Implementation of Energy Fluxes in Eulag with a New 3d Shadow Model

The last generation of the mesoscale meteorological model try to incorporate urban characteristics, like as Urban Canopy Model (UCM) as a module added to the mesoscale meteorological model WRF (Weather & Research Forecasting system) (NCAR and others). The UCM approach is a good initial and ideal approach to develop micro urban meteorological simulations over urban domains. However, the real urban structures are not simply geometric shapes and have no uniformity. Micro urban simulations require high detailed information. In order to take into the count the building morphology. we have used a Computational Fluid Dynamics (CFD) model named EULAG. The CFD model will be used in combination with a mesoscale meteorological model, WRF, to provide boundary and initial conditions. EULAG model do not include the fluxes calculation. We have included the energy fluxes calculation into the system for urban and natural cells. The net radiation play an important role in the energy balance equation and it is affected by the shadows, reflections and reemission by the walls of the buildings. A new three-dimensional urban solar radiation model (SHAMO) which has been developed by the authors of the present contribution. It has been developed to calculate short wave radiation over urban high resolution grids. Sky view factor and reflections are calculated using a three-dimensional ray tracking method. Some details about the speed-up of the algorithm will be presented in this paper. Direct and diffuse radiation partition is made taking into account the solar zenith angle and the sky conditions (cloudless conditions or cover conditions). We present results of the simulation obtained by using the EULAG-UCM model, with the new 3D shadow model. The radiation model is coupled with the heat transfer equations from UCM, which use the resistance network approach. The data produced by the urban solar radiation model has been used in large scale numerical experiments to simulate turbulent fluxes for urban areas; in this contribution over Madrid (Spain) city. We have applied a modified version of the EULAG (UCAR) micro scale model (CFD) which includes an energy balance equation to obtain the urban atmosphere/biosphere energy exchange. Results of the micro scale simulations and sensitivity analysis related to the solar radiation approach will be presented in this paper.