A global sensitivity analysis of thermal conditions in urban street
canyons to physical morphology and vegetation parameters
Abstract
Extreme heat exposure as a result of the interactions between heat waves
and urban heat islands can lead to resident fatalities. Heat exposure is
already the leading environmental cause of death, and with global
climate change and growing urban populations, risk of heat exposure
fatality is expected to become more severe, especially among
marginalized groups. These conditions make the spatial heterogeneity of
land surface temperatures particularly relevant to urban planners, who
need to consider equitable, safe environmental conditions for all
residents. Within cities however, there can be much variation in surface
air temperatures, following physical heterogeneity of development and
vegetation, which have interactive effects on urban canyon-scale
microclimate. Yet data gaps in key parameters of physical heterogeneity
result in uncertainty in urban canyon scale air temperature variability.
In this study, we use a three-dimensional computational fluid dynamics
model, ENVI-met, to conduct a global sensitivity analysis of physical
morphology and vegetation parameters (e.g. aspect ratio, orientation
toward prevailing winds and green coverage) in idealized urban street
canyons to quantify both parameter uncertainty and scenario variability.
Our findings demonstrate although vegetation parameters have a great
influence on modifying canyon’s surface temperature, their cooling
effect strongly depend on canyon’s physical morphology conditions. The
results of those sensitivity analysis can be used to develop a
policy-relevant typology of street canyons that can be applied in an
adaptive planning framework as one component of population risk
quantification.