First MAX-DOAS observations of tropospheric NO2 and H2CO in Central Africa: impact on air quality and validation of the TROPOMI satellite instrument

This thesis addresses air pollution in Central Africa, with a focus on nitrogen dioxide (NO2), formaldehyde (H2CO), and aerosol pollution. Recent studies, utilizing satellite observations, reveal peaks in these pollutants, primarily attributed to biogenic emissions from the region's extensive forests, but also from biomass burning, forest fires, and charcoal production. The lack of ground-level measurements in Central Africa is emphasized.
The thesis operationalizes a remote sensing instrument based on Differential Optical Absorption Spectroscopy (DOAS) in Kinshasa. Data collected from May 2017 to July 2021 establish a pollution database, revealing significant levels of NO2, H2CO, and aerosols, particularly during the dry season. Daily cycles are identified, showing elevated levels around noontime.
Initial validation exercises of the TROPOMI satellite instrument demonstrate good agreement with ground observations, considering corrections based on the use of more representative MAX-DOAS measured profile as a priori information in the TROPOMI product. Evaluation of the GEOS-Chem model indicates its accuracy in replicating real atmospheric conditions, emphasizing the significant impact of biomass burning on NO2 and H2CO pollution.
This work underscores the need for more ground instruments in the sub-region. The need to inform the population is emphasized, as is the definition of effective measures to reduce pollution levels.