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Global satellite validation of SCIAMACHY O3 columns with GOME WFDOAS

Author(s): A. Bracher | M. Weber | K. Bramstedt | M. Coldewey-Egbers | L. N. Lamsal | J. P. Burrows

Journal: Atmospheric Chemistry and Physics Discussions
ISSN 1680-7367

Volume: 5;
Issue: 1;
Start page: 795;
Date: 2005;
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Global stratospheric ozone columns measured by SCIAMACHY (Scanning Imaging Spectrometer for Atmospheric Chartography; data versions 5.01 and 5.04) aboard the recently launched Environmental Satellite (ENVISAT) from January to June 2003 were compared to collocated total ozone data from GOME (Global Ozone Monitoring Experiment on ERS-2) retrieved using the weighting function DOAS algorithm (WFDOAS; Version 1.0) in order to assess the level-2 data (trace gas data) retrieval accuracy from SCIAMACHY. The large number of collocated total ozone data from the two instruments which are flying in the same orbit were spatially binned into regular 2.5° and 2.5° grids and then compared. This binning method shows similar results than direct comparisons but is about thousand times faster. Results of these satellite comparisons show that SCIAMACHY O3 vertical columns (version 5.01/5.04) are on average 1% (±2%) lower than GOME WFDOAS and scatter increases at solar zenith angles above 85° and at low total ozone values. Results show dependencies on the seasonal cycle, latitudes, and total ozone amounts which are explained by the implementation of an old GOME algorithm based on GOME Data Processor (GDP) version 2.4 algorithm for the SCIAMACHY operational product. A reprocessing with an algorithm equivalent to GOME GDP version 4.0 and/or GOME WFDOAS V1.0 will improve significantly the quality of the SCIAMACHY ozone product. Since GOME lost its global coverage in July 2003 due to data rate limitation, continuation of the total ozone time series with SCIAMACHY is of highest importance for long-term trend monitoring.
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