The South East Atlantic Ocean (SEAO) provides a natural laboratory for analysing the full range of aerosol perturbations. From June to September, the biomass burning aerosols emitted in Southern Africa are mostly transported westwards through the free troposphere. These absorbing particles are then frequently observed above the extensive stratocumulus deck covering the SEAO. Recent studies based on satellite observations have shown that the Direct Radiative Effect of the above-cloud aerosols is typically strong over the SEAO and can reach instantaneous values larger than +130W.m-2. However, there is a large spread in the DRE from climate models and they fail to reproduce such high radiative impact. This highlights the need to better constrain both aerosol and cloud properties.
Until recently, there has been a relative dearth of observations of biomass burning above clouds as passive sensor retrievals of aerosols and clouds are generally mutually exclusive. In the last decade, there has been a growing interest from the scientific community for aerosols above clouds and new algorithms have been developed in order to observe aerosols above clouds. However, these techniques have been applied to instruments on polar orbiting satellites only, which implies one single observation per day. The cloud cover in the SEAO is subjected to an important diurnal cycle which modulates the DRE of aerosols during the day. In this talk, a method to retrieve aerosol and cloud properties from SEVIRI will be presented. The satellite instrument, on-board the geostationary platform MSG, provides a full-disc observation every 15 minutes, offering a unique opportunity to monitor the evolution of the cloud cover and to track aerosol plumes over the SEAO. The performance of the retrieval will be assessed by a comparison with the results obtained with MODIS as well as the measurements acquired during the CLARIFY-17 campaign.