In mid-2010 the ESA Climate Change Inititative project aerosol_cci started. It was established to create consistent prototype algorithms for the production of long-term aerosol data sets from several European earth observation sensors. Nadir measurements for total column retrievals and stratospheric aerosol profiles from limb sounders are at the focus of attention. The project builds on eight existing algorithms for ATSR, MERIS, SCIAMACHY, POLDER, GOMOS and similar instruments. After three year a first global data set for 2008 will be produced to demonstrate for different climate zones and seasons the capabilities to monitor major aerosol regimes.
In its first phase an in depth analysis and comparison of retrieval results for a limited test data set and specific case studies are being conducted in order to understand the strengths and weaknesses of each algorithm. Through intercomparison and validation against other satellite and ground-based reference data sets the reasons for differences among various satellite retrieval algorithms are to be explored in detail. At the same time, elements of community algorithms and harmonized retrieval will be developed. This analysis includes the different assumptions and algorithmic approaches for modeling optical aerosol properties, how to deal with surface reflectance and its anisotropy, cloud masking, and the use of auxiliary data sets.