Effects of urban and landscape elements on air temperature in a high-density subtropical city

Abstract

In this study, we examined the effects of key urban (road cover, building volume ratio, and proximity to sea) and landscape (water body, tree cover, shrub cover, turf cover, park area, and sky view factor) parameters on air temperature, and the impacts of weather conditions on landscape-temperature relationship. One hundred temperature sensors were installed in fourteen urban parks in Hong Kong during summer season to collect continuous air temperature data. Linear mixed-effect models showed that the effects of weather (cloud amount, solar radiation and wind speed) on landscape-temperature relationships were minor (<0.2 °C). Therefore, the landscape effects were further investigated using the entire dataset regardless of weather conditions. In a circular buffer zone with a 20-m radius, a 10% increase in road density caused a 0.059 °C rise in daytime mean air temperature while the same increase in tree cover and shrub cover led to a 0.052 and 0.041 °C drop in temperature, respectively. A 0.849 °C rise could be expected when sky view factor increased from 0 to 1. The proximity to the sea also had a significant daytime cooling effect (0.784 °C/1000 m). The night-time landscape effects were similar to the daytime except that the strengths of the effects on air temperature were weaker. The obtained results can be used by landscape designers and urban planners for modifying the landscape to bring cooling effects and tackle heat-island and climate-change impacts.