Temporal Variability of Inefficient Combustion Sources in Africa and the Impact on Pollution over the Atlantic Ocean

Carbon monoxide (CO) is a precursor for the greenhouse gas ozone, a tracer of inefficient combustion, and a diagnostic for hydroxyl radical (OH) oxidant concentrations. Satellite observations of CO show a long-term decline in global total column concentrations that is speculatively due to emission controls and increased combustion efficiency of pollution sources. The African outflow region over the Atlantic Ocean is impacted by inefficient combustion from Africa that should be sensitive to the proliferation of unregulated pollution and the use of biomass and charcoal to meet energy needs in the absence of electricity, as well as variability in dry season open fires due to agricultural expansion and precipitation changes. Here we focus on temporal changes in CO over the Atlantic Ocean using CO from MOPITT (1999 launch) following validation with aircraft measurements of CO from the HIPPO (2009-2011) and ATom-1 and ATom-2 (2016-2017) campaigns. The GEOS-Chem chemical transport model is used with MOPITT averaging kernels to account for instrument vertical sensitivity. We further use GEOS-Chem, with updated regional anthropogenic emissions from DICE-Africa, to assess the contribution of anthropogenic and open fires to changes in CO over the Atlantic Ocean and determine the implications for climate and the oxidative capacity of the atmosphere.