FDR4ATMOS: New release of SCIAMACHY Level 1 and Level 2 products

Abstract

The project FDR4ATMOS (Fundamental Data Records in the domain of satellite Atmospheric Composition), initiated by the European Space Agency (ESA), aims to generate well-characterised, long-term records of calibrated and quality-controlled Earth Observation (EO) sensor data (Level 1), capitalising measurements acquired by instruments embarked on legacy remote sensing satellites. Task A of this project covers the improvement of the SCIAMACHY Level 1b degradation correction, with the aim to remove Ozone trends from the Level 2 data that were introduced during the development of baseline version 9 (both data sets not released). Enhanced SCIAMACHY calibration algorithms for improved Ozone total column data: After the full re-processing of the SCIAMACHY mission with the previous processor version, the validation analysis showed that the total Ozone column drifted downward by nearly 2% w.r.t. ground-based reference instruments over the mission lifetime. This unexpected drift was attributed to changes in the degradation correction in the Level 1 processor, that led to subtle changes in the spectral structures. These deviations were erroneously misinterpreted as an atmospheric signature. In response, corrective measures were implemented in the Level 0-1 processor and a full mission re-processing was done. Integration of Calibrated Lunar Data into SCIAMACHY Level 1b Product: As a major improvement, calibrated lunar data have been added to Level 1, covering the whole spectral range of SCIAMACHY and the full mission time. In the new Level 1b product we provide the individual scans of the moon as well as disk-integrated and calibrated lunar irradiance and reflectance. Over the course of the mission, the instrument performed regular lunar observations building up a unique 10-year data set of lunar spectra spanning from UV to SWIR wavelengths with moderately high spectral resolution. Using the newly calculated SCIAMACHY Level 1 Earthshine data, we reprocessed all Level 2 data to newly retrieve trace gas columns and profiles as well as aerosol and cloud products. In this version of the product a tropospheric BrO column was introduced and the limb cloud algorithm was updated. Moreover, these Level 1 version 10 and Level 2 version 7.1 products mark the transition from the ENVISAT byte stream format to the netCDF format that is aligned with the product format of other atmospheric sensors like the Sentinels. The paper will present the improvements in both Level 1 and Level 2 products together with the results of the quality control and validation analyses.