Improving surface-layer forecasting in urban environments with a mesoscale atmospheric model

The urbanized version of the Global Environmental Multiscale (GEM) atmospheric model employs the Town Energy Balance (TEB) parameterization scheme for representing the urban canopy and its interaction with the atmosphere. In the current implementation, TEB provides the lower boundary conditions (i.e., surface fluxes) to GEM's vertical diffusion scheme for atmospheric turbulence, based only on information from the surface and from the lowest atmospheric level, presently located well above the urban canopy in the inertial sublayer. The focus of the present work is to improve this GEM implementation of TEB by adding vertical levels near the surface and within the urban canopy in order to better represent profiles of air temperature, humidity, and winds in the urban canopy and in the surface layer. Surface fluxes computed using the TEB model are allowed to interact with multiple vertical levels inside and adjacent to the urban canopy. The new urban modelling system is being tested for two intensive observational periods of the Joint Urban 2003 experiment held in Oklahoma City, USA. Preliminary results reveal the potential of the new urban modelling approach for improving near-surface forecasting. Elaborate results pertinent to the effects of the new urban modelling on the surface and near-surface forecasting and its comparison with observations will be presented at the symposium.