Advancing urban shade mapping for planning: Integrating shade demand and greening potential

Abstract

Shade is an effective measure for reducing outdoor heat exposure. More infrastructure is needed to protect urban populations from direct sunlight during outdoor travels in hot weather, but shade is often overlooked in planning. This research uses the metropolitan area of Nanjing, China, as a case study to explore the spatiotemporal dynamics of population movement and shade, utilizing data from mobile phones and airborne LiDAR. The results reveal a dynamic spatial correlation between shade coverage and outdoor population density: positive in the morning and late afternoon and negative at midday, which indicates a spatial mismatch during high solar elevation angles. This study assesses the potential for developing green spaces to provide shade infrastructure, recognizing the community as the fundamental planning unit for human activities. We found that only 17 % of communities in Nanjing possess a high potential for greening. The greening potential of most communities does not meet their shade demand. We introduce the concept of shade-optimized zoning and develop shade infrastructure optimization strategies based on the “necessity-feasibility” framework. This urban shade planning analysis framework includes shade mapping, shade infrastructure demand classification, an assessment of shade potential, shade optimization zoning, and a solution proposal to promote climate-resilient cities.