154
S. Ren et al.
observation networks suggest that the inclusion of TEB scheme improves the forecasts of both surface temperature and pollutant mixing ratios.
24.1 Introduction
With rapid urbanization, the population in cities has been increasing dramatically
around the globe. The urbanization leads to the significant change in urban meteorological conditions such as meso- and microscale urban heat island (UHI) effects,
urban flooding, precipitation, humidity, fog, visibility, street canyon winds and surface energy fluxes. In addition, the change of urban meteorology and climate can
cause elevated concentration levels for gaseous pollutants and aerosols, and consequently change the urban air quality. These changes are the direct consequence of the
change of land coverage [1] and large amount of energy consumption from heating
or cooling buildings and from local transportation within big cities.
As the majority of exceedances of air quality (AQ) standards occur in urban areas,
accurate predictions of the major pollutants are extremely important for the health of
the urban population. In the GEM-MACH URBAN project, the Canadian air quality
model (GEM-MACH) and the town energy balance model (TEB) [2] are employed
to investigate the impact of the urban canopy on the production and transport of
pollutants within urban areas. Some results are shown in the following sections.
24.2 Urbanizing GEM-MACH with TEB
The TEB model can describe the complex urban fabric and the heat and momentum
exchange mechanism between the urban surface and the atmosphere. Figure 24.1
shows some TEB parameters describing the urban fabric in the Great Toronto Area
(GTA). These parameters are important for computing the heat storage within the
urban canopy. It can be seen from Fig. 24.1 that downtown Toronto has a very high
density of high buildings, large aspect ratio and roughness height. A climatological
sensible heat flux from traffic is used. The magnitude of the traffic heat flux in urban
centers is about 20 W/m
2 .
24.3 Impacts of TEB on Temperature and Air Quality
Health Index
The energy balance above the urban canopy can be changed significantly by the
trapped short and long wave radiations by buildings within the urban canopy, and
by anthropogenic activities (e.g., [2, 3]). This change leads to higher temperature in
S. Ren et al.
observation networks suggest that the inclusion of TEB scheme improves the forecasts of both surface temperature and pollutant mixing ratios.
24.1 Introduction
With rapid urbanization, the population in cities has been increasing dramatically
around the globe. The urbanization leads to the significant change in urban meteorological conditions such as meso- and microscale urban heat island (UHI) effects,
urban flooding, precipitation, humidity, fog, visibility, street canyon winds and surface energy fluxes. In addition, the change of urban meteorology and climate can
cause elevated concentration levels for gaseous pollutants and aerosols, and consequently change the urban air quality. These changes are the direct consequence of the
change of land coverage [1] and large amount of energy consumption from heating
or cooling buildings and from local transportation within big cities.
As the majority of exceedances of air quality (AQ) standards occur in urban areas,
accurate predictions of the major pollutants are extremely important for the health of
the urban population. In the GEM-MACH URBAN project, the Canadian air quality
model (GEM-MACH) and the town energy balance model (TEB) [2] are employed
to investigate the impact of the urban canopy on the production and transport of
pollutants within urban areas. Some results are shown in the following sections.
24.2 Urbanizing GEM-MACH with TEB
The TEB model can describe the complex urban fabric and the heat and momentum
exchange mechanism between the urban surface and the atmosphere. Figure 24.1
shows some TEB parameters describing the urban fabric in the Great Toronto Area
(GTA). These parameters are important for computing the heat storage within the
urban canopy. It can be seen from Fig. 24.1 that downtown Toronto has a very high
density of high buildings, large aspect ratio and roughness height. A climatological
sensible heat flux from traffic is used. The magnitude of the traffic heat flux in urban
centers is about 20 W/m
2 .
24.3 Impacts of TEB on Temperature and Air Quality
Health Index
The energy balance above the urban canopy can be changed significantly by the
trapped short and long wave radiations by buildings within the urban canopy, and
by anthropogenic activities (e.g., [2, 3]). This change leads to higher temperature in