Benefits and limitations of the synergistic aerosol retrieval SYNAER

Abstract

At the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) a synergistic aerosol retrieval method called SYNAER was developed (Holzer-Popp, et al., 2002a). This algorithm exploits the complementary information of a radiometer and a spectrometer onboard a single satellite platform in order to extract aerosol optical depth (AOD) and speciation (aerosol type) as choice from a representative set of 40 pre-defined mixtures of water-soluble, soot, mineral dust, and sea salt aerosol components. Recently, the algorithm was transferred to a new sensor combination onboard the European environmental satellite platform ENVISAT to achieve better spatial and temporal coverage (Holzer-Popp, et al., 2008). A thorough evaluation of the aerosol retrieval against multi-spectral ground-based observations from AERONET was conducted, allowing us to improve the methodology. The evaluation included a stringent analysis of the information content for different surface-atmosphere conditions and illuminations as well as the investigation of critical steps of the algorithm. A preliminary validation of the new version shows the potential to estimate the aerosol type from space (AOD error around 0.1 from UV (ultraviolet) to NIR (near infrared), which is in excellent agreement with the expected noise level. This paper provides a comprehensive summary of the SYNAER methodology which is applied to ENVISAT data, in particular highlighting the information content analysis and the upgrades which were made during the transfer to ENVISAT (Holzer-Popp, et al., 2008).