Key Parameters for Urban Heat Island Assessment in A Mediterranean Context: A Sensitivity Analysis Using the Urban Weather Generator Model

Although Urban Heat Island (UHI) is a fundamental effect modifying the urban
climate, being widely studied, the relative weight of the parameters involved in its generation is
still not clear. This paper investigates the hierarchy of importance of eight parameters responsible
for UHI intensity in the Mediterranean context. Sensitivity analyses have been carried out using
the Urban Weather Generator model, considering the range of variability of: 1) city radius, 2)
urban morphology, 3) tree coverage, 4) anthropogenic heat from vehicles, 5) building’s cooling
set point, 6) heat released to canyon from HVAC systems, 7) wall construction properties and 8)
albedo of vertical and horizontal surfaces. Results show a clear hierarchy of significance among
the considered parameters; the urban morphology is the most important variable, causing a
relative change up to 120% of the annual average UHI intensity in the Mediterranean context.
The impact of anthropogenic sources of heat such as cooling systems and vehicles is also
significant. These results suggest that urban morphology parameters can be used as descriptors
of the climatic performance of different urban areas, easing the work of urban planners and
designers in understanding a complex physical phenomenon, such as the UHI.