Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, CH, CY, DE, DK, EE, ES, FI, FR, GR, HU, IT, LT, NL, NO, PL, PT, RO, SE, TR, UK
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Abstract
(Englisch)
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Air quality becomes a serious health concern in modern societies, and this has connections with the growth of urban areas. Millions of people are today exposed to high levels of pollutant concentrations. Emission control strategies have to be envisaged and rigourously practiced, with the help of pollution forecast models. Numerical prediction should again play a crucial role in this context, but various roadblocks need first to be alleviated before gaining in credibility. Air quality models require an integrated approach to simulate the local urban scale (< 1-5 km) and surrounding meso-scale (1-200 km). This is synonymous to couple large-scale weather forecasting models (NWP) with sub-scale air quality models (AQ). Only under these conditions can the “boundary conditions” between the two environments be transcended and accounted for rigourously. The increasing predictive -or resolving- capabilities of NWP’s is allowing these to penetrate (in terms of resolution) deeper within the sub-scale or city-scale domains. Air quality models (such as CAMx, AUSTAL, MISKAM) require, on the other hand, a sort of “super-scale boundary conditions” that can be provided only by NWP’s, e.g. MM5. The link between the two is therefore obvious, and that is the pillar of our project. Existing sub-scale models have proven disappointing in describing the flow and turbulence fields accurately enough to be used for pollution transport studies. Difficulties also arise from the treatment of heterogeneous surface characteristics such surface roughness, and phase-change processes (evaporation). Particle dispersion in low momentum conditions is an additional chalenge that requires more attention. The same is true for production of secondary pollutants, such as ozone during meso-scale transport. Flow and turbulence models constitute therefore the cornerstone of the assessment process and can influence substantially the results of subsequent modules (e.g. phisico-chemistry). With this proposal we intend to help develop a better sub-scale parameterization model by use of a sophisticated modelling approach, transcending RANS. We intend to use the Large-eddy Simualtion (LES) approach for the flow around a matrix of cubical obstacles, representing a typical sub-urban area. Expected outcome of this work include: improving the urban parameterization in the mesocale models, and promote the knowledge on the interactions between urban sub-scale and large-scale phenomena. This will increase the credibility of existing pollutant concentration simulation codes, which form the main instrument for defining appropriate strategical actions.
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