Ozone monitoring with the GOMOS-ENVISAT experiment version 5
1LATMOS-IPSL, CNRS/INSU, UMR 8190, UVSQ, UPMC, Verrières le Buisson, France
2ACRI-ST, Sophia Antipolis, France
3Institute of Applied Physics, University of Bern, Bern, Switzerland
4Oeschger Centre for Climate Chnage Research, University of Bern, Bern, Switzerland
5FMI, Helsinki, Finland
6RIVM, Bilthoven, The Netherlands
Abstract. The GOMOS ozone profiles derived have been analyzed to evaluate the GOMOS ability to capture the long-term ozone evolution during its expected recovery phase. Version 5 of the GOMOS data has been compared with two of the longest ground-based instruments based on different techniques and already involved with many other previous space instrument validations. Increasing differences reported in 2006 indicate that some of the retrieved profiles are strongly biased. This bad retrieval is probably due to the increasing dark charge of the detectors combined with an inadequate method for its correction. This effect does not induce a continuous bias but is rather exhibiting a bimodal distribution including the correct profiles and the bad retrievals. For long-term analysis it is recommended to filter the data accordingly. The new method of dark charge estimate that is proposed to be implemented in the version 6 of the ESA algorithm, seems to reduce significantly the occurrence of such effects and will allow to monitor stratospheric ozone using GOMOS data with better confidence.