Aerosol Composition Retrieval from a combination of three satellite based instruments

As different aerosol components have different effects on the climate, it is important to retrieve their global distribution over the longest feasible period. For this reason, we develop an aerosol composition retrieval based on a combination of three different satellite-based instruments which cover with their precursor and planned successor instruments the time from 1995 until 2030. The current algorithm is working with SLSTR (Sea and Land Surface Temperature Radiometer) aboard Sentinel 3A and 3B, the Infrared Atmospheric Sounding Interferometer (IASI), and the Global Ozone Monitoring Experiment-2 (GOME-2), both on METOP A/B/C. These instruments provide complementary information content due to combining measurements in the UV and VIS from GOME-2 with measurements in the TIR from IASI and the added value of the second viewing direction from the dual-view of SLSTR.

The new retrieval algorithm ROCAS (Retrieval Of Composition of Aerosols from Satellite) will be presented. ROCAS combines the preprocessed Level 1 data form the three instruments in so called super-pixels and performs an Optimal Estimation based retrieval after cloud masking and spectral consistency filtering. Retrieved parameters are the surface albedo at different wavelengths, the surface temperature, atmospheric column relative humidity, aerosol optical depth (AOD) and the individual AOD contributions for five aerosol components (black carbon, organic carbon, sulphate, sea salt and mineral dust).

With ROCAS, we can observe the expected patterns of the individual aerosol components, such as mineral dust over the deserts and their outflow regions, and black and organic carbon where smoke by large fires is transported. We can also observe sulphate over industrial regions in India, the USA and Europe.

ROCAS has the potential to quantitatively monitor aerosol composition and with this additional information to refine our understanding of their climate impact. In this study we show initial retrieval results for the individual aerosol components including a case study, a first validation and a comparison to other datasets including retrieval results from active instruments (EarthCare) and model data. The presentation will conclude with a discussion of the unique capabilities / additional information content for aerosol composition monitoring and remaining limitations of ROCAS.