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

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.

How to understand the heat island effects in high-rise compact urban canopy?

“…Buildings with more than 16 floors are classified as high-rise buildings to adapt to the characteristics of urban buildings in China. This is because a large number of buildings in cities of China have a height of more than 30 floors, and Stewart & Oke's LCZs classifications were not fully applicable (Zhang et al 2021).…”

Urban Heat Island Mitigation Strategy based on Local Climate Zone Classification using Landsat 8 satellite imagery

“…The term of Urban Heat Islands intensity is equivalent to Urban Heat Signature, which explains different temperature built-up area and surface with vegetation [20]. Comparisons between the UHI intensity within different LCZ types revealed the significant influence of land coverage and surface structure properties on the local thermal environment [21]. According to the thermal characteristics of different urban structures, future cities will be managed and planned to mitigate the urban heat island.…”

Exploring seasonal diurnal surface temperature variation in cities based on ECOSTRESS data: A local climate zone perspective

“…Based on the location of the heat island, UHI effect can be divided into Subsurface UHI, Surface UHI, Canopy layer UHI and Boundary layer UHI ( 17 , 18 ). The UHI effect is usually quantified through urban heat island intensity (UHII) ( 19 ). It is defined as the difference between urban surface temperature and suburban surface temperature ( 20 ).…”

“…Meteorological station data have high temporal resolution and continuity; however, due to the limitations of observation instruments as well as the number and spatial location of meteorological stations, the data cannot reflect the overall spatial variation of urban temperature comprehensively. For example, Zhang et al ( 19 ) obtained long-time series temperature data from 50 stations for 3 years (2014, 2015, and 2017) to analyze the UHI characteristics of Xi'an during summer daytime; however, on-site measurement methods are often labor-intensive. In contrast, remote sensing inversion can be used to obtain large-scale surface temperature data in a short period of time and analyze the characteristics of the urban thermal environment on different scales ( 21 – 23 ).…”