Modelling the impact of high-rise buildings in urban areas on precipitation initiation

The impact of urban areas upon precipitation distribution has been studied for many years. However, the relative importance of the distribution and type of surface morphology and urban heating remains unclear, A simple model of the surface sensible heat flux is used to explore the impact of urban heterogeneity. Sensitivity experiments are carried out to test the validity of the model, and experiments with a schematic urban morphology are used to investigate the impact of different types of building arrays. It is found that high-rise buildings over relatively small areas may have just as much impact as somewhat lower buildings covering a much larger area. The urban area produces considerable spatial variation in surface sensible heat flux. Data from a C-band radar located to the north of Greater Manchester provides evidence that convective cells may be initiated by the sensible heat flux input generated by the high-rise buildings in the city centre when the atmospheric boundary layer is unstable. Copyright (C) 2007 Royal Meteorological Society.