eTheses Repository - University of Birmingham

development (GLA 2006) and differences in daytime and night time temperatures observed
between the measurement sites of Heathrow, London Weather Centre and Kew Gardens
(Hacker 2007). These findings are consistent with the some of the results obtained in this
PhD modelling study, as can be observed in Figure 6.1, for example the cool spot of
Richmond Park and the variation in magnitude of the UHI in the urban area.
The results in Figure 6.2 are broadly consistent with those reported in Wilby (2003) for a
central urban location (Westminster) in the city of London as seen in Figure 6.3. Wilby
(2003) plotted the diurnal cycle of the UHI for four urban locations with respect to the rural
station at Bracknell. For the central urban location of Westminster the heat island is
primarily a nocturnal phenomenon, reaching a peak just before 07:00, and the decreasing to
reach a minimum at 11:00. The UHI intensity increases directly after sunset. The
Westminster location will be most comparable to the results for the maximum UHI
intensity in Figure 6.2, since it represents the most highly urbanised of the four locations.
The difference is magnitude could be due to the difference in methodology between
experimental measurements and numerical modelling. The results presented in Wilby
(2003) were taken from six particular days in July and August 1999/2000 whereas the
scenario in this PhD study represents one particular case in August 1998. Whilst this case
study was selected due to being characterised by anti-cyclonic conditions favourable to
UHI development, it was not necessarily a particularly strong case. The UHI intensities
presented in Graves et al. (2001), showing a mean intensity between 2 and 3 ºC, are more
consistent with the numerical modelling in this chapter.
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