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| Titel |
Semi-Lagrangian methods in air pollution models |
| VerfasserIn |
A. B. Hansen, J. Brandt, J. H. Christensen, E. Kaas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 4, no. 2 ; Nr. 4, no. 2 (2011-06-24), S.511-541 |
| Datensatznummer |
250001665
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| Publikation (Nr.) |
 copernicus.org/gmd-4-511-2011.pdf |
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| Zusammenfassung |
Various semi-Lagrangian methods are tested with respect to advection
in air pollution modeling. The aim is to find a method fulfilling as many of
the desirable properties by Rasch andWilliamson (1990) and Machenhauer et al. (2008) as
possible. The focus in this study is on accuracy and local mass
conservation.
The methods tested are, first, classical
semi-Lagrangian cubic interpolation, see e.g. Durran (1999), second,
semi-Lagrangian cubic cascade interpolation, by Nair et al. (2002), third,
semi-Lagrangian cubic interpolation with the modified interpolation weights,
Locally Mass Conserving Semi-Lagrangian (LMCSL), by Kaas (2008), and
last, semi-Lagrangian cubic interpolation with a locally mass conserving
monotonic filter by Kaas and Nielsen (2010).
Semi-Lagrangian (SL)
interpolation is a classical method for atmospheric modeling, cascade
interpolation is more efficient computationally, modified interpolation
weights assure mass conservation and the locally mass conserving monotonic
filter imposes monotonicity.
All schemes are tested with advection
alone or with advection and chemistry together under both typical rural and
urban conditions using different temporal and spatial resolution. The methods
are compared with a current state-of-the-art scheme, Accurate Space
Derivatives (ASD), see Frohn et al. (2002), presently used at the National
Environmental Research Institute (NERI) in Denmark. To enable a consistent
comparison only non-divergent flow configurations are tested.
The
test cases are based either on the traditional slotted cylinder or the
rotating cone, where the schemes' ability to model both steep gradients and
slopes are challenged.
The tests showed that the locally mass conserving monotonic filter improved
the results significantly for some of the test cases, however, not for all.
It was found that the semi-Lagrangian schemes, in almost every case, were not
able to outperform the current ASD scheme used in DEHM with respect to
accuracy. |
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