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Upgrading photolysis in the p-TOMCAT CTM : model evaluation and assessment of the role of clouds.

Voulgarakis, A. and Savage, N. H. and Wild, Oliver and Carver, G. D. and Clemitshaw, K. C. and Pyle, J. A. (2009) Upgrading photolysis in the p-TOMCAT CTM : model evaluation and assessment of the role of clouds. Geoscientific Model Development, 2 (1). pp. 59-72. ISSN 1991-959X

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    Abstract

    A new version of the p-TOMCAT Chemical Transport Model (CTM) which includes an improved photolysis code, Fast-JX, is validated. Through offline testing we show that Fast-JX captures well the observed J(NO2) and J(O1D) values obtained at Weybourne and during a flight above the Atlantic, though with some overestimation of J(O1D) when comparing to the aircraft data. By comparing p-TOMCAT output of CO and ozone with measurements, we find that the inclusion of Fast-JX in the CTM strongly improves the latter's ability to capture the seasonality and levels of tracers' concentrations. A probability distribution analysis demonstrates that photolysis rates and oxidant (OH, ozone) concentrations cover a broader range of values when using Fast-JX instead of the standard photolysis scheme. This is not only driven by improvements in the seasonality of cloudiness but also even more by the better representation of cloud spatial variability. We use three different cloud treatments to study the radiative effect of clouds on the abundances of a range of tracers and find only modest effects on a global scale. This is consistent with the most relevant recent study. The new version of the validated CTM will be used for a variety of future studies examining the variability of tropospheric composition and its drivers.

    Item Type: Article
    Journal or Publication Title: Geoscientific Model Development
    Uncontrolled Keywords: Tropospheric chemistry ; short-wave radiation ; photolysis
    Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
    Departments: Faculty of Science and Technology > Lancaster Environment Centre
    ID Code: 27976
    Deposited By: Mr Richard Ingham
    Deposited On: 27 Oct 2009 14:59
    Refereed?: Yes
    Published?: Published
    Last Modified: 06 Sep 2013 19:32
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/27976

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