Evaluation of an urban surface exchange parameterization for mesoscale models

In the last decade several urban parameterizations for mesoscale models have been proposed. Differences between the approaches reflect mainly the different aims of the simulations, from weather forecasts, to climatological studies (to evaluate Urban Heat Island mitigation strategies, for example). In this contribution, the BEP scheme (Martilli et al. 2002), is run in 1D mode, and compared to measurements recorded in the city of Basel (Switzerland), for the BUBBLE campaign. Such scheme was designed mainly for air quality simulations. As a consequence it pays particular attention to simulate features of the urban canopy layer, where emissions are located and people live. Several comparisons will be presented, like vertical profiles and time evolution of mean and turbulent fluxes, taking full benefit from the measurements intensive campaign. The comparisons show that the scheme proposed represent an improvement compared to traditional approaches that are not designed to reproduce features in the urban canopy. However, the scheme is still deficient for several aspects, and improvements are needed. Future developments of the scheme will be mentioned. They will be based on a further improvement of the dynamical part based on CFD high resolution simulations, and on the introduction of some elements of building energy (heating, ventilation, air conditioning) in order to make the parameterization useful also for urban climatological studies.