Analyzing the Characteristics of UHI (Urban Heat Island) in Summer Daytime Based on Observations on 50 Sites in 11 LCZ (Local Climate Zone) Types in Xi’an, China

Yunwei Zhang,Zhaolin Gu,Dian Zhou,Xiaoqian Zhang,Jili Zhang

doi:10.3390/su13010083

Yunwei Zhang, Zhaolin Gu + Show 3 more

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https://doi.org/10.3390/su13010083

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Abstract

Urbanization has induced significant changes on local climate in urban areas. For sustainable urban planning, it is necessary to identify the distribution characteristics of urban heat island (UHI) and the effects of land cover properties. In situ measurements are frequently carried out to obtain critical data in urban climate studies. However, long-time continuous observations on multiple sites are still rare, even though they would be useful in mapping the distribution of UHI intensity. In the current work, three observation campaigns were carried out in Xi’an, China. Pedestrian- level air temperatures (PLAT) were measured with potable micro-environment stations on 50 sites in 11 local climate zone (LCZ) types. The normalized PLAT was used to investigate the canopy layer UHI characteristics and the effects of LCZ types. Results revealed that the land coverage type and the surface structure have significant influence on the local climate. The PLAT in high-surface-fraction building covered areas was higher than that in low-surface-fraction building covered areas. In areas with similar building surface fraction, building height influences the UHI magnitude as well, as tall buildings would provide more shielding on the pedestrian level. The average UHI magnitude and the standard deviation within each LCZ type were calculated by statistical analysis of the observed results, which proved to be useful for UHI mapping based on the LCZ classification results in urban areas.

Highlights

With rapid urbanization, more and more people migrate to urban areas
The underlying surface structure in urban areas have been changed dramatically by decreasing of vegetation ratio and increasing of impervious surface, which result in serious environmental issues, e.g., the urban heat island (UHI) problems [2,3,4]
The UHI intensity could be denoted as air temperature differences between urban and rural area [5]

Summary

Introduction

More and more people migrate to urban areas. The urbanization ratio in China has increased from 17.92% in 1978 to 58.52% in 2017 [1]. The underlying surface structure in urban areas have been changed dramatically by decreasing of vegetation ratio and increasing of impervious surface, which result in serious environmental issues, e.g., the urban heat island (UHI) problems [2,3,4]. The UHI intensity could be denoted as air temperature differences between urban and rural area [5]. The selection of temperature measurement sites is important. It has been verified that the calculated UHI intensities with measured air temperatures on different sites would be different. The LCZ scheme with a total of 17 LCZ types, including ten “built types”

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Conclusion