Abstract: The FOCI project (https:/ /www.project-foci.eu/wp/) aims to better understand the impacts of key non-CO2 radiative forcers, to assess where and how they arise, and their impact on the climate system. The project will find and test an effective implementation of them into global Earth System Models (ESMs) and into Regional Climate Models (RCMs), and hopes to subsequently use these tools to investigate mitigation and adaptation policies incorporated in selected scenarios of future development, targeted at Europe and other regions of the world. In this context, one contemplated region of FOCI interests is Central/South America. In this study, we will focus on South America, specifically in southeastern Brazil, where one of the most populated cities in the world is located: the Metropolitan Area of São Paulo (MASP). The new version of RegCM5 will be used for both climate and climate-chemistry mode simulations in high resolution, with nested domain around São Paulo city for a convection-permitting simulation, also with and without chemistry selected. The aim is to explore results of one year simulation driven by “perfect” boundary conditions of ERA and from assimilated chemistry by Copernicus Atmosphere Monitoring Service (CAMS) in terms of selected climate characteristics and chemical species concentrations, that is, to assess the impact of chemistry on atmospheric variables, such as radiation, temperature and precipitation, with specific emphasis in urban heat island conditions. RegCM5 is one of the assigned RCMs involved in FOCI, and performs remarkably well in the South America domain; moreover is being actively used under the CORDEX initiative.

Keywords: South America, FOCI Project, RegCM5, convection-permitting, CAMS