Separate and Combined Impacts of Building and Tree on Urban Thermal Environment from Two- and Three-Dimensional Perspectives
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Building and Environment 194 (2021) 107650 Contents lists available at ScienceDirect Building and Environment journal homepage: www.elsevier.com/locate/buildenv Separate and combined impacts of building and tree on urban thermal environment from two- and three-dimensional perspectives Jike Chen a, Wenfeng Zhan b,c, Shuangen Jin a,g,<, Wenquan Han d, Peijun Du e, Junshi Xia f, Jiameng Lai b,c, Jiufeng Li b,c, Zihan Liu b,c, Long Li b,c, Fan Huang b,c, Haiyong Ding a a School of Remote Sensing & Geomatics Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China b Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210023, China c Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, 210023, China d Nanjing Institute of Surveying, Mapping & Geotechnical Investigation, Co. Ltd Nanjing 210019, China e Key Laboratory for Land Satellite Remote Sensing Applications of Ministry of Natural Resources, Nanjing University, Nanjing 210093, China f RIKEN Center for Advanced Intelligence Project, RIKEN, Tokyo 103-0027, Japan g Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai 200030, China ARTICLEINFO ABSTRACT Keywords: Separate impacts of building and tree on the urban thermal environment have been studied extensively, but Land surface temperature their combined impacts, especially from both the horizontal (i.e., two-dimensional (2D)) and vertical (i.e., Building three-dimensional (3D)) perspectives remain largely unclear. Based on satellite thermal data and elaborate Tree 2D and 3D urban morphology, herein we simultaneously investigate the separate and combined impacts of Landscape pattern building and tree over Nanjing in China from both the 2D and 3D perspectives. We further examine the day– Multi-dimensional characteristics night contrast together with the sensitivity of such impacts to scale. Our results show that, when compared with urban structures from a single dimension, the combination of 2D and 3D structures is more capable of predicting urban land surface temperatures (LSTs) for both day and night. The assessments further illustrate that the separate and combined impacts of building and tree on LSTs are usually more significant when the spatial scale increases. As for the separate impacts of building and tree, 2D structure affects more urban thermal environment than 3D structure at all spatial scales during the day, but an opposite trend occurs at night. Moreover, for the combined impact of building and tree on LST across different scales, daytime and nighttime LSTs are respectively dominated by 2D and 3D building structures. Combining 2D and 3D structures improves the explained LST variation by 7.3%–11.1% and 25.3%–37.7% for day and night, respectively when compared to using 2D structures only. These findings emphasize the need to incorporate both 2D and 3D urban morphology to improve the urban thermal environment. 1. Introduction and Reflection Radiometer (ASTER) [12] and Landsat Thematic Mapper (TM) [13]). In addition to thermal data, satellite remote sensing further Urbanization is a complex process characterized by the transition facilitates the investigation of SUHI by obtaining detailed information of natural landscape into impervious surfaces [1,2]. One of the most on urban fabrics and geometry (e.g., on buildings and trees) with phenomenal effects of this landscape transition is the urban heat island high-resolution visible and near-infrared images [14,15]. (UHI) [3]. UHI is able to increase the consumption of energy and SUHI (or LST) is closely associated with urban morphology from water as well as exert a great threat to public health, and it has been both the two-dimensional (2D) and three-dimensional (3D) perspec- therefore investigated over global cities [4–6]. Recent decades has been tives [16]. From the 2D perspective, previous concerns have been witnessing an increasing amount of studies on surface UHI (SUHI) concentrating on the relationships between SUHI (or LST) and land- with remote sensing [7–11], mostly because of the wide availability scape pattern (including composition and configuration [17], especially of satellite-derived land surface temperature (LST) data acquired from for building and tree [18,19]. Previous studies have demonstrated that various satellite sensors (e.g., Advanced Spaceborne Thermal Emission the effect of the spatial configuration of building and tree on LST varied < Correspondence to: Nanjing University of Information Science & Technology, No. 219 Ningliu Road, Pukou District, Nanjing, 210044, China. E-mail address: [email protected] (S. Jin). https://doi.org/10.1016/j.buildenv.2021.107650 Received 10 July 2020; Received in revised form 25 December 2020; Accepted 24 January 2021 Available online 13 February 2021 0360-1323/© 2021 Elsevier Ltd. All rights reserved. J. Chen et al. Building and Environment 194 (2021) 107650 with position, orientation, and arrangement [18], and their in-between 2. Study area and data relationships demonstrated a day–night contrast [18,20]. It is further suggested that the relationships between LST and the 2D 2.1. Study area landscape pattern are scale-dependent [21]. A single scale of analysis is always arbitrary, and thus generates mismatching results between As the capital of Jiangsu Province, China, Nanjing city is situated researches [22]. Investigation of the relationship between LST and in the center of the lower reaches of the Yangtze River and has a landscape pattern was therefore recommended at different scales si- population of more than 8.2 million. Nanjing is characterized by a multaneously (i.e., statistical units of varying size) [23]. For instance, subtropical monsoon climate with four pronounced seasons, and is among various scales, the unit sizes of 660 and 720 m were found the acknowledged as one of the ``Four Furnace Cities" in China due to its hot most appropriate to examine the sensitivity of the relationship between and humid summer [36]. The monthly mean temperature ranges from LST and landscape composition [24]. This may be explained by the fact 2.2 ◦C in January to 28.6 ◦C in July, with a maximum temperature the interactions and exchanges across land cover patches exerted the more than 40 ◦C. It is reported that an increasing number of hot most important influences on the heat exchange at these scales [25]. days and nights were observed, and heat waves are predicted to be In addition, current studies indicated that different influencing factors more frequent in Nanjing [37]. Therefore, research into the impacts may reflect ecological processes at different scales, and thus their of building and tree on the urban thermal environment of Nanjing was relative importances controlling urban thermal environment appear to considered as an ideal case. The study area in this research is located vary with the spatial scale [25,26]. Considering that 3D urban morphology can regulate urban thermal in the central downtown of Nanjing, covering a total of area about 2 environment by affecting air circulation, solar radiation and evapotran- 205 km (Fig.1). spiration within urban canyons [27–29], a few studies emerged recently to explore the control of urban morphology on LST from the 3D per- 2.2. Data and pre-processing spective. Studies have illustrated that there existed a strong relationship between vegetation height and LST, and LST decreased at an increasing 2.2.1. Land surface temperature rate with vegetation height [30]. Similar to the 2D perspective case, the Given that our study was devoted to explore how building and relationships between LST and vertical tree structure during the day tree interact to impact diurnal LST, ASTER LST was used owing to differed from those at night [31]. Regardless of different seasons, the its ability of providing daytime and nighttime LSTs with high spatial taller the height of buildings are, the cooler urban thermal environment resolution. In this work, LST data was obtained from ASTER surface is during the day [32]. kinetic temperature product1 (i.e., AST 08) with the unit of 90 m (https: Some recent studies attempted to investigate the impacts of building //lpdaac.usgs.gov/products/ast_08v003/). The ASTER surface kinetic and tree on UHI from both 2D and 3D perspectives, and found that temperature is retrieved by adopting Planck's Law using the emissivity combining 2D and 3D urban morphology could better explain LST vari- values from temperature-emissivity separation (TES) approach, which ations. However, there is a difference in relative importance between utilizes atmospherically correct ASTER surface radiance (TIR) data. The 2D and 3D building indicators towards regulating LST. LST was ob- absolute accuracy of ASTER LST was within ,1.5 K [12,14,38]. To served more dependent on the 3D than 2D building indicators in Yazd, make the acquisition time of LST data as closest as possible to the date Iran [33], while an opposite trend occurred in Wuhan, China [34]. of airborne LiDAR data, together with the data quality and availabil- Indicators such as building height, percent cover of building, and 3D ity, daytime LST image was obtained about five hours and forty one spatial orientation of buildings were found to be the strongest controls minutes after sunrise with 11:00 a.m on May 1, 2011, while nighttime among all the 2D and 3D building indicators [33,35]. LST image was acquired about five hours and six minutes after sunset Building and tree are mostly mutually inclusive over urban land- with 22:19 p.m on April 4, 2011. The surface kinetic temperature scape. While the separate impacts of building and tree on local thermal was converted into Celsius degree for further LST analysis (Fig.2(c) environment have been analyzed, their combined impacts of building and (d)). Although there was an approximate two-year time difference and tree from both the 2D and 3D perspectives remain largely unclear.