214
actually expected to decrease when SVF increases. Also the effect of having the
green (last solution of Table 7.7 ) was probably underestimated because the model
does not consider the cooling effect due to evapotranspiration.
The measures just described can be suggested both in new and built areas, in case
of a redevelopment of an existing urban area. Within the frame of the European
Project “UHI”, the Authors conducted simulations using the ENVImet model
(Bruse and Fleer 1998 ) in order to quantify the effect of selected mitigation actions
(usable in already built areas) in the pilot are of via Pindemonte.
ENVI-met is a three-dimensional microclimate model designed to simulate the
surface-plant-air interactions in urban environment with a typical resolution of 0.5–
10 m in space and 10 s in time. The model area is described in Fig. 7.4 and Fig. 7.5 .
The main area is a 99 × 70 × 30 grid (in a x,y,z tridimensional reference system),
with a 5 × 5 × 3 m grid dimension. An appropriate number of nesting grids (fi ve) has
been set in order to minimize boundary effects. Four specifi c points of interest have
been identifi ed in the zone to characterize the air temperature (at 2 m above ground)
during 24 h, from 6 am to 6 pm. Simulations lasted 72 h, but only the last 24 h have
been considered for the results. The daily mean air temperature of the days before
the start simulation ones (Table 7.8 ) have been used as initial air temperature at 6 am
of the fi rst day. As requested by the Project, four characteristic days representative
of the four seasons were considered. Simulations used the default values of ENVImet
except for the ones reported in Table 7.8 .
To measure the UHI intensity, simulations have been extended in the rural zone
just outside Padua (Via Roma), in the same point where the previously described
experimental measurements have been conducted during 2012 summer. Four scenarios were supposed besides the actual one (“AsIs” scenario):
– “Green ground”: increasing the pervious surfaces of the area from 18 % to 23 %
by planting trees, 10 m height, within the urban canyon and the main road of the
area, and converting an impervious zone – eg asphalt car park surface – to a pervious zone by planting grass. The main effects were: Sky View Factor decreases
for the presence of trees along the streets; impervious surface fraction decreases
(and pervious surface fraction increases) because green area increases; albedo
slightly increases; other thermo-physical properties of the surfaces/materials
remain quite the same;
– “Cool pavements”: substituting all the traditional asphalt (albedo 0.2) and concrete (albedo 0.4) (roads and pavements) with “cool materials”, that is materials
with an higher albedo (0.5). The main effects were that albedo signifi cantly
increases while other properties remain the same;
– “Cool roofs”: using of “cool materials” for the horizontal impervious surfaces of
roof. In particular albedo has been increased from 0.3 to 0.6 for roofs;
– “Green ground + cool pavements”: scenario with both the mitigation actions just
described simultaneously.
M. Noro et al.
actually expected to decrease when SVF increases. Also the effect of having the
green (last solution of Table 7.7 ) was probably underestimated because the model
does not consider the cooling effect due to evapotranspiration.
The measures just described can be suggested both in new and built areas, in case
of a redevelopment of an existing urban area. Within the frame of the European
Project “UHI”, the Authors conducted simulations using the ENVImet model
(Bruse and Fleer 1998 ) in order to quantify the effect of selected mitigation actions
(usable in already built areas) in the pilot are of via Pindemonte.
ENVI-met is a three-dimensional microclimate model designed to simulate the
surface-plant-air interactions in urban environment with a typical resolution of 0.5–
10 m in space and 10 s in time. The model area is described in Fig. 7.4 and Fig. 7.5 .
The main area is a 99 × 70 × 30 grid (in a x,y,z tridimensional reference system),
with a 5 × 5 × 3 m grid dimension. An appropriate number of nesting grids (fi ve) has
been set in order to minimize boundary effects. Four specifi c points of interest have
been identifi ed in the zone to characterize the air temperature (at 2 m above ground)
during 24 h, from 6 am to 6 pm. Simulations lasted 72 h, but only the last 24 h have
been considered for the results. The daily mean air temperature of the days before
the start simulation ones (Table 7.8 ) have been used as initial air temperature at 6 am
of the fi rst day. As requested by the Project, four characteristic days representative
of the four seasons were considered. Simulations used the default values of ENVImet
except for the ones reported in Table 7.8 .
To measure the UHI intensity, simulations have been extended in the rural zone
just outside Padua (Via Roma), in the same point where the previously described
experimental measurements have been conducted during 2012 summer. Four scenarios were supposed besides the actual one (“AsIs” scenario):
– “Green ground”: increasing the pervious surfaces of the area from 18 % to 23 %
by planting trees, 10 m height, within the urban canyon and the main road of the
area, and converting an impervious zone – eg asphalt car park surface – to a pervious zone by planting grass. The main effects were: Sky View Factor decreases
for the presence of trees along the streets; impervious surface fraction decreases
(and pervious surface fraction increases) because green area increases; albedo
slightly increases; other thermo-physical properties of the surfaces/materials
remain quite the same;
– “Cool pavements”: substituting all the traditional asphalt (albedo 0.2) and concrete (albedo 0.4) (roads and pavements) with “cool materials”, that is materials
with an higher albedo (0.5). The main effects were that albedo signifi cantly
increases while other properties remain the same;
– “Cool roofs”: using of “cool materials” for the horizontal impervious surfaces of
roof. In particular albedo has been increased from 0.3 to 0.6 for roofs;
– “Green ground + cool pavements”: scenario with both the mitigation actions just
described simultaneously.
M. Noro et al.