Ozone_cci 2nd User Workshop

28 May 2024, 16:00 → 29 May 2024, 20:00 Europe/Brussels

Microsoft Teams

Background

The European Space Agency’s Climate Change Initiative (CCI) aims to realise the full potential of the long-term Earth Observation archives collected by ESA and Third Party satellite missions. Since 2010, the Ozone CCI team (https://climate.esa.int/en/projects/ozone) has been developing, maturing, generating and sustaining multiple complementary multi-decadal satellite ozone Climate Data Records (CDRs) tailored for climate monitoring, climate research and climate modelling applications. The CCI portfolio consists of total and tropospheric ozone column data products as well as vertically resolved ozone products by nadir and limb-viewing sensors.

Workshop objectives

This second user workshop will be an online event, aimed at

• bringing together scientists involved in the generation of ozone Climate Data Records, as well as (potential) users of such multi-decadal ozone time series, and the broader ozone and climate communities;
• presenting the state of the art in ozone Climate Data Record production;
• discussing results from major Climate Data Record users, e.g., stratospheric ozone assessments for WMO/UNEP, tropospheric ozone assessments for TOAR II, studies focusing on UT/LS, evaluation of climate modelling, data assimilation and reanalysis;
• collecting and updating user requirements for ozone Climate Data Records;
• discussing remaining challenges for the generation of ozone Climate Data Records.

Tuesday, 28 May

1 Welcome and introduction

Speakers: Martin Dameris (DLR), Michiel Van Weele (KNMI)

Tropospheric ozone: Keynotes, CCMs

2 Keynote - Harmonization of tropospheric ozone data for TOAR II

After a first successful phase of the Tropospheric Ozone Assessment Report (TOAR), which e.g. provided the first global scale view of all available surface ozone observations, the most extensive evaluation of historical (pre 1975) ozone observations and the first intercomparison of satellite ozone products, TOAR is now nearly the end of its second phase (TOAR-II, 2020-2024). TOAR-II will produce an updated assessment of tropospheric ozone’s global distribution and trends, along with distributions and trends of ozone precursor emissions, and aims to quantify the impacts of tropospheric ozone on climate, human health and vegetation (e.g., crops).

One primary goal of TOAR-II is to understand the wide variety of distribution, trends and variability in (free-)tropospheric ozone measured with satellites in TOAR-I and reported in Gaudel et al. (2018). Therefore, it is required to characterize the effects of differences in measurement vertical sensitivity and sampling on the tropospheric ozone distribution and trends. Different TOAR-II Focus Working Groups try to address this challenge from their own perspectives (satellite data, ground-based and in-situ data, and chemical reanalysis model output), but with the harmonization of the tropospheric ozone data as a necessary, intermediate step.

In this contribution, we will report on the harmonization activities in the satellite ozone and HEGIFTOM (“Harmonization and Evaluation of Ground-based Instruments for Free-Tropospheric Ozone Measurements”) focus working groups and present some first results of worldwide tropospheric ozone column trend estimates.

Speaker: Roeland Van Malderen (Royal Meteorological Institute of Belgium)

3 Overview of tropospheric ozone Climate Data Records by ESA CCI

Speaker: Daan Hubert (BIRA-IASB)

4 Bringing chemistry climate models and observations together: Our experience with CCMi

Chemistry climate models (CCMs) are constructed to encapsulate our understanding of important atmospheric processes affecting the chemical state of the atmosphere, subject to the fundamental constraint imposed by our computational capacity to produce results in a reasonable amount of time. These models are routinely used to provide simulations to inform science and policy, including going back in time to long before our direct observational record began and going into the future to make projections. The central role of CCMs in testing our understanding of atmospheric processes and making projections argues for regular assessments of models against available observations, but motivating efforts to bridge the gap between observations and models is not always easy. The Chemistry Climate Model initiative (CCMi), the successor to the CCMVal activity, regularly organizes a set of coordinated model experiments to test CCMs and provide projections. This presentation will discuss the successes and challenges CCMi has faced testing models against observations.

Speaker: Dave Plummer (ECCC, Canada)

5 Shifting patterns of global emissions and tropospheric ozone linked to human activity and natural processes derived from a decadal chemical reanalysis

Changes in economic activity and emission controls over the past several decades have led to substantial changes in anthropogenic emissions globally. Meanwhile, climate change has been a key factor in increasing the risk and extent of natural processes such as extreme wildfire events. Satellite measurements have been used to explore these changing global patterns. However, the attribution to individual emission sources and chemical processes remains unclear due to the difficulty of combining multiple types of observations and the complex chemical mechanisms relating emissions to atmospheric concentrations.

We have developed a state-of-the-art chemical data assimilation (DA) system, MOMO-Chem, to combine various satellite observations with chemistry transport models. This framework has successfully been used to produce Tropospheric Chemistry Reanalysis version 2 (TCR-2) and applied to quantify emission changes and their impacts on ozone for the past decade by ingesting a suite of satellite measurements of various chemical species, including those from Aura, Aqua, and Terra (Miyazaki et al., 2020a, 2020b, 2020c, 2021, 2022).

Recently, we extended the framework to utilize multi-sensor data from the new generation satellites, including CrIS and VIIRS from Suomi-NPP and JPSS, Sentinel-5P TROPOMI, and long-term satellite data from other satellites to characterize processes that form ozone, aerosols, and other pollutants in the atmosphere and attribute changes in their concentrations to short- and long-term variations in human and natural activity. By utilizing the new generation satellite data, we simultaneously optimize anthropogenic and biogenic emissions of NOx, SO2, VOCs, CO, and aerosols to provide an improved representation of global tropospheric profiles of ozone and to better represent driving mechanisms of decadal changes of various chemical species, their chemical regime, and the oxidative capacity.

I will also discuss recent applications of the extended chemical reanalysis, such as the impacts of COVID-19, wildfires, and decadal changes, to provide a greatly enhanced understanding of multi-year changes in tropospheric ozone and their response to changes in emission efficiency and human activity.

Speaker: Kazuyuki Miyazaki (NASA Jet Propulsion Laboratory, California Institute of Technology)

6 Tropospheric ozone column datasets by combining nadir and limb satellite measurements

In this work, we present the tropospheric ozone datasets, which are created using combination of total ozone column data from nadir instruments (OMI, GTO-ECV) with stratospheric ozone column dataset from several available limb-viewing instruments (MLS, OSIRIS, MIPAS, SCIAMACHY, OMPS-LP, GOMOS). These datasets are included in the Ozone_cci+ Phase 2.

In the presentation, we will present the retrieval method and the results of its application. The analyses of tropospheric ozone variability and trends will be also presented.

Speaker: Viktoria Sofieva (Finnish Meteorological Institute)

17:35 Break

Tropospheric ozone: Observations

7 Decade-long ozone record from Suomi NPP OMPS

The Ozone Mapping and Profiler Suite (OMPS) comprises three complementary ozone sensors – Limb Profiler (LP), Nadir Profiler (NP) and Nadir Mapper (NM) - that scan the same region of the atmosphere within minutes to measure the global ozone distribution at high spatial and vertical resolution. The combination of limb and nadir instruments on the same platform enables the estimation of tropospheric ozone columns. Ozone measurements from the first OMPS on board of the Suomi NPP mission span for more than 12 years. In this study, we evaluate the new NASA version 2.6 ozone profile dataset derived from OMPS LP by comparing it with Aura Microwave Limb Sensor (MLS). The version 2.6 LP algorithm combines measurements from the ultraviolet (UV) and visible (VIS) parts of the spectra and employs second order Tikhonov regularization to retrieve a single vertical ozone profile between 12.5 km (or cloud tops) and 57.5 km with the vertical resolution of about 1.9 - 2.5 km between 20-55 km. The key improvement in version 2.6 is the reduction in relative drifts between LP ozone and correlative measurements, linked previously to a drift in the version 2.5 LP altitude registration. We evaluate monthly mean stratospheric ozone columns calculated from the LP profile measurements. Then we estimate monthly mean tropospheric columns using the total ozone columns derived from OMPS NM and compare them with the OMI/MLS tropospheric record.

Speaker: Natalya Kramarova (NASA GSFC)

8 Long-term tropospheric ozone column from SCIAMACHY+OMPS

Combining space-borne limb and nadir measurements in the UV-visible spectral range (limb-nadir matching, LNM) provides valuable information on tropospheric ozone. This study uses data from the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) (2002-2012) and Ozone Mapping and Profiler Suite on board of Suomi National Polar-Orbiting Partnership (OMPS/NPP, since 2012). Both instruments observe the atmosphere in both limb and nadir geometry. Tropospheric ozone columns are retrieved globally by subtracting the stratospheric ozone column calculated from limb observations from the total ozone column derived from the nadir measurements.
Tropospheric ozone retrievals calculate the tropospheric ozone column using different upper altitude limits. In the case of the LNM technique, the upper limit is defined by the thermal and/or dynamical tropopause. Phase II of the Tropospheric Ozone Assessment Report (TOAR-II) uses different pressure levels for different latitudes as an upper limit for the tropospheric column.
After updating and improving the SCIAMACHY-LNM and the OMPS/NPP-LNM datasets, we are working to obtain a long-term dataset of tropospheric ozone (2002-2023) by merging them. Here, we present the challenges we face in harmonising and converting the dataset for different definitions of column heights as prescribed in TOAR II.

Speaker: Andrea Orfanoz-Cheuquelaf (IUP. University of Bremen)

9 Quantification and evaluation of tropospheric TROPESS ozone trends using CrIS, AIRS, and OMI satellite products

We present an analysis of ozone data products retrieved from multiple satellite observations. Specifically, we highlight data from the TRopospheric Ozone and its Precursors from Earth System Sounding (TROPESS) project which is a NASA effort that provides retrievals of atmospheric ozone utilizing radiances from a variety of different satellite instruments. The multispectral retrievals of ozone utilize the Multi-Spectra, Multi-Species, Multi-Sensors Retrievals of Trace Gases (MUSES) retrieval framework to produce consistent estimations of ozone from different satellite radiances. TROPESS ozone data products are retrieved from the Atmospheric Infrared Sounder (AIRS), the Ozone Monitoring Instrument (OMI), the Cross-track Infrared Sounder (CrIS) instruments, and combinations of these satellites.

Ozone products are evaluated against global ozonesonde data provided by the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). Satellite products are evaluated against both harmonized ozonesonde data (60 sites) and original WOUDC data (44 sites). Satellite-sonde bias is quantified globally and locally dating from 2002 to the present. Trends in ozone are also presented and evaluated globally and regionally. We present results for tropospheric profiles, tropospheric columns, and total ozone columns. We find that the magnitude of ozone vertical profiles and columns agree between satellites to a high degree, but we are still investigating the trends seen in the different data sets. We investigate the causes of these differences between satellites, including instrument type and vertical sensitivity of the retrievals. We show ongoing work wherein the averaging kernels for each TROPESS product are applied to ozone predictions from the MOMO-Chem Reanalysis framework to investigate the impact of satellite vertical sensitivity on ozone distribution.

Speaker: Elyse Pennington (NASA JPL)

10 Tropical Tropospheric Ozone observed by European Satellites from ERS-2/GOME (1995) to S5P/TROPOMI (2024) and resulting trends

A tropospheric ozone Climate Data Record from 1995 until end 2023 has been generated within ESA’s Climate Change Initiative programme. The GOME-type Tropical Tropospheric Ozone Essential Climate Variable (GTTO-ECV) satellite data record combines data from GOME, SCIAMACHY, OMI, the three GOME-2 missions and TROPOMI. The retrieval is based on the Convective Cloud Differential technique, which limits the coverage to the tropical belt (20°S to 20°N). We generated two data sets of monthly means at 1° x 1° spatial resolution. The first data set limits the troposphere to 270 hPa that pressure level is used in the operational S5P data set. The second retrieval corresponds to a tropospheric column up to 200 hPa as in the previous CCI data release (Heue et al., 2016). Also S5P data were reanlysed for the second data set with 200 hPa tropopause height. Besides a consistent reprocessing of the CCD data for individual sensors, we also updated the harmonising scheme. The mean bias as well as the mean annual cycle relative to the reference instrument (OMI) are used to correct for the differences between the sensors.

Heue et al (2016) inferred a mean tropospheric ozone trend of +0.7±0.1 DU/decade (1995-2015) from the previous GTTO-ECV version. Did the trend change with the extended and improved data set? The GTTO-ECV data record will be used to investigate the tropical mean trend as well as temporal and local changes in the trends or extreme events.

Speaker: Klaus-Peter Heue (DLR)

11 CMIP6

Speaker: Paul Griffiths (National Centre for Atmospheric Science, University of Cambridge, Chemistry Department, Cambridge, UK)

12 Discussion user needs / requirements

Speakers: Michiel Van Weele (KNMI), Martin Dameris (DLR), Daan Hubert (BIRA-IASB)

Wednesday, 29 May

13 Welcome and introduction

Speakers: Martin Dameris (DLR), Michiel Van Weele (KNMI)

Stratospheric (and total) ozone: Keynotes, CCMs

14 Keynote - On today’s challenges in understanding the ozone layer

In this talk, I will provide a personal perspective on current challenges in the field of stratospheric ozone science and observing. The talk will include a discussion of how long-term datasets inspired novel worldwide research that inspired public policy and led to new directions in understanding heterogeneous chemistry and atmospheric composition. I summarize my view of current challenges inspired by both expected and unexpected events, including evaluation of the emergence of ozone recovery (or not), wildfire smoke, and the eruption of the Hunga Tonga volcano, and I will relate these to the atmospheric observing system.

Speaker: Prof. Susan Solomon (Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology)

15 Keynote - The 2026 WMO/UNEP Ozone Assessment

The Montreal Protocol on Substances that Deplete the Ozone Layer mandates a quadrennial report from their Scientific Assessment Panel under Article 6 of the agreement. The most recent assessment was the “Scientific Assessment of Ozone Depletion 2022” (https://ozone.unep.org/system/files/documents/Scientific-Assessment-of-Ozone-Depletion-2022.pdf). The potential areas of focus for the 2026 report were formulated at the 35th Meeting of the Parties in Nairobi, Kenya in October 2023 under Decision XXXV/3. In this talk, I will cover some of the main findings of the 2022 Assessment and briefly discuss the areas of focus for the 2026 report.

Decision XXXV/3 areas of focus specifically included:
a) An assessment of the state of the ozone layer and its future evolution;
b) An evaluation of global and polar stratospheric ozone, including the Antarctic ozone hole and Arctic winter and spring ozone depletion and the predicted changes in these phenomena;
c) An updated assessment of past and projected contributions of the Montreal Protocol to mitigating climate change in terms of total avoided CO2-equivalent emissions and avoided temperature increase;
d) An evaluation of trends in the top-down derived emissions, abundances and fate in the atmosphere of trace gases of relevance to the Montreal Protocol, in particular controlled substances and other substances of importance to the ozone layer, which should include a comparison of top-down estimations and available bottom-up estimations of such emissions with a view to identifying currently unknown emission sources and explaining discrepancies between emissions derived from reported information and observed atmospheric concentrations (in cooperation with the Technology and Economic Assessment Panel);
e) An evaluation of consistency with reported production and consumption of those substances and the likely implications for the state of the ozone layer, including its interaction with the climate system;
f) An assessment of the interaction between changes in stratospheric ozone and the climate system, including consideration of related policy scenarios;
g) Information regarding scenarios designed to contribute further to ozone layer protection and climate change mitigation, and a presentation of their benefits in terms of impacts on total column ozone and equivalent effective stratospheric chlorine, advancing the recovery of the ozone layer, and avoiding CO2-equivalent emissions, as relevant;
h) Early identification and quantification of any substances that could be of concern for the ozone layer and relevant for the implementation of the Montreal Protocol and the objectives of the Vienna Convention for the Protection of the Ozone Layer, including other halogenated gases, in particular those with high global warming potential, breakdown products of controlled substances and their alternatives that are very persistent, such as perfluoro- and polyfluoroalkyl substances, including trifluoroacetic acid, N2O and very short-lived substances such as dichloromethane, and their main sources of emissions;
i) An assessment of information and research related to solar radiation modification, in particular stratospheric aerosol injection and its potential effects on the ozone layer and relevant information on the potential effects of supersonic aircraft, rockets, satellites, wildfires and volcanic eruptions on the stratospheric ozone layer;
j) Identification and quantification of any other issues relevant to the objectives of the Vienna Convention for the Protection of the Ozone Layer and the Montreal Protocol.

Speaker: Dr Paul Newman (NASA Goddard Space Flight Center)

16 Overview of stratospheric and total ozone Climate Data Records by ESA CCI

Speaker: Daan Hubert (BIRA-IASB)

17 Future volcanic eruptions delay healing of the Antarctic ozone layer

At present, volcanic sulfate aerosols can lead to stratospheric ozone loss under the presence of anthropogenic chlorofluorocarbons (CFCs). Previous Chemistry Climate Model Initiative (CCMI-1) simulations showed that the Antarctic ozone hole is expected to be recovered by around 2060, although these simulations did not consider future volcanic eruptions. While atmospheric CFC levels have declined since the 1980s, future volcanic eruptions producing stratospheric volcanic sulfate aerosol may lead to a net increase in stratospheric column ozone. However, it remains uncertain whether future volcanic eruptions will lead to an earlier or a delayed recovery in Antarctic stratospheric ozone.

To investigate how future volcanic eruptions affect Antarctic ozone recovery, we generated 1000 stochastic future eruption scenarios based on an array of bipolar ice cores, satellite measurements and geological records spanning the last 11,500 years. We selected the low-end, median and high-end future stochastic scenarios based on ranked total SO2 mass and performed simulations from 2015 to 2100 using the UKESM-VPLUME plume-aerosol-chemistry-climate modelling framework with interactive sulfur chemistry and aerosol microphysics. Our model results show that future volcanic eruptions can delay the recovery of the Antarctic October-mean ozone mass deficit by 3 to 6 years, and October-mean ozone hole area (with an area threshold of 1 million km2) for up to 11 years. Our findings offer insights into the role of future volcanic eruptions in affecting Antarctic ozone recovery, as opposed to a previous modelling study suggesting no effects on polar ozone recovery. We also highlight the importance of incorporating interactive sulfur chemistry and aerosol microphysics in future modelling studies to assess the impact of volcanic eruptions on stratospheric ozone.

Speaker: May M. M. Chim (Centre for Atmospheric Science, Yusuf Hamied Department of Chemistry, University of Cambridge)

18 Role of natural variability and ozone transport in understanding recent trends in lower stratosphere ozone

Lower stratospheric ozone between 60S and 60N has continued to decline since 1998, in spite of the reduction of ozone-depleting substances as a result of the Montreal Protocol. Previous studies have shown that Chemistry Climate Models are not able to reproduce these negative trends in mid-latitudes, but the underlying reason for this discrepancy between models and observations remains unknown.

In this work, we reassess recent trends in lower stratospheric ozone using the new simulations from the Chemistry Climate Model Initiative 2022 (CCMI-2022). Historical simulations with observed sea surface temperatures (SSTs) and nudged QBO (ref-D1), and fully-coupled atmosphere-ocean simulations (ref-D2) are available spanning up to 2018, which allows a better analysis of the role of natural variability in recent ozone trends compared to previous studies.

CCMI-2022 models present a slight improvement in capturing lower stratospheric ozone trends in mid-latitudes compared to previous studies that used CCMI-1 and CCMVal models. The observational trend now lies inside the 90% confidence interval of the models’ trend distribution. However, the majority of the models are still not able to reproduce the observed pattern of negative trends in the tropics extending into mid-latitudes. The spread in the trends is dominated by intermodel differences, while natural variability from SSTs and QBO is not decisive in explaining the negative mid-latitude trends. The role of the different ozone transport representations is also explored.

Speaker: Samuel Benito-Barca (Universidad Complutense de Madrid)

17:40 Break

Stratospheric (and total) ozone: Observations

19 The coherent set of total ozone and ozone profile climate data records based on a series of GOME-type nadir UVN satellite sensors

We present the coherent pair of the GOME-type Total Ozone Essential Climate Variable (GTO-ECV) and the novel GOME-type Ozone Profile Essential Climate Variable (GOP-ECV) data records. Both GTO-ECV and GOP-ECV cover more than two and a half decades starting in mid-1995, and both rely on measurements performed with an extended series of European nadir-viewing satellite sensors including GOME, SCIAMACHY, GOME-2, and OMI. On top of that, TROPOMI data has been ingested in the total ozone record. Ozone information from the individual instruments is harmonized and finally merged in order to generate a consistent long-term product with global coverage that is suitable for applications relevant to climate studies.
The first version of GOP-ECV has recently been developed in the framework of the European Space Agency’s Climate Change Initiative+ ozone project (Ozone_cci+), while the well-matured total ozone data set GTO-ECV is by now extended and released on a quasi-operational basis as part of the EU Copernicus Climate Changes Service (C3S) together with an internal DLR project. Both data records benefit from the common retrieval algorithms that are used to derive the total columns (GOME direct fitting version 4 algorithm) and the ozone profiles (Rutherford Appleton Laboratory retrieval scheme), respectively. Remaining inter-sensor deviations are minimized by means of a bias correction with respect to the reference sensor OMI. In case of the ozone profile record the approach comprises a follow-up step. The profiles are clustered using machine learning techniques, and for each class a Neural Network approach is used to compute the profiles’ Jacobians, which provide information about the altitude-dependent change of the partial columns due to a change in the total column. This facilitates a refined scaling of the profiles as a function of the total column from the GTO-ECV record. Thereby, full consistency between total ozone and ozone profile data records is achieved.
The monthly mean products are freely available and common applications include the estimation of (height-resolved) decadal trends in order to determine robust ozone recovery signals and the evaluation of Chemistry-Climate Model simulations.

Speaker: Melanie Coldewey-Egbers (German Aerospace Center)

20 Performance of NOAA S-NPP OMPS Nadir Instruments for Long-term Ozone Records

The design of the Ozone Mapping and Profiler Suite (OMPS) Nadir Mapper and Nadir Profiler includes a pair of solar diffusers. The working diffuser is used every two weeks and the reference diffuser is used once a year. Combined with a stable orbit -- fixed Equator crossing time -- these measurements have proven to provide a very good set of data for characterizing the changes in the S-NPP OMPS Nadir instruments over the last twelve years. This talks presents the results of this characterization as well as additional measurements and analysis to confirm the performance.

Speaker: Lawrence Flynn (NOAA)

21 Merged long-term datasets of ozone profiles developed in the ESA Climate Change Initiative

Creating homogenized long-term ozone datasets using profile data by limb-viewing measurements from European and ESA Third Party satellite Missions is one of the objectives of the ESA Climate Change Initiative (Ozone-CCI) project.
In the framework of Ozone-CCI, several datasets of ozone profiles are created. The datasets from individual instruments are collected in the user-friendly HARMonized dataset of OZone profiles (HARMOZ).
For trend analyses, two long-term merged datasets of ozone profiles have been created. One is the SAGE-CCI-OMPS+ climate data record of monthly zonal mean ozone profiles. This dataset covers the stratosphere and combines measurements by nine limb and occultation satellite instruments – SAGE II, OSIRIS, MIPAS, SCIAMACHY, GOMOS, ACE-FTS, OMPS-LP, POAM III, and SAGE III/ISS, from 1984 to present. Another dataset is the MErged GRIdded Dataset of Ozone Profiles (MEGRIDOP) with a resolved longitudinal structure, which covers the period from late 2001 to the present. MEGRIDOP is derived from data by OSIRIS, MIPAS, SCIAMACHY, GOMOS, MLS, and OMPS-LP; it contains monthly mean ozone profiles in the altitude range from 10 to 50 km in bins of 10° latitude x 20° longitude. SAGE-CCI-OMPS+ and MEGRIDOP have been actively used in various assessments of ozone trends, including their regional and seasonal dependence.
We are currently working on a new merged daily gap-free 1° x 1° dataset of stratospheric ozone profiles (HIRES-LIMB), which is created from ozone data by OSIRIS, MIPAS, SCIAMACHY, GOMOS, MLS, OMPS-LP, SAGE III/ISS, and ACE-FTS using data homogenization and kriging-type interpolation.
In the presentation, we will show the obtained results, including updated analyses of stratospheric ozone trends.

Speaker: Viktoria Sofieva (Finnish Meteorological Institute)

22 SWOOSH ozone updates, their implications for variability and trends, and preparing for the loss of the Aura Microwave Limb Sounder

The Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) database is a monthly mean merged data set of vertically resolved ozone and water vapor data from a subset of limb profiling instruments operating since the 1980s. In this presentation, we summarize recent updates and improvements to SWOOSH ozone data that were made as part of the current version 2.7. Changes include updated versions of existing data sets, new sources of data, and additional ancillary information for quantifying uncertainties. We also assess the impact on variability and trends due to the source data updates (e.g., Aura MLS v5.0) and inclusion of new satellite records to SWOOSH from ACE-FTS, SAGE III/ISS, and OMPS-Limb Profiler. Finally, we discuss plans to continue the SWOOSH record following the expected loss of Aura MLS in the coming years, and the potential impacts of this loss on the uncertainty of the SWOOSH merged record.

Speaker: Sean Davis (NOAA Earth System Research Laboratory)

23 Retrieval and merging of ozone profiles from SCIAMACHY and OMPS limb observations to study long-term trends

Observations in limb geometry from satellite platforms provide information with high spatial and temporal coverage and a good vertical resolution. Ozone profiles from SCIAMACHY (2002-2012) and OMPS-LP onboard Suomi-NPP (2012-present) have been retrieved at the University of Bremen using the same radiative transfer model, spectroscopic databases and a similar retrieval algorithm. Within the current CCI project, we have started the retrieval of OMPS-LP onboard NOAA-21, which was lunch at the end of 2022.

The SCIAMACHY and OMPS-LP data sets have been merged, to obtain a consistent time series of ozone global distributions. The final plan is to include in the merged data set also the observations from the sensor onboard NOAA-21. This will extend the data set into the 2030s, when also ALTIUS data are expected to be available.

For the merging, because of the short overlap of the two missions, measurements performed by the MLS instrument have been used as a transfer function, to provide a statistically significant bias estimate. Monthly latitude- and longitude-resolved time series of ozone profiles were calculated, exploiting the high spatial resolution of the data sets. We then use this merged data set to study long-term ozone changes: a multi-linear regression model was applied over the 2003-2023 period, including fit proxies to account for QBO, ENSO, solar forcing and stratospheric dynamics. We explore zonally averaged and longitudinally resolved trends.

Speaker: Carlo Arosio (Institute of Environmental Physics, University of Bremen)

24 Discussion user needs / requirements

Speakers: Michiel Van Weele (KNMI), Martin Dameris (DLR), Daan Hubert (BIRA-IASB)