Scales of Climate in Designing with the Desert - Design with the Desert: Conservation and Sustainable Development - page 68

TABLE 3.7
Modeled Urban Canyon Geometries and Anticipated Flow Regimes a

L/H Ratios c W (ft) H/W Ratios Type of Flow

Cubic canyon (66/66 ft) 66 1.0 Skimming flow

131 0.5 Wake interference

262 0.25 Isolated roughness

Short canyon (197/66 ft) 66 1.0 Skimming flow

131 0.5 Wake interference

262 0.25 Isolated roughness

Medium-length canyon
(328/66 ft)

66 1.0 Skimming flow

131 0.5 Wake interference

262 0.25 Isolated roughness

Long canyon (459/66 ft) 66 1.0 Skimming

131 0.5 Wake interference

262 0.25 Transition to isolated roughness

Source: Hunter, I. et al., Energy Build ., 15, 315, 1990/1991.
L, canyon length (first number in parenthesis); H, height of canyon (second number in
parenthesis); W, canyon width.
a Wind direction assumed perpendicular to the canyon. Well-spaced flow elements create
isolated flow of turbulent air moving around buildings; moderate compactness leads to
what is called “wake interference” as disturbed air has insufficient distance to readjust
before encountering next building; very compact building arrays cause mesoscale
skimming over the top of the canyon and air is decoupled from within the canyon and
above roof height. Data given earlier illustrates the geometries and flow types.

For each of these seemingly simple scenarios, an integrated set of views of benefits and
liabilities for citizens and their quality of life in the city should be evaluated. This is often
done by considering mitigation schemes (e.g., increase albedo and amount of vegetation)
to cool down city temperatures and reduce pollution problems as well. * The acceptance of
strategies for mitigation depends on the will of cities to design, plan, and evaluate the sig-
nificance of local-induced climate change in the context of ongoing global changes. 16 This
will is more and more emerging among cooling-community advocates for many cities. 17

3.6 Conclusions
Climate is often assumed as a background environmental factor against which we can plan
for today and tomorrow. I hope that the aforementioned gives some appreciations for the
fact that climate can be considered to be arranged according to scale effects which cause
interactions we should be studying in depth. Climate is not static, contrary to its apparent
definition as simply an ensemble of weather. Climate may change due to anthropogenic
as well as natural forces. Climate records for the past 100 years vary in their quality and
quantity, both in space and time. Employing records to solve real-world problems can
be one of the most challenging applied endeavors, requiring a close association between

* http://www.heatislandmitigationtool.com/ (accessed July 15, 2009).