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Urban climate modelling

Abstract:

Thanks to the increase in computational resources, regional climate models are able to resolve urbanization in regional climate models. Therefore, different urban parameterizations have been integrated COSMO-CLM. They include the Town Energy Budget (TEB), the Building Energy Parameterization (BEP) with a Double-Canyon Radiation Scheme (DCEP), and the urban upgrade of the standard soil module of COSMO-CLM (TERRA-URB). These urban parametrizations vary in their physical approach, complexity, computational cost and number of needed parameters. The urban intercomparison project investigates the impact of using different urban parameterizations for regional climate modelling at 1km horizontal resolution during 2002. Hereby, the COSMO-CLM configuration and boundary conditions of each simulation is unaltered except for the urban parameterization. Each of these simulations are compared and evaluated against surface-flux and temperature measurements from intensive observation camaign at Basel (BUBBLE), and vertical profiles of temperatures and wind over Berlin. We explore the impact of the urban parametrization on the surface fluxes and the resulting differences in near-surface temperature and wind fields, in particular the circulation and vertical extent of the UHI. Our study aims to facilitate the choice of a particular urban parameterization (complexity) with regard to the users' application in mind. Hereby, the intercomparison of urban models with different complexity should identify specific important processes that are relevant for a specific aim. Finally, we want to bring the urban parameterizations to one of the COSMO5.x releases, so that they can be readily used in both NWP and climate simulations.