Impact of African Urban Agglomerations to Global Air Quality

Anthropogenic pollution in Africa is dominated by inefficient combustion processes. Combined with rapid economic and population growth, air quality is expected to degrade. However, only few surface observations are available to study these changes. We investigate emissions of pollutants produced from combustion processes with bottom-up emission inventory from Copernicus Atmosphere Monitoring Service (CAMS), in conjunction with satellite retrievals from MOPITT (CO), TROPOMI (CO, NO₂) and OMI QA4ECV (NO₂). We associate these patterns with African development indicators (e.g., GDP, population, and energy consumption) during the period 2005-2016. For the biggest ten countries (in terms of population), our preliminary results show that the CAMS inventory reveals a temporal trend in emissions from Africa, but a consistent combustion pattern across the countries is not apparent. It also appears that these emission patterns differ (in trends and magnitude) from those derived from satellite retrievals. More specifically, these ten countries account for more than half and about 24% of the CO and NO_x African anthropogenic emissions, respectively. The African continent contributes about 20% and 13% to the global CO and NO_x anthropogenic emissions. Among those top ten countries, we select the five biggest cities to focus on revealing the contribution of these cities in Africa to global air quality based on data of co-emitted pollutants. We run the Community Atmosphere Model with chemistry (CAM-chem) ensemble simulations using the CAMS inventory to examine the associated abundance of these emissions. We use tagged CO tracers in CAM-chem to track emissions from these cities and investigate the contributions of these anthropogenic source regions to levels of air pollution across Africa and the globe in recent decades.