Quality Assessment of the AC SAF GOME-2 gridded ozone profile data records

Abstract. One of the objectives of the Atmospheric Composition SAF is to produce satellite-derived monthly mean data records that are valuable for operational, scientific, and other applications. One of these data records is the gridded global GOME-2A/B/C ozone profile data set presented in this paper. This data record covers the period 2007–2024 and consists of ozone partial columns on a 0.25 degree × 0.25 degree grid with 40 vertical layers, with the associated (averaged) averaging kernel (AK) and the a priori needed to use the data in other applications. This paper presents the GOME-2 instrument, the (level-2) ozone profile retrieval method and the subsequent gridding procedure used to generate the level-3 product. We discuss the methodology for averaging AKs in latitude bands and demonstrate that the principal structural features are preserved. We provide a description of the balloon sounding, lidar, FTIR and microwave radiometers validation data and methods, and then perform a quality assessment of the gridded ozone profile product through comparison with these independent data sources for the tropics, mid-latitude and polar latitude bands and in three vertical regions: the Troposphere, and the Lower and Upper Stratosphere. Detailed analyses of absolute and relative differences are provided for each region and height range. The results demonstrate a high level of consistency across the three GOME-2 instruments (with GOME-2A used only up to 2018), underscoring the reliability of the GOME-2 constellation for long-term ozone monitoring. In the troposphere, all three sensors tend to slightly overestimate ozone, with absolute differences (AD) of roughly +1 to +3 DU in mid-latitudes and up to +7.5 DU in the tropics for Metop-C. In lower stratosphere, all sensors show a small negative bias, typically between −3 and −7 DU (RD ≈ −3 % to −7 %), corresponding to a modest underestimation of ozone concentrations. In the upper stratosphere, biases are minimal across all sensors, with absolute difference values, close to zero (−0.1 to −0.4 DU) and extremely low variability (STDEV ≈ 0.1–0.2 DU). These findings underscore the reliability of the GOME-2 constellation for long-term ozone analyses and the potential for merged multi-sensor time series without significant inter-calibration artifacts suitable for climate and atmospheric research.