A Cross-Scale Analysis of the Correlation between Daytime Air Temperature and Heterogeneous Urban Spaces

Sihong Du,Xing Shi,Yongdong Lu,Sijie Zhu,Yanxia Li,Chao Wang,Zhichao Tian

doi:10.3390/su12187663

Abstract

The problem of the urban thermal environment is becoming increasingly noticeable in the process of modern urban development. The temperature patterns in central business districts can be more complicated due to the heterogeneous urban spaces and diverse building forms, which need more cross-scale research. This study investigated the correlation between air temperature and urban morphology in a heterogeneous urban district in northeastern China. The thermal environment of the studied district in the summertime was simulated by ENVI-met. A total of 12 morphological indicators were selected to describe the geometric features of the studied district. Curve estimation was employed to quantify the correlation between air temperature and morphological indicators. The results indicate different effects of the morphological indicators of the air temperature on different scales. On a mesoscale, the compactness (Com), building footprint ratio (BFR), enclosure degree (ED) and total height to total floor area ratio (HA) had a significant correlation with the air temperature. On a microscale, only the BFR and ED had relatively steady correlations with the air temperature. The correlation between air temperature and morphological indicators could be influenced by the heterogeneity of the urban morphology, including the diversity of the heights and footprints of buildings and the irregularity of building horizontal arrangement.

Highlights

With the population increase and economic development, the urbanization level of the world has been rising
The coefficient of determination (R2), root mean square error (RMSE) and mean absolute percentage error (MAPE) between the measured and simulated temperatures of the evaluation scenario were calculated to evaluate the reliability of the ENVI-met model
The R2 ranged from 0.79 to 0.92, the RMSE ranged from 0.68 to 1.57 and the MAPE ranged from 3.42% to 7.00%, which is consistent with a previous study [44]

Summary

Introduction

With the population increase and economic development, the urbanization level of the world has been rising. According to a prediction by the UN, 68% of the world’s population will live in cities by 2050 [1]. One of them is the urban heat island (UHI) effect and the associated deterioration of the urban thermal environment. A UHI refers to the phenomenon where the temperature in urban areas is higher than that in rural areas [2]. UHIs may deteriorate the outdoor thermal environment, decrease people’s thermal comfort level and even impact regional atmospheric pollution [3,4]. The increase in the indoor cooling load caused by UHIs leads to more consumption of energy and other resources [5]. Hot weather exacerbated by a UHI can result in heat-related illnesses and even death [6]

Methods

Results

Conclusion