The effects of 2D and 3D building morphology on urban environments: A multi-scale analysis in the Beijing metropolitan region

Building morphology has critical impacts on urban environments. However, the association between building morphology and urban environments across different scales and seasons remains understudied. This study investigated the effect of 2D/3D building morphology on seasonal urban climate and air quality in the residential areas (with radii of <= 200 m), blocks (= 500 m), and communities (= 1000 m) around the observation stations in Beijing, using correlation and regression analysis. Results showed that the associations between building morphology and urban environments were highly scale- and season-dependent, with the 3D indicators showing stronger associations with urban environments than the 2D indicators. The correlation between building morphology and air temperature was significant at all seasons, and became stronger as the scales increased. Significant correlation was mainly found on 500- and 1000-m scales for wind velocity, and the degree was the weakest in summer. Relative humidity was largely affected by building morphology in autumn and winter, especially on small scales. Building volume density had the greatest impact on air temperature, and could explain more than 60% of its variance; building height density exerted the strongest influence on wind speed, and a 10% increase in it reduced wind speed by 1.8 m/s. Building height range and density were closely related to PM2.5 concentrations in spring and autumn due to local air pollutants emissions from buildings. To reduce building density with increased height and restrict building height range should be considered for urban planning in Beijing.