eTheses Repository - University of Birmingham

for the implementation of BEP in the TVM model. There is a large variety in the depth of
the neutral layer for different studies using urban canopy models, and the results in this
study, as well as that of Hamdi (2005) and Martilli (2003) are at the lower end of the scale,
with a depth of around 40-60 m. The height of the neutral layer will depend on the rural
conditions surrounding the urban area, as well as the specific urban conditions such as
building heights and wind speed. The height of the neutral layer will also typically decrease
during the night.
There is a difference of more than 3 K in the potential temperature at the lowest grid level,
between the urban_BEP and Orig simulations. This illustrates the nocturnal urban heat
island (UHI) which is not simulated by the Orig simulation, due to the fact that it does not
fully take into account the shadowing and trapping of radiation in the street canyon, as well
as the partitioning and storage of the daytime solar radiation in the urban building
materials.
Figure 4.2 shows the vertical profile of the wind speed at the centre of the rural domain
(yellow), the Orig urban domain (green) and the urban_BEP domain (black) at 04:00 of the
second day of simulation.
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