eTheses Repository - University of Birmingham

2.5 Summary
This review has considered the urban modifications to the mechanical, thermal and
hydrological properties of the atmosphere. It is difficult to make representative
measurements of urban modifications, and to represent all the effects of the urban surface
in a model. Modelling studies are however a useful way of investigating effects of the
urban surface that can not be easily measured at representative scales and of providing
information regarding the impact of past and future examples of urban land cover.
Mesoscale modelling studies on the effects of urbanisation to date are limited, and few
studies exist which use a sophisticated parameterisation of the urban surface to simulate
urban effects.
Possible ways of representing the urban surface in mesoscale models are reviewed. In order
to address the aims of this study of understanding how changes in land cover due to
urbanisation have affected the London region, a multi-layer urban canopy scheme (BEP) is
implemented into the mesoscale model METRAS. This sophisticated treatment of the
urban surface, together with that fact that the model is run at a much higher spatial
resolution than past studies (1 km compared to for example 10 km for Trusilova et al.
(2006)) make it possible to investigate the effect of urbanisation for a single area in much
greater detail, with input data specific to the city of London rather than representative of all
European cities, and past and future urbanisation scenarios, as well as a base line with no
urban areas, specific to London. As for many past studies, the focus will be on
representative cases of anti-cyclonic conditions which are favourable to the development of
urban effects such as the urban heat island, rather than long term model runs which are
computationally very expensive and which, when average monthly or seasonally, smooth
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