Determination of Cloud Parameters from SCIAMACHY Data for the Correction of Tropospheric Trace Gases

For the accurate retrieval of tropospheric trace gases from SCIAMACHY the availability of cloud parameters is crucial. In this paper we present a new algorithm for the retrieval of cloud fraction from SCIAMACHY data, the Heidelberg Iterative Cloud Retrieval Utilities (HICRU). The reliability of the results are proven through intercomparision with cloud fractions from the FRESCO algorithm and images from Meteosat. The new algorithm for SCIAMACHY is based on the already well validated HICRU algorithm developed for the retrieval of cloud fractions from GOME data. We use broad band spectrometers with high spatial resolution, the Polarization Monitoring Devices. The retrieval applies the widely used threshold method. Our sophisticated, iterative calculation of thresholds including image sequence analysis makes the algorithm also reliable in regions like deserts, which requires a very accurate set of thresholds.