Impact of urban morphology on outdoor air temperature and microclimate optimization strategy base on Pareto optimality in Northeast China

Abstract The urban microclimate is affected by the urban morphology parameters. The objective of this study was to investigate the correlation between air temperature and urban morphology parameters in a cold-climate city in China. Field measurements were performed to record the microclimate parameters at 27 points in a 10 km2 urban area in Harbin, China. Multilinear regression models were created to investigate the effects of the urban morphology parameters on the outdoor air temperature. Several interesting findings were obtained. First, the degree of influence of urban morphology on temperature was time-dependent and spatial-dependent, and the largest influence was observed in a 100 m radius around the point of interest. Second, an increase in the green plot ratio of 0.5 decreased (increased) the daytime average temperature by 0.8 °C (1.3 °C) in the summer (winter). For the same street width, a 10 m increase in the building height decreased the daytime temperature by 0.06 °C, and for the same building height, a 10 m increase in the street width increased the daytime temperature by 0.17 °C in summer. The daytime average temperature was significantly affected by the number of building floors; however, when the building had more than 20 floors, the temperature did not change significantly with the building height. In addition, a multi-objective optimization framework based on Pareto optimality was used to ascertain the optimal urban morphology layout considering the urban microclimate. The optimal wind and thermal environments were achieved at building densities ranging from 20% to 30% and building plot ratios ranging from 3 to 5.