Chemical ozone loss in the tropopause region on subvisible ice clouds, calculated with a chemistry‐transport model

Bregman, B.; Wang, P.-H.; Lelieveld, Jos

doi:10.1029/2001jd000761

Cited by 26 publications

(28 citation statements)

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“…While changes in transport in the lowermost stratosphere could explain at least part of the observed trend (Fusco and Salby, 1999;Salby and Callaghan, 2004;Hood and Soukharev, 2005), chemical ozone loss due to halogen chemistry is also thought to play a significant role (Salawitch et al, 2005;Solomon et al, 1997). Besides higher than previously suggested and still slightly increasing amounts of bromine in this region (Dorf et al, 2006), catalytic ozone destruction by ClO produced as a result of heterogeneous chlorine activation on sulphate aerosol and on ice-particles in cirrus clouds has been suggested (Borrmann et al, 1996Bregman et al, 2002;Keim et al, 1996;Solomon et al, 1997;Thornton et al, 2003Thornton et al, , 2005.…”

Section: Introductionmentioning

confidence: 88%

Evidence for heterogeneous chlorine activation in the tropical UTLS

et al. 2011

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Abstract. Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brazil, February 2005) and SCOUT-O 3 (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10-20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt -significantly exceeding those expected from gas phase chemistry -were observed in air masses of a more tropospheric character. Most of these observations are associated with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation in the tropical upper troposphere lower stratosphere (UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. However, to reproduce the ClO observations in these simulations, O 3 mixing ratios higher than observed had to be assumed, and at least for one of these flights, a significant denoxification is in contrast to the observed NO levels, suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.

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Section: Introductionmentioning

confidence: 88%

Evidence for heterogeneous chlorine activation in the tropical UTLS

et al. 2011

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“…Therefore thin populations of small particles like represented by subvisual cirrus clouds could play a role in this respect. For this issue, which is a matter of current debate [e.g., Bregman et al , 2002], also detailed knowledge of the chemical composition of the cloud particles is critical.…”

Section: Introductionmentioning

confidence: 99%

In situ measurements of background aerosol and subvisible cirrus in the tropical tropopause region

et al. 2002

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[1] In situ aerosol measurements were performed in the Indian Ocean Intertropical Convergence Zone (ITCZ) region during the Airborne Polar Experiment-Third European Stratospheric Experiment on Ozone (APE-THESEO) field campaign based in Mahe, Seychelles between 24 February and 6 March 1999. These are measurements of particle size distributions with a laser optical particle counter of the Forward Scattering Spectrometer Probe (FSSP)-300 type operated on the Russian M-55 high- altitude research aircraft Geophysica in the tropical upper troposphere and lower stratosphere up to altitudes of 21 km. On 24 and 27 February 1999, ultrathin layers of cirrus clouds were penetrated by Geophysica directly beneath the tropical tropopause at 17 km pressure altitude and temperatures below 190 K. These layers also were concurrently observed by the Ozone Lidar Experiment (OLEX) lidar operating on the lower- flying German DLR Falcon research aircraft. The encountered ultrathin subvisual cloud layers can be characterized as (1) horizontally extending over several hundred kilometers, (2) persisting for at least 3 hours (but most likely much longer), and (3) having geometrical thicknesses of 100-400 m. These cloud layers belong to the geometrically and optically thinnest ever observed. In situ particle size distributions covering diameters between 0.4 and 23 mum obtained from these layers are juxtaposed with those obtained inside cloud veils around cumulonimbus (Cb) anvils and also with background aerosol measurements in the vicinity of the clouds. A significant number of particles with size diameters around 10 mum were detected inside these ultrathin subvisible cloud layers. The cloud particle size distribution closely resembles a background aerosol onto which a modal peak between 2 and 17 mum is superimposed. Measurements of particles with sizes above 23 mum could not be obtained since no suitable instrument was available on Geophysica. During the flight of 6 March 1999, upper tropospheric and lower stratospheric background aerosol was measured in the latitude band between 4degreesS and 19degreesS latitude. The resulting particle number densities along the 56th meridian exhibit very little latitudinal variation. The concentrations for particles with sizes above 0.5 m m encountered under these background conditions varied between 0.1 and 0.3 particles/cm(3) of air in altitudes between 17 and 21 km

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“…The TM3 model has been used widely in the modeling community (e.g. Dentener et al, 1999;Peters et al, 2001;Houweling et al, 1998;Van den Broek et al, 2000;Bregman et al, 2001Bregman et al, , 2002. The original version of the model has been developed by Heimann (1995); Heimann and Keeling (1989).…”

Section: Model Descriptionmentioning

confidence: 99%

Key aspects of stratospheric tracer modeling using assimilated winds

2006

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Abstract. This study describes key aspects of global chemistry-transport models and their impact on stratospheric tracer transport. We concentrate on global models that use assimilated winds from numerical weather predictions, but the results also apply to tracer transport in general circulation models. We examined grid resolution, numerical diffusion, air parcel dispersion, the wind or mass flux update frequency, and time interpolation. The evaluation is performed with assimilated meteorology from the "operational analyses or operational data" (OD) from the European Centre for MediumRange Weather Forecasts (ECMWF). We also show the effect of the mass flux update frequency using the ECMWF 40-year re-analyses (ERA40).We applied the three-dimensional chemistry-transport Tracer Model version 5 (TM5) and a trajectory model and performed several diagnoses focusing on different transport regimes. Covering different time and spatial scales, we examined (1) polar vortex dynamics during the Arctic winter, (2) the large-scale stratospheric meridional circulation, and (3) air parcel dispersion in the tropical lower stratosphere.Tracer distributions inside the Arctic polar vortex show considerably worse agreement with observations when the model grid resolution in the polar region is reduced to avoid numerical instability. The results are sensitive to the diffusivity of the advection. Nevertheless, the use of a computational cheaper but diffusive advection scheme is feasible for tracer transport when the horizontal grid resolution is equal or smaller than 1 degree. The use of time interpolated winds improves the tracer distributions, particularly in the middle and upper stratosphere. Considerable improvement is found both in the large-scale tracer distribution and in the polar regions when the update frequency of the assimilated winds is increased from 6 to 3 h. It considerably reduces the vertical dispersion of air parcels in the tropical lower stratosphere.Correspondence to: B. Bregman (bregman@knmi.nl) Strong horizontal dispersion is not necessarily an indication of poor wind quality, as observations indicate. Moreover, the generally applied air parcel dispersion calculations should be interpreted with care, given the strong sensitivity of dispersion with altitude.The results in this study provide a guideline for stratospheric tracer modeling using assimilated winds. They further demonstrate significant progress in the use of assimilated meteorology in chemistry-transport models, relevant for both short-and long-term integrations.

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Chemical ozone loss in the tropopause region on subvisible ice clouds, calculated with a chemistry‐transport model

Cited by 26 publications

References 64 publications

Evidence for heterogeneous chlorine activation in the tropical UTLS

Evidence for heterogeneous chlorine activation in the tropical UTLS

In situ measurements of background aerosol and subvisible cirrus in the tropical tropopause region

Key aspects of stratospheric tracer modeling using assimilated winds

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