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Abstract
Past decades have seen substantial efforts devoted to observing, assessing, and documenting the urban heat island (UHI) phenomenon. However, the discrepant criteria of non-urban references and ambiguous distinctions between urban and rural landscapes pose great challenges in measuring UHI magnitudes and spatial extents. This study goes beyond the conventional urban-rural dichotomy and introduces a new two-step approach based on the continuous transition of thermal environments along urban-rural gradients. The approach is applied to quantify Surface UHI (SUHI) intensities and footprints across 283 Chinese cities from 2005 to 2018 using multiple satellite-derived data sources. The results include: 1) The two-step approach avoids the limitations in subjective rural reference selections and provides reliable quantification of SUHI characteristics in various cities over time. 2) The SUHI footprints extracted by our approach are more reasonable than those obtained by two existing methods, with footprint ratios generally ranging within 0 − 6 times the urban area. 3) The two-step approach provides more concentrated estimates of SUHI intensity. Typically, ignoring heat sources in non-built-up areas can cause an overestimation of SUHI effect and misidentification of remote rural areas with high temperatures. Overall, the two-step approach enables more accurate estimates of SUHI effect, thereby facilitating policy-making for SUHI mitigation.
Data and codes availability statement
The data, codes, and instructions that support the findings of this study are available with the identifier(s) at the private link: https://doi.org/10.6084/m9.figshare.24760761.
Acknowledgments
We sincerely thank the editors and four anonymous reviewers for their helpful comments. We would also like to extend our thanks to Dr. Weifeng Li at The University of Hong Kong for his valuable suggestions and support for this research.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Notes
1 City districts (shiqu) in China constitute the urban core of prefecture-level administrative units, which include urban and suburban districts (chengqu and jiaoqu) but not suburban counties.
2 Please note that the static rural reference values can be impacted by landscape changes in rural areas resulting from urban sprawl or plant growth (Wang Citation2022). These values are sensitive to the ecological context (e.g., desert shrub-land) and the measurement of surrounding rural areas (i.e., how far is enough from the urban core to represent the unaffected area).
3 The reason for creating a buffer zone from the edge of urban built-up areas is that the critical circle is unable to represent the actual range of SUHI due to the irregular shapes of urban areas (Peng et al. Citation2020).
Additional information
Funding
Notes on contributors
Anqi Zhang
Anqi Zhang is an Assistant Professor in the School of Architecture and Art at Central South University, Changsha, Hunan, China. Her research interests include urban morphology, spatial analytics, and applications of geographical open data in urban and environmental studies. In this paper, her contributions include model implementation, visualization, writing and revision of the original manuscript.
Chang Xia
Chang Xia is an Associate Professor in the School of Public Administration at Hunan University, Changsha, Hunan, China. His research interests include urban modelling, urban morphology, hazard adaptation, and applications of GIS and big data. In this paper, his contributions include conceptualization of the research idea, writing and revision of the original manuscript.