eTheses Repository - University of Birmingham

simulation was carried out in which the urban albedo is either reduced to 0.15, a value at
the lower end of the range suggested by Taha (1997), or increased to 0.30. It is expected
that the decrease in the albedo to a value 0.5 lower than the rural surroundings would
enhance the temperature over the urban area, and vice versa.
The two simulations were therefore carried out with the following parameters:
• alb1: Albedo for all three surface types increased to 0.30
• alb2: Albedo reduced to 0.15, the urban value used by Sailor (1998) and Atkinson
(2003)
In Figure 4.17 it is apparent that if the albedo of the urban surfaces is reduced to 0.15 then
temperatures over the city increase by up 0.2 K. On the other hand increasing the albedo of
all three urban surface types (roofs, roads and walls) determines a net reduction in the
temperature near to the urban surface which is observed during the daytime, whereas night
time temperatures are very similar. Around 06:00 the results, especially for the high albedo
situation, appear to show an uncertain behaviour; however this is likely to be due to the fact
this time corresponds to sunrise and the fact these are point measurements, not averaged
over the urban surface. The maximum reduction observed is 0.4 K, and it peaks around
midday when the solar radiation is highest. These results compare well with those in the
literature discussed above.
114