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| Titel |
Systematic reduction of complex tropospheric chemical mechanisms, Part I: sensitivity and time-scale analyses |
| VerfasserIn |
L. E. Whitehouse, A. S. Tomlin, M. J. Pilling |
| 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 ; 4, no. 7 ; Nr. 4, no. 7 (2004-10-05), S.2025-2056 |
| Datensatznummer |
250002047
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| Publikation (Nr.) |
 copernicus.org/acp-4-2025-2004.pdf |
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| Zusammenfassung |
| Explicit mechanisms describing the complex degradation pathways
of atmospheric volatile organic compounds (VOCs) are important, since they allow the study of the
contribution of individual VOCS to secondary pollutant formation.
They are computationally expensive to solve however, since they
contain large numbers of species and a wide range of time-scales causing
stiffness in the resulting equation systems. This paper and the following companion paper
describe the application of systematic and automated methods for reducing such
complex mechanisms, whilst maintaining the accuracy of the model with respect to important
species and features. The methods are demonstrated via application to version
2 of the Leeds Master Chemical Mechanism. The methods of Jacobian analysis and
overall rate sensitivity analysis proved to be efficient and capable of
removing the majority of redundant reactions and species in the scheme across a wide range of
conditions relevant to the polluted troposphere. The application of principal component analysis of the rate sensitivity
matrix was computationally expensive due to its use of the
decomposition of very large matrices, and did not produce significant reduction over and above the
other sensitivity methods. The use of the quasi-steady state approximation (QSSA) proved to be an extremely successful
method of removing the fast time-scales within the system, as demonstrated by a local perturbation analysis
at each stage of reduction. QSSA species were automatically selected via the calculation of instantaneous
QSSA errors based on user-selected tolerances. The application of the QSSA led to the removal of a large number of alkoxy radicals
and excited Criegee bi-radicals via reaction lumping. The resulting reduced mechanism was shown to
reproduce the concentration profiles of the important species selected from the full mechanism over a wide range of
conditions, including those outside of which the reduced mechanism was generated. As a result of a reduction in the
number of species in the scheme of a factor of 2, and a reduction in stiffness, the computational time
required for simulations was reduced by a factor of 4 when compared to the full scheme. |
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