Ozone and Temperature Retrieval Results from GOMOS Validated with CHAMP and ECMWF

Abstract

Data from the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on-board the European environmental satellite Envisat have been used for retrieval of ozone and temperature profiles by new algorithms, followed by profile validation. We discuss ozone profiles, determined from GOMOS transmission data, validated with operational GOMOS ozone profiles and ECMWF (European Centre for Medium-Range Weather Forecasts) analysis data. For ozone we developed an optimal estimation retrieval scheme, using sensibly selected channels from the Spectrometer A transmission spectra within 260 nm to 340 nm and 602 nm to 634 nm. Furthermore, profiles of a new GOMOS temperature profile retrieval are compared to CHAMP (CHAllenging Minisatellite Payload) and ECMWF analysis data. GOMOS temperatures are gained by exploiting pointing data of the Steering Front Assembly (SFA) and the Star Acquisition and Tracking Unit (SATU), which provide information on the refraction of the star light in the atmosphere and thus allow to derive refractive bending angle profiles. The bending angle profiles are then converted via refractivity and pressure profiles to temperature profiles. Bending angles were assumed to have errors of 3 μrad. Statistical optimization of observed bending angles with model bending angles was used to provide adequate data quality for the Abel transform from the stratopause region upwards, which led to a significant gain in temperature retrieval accuracy up to 40 km height due to suppressed downward propagation of errors induced by Abel transform and hydrostatic integral. Based on data from year 2002, a set of GOMOS ozone and bending angle derived temperature profiles is validated and discussed.