Modelling the impact of urbanisation on regional climate

Urbanisation is an extreme form of land-use change since it radically alters the physical properties of the Earth's surface and may also affect its thermal, radiative and aerodynamic characteristics. On local to regional scales the impact of land-use change on climate is especially important. Recent studies suggest that increasing urbanisation patterns may have an affect on mean temperature at a regional scale. However, such studies typically rely on statistical analysis of empirical data such as population trends or night light to parameterise urban form and results can often be dependent on the methods used to classify urban and rural areas. Thus it is very difficult to develop a process based understanding of the underlying causes of warming at a regional scale.

The development of sophisticated urban canopy schemes to parameterise the urban surface in mesoscale models offers an alternative approach to studying this phenomenon. This paper uses the non-hydrostatic mesoscale model METRAS (MEsoscale TRAnsport and Stream Model) coupled with an urban canopy scheme and a simple vegetation scheme to explore the effect of urbanisation on regional climate. The urban canopy scheme used will aim to represent the dynamic and thermodynamic effects of the urban surface, for example the shadowing and trapping of radiation and the impact of the horizontal and vertical surfaces on the momentum and turbulent kinetic energy equations.

The impact of urbanisation on regional climate is explored using select historical data for the city of London. The aim is to investigate how changes in urban form through time have related to trends in regional climate. The results of such a study have important implications for our understanding of the impact of urbanisation on long term temperature records (often used to assess trends in global climate change) in urban and rural locations.