Contaminant transport and dispersion modeling in urban areas using two way coupling between mesoscale (WRF) and urban-scale (EULAG) models (Formerly 14.1)

To investigate small-scale transport and dispersion (T&D) within urban areas as well as to improve urban parameterizations in mesoscale models, we coupled a LES-based urban transport and dispersion model (EULAG) with the mesoscale Weather Research and Forecasting (WRF) model. EULAG explicitly resolves the detailed building geometry structures using the boundary (IB) approach while WRF parameterize the thermal and dynamic effects of urban through its urban canopy model.

We demonstrate potential benefits of two-way coupling between these two modeling system, evaluate the coupled model with data collected from the Oklahoma City Joint Urban 2003 (JU2003) experiment, and focus particularly on the accuracy of the transport and dispersion of a SF6 tracer gas. We perform high-resolution mesoscale calculations (500 meter grid spacing) by using the WRF model and downscale the velocity, temperature, pressure and turbulence fields to 3-6 meter grid spacing to supply EULAG initial and boundary conditions. In the feedback process the detailed urban flow information coming from urban aerodynamic features, computed by EULAG is upscaled to the WRF model by averaging over the mesoscale grid volume, improving the accuracy of the modeled mesoscale conditions.