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| Titel |
Semi-Lagrangian Methods in Air Pollution Models. |
| VerfasserIn |
A. Buus Hansen, E. Kaas, J. H. Christensen, J. Brandt |
| 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 |
250025285
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| Zusammenfassung |
| Various semi-Lagrangian methods are tested for use in air pollution model-
ing. The aim is to find a method fulfilling as many of the desirable properties
by Rasch and Williamson (1990) and Machenhauer et al. (2008) as possi-
ble. The focus is on accuracy, local mass conservation and computational
efficiency.
The methods tested are, first, classical semi-Lagrangian cubic interpola-
tion, see e.g. Durran (1999), second, semi-Lagrangian cubic cascade inter-
polation, by Nair et al. (2002), third, semi-Lagrangian cubic interpolation
with the modified interpolation weights, by Kaas (2008), and last, semi-
Lagrangian cubic interpolation with a locally mass conserving monotonic
filter by Kaas and Nielsen (2008).
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 con-
serving monotonic filter imposes monotonicity.
All schemes are tested with advection alone or with advection and chem-
istry 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 presently used at the National Environmental Re-
search Institute (NERI) in Denmark.
The test cases are based either on the traditional slotted cylinder, see
e.g. Zerroukat et al. (2002), or the rotating cone, see e.g. Molenkamp (1968)
and Crowley (1968), where the schemes’ ability to model both steep gradi-
ents and slopes are challenged.
The tests showed that the locally mass conserving monotonic filter im-
proved 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 currently used ASD scheme used in DEHM,
see e.g. Frohn et al. (2002).
The present study is a part of the research of the Center for Energy, Envi-
ronment and Health, financed by The Danish Strategic Research Program
on Sustainable Energy. |
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