Characterizing urban densification and quantifying its effects on urban thermal environments and human thermal comfort

Urban landscape patterns have a critical impact on urban thermal environments. Previous research was mainly focused on outward urban expansion, while the impact of urban densification on urban thermal environments has been infrequently investigated. This study first analyzed the 3D urban landscape patterns across central Wuhan in 2008 and 2018, and explored urban densification modes using multivariate clustering analysis based on the differences in the landscape metrics between 2008 and 2018. Second, the landscape metrics and other urban canopy parameters were incorporated into a mesoscale model coupled with an urban canopy model to quantify the impact of urban densification on urban mesoscale thermal environments in central Wuhan. Results showed that urban densification mainly took place between the 2nd- and 3rd-ring roads. The high-rise, mid-density urban densification, the most intensive urban densification mode in central Wuhan, led to warming of 1.3 °C, drying of 0.5 g/kg, a decrease in wind speed by 1.7 m/s, and an increase in heat stress by 1.7 °C to a maximum extent through the day. The mid-rise, mid-density urban densification had weaker impacts on air temperature, relative humidity, and human thermal comfort, but a stronger impact on wind speed than the low-rise, high-density urban densification. Findings of this study help a comprehensive understanding of the impact of urban land-change process on urban mesoscale climate, and provide practical implications for urban planning to improve urban living environments in Wuhan.