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| Titel |
Retrievals of chlorine chemistry kinetic parameters from Antarctic ClO microwave radiometer measurements |
| VerfasserIn |
S. Kremser, R. Schofield, G. E. Bodeker, B. J. Connor, M. Rex, J. Barret, T. Mooney, R. J. Salawitch, T. Canty, K. Frieler, M. P. Chipperfield, U. Langematz, W. Feng |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 11 ; Nr. 11, no. 11 (2011-06-01), S.5183-5193 |
| Datensatznummer |
250009796
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| Publikation (Nr.) |
 copernicus.org/acp-11-5183-2011.pdf |
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| Zusammenfassung |
| Key kinetic parameters governing the partitioning of chlorine species in the
Antarctic polar stratosphere were retrieved from 28 days of chlorine monoxide
(ClO) microwave radiometer measurements made during the late winter/early
spring of 2005 at Scott Base (77.85° S, 166.75° E).
During day-time the loss of the ClO dimer chlorine peroxide (ClOOCl) occurs
mainly by photolysis. Some time after sunrise, a photochemical equilibrium is
established and the ClO/ClOOCl partitioning is determined by the ratio of the
photolysis frequency, J, and the dimer formation rate, kf. The
values of J and kf from laboratory studies remain uncertain to a
considerable extent, and as a complement to these ongoing studies, the goal
of this work is to provide a constraint on that uncertainty based on
observations of ClO profiles in the Antarctic. First an optimal estimation
technique was used to derive J/kf ratios for a range of Keq
values. The optimal estimation forward model was a photochemical box model
that takes J, kf, and Keq as inputs, together with a
priori profiles of activated chlorine (ClOx = ClO+2×ClOOCl), profiles of ozone, temperature, and pressure.
JPL06 kinetics are used as a priori in the optimal estimation and for all
other chemistry in the forward model. Using the more recent JPL09 kinetics
results in insignificant differences in the retrieved value of J/kf.
A complementary approach was used to derive the optimal kinetic parameters;
the full parameter space of J, kf, Keq and ClOx
was sampled to find the minimum in differences between measured and modelled
ClO profiles. Furthermore, values of Keq up to 2.0 times larger than
recommended by JPL06 were explored to test the sensitivity of the J/kf
ratio to changes in Keq. The results show that the retrieved
J/kf ratios bracket the range of 1.23 to 1.97 times the J/kf
value recommended by JPL06 over the range of Keq values
considered. The retrieved J/kf ratios lie in the lower half of the
large uncertainty range of J/kf recommended by JPL06 and towards the
upper portion of the smaller uncertainty range recommended by JPL09. |
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