The main objective of CAFE-Brazil is to study tropospheric oxidant photochemistry in combination with particle formation and growth mechanisms under clean, pristine conditions over the Amazon rainforest, and contrast the results with those in marine and polluted conditions, in part from previous measurement campaigns. The measurements will constrain process and environmental modelling to generalize the results to regional and global scales, e.g. to study the atmospheric oxidation capacity and the abundance of fine particulate matter in relation to climate and planetary health. CAFE-Brazil will employ the German HALO research aircraft from Manaus in winter 2022/23. It will investigate how biogenic VOC emissions influence oxidation chemistry at low NOx concentrations, radical cycling, and how and where in the tropospheric column this relates to aerosol formation, growth, i.e. particle size and number distribution and chemical composition. The HALO measurements will be coordinated with those from the Amazonian Tall Tower Observatory (ATTO), located near Manaus at a remote location within the forest. A similar set of instrumentation as that deployed on HALO is installed on the ATTO tower. This will provide the unique opportunity to link the measurements in and directly above the forest to aerosol and oxidation processes in the atmosphere aloft.