Pivotal Contributions of Urban Effects to the Intensity and Health Impacts of the 2024 Record-Breaking Heatwave over Yangtze River Delta

During the summer of 2024, a record-breaking heatwave occurred in the Yangtze River Delta urban agglomeration, posed widespread health and socio-economic challenges for local residents. Based on the Weather Research and Forecasting (WRF) model coupled with the Urban Canopy Model (UCM) and observations from 3000 automatic meteorological stations, we assess the heterogeneous contributions of urban effects —particularly land-use changes (LU) and anthropogenic heat emissions (AH) — to this extreme heat wave and further extent to the heat-related morbidity over Yangtze River Delta (YRD). The results quantify the contributions of individual and combined urban effects on the extreme heat wave at 3-km spatial resolution. The urban effects contribute to about 24% on the elevated daily mean temperature averaged across urban areas, with the LU play a more significant role than the AH. At night, urban effects contribute approximately 38% to the elevated surface temperature averaged across urban areas. The maximum contribution of combined urban effects is observed in downtown Shanghai. The contribution of combined urban effects to heat-related morbidity is greater at night than during the daytime, with an average value of 29% across all urban areas and a maximum of 48% in downtown Shanghai at night. These findings offer insights in identifying heat-vulnerable spots within cities and provide detailed information for designing targeted, region-specific strategies to enhance urban resilience and guide adaptive measures to mitigate the impacts of future heatwaves.