eTheses Repository - University of Birmingham

Abstract
Urban areas have well documented effects on climate, such as the urban heat island effect,
reduction of wind speeds, enhanced turbulence and boundary layer heights, and changes in
cloud cover and precipitation. This PhD examines the impact of the urban surface on the
major agglomeration of London on local and regional climate by means of the numerical
mesoscale model METRAS (Schlünzen 1988) coupled for the first time with the
sophisticated urban canopy scheme BEP, developed by Martilli et al. (2002).
The robustness of the new model is demonstrated through a series of simulations and
sensitivity studies for an idealised urban domain. The model is then configured for the
London region, and evaluated using data from a range of meteorological monitoring sites.
Implementation of the urban canopy scheme results in a marked improvement in model
performance. Under ideal meteorological conditions, peak urban heat island intensities of
up to 2.5 K are found during night time hours, with the timing and magnitude of the peak
showing good agreement with previous experimental studies for London.
The new model is then used to investigate how growth of the Greater London urban area
affects the urban heat island intensity. The results show that the relative fractions of urban
land cover and of vegetation within the urban area have important implications for the
near surface temperature, diurnal temperature range, wind speed and urban heat island
intensity.
The results also suggest that extensive future growth of the London urban area has the
potential to increase temperatures, with significant increases for both daytime and night
time. The specific forms of urban development, such as densification and spatial
expansion, have an impact on these fields. These results have important implications for
the design of cities and the management of urban climate.
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