CORDEX Flagship Pilot Study URB-RCC: Urban Environments and Regional Climate Change – Where We Are and Where We Are Going

Cities play a fundamental role in climate at local to regional scales through modification of heat and moisture fluxes, as well as affecting local atmospheric chemistry and composition, alongside air-pollution dispersion. Vice versa, regional climate change impacts urban areas and is expected to affect cities and their citizens increasingly in the upcoming decades when the share of the population living in urban areas is growing and is projected to reach about 70 % by 2050. This is especially critical in connection to extreme events, for instance, heat waves with extremely high temperatures exacerbated by the urban heat island effect, in particular during night-time, with significant consequences for human health.

From the perspective of recent regional climate model development with resolution achieving city scales within convection permitting RCMs, parameterization of urban processes plays an important role to understand local/regional climate change. The inclusion of the individual urban processes affecting energy balance and transport (i.e. heat, humidity, momentum fluxes, emissions) via special urban land-surface interaction parameterization of local processes becomes vital to simulate the urban effects properly. This enables improved assessment of climate change impacts in cities and planning adaptation and/or mitigation options, as well as adequate preparation for climate-related risks (e.g. heat waves, smog conditions, etc.).

We introduced this topic to the CORDEX platform, within the framework of flagship pilot studies on challenging issues and gaps in regional climate change knowledge. The main aims and progress of this activity will be presented, especially an analysis of Stage-0 experiments using case studies of heat wave and convection episode within ensemble of nearly 40 simulations for City of Paris with convection permitting RCMs from different groups over the world. Further outlook of long term (10 years – Stage 1 experiment) climate simulation with these models in common strategy to IMPETUS4CHANGE Horizon Europe Project will be presented as well, The development of Global Satellite Cities experiment will be introduced as another part of Stage 1 experiment. Outlooks for further experiments will be explained as well.