eTheses Repository - University of Birmingham

ecause finding a rural reference point which was not affected by the urban area in the
URB_BASE case was not reliable.
The UHI effect is one of the most rigorously researched examples of human induced
climate modification (e.g. Oke 1982). The intensity of the UHI can be assessed in a variety
of ways, which include trends in urban measurements at a single station (e.g. Jones et al.
1990; Philandras et al. 1999), the measurement of the urban-rural temperature difference
(e.g. Karl et al. 1988; Karaca et al. 1995), transects across an urban area (e.g. Klysik et al.
1999; Unger et al. 2001) and measurements using satellite observations (Roth et al. 1984;
Lee 1988). All these methods rely on the availability of adequate meteorological data, and
carry certain limitations (Lowry 1977). A further method consists of using an appropriate
numerical model to estimate changes in UHI intensity due to land cover changes (e.g.
Lamptey et al. 2005; Trusilova 2006; Velazquez-Lozada et al. 2006). A more complete
discussion of the UHI is contained within the literature review in Chapter 2.
Figure 6.2 shows the diurnal cycle of the maximum UHI intensity for the domain
representing the current state of urban land cover (URB_BASE). The UHI intensity here is
defined as:
UHI_intensity = max{ TURB_ BASE(
i,
j)
− TNOURB(
i,
j)
}
(Equation 6.3)
i,
j
This definition has the advantage that the UHI intensity represents a global characteristic of
UHI over the whole domain. As shown in Figure 6.2 the UHI intensity is most pronounced
during night time, reaching peak values between midnight and 07:00. The intensity
decreases after sunrise, reaching a minimum values in the early morning (around 9:00). The
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