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The second sub-project aims to develop a comprehensive modelling approach for the city of Hamburg. It will allow spatio-temporal high resolution regionalisation of urban climate change effects like rainfall extremes (flooding) or heat waves (associated with high ozone concentration). In order to enable a physically consistent simulation we propose a hierarchical modelling scheme of statistical and dynamical downscaling steps in which advanced surface parametrisation methods will take into account the topographic heterogeneity. This combination, which comprises design, implementation, and validation, will make use of:
consecutive dynamical downscaling steps for the mesoscale using the non-hydrostatic Regional Climate Model (RCM) Weather Research and Forecast (WRF, Done et al. 2004), forced by global atmospheric data (re-analyses and GCM scenario runs); statistical downscaling for the microscale (Böhner 2006) using advanced climate variables of higher spatial resolution and surface parametrisation methods (Böhner & Antonic 2008) in Geographical Information Systems (GIS) like SAGA GIS. This hierarchical model chain should close the gap between the scarce resolution of today's RCMs (3-5 km) and the needed resolution for urban management caused by limited computational power. Major conceptual objectives in the climate modeling context are: Firstly, to investigate the urban response to natural and anthropogenic perturbations during present and future time periods; secondly, to provide climatologic information for impact studies in the project framework at appropriate spatio-temporal scales.
It is foreseen to aggregate the work of WP I and III to improve the description of multi-scale characteristics of land-atmosphere interactions. In the end it should be a portable Urban Climate Model to make use of in every city affected of climate change.
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