Using the GTO-ECV total ozone and GOP-ECV ozone profile climate data records for analyzing global and regional trend patterns 1995-2021

In this study, we analyze global and regional patterns of total and height-resolved ozone trends 1995-2021 based on two data records: (1) the GOME-type Total Ozone Essential Climate Variable (GTO-ECV) generated in the framework of the European Union project Copernicus Climate Change Service (C3S) and (2) the GOME-type Ozone Profile Essential Climate Variable (GOP-ECV) developed in the framework of the European Space Agency’s Climate Change Initiative (ESA-CCI) ozone project. Both GTO-ECV and GOP-ECV combine measurements from a series of nadir-viewing ultra-violet satellite sensors of the GOME-type including GOME, SCIAMACHY, OMI, GOME-2A, and GOME-2B. On top of that, GTO-ECV incorporates also GOME-2C and TROPOMI/Sentinel-5P measurements. For the retrieval of the total columns the GOME Direct Fitting version 4 (GODFIT_V4) algorithm is used, and for the retrieval of ozone profiles the Rutherford Appleton Laboratory (RAL) scheme is applied. Both the total columns and the profiles from the single sensors are merged into two homogeneous long-term gridded level-3 data records, carefully taking into account and reducing inter-sensor differences. As a final step, the ozone profile record is homogenized with respect to the well-established GTO-ECV total column record in order to achieve consistency between both products. The homogenization relies on an altitude-dependent scaling of the profiles in order to match the total column product. We apply a standard multiple linear least-squares regression to both longitudinally-resolved data records and present estimates of the long-term trend and the correlations with explanatory variables such as the Quasi-Biennial Oscillation, the solar cycle, or the El Nino-Southern Oscillation index. Of particular interest are the search for signs of ozone recovery related to decreasing amounts of Ozone Depleting Substances, the evaluation of the long-term evolution in the lower stratosphere, and the investigation of regional structures in the observed trend patterns.