High-resolution mesoscale simulation of the microclimatic effects of urban development in the past, present, and future Hong Kong

Abstract

Anthropogenic modification of the natural environment has caused significant impacts on the local atmosphere and far-reaching changes to the global climate. Taking Hong Kong as a case study, high-resolution (250 m) mesoscale simulations are conducted using Meso-NH coupled with the multi-layer Town Energy Balance to investigate the effects of past (early 1960s), present (2018), and future (late 2040s) urban developments on the city's surface energy balance, heat island, boundary layer structure, and heat stress during a prolonged heatwave event. Overall, horizontal and vertical urban expansion has caused the urban areas to become warmer, drier, less ventilated, and more susceptible to hot nights. The dense built-up urban core in the Kowloon peninsula is also found to deepen the urban boundary layer and enhance the coastal urban heat island circulation. Reclaimed land exhibits the largest differences in 2-m air temperature relative to a no urban scenario due to the drastic change in surface thermal properties. Areas downwind of the planned artificial islands in East Lantau are expected to experience warmer and calmer conditions due to the altered wind field. Study findings raise awareness regarding the increasingly long durations of strong heat stress in urban areas and the need for heat stress mitigation.