Investigating global warming and future urbanization impacts on heat stress inmegacities- a multi-scalemodeling approach

The dual forcing of climate change and rapidly urban development on heat waves over the Greater Bay Area (GBA), China and Lagos, Nigeria are investigated by multi-scale numerical simulation with the Weather Research and Forecasting (WRF) model coupled with single-layer urban canopy model. Heat stress cases are dynamical downscaled for the GBA and Lagos, under different scenarios. Three experiments are designed: For the first one, historical climate background derived from ERA5 reanalysis data will be utilized as boundary conditions for WRF, and present urban information is used. For the second experiment, future projected climate forcing using CMIP6 is incorporated into ERA5, with present urban information used. For the third experiment, both future climate and future urban landuse data (2050) will be utilized. Model outputs will then serve as boundary conditions for the ENVI-met model, which simulates microclimate conditions and provides details about heat stress at the street scale in two megacities. Based on our previous work, both urbanization and climate change lead to near-future temperature rise over the GBA, with the intensity of extreme heat events greatly enhanced due to their joint effects. This study is envisaged to provide invaluable urban climate information for climate change risk identification, prediction, mitigation and adaptation, by assessing how global warming, future urbanization, and their dual forcing affect heat stress at the city scale with model. Results related to future heat waves will provide useful information to policy maker about climate-sensitive urban planning, nature-based mitigation strategies and public policies making in the future.