Quantitative evaluation of urban heat island effect based on the rotational scanning semivariogram model (RSSM) — A case study of Wuhan

The Urban Heat Island (UHI) effect significantly impacts urban thermal environments, making accurate quantification of its spatial footprint (SUHI FP) and intensity (SUHII) essential for ecological management. Existing methods, however, suffer from uncertainties due to arbitrary administrative boundaries and predefined models. To address this, we propose a Rotational-Scan Semi-variogram Model (RSSM) that incorporates spatial autocorrelation and anisotropy. Using 1 km × 1 km daily land surface temperature (LST) data, we construct a polar coordinate system centered on Wuhan's urban core and apply a rotational scanning window to derive directional autocorrelation ranges via semi-variogram analysis. These ranges are integrated to delineate SUHI FP, which then identifies the optimal background reference area (BRA) for SUHII calculation. Applying RSSM to Wuhan (2000–2022, summer), we reveal strong spatial anisotropy in SUHI effects, with FP exhibiting a “high-west/low-east, high-south/low-north” pattern and SUHII radiating outward in a peak-valley alternation. Temporally, SUHI intensified markedly in western/southwestern regions during 2005–2015 but showed mitigation post-2020. The RSSM framework provides a robust, data-driven approach to quantify UHI dynamics, offering actionable insights for urban ecological planning. • The model eliminates boundary & subjective threshold dependence in SUHI assessment. • Allows multidirectional SUHI analysis and adaptive background reference selection. • Wuhan's heat island grew 129 % (2000–2022), expanding northeast-southwest. • Rotational-Scan Semi-variogram Model can be migrated to other cities to study UHI.