Microclimatic analysis of “compact” urban canyons in an arid zone

While the modifying effects of a city's surface on its climate are well documented, there remains a need for useful micro-scale analyses of thermal comfort conditions which may be applied to urban design. In the present study, empirical data taken from extensive full-scale measurements in a number of low-rise urban street canyons in the arid Negev region of Israel are integrated with an energy-balance model representing the thermal exchanges between a pedestrian and the street canyon environment. Analysis of microclimatic parameters and overall energy balance suggests that in summer, overheating within the canyon is sensed primarily as a nocturnal phenomenon, and that during hours of substantial heat stress in a desert climate, the compact canyon is in fact a potential “cool island”, mainly due to internal solar shading. In winter, a compact geometry was found to provide relatively warm conditions, with the key factor being protection from strong winds during cold night hours.