Spatio-Temporal Evolution of Urban Thermal Environment and Its Driving Factors: Case Study Of
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bioRxiv preprint doi: https://doi.org/10.1101/2021.01.13.426518; this version posted January 13, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 1 Spatio-temporal evolution of urban thermal environment and its driving factors: Case study of 2 Nanjing, China 3 4 Zhang Menghan1, 2, Dong Suocheng1, 2, Cheng Hao1*, #a, Li Fujia1, 2*, #a 5 6 7 8 1 Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 9 Beijing, China 10 2 College of Resource and Environment, University of Chinese Academy of Sciences, Beijing, China 11 #a Current Address: Key Laboratory of Resource Utilization and Environmental Remediation, Institute 12 of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 13 China 14 15 * Corresponding author 16 Email: [email protected] (CH), [email protected] (LF) 17 18 19 20 21 22 23 24 bioRxiv preprint doi: https://doi.org/10.1101/2021.01.13.426518; this version posted January 13, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 25 Abstract 26 In recent years, with the rapid urbanization, the urban underlying surface has changed dramatically. 27 Various urban eco-environmental problems have emerged in the world, among which the urban heat 28 island effect has become one of the most obvious urban eco-environmental problems. In this study, 29 Nanjing, China is chosen as the study area. Based on the Landsat8 remote sensing image data in Nanjing 30 from 2014 to 2018, the land surface temperature is retrieved, the spatiotemporal variation track and 31 characteristics of the thermal environment pattern are systematically depicted, and its driving factors 32 are revealed. The results show that: in the past five years, the spatial pattern of heat field in Nanjing has 33 changed from scattered distribution in the periphery of the city to centralized in the center of the city, 34 and the heat island intensity has increased year by year. The changes of administrative divisions, the 35 layout of transportation trunk lines, the transfer of industrial centers, and ecological construction 36 projects are important driving factors for the evolution of land surface thermal environment pattern of 37 these regions. The research results will provide scientific and technological support for similar cities 38 with typical heat island effect in the world to make urban planning and development decisions, and to 39 govern and improve urban ecological environment. 40 Introduction 41 In recent years, with the continuous acceleration of urbanization, urban areas have become a hot spot for 42 cross-scale research on the driving factors of environmental change [1]. In the process of rapid urbanization, 43 many ecological and environmental problems appear in the developing countries represented by China, 44 which directly lead to the drastic changes of urban surface thermal environment. Whether the urban surface 45 thermal environment is good or not is one of the important indexes to measure the urban ecological 46 environment [2]. Urban areas generally exhibit higher air and surface temperatures than surrounding rural 47 areas [3], and tends to raise local temperatures, resulting in an urban heat island (UHI) [4]. UHI is a kind 1 bioRxiv preprint doi: https://doi.org/10.1101/2021.01.13.426518; this version posted January 13, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 48 of concentrated reflection and embodiment of urban space surface thermal environment to some extent [2], 49 and the phenomenon of UHI has long attracted great interest from scientists and urban planners. 50 Academia’s attention to the UHI has been more than 200 years of history [5-6]. In recent years, 51 with the rapid development of urbanization and ecological protection awareness of the world, UHI has 52 been more and more common concern of scholars at home and abroad. Scholars from all over the world 53 have carried out a lot of research on the characteristics [7-9], influencing factors [10-12], simulation 54 and countermeasures [13]and other aspects of UHI. Shastri, H et al for the first time analyzed the day 55 and seasonal characteristics of surface urban heat island intensity (SUHII) in urban centers of India 56 and found that SUHII in most urban areas was negative during the pre-monsoon summer. Wu, X et al 57 taking Dalian, a coastal city in China, as an example, revealed the dynamic mechanism of the UHI effect 58 for different seasons using the cubist regression tree algorithm and suggested that the UHI effect only 59 existed in spring and summer with moderate value, and no obvious UHIs can be found in autumn and 60 winter. Ngarambe, J et al explored the synergies between UHI and HW in Seoul city, and showed that 61 UHI is more intense during HW periods than non-heat wave (NHW) periods and the synergies were 62 relatively more intense in densely built areas and under low wind speed conditions. Yang, Q et al applied 63 temperature and land-cover classification datasets based on satellite observations to analyze that that 64 SUHII and its correlations with ΔLMs were profoundly influenced by seasonal, diurnal, and climatic 65 factors in 332 cities/city agglomerations distributed in different climatic zones of China. Manoli, G et 66 al introduced a coarse-grained model that links population, background climate, and analyzed 67 summertime differences between urban and rural surface temperatures (ΔTs) worldwide, showing that 68 urban–rural differences in evapotranspiration and convection efficiency are the main determinants of 69 warming. Sangiorgio, V et al established a multi-parameter calibration index for comprehensive 70 evaluation of UHI. It was found that urban albedo and the existence of green plants were the most 71 important factors affecting the potential absolute maximum urban heat island intensity (UHII) in urban 2 bioRxiv preprint doi: https://doi.org/10.1101/2021.01.13.426518; this version posted January 13, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 72 districts. Li, Y et al used the surface and vegetation characteristics of the region around Berlin 73 (Germany), and run the urban climate model driven by the same lateral climate conditions in order to 74 simulate the urban climate of various generated cities under the same weather conditions. 75 In the context of rapid urbanization, especially in developing regions [14], people are also 76 increasingly concerned about the risks posed by the urban heat island effect on urban residents [11,15- 77 17]. Mora, C et al conducted a global analysis of documented lethal heat events, and found 783 cases 78 of excess human mortality from 164 cities in 36 countries associated with heat. Werbin ZR et al pointed 79 out that the increasing exposure of urban heat island effect led to the increasing high mortality and 80 morbidity associated with high temperature, which posed an urgent threat to urban public health. 81 Manoli, G et al also pointed out that UHIs exacerbate the risk of heat-related mortality associated with 82 global climate change. Urban surface thermal environment is not only directly related to the quality of 83 urban living environment and residents' health, but also has a far-reaching impact on urban energy and 84 water consumption, ecosystem process evolution, biological phenology and sustainable economic 85 development [1,18-21]. Therefore, it is imperative to study the urban heat island effect and its 86 influencing factors, and at the same time, it becomes a particularly urgent problem to put forward 87 countermeasures to improve a series of risks and negative effects caused by it. 88 In this paper, Nanjing, China, with typical heat island effect, is selected as the case study. By using 89 Landsat8 remote sensing image data from 2014 to 2018, the surface temperature and surface feature 90 parameters of the third phase are obtained, on the basis of which, the thermal environment pattern of 91 Nanjing city and the characteristics of its spatio-temporal evolution are illustrated and the driving 92 factors and change of the urban thermal environment pattern under different space conditions are further 93 explored. The research results will provide scientific and technological support for similar cities with 94 typical heat island effect around the world to make urban planning and development decisions, and to 95 govern and improve urban ecological environment. 3 bioRxiv preprint doi: https://doi.org/10.1101/2021.01.13.426518; this version posted January 13, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 96 Materials and methods 97 Case study 98 Nanjing is located in the southwest corner of Jiangsu Province (Fig 1). It is located in the lower reaches 99 of the Yangtze River and adjacent to the Yangtze River and the East China Sea.