Micro-Swift-Spray (MSS): A New Modelling System for the Simulation of Dispersion at Microscale. General Description and Validation

Dispersion at microscale should be simulated using 3D codes, since they are able to account for very complex situations. Targets of these models can be road traffic simulations, such as the reconstruction of the high pollution episodes into street canyons or car parks or, more generally, the reconstruction of dispersion patterns generated by the presence of obstacles. These problems are traditionally solved using CFD models adapted to the atmospheric PBL, suitable only for short term simulations in a limited number of cases, due to their high CPU demand. Here we present a different approach to reproduce the microscale scenarios with a lower demand of computational time. It potentially allows a wider range of applications, such as emergency responses, statistical calculations of impacts due to different conditions and climatological or long term impacts. This method allows an exact representation of buildings directly generated by a GIS (as .shp files). A first guess of the 3D mean flow is computed using all available and relevant meteorological data (inside or outside the target domain). This field is then modified using analytical corrections due to the obstacles (Kaplan and Dinar, 1996).