eTheses Repository - University of Birmingham

accompanied by a reduction in city size, or a change in the surface energy balance. In this case
relationships previously established in the case of city growth can no longer be expected to apply
and population change alone is not capable of explaining observed trends in the London UHI
intensity (Lee 1992).
2.1.5 Other effects of the urban surface
Other effects of the urban areas include increased air pollution, and effects on the hydrological
cycle.
Air pollution is a serious health problem in many cities even under the current climate (Anderson
et al. 1996; COMEAP 1998). Human activities in urban and industrial areas are major sources of
pollutants (Fenger 1999) and carbon dioxide emissions (Svirejeva-Hopkins et al. 2004), and their
distribution and evolution is driven by the thermal and dynamic processes above the city (Sarrat
et al. 2006). Therefore the accurate representation of meteorological models is becoming
increasingly important in air pollution studies (Seaman 2000; Sarrat et al. 2006; Muller 2007;
Baklanov et al. 2008).
Increased air pollution in urban areas can also affect radiation transfer and the hydrological cycle
(Givati et al. 2004) and the amount of radiation received and lost at the surface (e.g. Oke 1988;
Stanhill et al. 1995; Jauregui et al. 1999). Climate change and urban expansion is expected to
cause further deterioration in air quality in large urban areas (Romero et al. 1999), and future
local and regional scale meteorology will have a major influence on the production, transport and
dispersal of pollutants. Any increase in the frequency of hot, anticyclonic weather in summer will
favour the creation of more temperature inversions trapping pollutants in the near-surface layer
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