1Finnish Meteorological Institute, Earth Observation, Helsinki, Finland
2Service d'Aeronomie, Paris, France
3BIRA-IASB, Brussels, Belgium
4ACRI ST, Sophia Antipolis, France
6EADS-Astrium, Toulouse, France
Abstract. The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument uses stellar occultation technique for monitoring ozone and other trace gases in the stratosphere and mesosphere. The self-calibrating measurement principle of GOMOS together with a relatively simple data retrieval where only minimal use of a priori data is required, provides excellent possibilities for long term monitoring of atmospheric composition.
GOMOS uses about 180 brightest stars as the light source. Depending on the individual spectral characteristics of the stars, the signal-to-noise ratio of GOMOS is changing from star to star, resulting also varying accuracy to the retrieved profiles. We present the overview of the GOMOS data characterization and error estimation, including modeling errors, for ozone, NO2, NO3 and aerosol profiles. The retrieval error (precision) of the night time measurements in the stratosphere is typically 0.5–4% for ozone, about 10–20% for NO2, 20–40% for NO3 and 2–50% for aerosols. Mesospheric O3, up to 100 km, can be measured with 2–10% precision. The main sources of the modeling error are the incompletely corrected atmospheric turbulence causing scintillation, inaccurate aerosol modeling, uncertainties in cross sections of the trace gases and in the atmospheric temperature. The sampling resolution of GOMOS varies depending on the measurement geometry. In the data inversion a Tikhonov-type regularization with pre-defined target resolution requirement is applied leading to 2–3 km resolution for ozone and 4 km resolution for other trace gases.