Quantifying urban sunlight accessibility across Chinese cities: Impacts from cloud cover and three-dimensional (3D) urban structure

Adequate sunlight exposure is crucial for human wellbeing, yet its accessibility in cities is significantly compromised by both could cover and complex three-dimensional (3D) urban structure. Here we adopted an analytical framework that integrated natural day length variations, cloud cover effects, and 3D urban structure to quantify actual sunlight duration in urban areas. By using high-resolution satellite products, fine-scale canopy height data, and detailed 3D building footprints, we mapped the spatiotemporal patterns of sunlight availability and quantified the relative contributions of cloud cover and urban structures on the loss of sunlight for Chinese cities. Our analysis reveals pronounced spatial disparities and trends in urban sunlight resources in China, underscoring the urgent need for evidence-based urban planning strategies that optimize natural light accessibility for sustainable urban development.