Validation of GOME total ozone by means of the Norwegian ozone monitoring network

G Hansen,F Tønnessen,T Svenøe,A Dahlback

doi:10.1007/s005850050770

Abstract

The Global Ozone Monitoring Experiment (GOME) onboard the ERS-2 satellite has been in operation since July 1995. The Norwegian ground-based total ozone network has played an important role both in the main validation during the commissioning phase and in the validation of upgraded versions of the analysis algorithms of the instrument. The ground-based network consists of various spectrometer types (Dobson, Brewer, UV filter instruments). The validation of the second algorithm version used until January 1998 reveals a very good agreement between GOME and ground-based data at solar zenith angles <60Â° and deviations of GOME total ozone data from ground-based data of up to Â±60 DU (~20%) at zenith angles >60Â°. The deviations strongly depend on the season of the year, being negative in summer and positive in winter/spring, The deviations furthermore show a considerable scattering (up to Â±25 DU in monthly average values of 5Â° SZA intervals), even in close spatial and temporal coincidence with ground-based measurements, especially in the high Arctic. The deviations are also dependent on the viewing geometry/ground pixel size with an additional negative offset for the large pixels used in the backswath mode and at solar zenith angles >85Â°, compared to forward-swath pixels.Key words. Atmospheric composition and structure (middle atmosphere Â· composition and chemistry; instruments and techniques)

Highlights

The ESA Global Ozone Monitoring Experiment (GOME), the ®rst European spaceborne UV-vis spec-Correspondence to: G
Approximate global coverage is reached with GOME within three days, if the instrument is run in the standard mode covering a ground path 960 km wide
The path is divided into three ground pixels of 320 km ́ 40 km

Summary

Introduction

The ESA Global Ozone Monitoring Experiment (GOME), the ®rst European spaceborne UV-vis spec-. G. Hansen et al.: Validation of GOME total ozone by means of the Norwegian ozone monitoring network main validation project, based on Dobson, Brewer and multi-channel ®lter instrument data from Oslo, Tromsù and Ny-AÊ lesund, was presented at this workshop and published in the proceedings (Hansen and Dahlback, 1996). While long-term agreement to within 1% between Dobson and Brewer measurements has been reported at middle latitudes and at high and moderate Sun elevation (De Backer and De Muer, 1991), there can be deviations of up to 4% (10±15 DU) under less favourable conditions (e.g., Dahlback et al, 1997; De Backer and De Muer, 1991) This suggests that after calibration against Dobson measurements, the GUV technique might be equivalent to standard techniques in terms of accuracy

Validation procedure

Findings

Conclusions