AEROSOL RETRIEVAL AND ATMOSPHERIC CORRECTION FOR MERIS DATA OVERLAKES

摘要

One of the objectives of the ENVISAT project AO-164 on “Environmental Research in the Eastern Alps” is therndevelopment of algorithms for retrieval of water quality parameters of lakes from MERIS data. In order to test and validaternatmospheric correction algorithms and to provide basic data for the development of algorithms for retrieval of limnologicalrnparameters and aerosol loadings, several field campaigns were carried out in summer 2003 on the lakes Garda (Italy) andrnMondsee (Austria) parallel to MERIS overflights. Field measurements of aerosol optical thickness (AOT) were used asrninput for atmospheric correction by means of the 6S model, and field spectra measured above the water surface were used tornvalidate the at-surface reflectance derived from MERIS data. The agreement between field and MERIS reflectance spectrarnis in general good. Some differences are found at short wavelengths which can be attributed to insufficient knowledge ofrnaerosol properties. The sensitivity of the radiative transfer model to changes in AOT and the aerosol model wasrninvestigated. For a day with strong variability in the aerosol loading the spatial gradient of AOT was estimated from MERISrndata and compared with the temporal evolution of AOT at a field measurement site.