OPTIMIZING THE EFFECT OF VEGETATION FOR PEDESTRIAN THERMAL COMFORT AND URBAN HEAT ISLAND MITIGATION IN A HOT ARID URBAN ENVIRONMENT

Rapid urbanization in Phoenix, Arizona has increased the nighttime temperature by 5°C, and the average daily temperatures by 3.1°C. The energy balance of urban surface paving materials is the main contributor to the phenomenon of the Urban Heat Island effect (UHI). Much of the literature dealing with mitigating UHI effects recommends extensive tree planting as the chief strategy for reducing the UHI. However, while the extensive tree canopy is beneficial in providing daytime shade for pedestrians, it may reduce the pavement surfaces ’ sky-view factor during the night, thereby reducing the rate of nighttime radiation to the sky. From a UHI mitigation perspective, it may be more beneficial to use low height vegetation that does not reduce the sky view factor as large shade trees would, increasing the urban surfaces ’ nighttime radiation potential. This paper proposes to use field data and simulation scenarios to optimize the use of vegetation for both improving daytime pedestrian thermal comfort as well as enhancing nighttime radiation. The CFD microscale and mesoscale urban scenarios simulation results can potentially give urban planners and architects insights on improving their recommendations for implementing landscape design strategies for optimal effect on both the pedestrian scale and larger urban forms