Satellite-observed relationships between land cover, burned area and atmospheric composition over the southern Amazon

Abstract. Land surface changes can have substantial impacts on the interactions between the biosphere and atmosphere. In South America, rainforests abundantly emit biogenic volatile organic compounds (BVOCs), which coupled with pyrogenic emissions from deforestation fires, can have substantial impacts on regional air quality. We use novel and long-term satellite records of trace gases, aerosol optical depth (AOD), vegetation and burned area to characterise the impacts of biogenic and pyrogenic emissions on atmospheric composition for the period 2001 to 2019 in the southern Amazon, a region of substantial deforestation. We find that the seasonal cycle for all of the atmospheric constituents peaks in the dry season (August–October) and that year-to-year variability in carbon monoxide (CO), formaldehyde (HCHO), nitrogen dioxide (NO₂), and AOD is strongly linked to burned area. We find a robust relationship between broadleaf forest cover and total column isoprene (R² = 0.59), while burned area exhibits an approximate 5^th root power law relationship with tropospheric column NO₂ (R² = 0.32), both in the dry season. Vegetation and burned area together show a relationship with HCHO (R² = 0.23). Overall, we provide a detailed observational quantification of biospheric process influences on southern Amazon regional atmospheric composition, which in future studies can be used to help constrain the underpinning processes in Earth System Models.