ON THE EFFECTS OF COMPLEX URBAN GEOMETRIES ON MESOSCALE MODELLING

The effects of urban structures on the atmosphere are studied using mesoscale models having a resolution ranging from a few meters to a few kilometers. Because of such a coarse resolution urban parameterizations are required to simulate the effects of the subgrid scales (buildings and canyons). Mostly, these parameterizations are developed by assuming a city to be comprised of an array of cubes. In the present study we attempt to verify this basic assumption by comparing spatially averaged quantities such as the velocity, turbulent kinetic energy and radiative exchanges in an urban domain comprising different geometrical structures. The spatially averaged velocity fields are computed using the Immersed Boundary Technique (IB) whereas the radiant exchanges are computed using a Simplified Radiosity Algorithm (which accounts for sky anisotropy).