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| Titel |
Arctic chlorine activation and ozone depletion: Comparison of chemistry transport models with satellite observations. |
| VerfasserIn |
J.-U. Grooß, T. Wegner, R. Müller, M. P. Chipperfield, W. Feng, M. L. Santee |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025225
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| Zusammenfassung |
| The accurate simulation of Arctic stratospheric ozone depletion has been an issue for two
decades. However, there are still notable quantitative discrepancies between the models and
observations. We show results from the SLIMCAT and CLaMS 3D chemistry-transport
models that differ in some aspects of simulated chlorine activation and descent in the polar
vortex.
Consequently, the estimates of accumulated ozone depletion in the polar vortex for these
two models in cold Arctic winters still largely disagree.
As shown recently by Santee et al. (JGR, 2008) using MLS and ACE data, the
extent of chlorine activation for the cold Arctic winter of 2004/2005 within the basic
SLIMCAT model is overestimated with the likely consequence of too much simulated
ozone depletion. In contrast, the CLaMS simulation for the same winter shows too
little chlorine activation compared to observations, and therefore likely too little
loss.
For SLIMCAT the version used by Santee et al. has been updated to replace the
equilibrium treatment of NAT PSCs with a Lagrangian microphysical scheme. This leads to
smaller regions of NAT particles and less denitrification, in better agreement with
observations. The impact of this on the modeled extent of chlorine activation will be
discussed.
For CLaMS we have changed the parameterization of heterogeneous reactions on liquid
aerosols from Carslaw et al. to that of Shi et al. (2001), with which chlorine activation on
liquid aerosol becomes more efficient. In turn, the simulated chlorine activation agrees better
with the observations.
The impact of these model changes on chlorine activation and ozone loss will be assessed
and remaining model-observation discrepancies will be discussed in terms of different
model formulations. We will also show the impact of recent lab measurements of
Cl2O2 absorption cross sections by von Hobe et al. (2009) on the simulated ozone
depletion.
References:
von Hobe, M., F. Stroh, H. Beckers, T. Benter, and H. Willner, The UV/Vis absorption
spectrum of matrix isolated dichlorine peroxide, ClOOCl, Phys. Chem. Chem. Phys. ,
doi:10.1039/B814373K, 2009.
Santee M. L., I. A. MacKenzie, G. L. Manney, M. P. Chipperfield, P. F. Bernath, K. A.
Walker, C. D. Boone, L. Froidevaux, N. J. Livesey, J. W. Waters, A study of stratospheric
chlorine partitioning based on new satellite measurements and modeling, J. Geophys. Res.,
113, D12307, doi:10.1029/2007JD009057, 2008.
Shi, Q., J. Jayne, C. Kolb, D. Worsnop, and P. Davidovits, Kinetic model for reaction of
ClONO2 with H2O and HCl and HOCl with HCl in sulfuric acid solutions, J. Geophys. Res.,
106, 24259-24274, 2001. |
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