Suchergebnisse

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.

Comparisons between satellite and ground-based measurements of the atmosphere are inevitably affected by natural variability due to mismatches in spatial and temporal co-location. These additional terms in the comparison error budget are quantified here for total ozone column comparisons using an Observing System Simulation Experiment. Even when using tight co-location criteria, atmospheric variability is found to impact the comparisons significantly. ; Part of this work was funded by the Belgian Science Policy Office (BELSPO) and ESA via the ProDEx projects A3C and ACROSAT, and by the EU H2020 project GAIA-CLIM (Ares(2014)3708963/Project 640276). The authors acknowledge the pioneering research carried out in 2008–2012 by C. De Clercq and S. Vandenbussche and funded by the EU FP6 project GEOmon (FP6-2005-Global-4-036677) and ProDEx project SECPEA.

Comparisons between satellite and ground-based measurements of the atmosphere are inevitably affected by natural variability due to mismatches in spatial and temporal co-location. These additional terms in the comparison error budget are quantified here for total ozone column comparisons using an Observing System Simulation Experiment. Even when using tight co-location criteria, atmospheric variability is found to impact the comparisons significantly. ; Part of this work was funded by the Belgian Science Policy O ce (BELSPO) and ESA via the ProDEx projects A3C and ACROSAT, and by the EU H2020 project GAIA-CLIM (Ares(2014)3708963/Project 640276). Finally, the 20 authors acknowledge the pioneering research carried out in 2008–2012 by C. De Clercq and S. Vandenbussche and funded by the EU FP6 project GEOmon (FP6-2005-Global-4-036677) and ProDEx project SECPEA.

This paper presents an extensive intercomparison and validation for the ozone (O3) product measured by the two Infrared Atmospheric Sounding Interferometers (IASIs) launched on board the MetOp-A and MetOp-B satellites in 2006 and in 2012 respectively. IASI O3 total columns and vertical profiles obtained from Fast Optimal Retrievals on Layers for IASI (FORLI) v20140922 software (running up until recently) are validated against independent observations during the period 2008-2014 on a global scale. On average for the period 2013-2014, IASI-A and IASI-B total ozone columns (TOCs) retrieved using FORLI are consistent, with IASI-B providing slightly lower values with a global difference of only 0.2±0.8%. The comparison between IASI-A and IASI-B O3 vertical profiles shows differences within ±2% over the entire altitude range. Global validation results for 7 years of IASI TOCs from FORLI against the Global Ozone Monitoring Experiment-2 (GOME-2) launched on board MetOp-A and Brewer-Dobson data show that, on average, IASI overestimates the ultraviolet (UV) data by 5-6% with the largest differences found in the southern high latitudes. The comparison with UV-visible SAOZ (Système d'Analyse par Observation Zénithale) measurements shows a mean bias between IASI and SAOZ TOCs of 2-4% in the midlatitudes and tropics and 7% at the polar circle. Part of the discrepancies found at high latitudes can be attributed to the limited information content in the observations due to low brightness temperatures. The comparison with ozonesonde vertical profiles (limited to 30km) shows that on average IASI with FORLI processing underestimates O3 by ∼ 5-15% in the troposphere while it overestimates O3 by ∼ 10-40% in the stratosphere, depending on the latitude. The largest relative differences are found in the tropical tropopause region; this can be explained by the low O3 amounts leading to large relative errors. In this study, we also evaluate an updated version of FORLI-O3 retrieval software (v20151001), using look-up tables recalculated ...