Satellite observations of aerosol and precursor gas distribution in Madagascar

The analysis of the spatio-temporal distribution of aerosols, nitrogen dioxide (NO2), formaldehyde (HCHO), and carbon monoxide (CO) in Madagascar is carried out considering several factors: fire phases and types of fuels burned.Savannah/grassland fires show a low fire radiative power (FRP) of 10 MW, while rainforests display an FRP greater than 100 MW.Early flame combustion generates significant emissions of NO2 (10 -4 mol/m 2 ), CO (4.10 -4 mol/m 2 ) in the smouldering phase, HCHO (6.10 -4 mol/m 2 ), and carbon aerosols (BC and BrC) with UVAI of 1.5.Smouldering combustion produces more CO and less absorbing organic aerosols (UVAI <0.5) or BC coated with OC.These pollutants, trapped in the atmospheric boundary layer (<3 km ASL), undergo physicochemical transformations under the influence of weather conditions including temperature and relative humidity.During the dry season, conducive to biomass fires, two types of pollution transport are observed.The first, on a regional scale, comes from the eastern regions causing a significant increase in PM2.5 concentrations (120 g/m 3 ) on 23 October 2023, in Antananarivo (and on 27 October), already continuously polluted by urban traffic.The second, on a larger scale, comes from South Africa bringing up to ~8.06.10 6 t of CO to the south of Madagascar on 18 October 2022.The use of satellite and surface observations, coupled with numerical modeling, proves to be important for advancing studies on air pollution and climate change related to aerosols and ozone (the SLCF) in Madagascar.