Global, regional and seasonal analysis of total ozone trends derived from the 1995–2020 GTO-ECV climate data record

Abstract

Abstract. In this study we present an updated perspective on near-global total ozone trends for the period 1995–2020. We use the GOME-type Total Ozone Essential Climate Variable (GTO-ECV) satellite data record which has been extended and generated as part of the European Space Agency’s Climate Change Initiative (ESA-CCI) and European Union Copernicus Climate Change Service (EU-C3S) ozone projects. The focus of our work is the analysis of regional patterns in the ozone trend as well as the investigation of its seasonal dependence. In the Southern Hemisphere we found regions that indicate statistically significant positive trends increasing from 0.6 ± 0.5 % decade−1 in the subtropics to 1.0 ± 0.9 % decade−1 in the middle latitudes and 2.8 ± 2.6 % decade−1 in the latitude band 60°–70° S. In the middle latitudes of the Northern Hemisphere the trend exhibits distinct regional patterns, i.e. latitudinal and longitudinal structures. Significant positive trends (∼1.5 ± 1.0 % decade−1) over the North Atlantic region as well as negative trends (−1.0 ± 1.0 % decade−1) over Eastern Europe were found. Moreover, these trends indicate a correlation with long-term changes in tropopause pressure. Total ozone trends in the tropics are not significant. Regarding the seasonal dependence of the trends we found only very small variations over the course of the year. However, we identified different behavior depending on latitude. In the latitude band 40°–70° N the positive trend maximizes in boreal winter from December to February. In the middle latitudes of the Southern Hemisphere (35°–50° S) the trend is maximum from March to May. Further south toward the high latitudes (55°–70° S) the trend denotes a relatively strong seasonal cycle which varies from 2 % decade−1 in December and January to 3.8 % decade−1 in June and July.

Global total ozone recovery trends attributed to ozone-depleting substance (ODS) changes derived from five merged ozone datasets

“…In the tropics the linear trend after 1995 is close to zero and insignificant (Fig. 2 and Coldewey-Egbers et al, 2022). Table 3 summarizes the MLR results in the broad zonal bands from the individual datasets and the median time series as well as the mean and median of the individual trends.…”

“…The main results from our earlier paper (W18) were latitude-dependent annual mean total ozone trends from the middle 1990s to 2016, which were reported to be on average +0.5 %/decade in the extratropics and only significant in the Southern Hemisphere (SH; W18). Since W18 was published, there have been three recent studies on global and regional ozone column trends (Bozhkova et al, 2019;Krzyścin and Baranowski, 2019;Coldewey-Egbers et al, 2022). Krzyścin and Baranowski (2019) derived total ozone column trends from a multivariate linear regression (MLR) applied to the Multi-Sensor Reanalysis-2 (MSR-2) total ozone dataset up to 2017 (van der A et al, 2015).…”

“…Attribution of physical and chemical processes to the long-term changes is therefore not possible, as also stated by the authors. Latitude-and longitude-dependent total ozone trends are reported by Coldewey-Egbers et al (2022) derived from the ESA/DLR GTO-ECV dataset, which is one of the five observational datasets used in this study. They report significant positive linear trends after 1995 over large regions in the extratropical Southern Hemisphere (SH), while in the tropics and Northern Hemisphere (NH) they are mostly insignificant.…”