ObjectivesUrban heat island effects are intensifying under climate change and rapid urbanization. However, how large-scale climate anomalies such as the El Niño-Southern Oscillation (ENSO) interact with urban morphology to shape surface urban heat island intensity (SUHII) remains unclear. This study compares Shanghai and Suzhou to examine how SUHII responds to ENSO intensity across Local Climate Zones (LCZs).MethodsSummer (June-August) land surface temperature data (2018-2022) were downscaled from MODIS using a random forest model and integrated with 100 m LCZ maps. SUHII was calculated relative to LCZ D and decomposed into inter- and intra-LCZ components. Linear and quadratic regressions were applied to quantify SUHII sensitivity to ENSO intensity, represented by the Oceanic Niño Index (ONI).ResultsENSO intensity appears to modulate SUHII. La Niña phases strengthen inter-SUHII in both cities, whereas El Niño generally weakens it. The ONI-SUHII linkage is LCZ-dependent, with compact built types exhibiting the strongest sensitivity; in Shanghai, compact LCZs show a response slope of -0.98 °C per ONI, exceeding open, industrial, and vegetated types. Intra-SUHII follows a nonlinear pattern, reaching minima under near-neutral ENSO conditions and increasing during stronger El Niño or La Niña phases. City-scale morphology further appears to condition this sensitivity: Shanghai's monocentric and high-density structure may contribute to the concentration of heat cores and amplifies ENSO-related variability, resulting in higher mean inter-SUHII (by 0.54 °C) and stronger ONI sensitivity than in polycentric Suzhou, where more dispersed urban form and cooling elements may help limit heat buildup.ConclusionsThese findings underscore the critical role of urban morphology in modulating climate-induced surface heat burden, offering valuable insights for climate-resilient urban planning in rapidly developing regions.
Lu et al. (Wed,) studied this question.