Global satellite validation of SCIAMACHY O3 columns with GOME WFDOAS

[摘要] Global stratospheric ozone columns derived from UV nadir spectra measured bySCIAMACHY (Scanning Imaging Spectrometer for Atmospheric Chartography; dataESA Versions 5.01 and 5.04) aboard the recently launched EnvironmentalSatellite (ENVISAT) from January to June 2003 were compared to collocatedtotal 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 fromSCIAMACHY. In addition, SCIAMACHY ozone columns retrieved with WFDOAS V1.0were compared to GOME WFDOAS for some selected days in 2003 in order toseparate data quality issues that either come from the optical performanceof the instrument or algorithm implementation. Large numbers of collocatedtotal ozone data from the two instruments, which are flying in the sameorbit about 30 min apart, were spatially binned into regular 2.5°times 2.5° grids and then compared. Results of these satellitecomparisons show that SCIAMACHY O₃ vertical columns (ESA Version5.01/5.04) are on average 1% (±2%) lower than GOME WFDOAS andscatter increases at solar zenith angles above 85° and at very low totalozone values. Results show dependencies on the solar zenith angle,latitudes, and total ozone amounts which are explained by the implementationof an outdated GOME algorithm based on GOME Data Processor (GDP) version 2.4algorithms for the SCIAMACHY operational product. The reprocessing with analgorithm equivalent to GOME WFDOAS V1.0 shows that the offset anddependencies on solar zenith angle, latitude, and total ozone disappear andthat SCIAMACHY WFDOAS data are within 1% of GOME WFDOAS. Since GOME lostits global coverage in July 2003 due to data rate limitation, continuationof the total ozone time series with SCIAMACHY is of highest importance forlong-term trend monitoring. Since the beginning of its operation in March2002 the SCIAMACHY instrument has performed stable. With the application ofproper algorithms to retrieve total ozone, SCIAMACHY will be able tocontribute to the global long term satellite total ozone record and it hasthe potential to achieve the high accuracy of GOME total ozone.

[学科分类] 大气科学