Multi-scale exploration of the influence mechanism of 2D/3D morphological characteristics of island cities on LST

• The effects of urban morphology factors on LST are significant varied at multi spatial scales. • The impact of urban morphology factors on LST is more significant at the scale of 600*600 m. • The interaction of 2D and 3D morphology factors can better explain the effect on LST. The scale and morphological features of urban construction are critical factors influencing the urban heat island effect (UHIE). Urban spatial morphological features will have different effects on LST at different spatial scales, especially the combination of two-dimensional (2D) and three-dimensional (3D) urban morphology factors. Therefore, it is of great significance to clarify the impact of 2D and 3D urban morphological characteristics on LST at different spatial scales. Moreover, island cities, as a distinct urban typology, have received limited attention in this field. To address these gaps, we explore the interaction of 2D/3D urban morphological factors on LST at multiple spatial scales in Xiamen Island, and employs the XGBoost-SHAP model to investigate the interactions between 2D (eleven factors) and 3D (four factors) urban morphology factors on LST across six spatial scales (90*90 m, 300*300 m, 600*600 m, 900*900 m, 1200*1200 m, and 1500*1500 m). The key findings are as follows: (1) Both 2D and 3D urban morphological features significantly influence LST across all six spatial scales. (2) The effects of 2D and 3D factors are most pronounced at the 600*600 m scale, with notable variations in the urban morphological determinants of LST across different scales. (3) When the spatial scale exceeds 600*600 m, landscape composition factors exert a stronger influence on LST compared to landscape configuration factors. (4) Through interaction analysis, we find that two different urban morphological factors will have different effects on urban LST in different intervals, even for their effects on the increase and decrease of urban LST are very different, which can further explain the influence of 2D and 3D urban morphological characteristics on urban LST. Overall, this study enhances the understanding of the interplay between 2D and 3D urban morphology in shaping LST and offers practical recommendations for optimizing urban construction scale and intensity. These findings provide a scientific basis for formulating urban development strategies aimed at mitigating the UHIE and fostering climate-resilient urban environments.