# Characteristics of Urban Heat Island in China and Its Influences on Building Energy Consumption
## 1 Introduction  
With the rapid urbanization, the residents in urban areas increased from 30% in the 1950s to over 56% in 2021, worldwide. It will continue to rise to 66% by 2050 [1]. Because of the tremendous modification of underlying surfaces and energy balance [2; 3; 4; 5; 6] and anthropogenic heat emissions [7], a specific phenomenon, i.e., urban heat island (UHI), presents in urban areas. The UHI phenomenon was first studied and documented by [PERSON] [8] and then was systematically investigated by many studies [9; 10; 11; 12; 13; 14]. The UHI not only increases the air temperature in the urban area but also affects its adjacent rural areas through urban heat-dome flow; [15; 16; 17] reported that during the day in summer, the UHII in Beijing is more than 2 \({}^{\circ}\)C and the footprint of the UHI is more than 1900 km\({}^{2}\). Relative hot temperature induces building-scale and city-scale buoyancy-driven flows [18; 19; 20], which affect thermal comfort, pollutant dispersion, and building energy consumption [21; 22; 23]. The influence of UHII on building energy consumption have been found by many studies [24; 25; 26]. As the building sector accounts for approximately 31% (ranging from 22% to 57%) of global energy consumption, the UHI effect on building energy consumptiondraws increasingly more attention under the background of carbon neutrality goals [27]. UHI could have a great impact on building energy consumption by increasing cooling load and reducing heat load [28; 29]. [PERSON] et al. [30] suggested that urbanization has a significant effect on the spatial distribution of the number of cooling and heating degree days by analyzing the relationship between the average temperature and daily electricity consumption in Shanghai from 2003 to 2007. [PERSON] et al. [31] found that the cooling energy of a small office building located in the urban area of Boston is 22% and 42% higher compared to those located in two rural sites, respectively. [PERSON] et al. [32] showed that UHI formation caused an increased average electricity consumption of 2600 GWh (i.e., 11.4%) annually in eight districts of Delhi during the period April 2012 to March 2017. [PERSON] et al. [33] found that the daily heating load in urban areas was significantly lower than that in rural areas, which was 10.1% and 7.5% less for residential and office buildings, respectively, in Tianjin. Undoubtedly, the annual building energy consumption would be increased significantly in a hot climate where the cooling load dominates. However, it is still not clear whether the annual building energy consumption would be increased or decreased in a hot summer/cold winter climate, or in a cold/severe cold climate. Since the building energy consumption can be increased in summer and decreased in winter, the characteristics of UHI temporal variation also affects the annual overall energy consumption. For example, if the UHI is stronger in winter and weaker in summer, it would benefit the reduction in building energy consumption. In this study, the mechanisms of the UHI effect on the annual building energy consumption in different climate regions of China is investigated. High spatial-temporal quantification of UHI is important to simulate the building energy consumption annually [34; 35]. The UHI is usually quantified by the canopy-layer urban heat island intensity (UHII, [36; 37; 38]) or surface urban heat island intensity (SUHI, [39]). SUHII can be easily obtained based on satellite remote sensing infrared images with high spatial resolution at the city scale [40]. However, the temporal resolution of remote sensing images is low due to the limitation of satellite availability. Moreover, the deviation is excessively large for modeling building energy consumption when the SUHI is used [41]. Therefore, the UHII in the urban canopy layer was adopted in this study for modeling building energy consumption. [PERSON] et al.