Emissions of toxic gases and aerosols in southern Africa observed during the 2019 JJASO period

Abstract

There are several different types of sources responsible for the emissions of carbon monoxide (CO), sulphur dioxide (SO2), nitrogen dioxide (NO2) and aerosols in Africa. These emissions make the African continent vulnerable to the impacts on climate change, human health and the environment. It has been shown that the southern African emissions are dominant in the winter season (JJA). However, few studies have been done to study the winter and spring season in unison to understand these emissions. Therefore, in this study, both satellite data, such as Sentinel-5P and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), and reanalysis data from Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), were used to study emissions in the 2019 JJASO period. Furthermore, the sequential Mann-Kendall (SQMK) test was used to study the trends of SO2, CO, Angstrom exponent and UV aerosol index data during the 2019 JJASO period. The results from sentinel-5P showed the dominance of CO and NO2 in the Democratic Republic of the Congo (DRC) and dominance of SO2 and NO2 in the Republic of South Africa (RSA). These emissions were largely from wildfires and coal-fired power stations, respectively. However, an SO2 hot spot was also observed over the DRC region which was found to be from an active volcano. CALIPSO data agreed with these observations and further showed the maximum vertical distribution of these aerosols and gases to be at ~ 2 km. The SQMK test of Angstrom exponent and UV aerosol index showed that aerosol dominance from emissions change during the JJASO period. Therefore, studying the JJASO period does give a better understanding of emissions in southern Africa.