Impact of Inhomogeneous Urban Morphology on Urban Heat Island and Air-Conditioning Load During Heat Wave Event

Elevated temperature would surge power demand for space cooling. This study examines the urban heat island (UHI) and air-conditioning (AC) load in Hong Kong during a heat wave event (June 23 to 28, 2016) using the mesoscale Weather Research and Forecasting (WRF) model. Local climate zone (LCZ) and building categories (LCZBCs) are integrated into WRF for the first time, handling landuse and building configuration. The urban morphology parameters (UMPs) in LCZ are clustered into three groups: urban structure, vegetation fraction, and impervious surface thermal properties. Our results show that urban structure induces a higher UHI intensity (UHII) at nighttime than daytime. The difference in urban-rural building/street structure is the key factor in compact (LCZ1) and open (LCZ4) high-rise areas, especially commercial-dominant ones, in which the UHII and AC load are increased by 40.33% and 34.52%, respectively. Besides, greenery is found to be most effective to mitigate UHI problems and lessen AC demand in middle-rise (LCZ2&5) and low-rise (LCZ3&6&8&10) areas. Its benefit is most prominent for residential-dominant areas that could reduce the UHII and AC load as much as 106.26% and 53.13%, respectively. In contrast to rural pavement, urban impervious surfaces induce negligible increases in temperature (4.75%) and AC load (2.33%).