Keywords: internal layers, roughness layer, soil models, urban atmosphere, urban pollution, air pollution, environmental pollution, modelling, transport diffusion, atmospheric dispersion models
Modelling urban canopy and terrain for transport diffusion simulations at sub-mesoscales
Studies of the transport and dispersion of atmospheric pollutants at the scale of a part or the whole of an urban agglomeration require numerical simulations over domains between a few kilometres and a few tens of kilometers (sub-meso scale to meso-y scale). Current computer capabilities do not allow for a grid resolution sufficiently fine to explicitly simulate the flows at the scale of urban constructions (buildings, streets, trees, etc.) which are known to have a large influence on the dynamics and thermodynamics of the lowest atmospheric layers. It is then necessary to replace the real soils and these constructions by 'apparent grounds'. In turn, this implies the development of parametric relationships to express the fluxes of momentum, sensible heat, and latent heat or water vapour, as a function of the characteristic parameters of the apparent ground. In addition, it is necessary to develop methods and numerical tools to allow the generation of maps of these ground fluxes over the city, from the analysis of these functions and the characteristics of the city quarters drawn from geographical/geometrical databanks.