Urban Environments and Regional Climate Change - CORDEX Flagship Pilot Study URB-RCC

Cities play a fundamental role on 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 increasingly affect cities and their citizens in the upcoming decades. Simultaneously, the share of the population living in urban areas is growing, and is projected to reach about 70 % of the world population up to 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. Additionally, from the perspective of recent regional climate model developments with increasing resolution down to the city scale, proper parameterization of urban processes is starting to play an important role to understand local/regional climate change. This is valid for coupled atmospheric chemistry as well, thus even air pollution modelling has to consider the urban environment. 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 distinct local processes becomes vital to simulate the urban effects properly. This will enable improved assessment of climate change impacts in the cities and inform adaptation and/or mitigation options by urban decision-makers, as well as adequately prepare for climate related risks (e.g. heat waves, smog conditions etc.). Cities are becoming one of the most vulnerable environments under climate change. In 2013, the CORDEX community identified cities to be a prime scientific challenge. Therefore, we proposed this topic to become an activity at CORDEX platform, within the framework of so-called flagship pilot studies, which was accepted and the FPS URB-RCC activity was started in May 2021. Main aims and planning of this activity will be presented together with a call for potential participation in ensemble experiment for selected city following adopted coordinated simulations protocol. Preliminary results from the analysis of already available data will be presented as well.