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| Titel |
Simulating pollutant transport in complex terrain with a Lagrangian particle dispersion model |
| VerfasserIn |
B. Szintai, P. Kaufmann, M. W. Rotach |
| 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 |
250021279
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| Zusammenfassung |
| Lagrangian particle dispersion models (LPDMs) are among the most sophisticated tools to
simulate atmospheric dispersion of pollutants, and are widely used in emergency response
systems. In these systems, LPDMs should be coupled with a numerical weather prediction
(NWP) model, which provides information from the mean wind as well as from the
turbulence state of the atmosphere. Mean wind can directly be used from the NWP
model, while turbulence characteristics have to be parameterized by a so-called
meteorological pre-processor. In most cases, to diagnose turbulence variables, meteorological
pre-processors use similarity theory approaches, which are based on turbulence datasets over
flat and homogeneous surface. However, turbulence structure in complex terrain,
such as in steep and narrow Alpine valleys, can be substantially different from flat
conditions.
In this study a new scaling approach from Weigel et al. (2007), based on measurements
and model simulations of the Riviera Project in the framework of the Mesoscale Alpine
Program (MAP), is investigated with respect to pollutant dispersion. In the Riviera Project,
analysis of turbulence measurements in a steep and narrow Alpine valley showed that
daytime profiles of Turbulent Kinetic Energy (TKE) scale very well if the convective
velocity scale w* is obtained from the sunlit eastern slope rather than from the surface
directly under the measured profiles. This scaling behaviour was also reproduced by
high-resolution Large Eddy Simulation runs. To improve the performance of the
dispersion model in complex terrain, this new scaling approach is introduced in the
meteorological pre-processor of the LPDM and results are validated with a real tracer
experiment.
For the evaluation of the dispersion model, the TRANSALP tracer experiment is used.
During this experiment passive tracers were released and detected in an Alpine valley in
Southern Switzerland on two days in October 1989. To simulate this case the operational
emergency response system of MeteoSwiss is applied, which consists of the NWP model
COSMO and the particle dispersion model LPDM. As the valleys where the experiment
took place are approximately 1 km wide, a very high horizontal resolution of 1
km is used in the COSMO simulations, instead of the operational resolution of
2.2 km. The dispersion model is run both with the original pre-processor using
flat-terrain scaling and the new one, applying the novel scaling approach fitted for Alpine
valleys. The new scaling method results in higher turbulence values and thus lower
concentrations in the valley, which show good agreement with the measured values. |
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