2larger oxidizing capacity in the troposphere and therefore a shorter...

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“…Whether the Langmuir or Henry's law coefficient is superior to parameterize the uptake of trace gases to solid ice is an open question also in research focusing on the upper troposphere (Neu and Prather, 2012). As the interaction of trace gases with wet snow differs significantly from dry snow (Clapsaddle and Lamb, 1989;Herbert et al, 2006b;BartelsRausch et al, 2012b), this finding holds as long as the snow is dry and liquid water is not present.…”

Section: Atmospheric Implicationmentioning

confidence: 59%

Diffusion of volatile organics through porous snow: impact of surface adsorption and grain boundaries

et al. 2013

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Abstract. Release of trace gases from surface snow on earth drives atmospheric chemistry, especially in the polar regions. The gas-phase diffusion of methanol and of acetone through the interstitial air of snow was investigated in a well-controlled laboratory study in the temperature range of 223 to 263 K. The aim of this study was to evaluate how the structure of the snowpack, the interaction of the trace gases with the snow surface, and the grain boundaries influence the diffusion on timescales up to 1 h. The diffusive loss of these two volatile organics into packed snow samples was measured using a chemical ionization mass spectrometer. The structure of the snow was analysed by means of X-ray-computed micro-tomography. The observed diffusion profiles could be well described based on gas-phase diffusion and the known structure of the snow sample at temperatures &geq; 253 K. At colder temperatures, surface interactions start to dominate the diffusive transport. Parameterizing these interactions in terms of adsorption to the solid ice surface, i.e. using temperature-dependent air–ice partitioning coefficients, better described the observed diffusion profiles than the use of air–liquid partitioning coefficients. No changes in the diffusive fluxes were observed by increasing the number of grain boundaries in the snow sample by a factor of 7, indicating that for these volatile organic trace gases, uptake into grain boundaries does not play a role on the timescale of diffusion through porous surface snow. For this, a snow sample with an artificially high amount of ice grains was produced and the grain boundary surface measured using thin sections. In conclusion, we have shown that the diffusivity can be predicted when the structure of the snowpack and the partitioning of the trace gas to solid ice is known.

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Toward a more physical representation of precipitation scavenging in global chemistry models: cloud overlap and ice physics and their impact on tropospheric ozone

Cited by 108 publications

References 67 publications

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)

Diffusion of volatile organics through porous snow: impact of surface adsorption and grain boundaries

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