Changes in biomass burning, wetland extent, or agriculture drive atmospheric NH3 trends in select African regions

Atmospheric ammonia (NH3) is a precursor to fine particulate matter and a source of nitrogen (N) deposition that can adversely affect ecosystem health. The main sources of NH3 – agriculture and biomass burning – are undergoing are or expected to undergo substantial changes in Africa. Although evidence of increasing NH3 over parts of Africa has been observed, the mechanisms behind these trends are not well understood. Here we use observations of atmospheric NH3 vertical column densities (VCDs) from the Infrared Atmospheric Sounding Interferometer (IASI) along with other satellite observations of the land surface and atmosphere to evaluate how NH3 concentrations have changed over Africa from 2008 through 2018, and what has caused those changes. In West Africa NH3 VCDs are observed to increase during the late dry season, with increases of over 6 % yr-1 in Nigeria during February and March (p