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The thermal infrared nadir spectra of IASI (Infrared Atmospheric Sounding Interferometer) are successfully used for retrievals of different atmospheric trace gas profiles. However, these retrievals offer generally reduced information about the lowermost tropospheric layer due to the lack of thermal contrast close to the surface. Spectra of scattered solar radiation observed in the near-infrared and/or shortwave infrared, for instance by TROPOMI (TROPOspheric Monitoring Instrument), offer higher sensitivity near the ground and are used for the retrieval of total-column-averaged mixing ratios of a variety of atmospheric trace gases. Here we present a method for the synergetic use of IASI profile and TROPOMI total-column level 2 retrieval products. Our method uses the output of the individual retrievals and consists of linear algebra a posteriori calculations (i.e. calculation after the individual retrievals). We show that this approach has strong theoretical similarities to applying the spectra of the different sensors together in a single retrieval procedure but with the substantial advantage of being applicable to data generated with different individual retrieval processors, of being very time efficient, and of directly benefiting from the high quality and most recent improvements of the individual retrieval processors. We demonstrate the method exemplarily for atmospheric methane (CH4). We perform a theoretical evaluation and show that the a posteriori combination method yields a total-column-averaged CH4 product (XCH4) that conserves the good sensitivity of the corresponding TROPOMI product while merging it with the high-quality upper troposphere–lower stratosphere (UTLS) CH4 partial-column information of the corresponding IASI product. As a consequence, the combined product offers additional sensitivity for the tropospheric CH4 partial column, which is not provided by the individual TROPOMI nor the individual IASI product. The theoretically predicted synergetic effect is verified by comparisons to CH4 reference data obtained from collocated XCH4 measurements at 14 globally distributed TCCON (Total Carbon Column Observing Network) stations, CH4 profile measurements made by 36 individual AirCore soundings, and tropospheric CH4 data derived from continuous ground-based in situ observations made at two nearby Global Atmospheric Watch (GAW) mountain stations. The comparisons clearly demonstrate that the combined product can reliably detect the actual variations of atmospheric XCH4, CH4 in the UTLS, and CH4 in the troposphere. A similar good reliability for the latter is not achievable by the individual TROPOMI and IASI products.

This work presents an evaluation of modeled atmospheric concentrations of O3, CO and CH4 from eleven models, as presented in the most recent assessment report by the Arctic Monitoring and Assessment Programme (AMAP) on short-lived climate forcers. AMAP is a scientific working group that was created to advise the Arctic Council on matters of Arctic pollution, climate change and the associated threats to local ecosystems and health. This framework is then used to inform policy and decision making through science-based assessments. The current report focuses on the impacts of Short-Lived Climate Forcers (SLCFs) on the Arctic climate, atmospheric chemistry, and human health. The report presents model-measurement comparisons to assess the performance of atmospheric modelling of SLCFs in the Arctic for the years 2008, 2009, 2014 and 2015. The 3-hourly mixing ratios of select SLCFs and related gases are modelled by CESM, CMAM, DEHM, EMEP-MSC-W, GEM-MACH, GEOS-Chem, MATCH, MATCH-SALSA, MRI-ESM2, UKESM1 and WRF-Chem. This presentation will compare these outputs to corresponding trace gas measurements from ground-based Fourier Transform Infrared (FTIR) spectrometers. The FTIR instruments used are part of the Network for the Detection of Atmospheric Composition Change (NDACC) Infrared Working Group, with emphasis on results from the Canadian High Arctic site at the Polar Environment Atmospheric Research Laboratory, in Eureka, Nunavut (80.05ºN, 86.42ºW). Analyses are performed by converting model outputs into smoothed partial columns of O3, CO and CH4, at the locations of the FTIR instruments. Comparisons include seasonal cycle analysis, percent differences and regression analysis.

International audience; The Arctic winter of 2019-2020 was characterized by an unusually persistent polar vortex and temperatures in the lower stratosphere that were consistently below the threshold for the formation of polar stratospheric clouds (PSCs). These conditions led to ozone loss that is comparable to the Antarctic ozone hole. Ground-based measurements from a suite of instruments at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Canada (80.05°N, 86.42°W) were used to investigate chemical ozone depletion. The vortex was located above Eureka longer than in any previous year in the 20-year dataset and lidar measurements provided evidence of polar stratospheric clouds (PSCs) above Eureka. Additionally, UV-visible zenith-sky Differential Optical Absorption Spectroscopy (DOAS) measurements showed record ozone loss in the 20-year dataset, evidence of denitrification along with the slowest increase of NO2 during spring, as well as enhanced reactive halogen species (OClO and BrO). Complementary measurements of HCl and ClONO2 (chlorine reservoir species) from a Fourier transform infrared (FTIR) spectrometer showed unusually low columns that were comparable to 2011, the previous year with significant chemical ozone depletion. Record low values of HNO3 in the FTIR dataset are in accordance with the evidence of PSCs and a denitrified atmosphere. Estimates of chemical ozone loss were derived using passive ozone from the SLIMCAT offline chemical transport model to account for dynamical contributions to the stratospheric ozone budget.

The Arctic Monitoring and Assessment Programme (AMAP) is an Arctic Council Working Group focused on studying the Arctic environment and the impacts of climate change, providing detailed reports to inform policy development. Previous AMAP reports analysed the impacts of black carbon, tropospheric O3 and CH4 on the Arctic. The 2021 AMAP report is focused on the impact of Short-Lived Climate Forcers (SLCFs) on the Arctic climate, atmospheric chemistry, and human health. SLCFs are gases and aerosols that influence Earth’s radiative budget, with lifetimes shorter than that of CO2. Advantageously, working towards mitigation on these timescales may enable expedited climatological and radiative impacts. The work presented here evaluates the modeled concentrations of O3, NO, NO2, CH4, and CO from eleven AMAP models: CESM, CMAM, DEHM, EMEP-MSC-W, GEM-MACH, GEOS-Chem, MATCH, MATCH-SALSA, MRI-ESM2, UKESM1 and WRF-Chem. The modelled mixing ratios are output at three-hour intervals for the years 2008, 2009, 2014 and 2015, on model-defined grid spacing and pressure levels. These outputs are assessed against corresponding trace gas measurements from ground-based Fourier Transform Infrared (FTIR) spectrometers. The FTIR instruments used in this analysis are at the University of Toronto Atmospheric Observatory, in Toronto, Ontario (43.66ºN, 79.40ºW) and the Polar Environment Atmospheric Research Laboratory, in Eureka, Nunavut (80.05ºN, 86.42ºW). These sites have been operating since 2001 and 2006, respectively, as part of the Network for the Detection of Atmospheric Change (NDACC) Infrared Working Group. The objective of these comparisons is to assess how well the models reflect the measured state of seasonal cycles in total columns, and when applicable, in partial columns. Given the scarcity of Arctic-based research stations, the PEARL FTIR provides a valuable long-term trace gas dataset for model evaluation, which has not yet been utilized by the AMAP SLCF expert group.

Peroxyacetyl nitrate (PAN) is the main tropospheric reservoir of NOx (NO þ NO2). Its lifetime can reach several months in the upper cold troposphere. This enables the long-range transport of NOx radicals, under the form of PAN, far from the regions of emission. The subsequent release of NOx through the PAN thermal decomposition leads to the efficient formation of tropospheric ozone (O3), with important consequences for tropospheric oxidative capacity and air quality. The chemical properties of PAN have stimulated the progressive development of remote-sensing products by the satellite community, and recent additions open the prospect for the production of decadal and near-global time series. These products will provide new constraints on the distribution and evolution of this key trace gas in the Earth's atmosphere, but they will also require reliable measurements for validation and characterization of performance. We present an approach that has been developed to retrieve PAN total columns from ground-based high-resolution solar absorption Fourier transform infrared (FTIR) spectra. This strategy is applied to observations recorded at remote FTIR stations of the Network for the Detection of Atmospheric Composition Change (NDACC). The resulting data sets are compared with total column time series derived from IASI (Infrared Atmospheric Sounding Interferometer) satellite observations and to a global chemical transport model. The results are discussed in terms of their overall consistency, mutual agreement, and seasonal cycles. Noticeable is the fact that the FTIR data point to substantial deficiencies in the global model simulation over high latitudes, a poorly sampled region, with an underestimation of the PAN columns during spring, at the peak of the seasonal cycle. Finally, we suggest avenues for development that should make it possible to limit intra- or intersite biases and extend the retrieval of PAN to other NDACC stations that are more affected by water vapor interferences., SCOPUS: ar.j, info:eu-repo/semantics/published

International audience; This paper reports on consolidated ground-based validation results of the atmospheric NO2 data produced operationally since April 2018 by the TROPOMI instrument on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5p) satellite. Tropospheric, stratospheric, and total NO2 column data from S5p are compared to correlative measurements collected from, respectively, 19 Multi-Axis DOAS (MAX-DOAS), 26 NDACC Zenith-Scattered-Light DOAS (ZSL-DOAS), and 25 PGN/Pandora instruments distributed globally. The validation methodology gives special care to minimizing mismatch errors due to imperfect spatio-temporal co-location of the satellite and correlative data, e.g., by using tailored observation operators to account for differences in smoothing and in sampling of atmospheric structures and variability, and photochemical modelling to reduce diurnal cycle effects. Compared to the ground-based measurements, S5p data show, on an average: (i) a negative bias for the tropospheric column data, of typically −23 to −37 % in clean to slightly polluted conditions, but reaching values as high as −51 % over highly polluted areas; (ii) a slight negative bias for the stratospheric column data, of about −0.2 Pmolec/cm2, i.e. approx. −2 % in summer to −15 % in winter; and (iii) a bias ranging from zero to −50 % for the total column data, found to depend on the amplitude of the total NO2 column, with small to slightly positive bias values for columns below 6 Pmolec/cm2 and negative values above. The dispersion between S5p and correlative measurements contains mostly random components, which remain within mission requirements for the stratospheric column data (0.5 Pmolec/cm2), but exceed those for the tropospheric column data (0.7 Pmolec/cm2). While a part of the biases and dispersion may be due to representativeness differences, it is known that errors in the S5p tropospheric columns exist due to shortcomings in the (horizontally coarse) a-priori profile representation in the TM5-MP chemistry transport model used in the S5p retrieval, and to a lesser extent, to the treatment of cloud effects. Although considerable differences (up to 2 Pmolec/cm2 and more) are observed at single ground-pixel level, the near-real-time (NRTI) and off-line (OFFL) versions of the S5p NO2 operational data processor provide similar NO2 column values and validation results when globally averaged, with the NRTI values being on average 0.79 % larger than the OFFL values.

International audience; The amplitude of ozone depletion in the Arctic is monitored every year since 1994 by comparison between totalozone measurements of SAOZ / NDACC UV-Vis spectrometers deployed in the Arctic and 3-D chemical transportmodel simulations in which ozone is considered as a passive tracer.When SAOZ measurements are missing for various reasons, lack of sunlight, station closed or instrumentfailure, they are replaced by IASI Metop-A or IASI Metop-B overpasses above the station. These measurements inthe thermal Infrared are available all year around, at all latitudes even in the polar night. IASI data have been com-pared to SAOZ and to 3-D CTM REPROBUS and the agreement is better than 3% at the latitude of the polar circle.The method allows determining the evolution of the daily rate of the ozone destruction and the amplitudeof the cumulative loss at the end of the winter. The amplitude of the destruction varies between 0-10% in relativelywarm and short vortex duration years to 25-39% in colder and longer ones.However, as shown by the unprecedented depletion of 39% in 2010/11, the loss is not only dependent onthe extension of the vortex in spring, but also on its strength limiting its re-noxification by import of nitrogenoxide species from the outside, as reported by the rapid increase of total NO2columns measured by the SAOZinstruments.Shown in this presentation will be the evolution of ozone loss and re-noxification in the Arctic during thewinter 2018/19 compared to that of previous winters.Compared to observed SAOZ/IASI O3loss, REPROBUS and SLIMCAT CTM simulations are showingsimilar losses, however the agreement may vary from one year to the other, depending on the assumptions ofvortex strength and isolation. The comparison between ozone loss amplitudes and ozone loss rates, seen each yearsince 1994 by SAOZ and the two CTM simulations will be followed by a discussion of possible causes in theirvariable amplitude

International audience; From August 17-22, 2017, simultaneous enhancements of ammonia (NH3), carbon monoxide (CO), hydrogen cyanide (HCN) and ethane (C2H6) were detected from ground-based solar absorption Fourier-transform infrared (FTIR) spectroscopic measurements at two high-Arctic sites: Eureka, Nunavut (80.05N, 86.42W) and Thule, Greenland (76.53N, 68.74W). These enhancements were attributed to wildfires in British Columbia and the Northwest Territories using FLEXPART back-trajectories and fire locations from MODIS and found to be the greatest observed enhancements in more than a decade of measurements at Eureka (2006-present) and Thule (1999-present). Observations of gas-phase NH3 from these wildfires illustrates that NH3 may undergo long-range transport and therefore wildfires may be a considerable source of NH3 in the summertime high-Arctic. However, the mechanisms leading to the long-range transport of wildfire emissions of NH3 and its potential impacts on the biosphere, air quality and climate of the high-Arctic are not well understood.In this study, enhancement ratios of NH3, HCN and C2H6 with respect to CO are calculated for fire-affected measurements at Eureka and Thule. The enhancement ratios of NH3, HCN and C2H6 are found to be different between sites and are observed to be strongly dependent on the time of measurement, which suggests that transport patterns of the smoke plume and differences in burning phase may have a strong influence on the measured concentrations of NH3. To further investigate these differences, satellite observations of NH3 and CO from the Infrared Atmospheric Sounding Instrument (IASI) are used to examine the spatial and temporal variabilities of NH3 during transport. Comparisons of IASI to high-resolution (0.25 x 0.3125) GEOS-Chem model results using Global Fire Assimilation System (GFAS) biomass burning emissions are also performed to evaluate the emission inventories and investigate the physical and chemical properties influencing the long-range transport of NH3 to the high-Arctic. Comparisons of GEOS-Chem model runs with and without seabird NH3 emissions show that wildfires are a considerable source of NH3 in the Arctic, leading to widespread enhanced surface NH3 concentrations in the Arctic, while seabird NH3 emissions results in local NH3 enhancements near the seabird colonies. These results indicate wildfire NH3 may be an important episodic source of NH3 in the Arctic in addition to the local seabird source.

International audience; Transport of biomass burning emissions into the Arctic can cause episodic enhancements of multiple trace gas species. We present a multi-year time series of the total columns of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) measured using Fourier Transform Infrared (FTIR) solar absorption spectroscopy at six high-latitude sites: Eureka, Nunavut; Ny Alesund, Norway; Thule, Greenland; Kiruna, Sweden; Poker Flat, Alaska; and St. Petersburg, Russia, and at three mid-latitude sites; Zugspitze, Germany; Jungfraujoch, Switzerland; and Toronto, Ontario. For each site, the inter-annual trends and seasonal variabilities of the CO total column time series are determined and enhancements above ambient levels are used to identify possible wildfire pollution events. Correlations of HCN and C2H6 with CO, back-trajectories from HYSPLIT and FLEXPART, and fire locations from the Moderate Resolution Spectroradiometer (MODIS) confirm the detections and identify the source regions. The GEOS-Chem chemical transport model is run in tagged mode to determine the relative contributions to the observed enhancements from continental-scale biomass burning source regions.Exceptional emissions of CO, HCN, C2H6, and ammonia (NH3) from the 2017 North American wildfires were measured at Eureka and Thule, indicating that wildfires may be a major source of NH3 in the summertime high Arctic. The enhancement ratios of the long- lived species HCN and C2H6 are found to be comparable between sites, but for NH3, the enhancement ratios are strongly dependent on the transport patterns of the smoke plumes. Satellite measurements of NH3 from the Infrared Atmospheric Sounding Instrument (IASI) and Cross-track Infrared Sounder (CrIS) are used to examine the spatial and temporal variabilities of NH3. Comparisons to a high-resolution (0.25° x 0.3125°) nested run of GEOS-Chem using emissions from the Global Fire Assimilation System (GFAS) are performed to evaluate the emission inventories and assess the long-range transport of NH3 to the high Arctic.

International audience; We present a multi-year time series of the total columns of carbon monoxide (CO), hydrogen cyanide (HCN) and ethane (C2H6) obtained by Fourier Transform Infrared (FTIR) spectrometer measurements at nine sites. Six are high-latitude sites: Eureka, Nunavut; Ny Alesund, Norway; Thule, Greenland; Kiruna, Sweden; Poker Flat, Alaska and St. Petersburg, Russia and three are mid-latitude sites; Zugspitze, Germany; Jungfraujoch, Switzerland and Toronto, Ontario. For each site, the inter-annual trends and seasonal variabilities of the CO total column time series are accounted for, allowing ambient concentrations to be determined. Enhancements above ambient levels are then used to identify possible wildfire pollution events. Since the abundance of each trace gas species emitted in a wildfire event is specific to the type of vegetation burned and the burning phase, correlations of CO to the other long-lived wildfire tracers HCN and C2H6 allow for further confirmation of the detection of wildfire pollution. Back-trajectories from HYSPLIT and FLEXPART as well as fire detections from the Moderate Resolution Spectroradiometer (MODIS) allow the source regions of the detected enhancements to be determined while satellite observations of CO from the Measurement of Pollution in the Troposphere (MOPITT) and Infrared Atmospheric Sounding Interferometer (IASI) instruments can be used to track the transport of the smoke plume. Differences in travel times between sites allows ageing of biomass burning plumes to be determined, providing a means to infer the physical and chemical processes affecting the loss of each species during transport. Comparisons of ground-based FTIR measurements to GEOS-Chem chemical transport model results are used to investigate these processes, evaluate wildfire emission inventories and infer the influence of wildfire emissions on the Arctic.

International audience; The amplitude of ozone depletion in the Arctic is monitored every year since 1994 by comparison between total ozone measurements of eight SAOZ / NDACC UV-Vis spectrometers deployed in the Arctic and 3-D chemical transport model simulations in which ozone is considered as a passive tracer. The method allows determining the evolution of the daily rate of the ozone destruction and the amplitude of the cumulative loss at the end of the winter. The amplitude of the destruction varies between 0-10% in relatively warm and short vortex duration years to 25-39% in colder and longer ones. However, as shown by the unprecedented depletion of 39% in 2010/11, the loss is not only dependent on the extension of the vortex in spring, but also on its strength limiting its re-noxification by import of nitrogen oxide species from the outside, as reported by the total NO2 columns measured by the SAOZ instruments. Shown in this presentation will be the evolution of ozone loss and re-noxification in the Arctic during the winter 2016/17 compared to that of previous winters. Compared to observed SAOZ O3 loss, REPROBUS and SLIMCAT CTM simulations are showing differences varying between 0% and 7% depending on the assumptions of vortex strength and isolation. The comparison between ozone loss amplitudes and ozone loss rates, seen each year since 1994 by SAOZ and the two CTM simulations will be followed by a discussion of possible causes in their variable amplitude.

International audience; NASA's Orbiting Carbon Observatory-2 (OCO-2) has been measuring carbon dioxide column-averaged dry-air mole fraction, XCO2, in the Earth's atmosphere for over 2 years. In this paper, we describe the comparisons between the first major release of the OCO-2 retrieval algorithm (B7r) and XCO2 from OCO-2's primary ground-based validation network: the Total Carbon Column Observing Network (TCCON). The OCO-2 XCO2 retrievals, after filtering and bias correction, agree well when aggregated around and coincident with TCCON data in nadir, glint, and target observation modes, with absolute median differences less than 0.4 ppm and RMS differences less than 1.5 ppm. After bias correction, residual biases remain. These biases appear to depend on latitude, surface properties, and scattering by aerosols. It is thus crucial to continue measurement comparisons with TCCON to monitor and evaluate the OCO-2 XCO2 data quality throughout its mission.

International audience; The amplitude of ozone depletion in the Arctic is monitored every year since 1994 by comparison between total ozone measurements of eight SAOZ/NDACC UV-Vis spectrometers deployed in the Arctic and 3-D Chemical Transport Model (CTM) simulations in which ozone is considered as a passive tracer. The method allows determining the evolution of the daily rate ozone destruction and the amplitude of the cumulative loss at the end of the winter

International audience; We report observations of NO nightglow with the SPICAM experiment on board the Mars Express (MEx) spacecraft. NO molecules emit a UV photon when N and O atoms (produced at high altitude in the thermosphere) recombine. Therefore, this emission is a tracer of the atmospheric dynamics in the in the lower thermosphere where O and N atoms are produced, and below, in the altitude region 50-100 km where the emission is detected. A new retrieval method has been developed to analyse the measurements from this instrument in the stellar occultation mode without slit, and retrieve the absolute brightness of the emission. We present the results from the processing of more than 2000 orbits, providing the first global latitude-season distribution of the emission, established over three Martian years. The results are globally consistent with previously available measurements of dedicated limb nightglow obtained during the first Martian year of MEx (MY27). We compared the ensemble of both data sets withthe predictions of the LMD-MGCM, with the addition of the full chemistry of N atoms. We find an overall agreement between the observed and modelled airglow intensities, but discrepancies are also found. The frequency and magnitude of the NO airglowobservations show important asymmetries between the Northern and the Southern hemispheres. There is no detection of emission near the poles during equinox conditions, while the model predicts that it should be most intense because of a circulation with two descending branches at the poles.

The goal of this study is to determine how H2O and HDO measurements in water vapor can be used to detect and diagnose biases in the representation of processes controlling tropospheric humidity in atmospheric general circulation models (GCMs). We analyze a large number of isotopic data sets (four satellite, sixteen ground-based remote-sensing, five surface in situ and three aircraft data sets) that are sensitive to different altitudes throughout the free troposphere. Despite significant differences between data sets, we identify some observed HDO/H2O characteristics that are robust across data sets and that can be used to evaluate models. We evaluate the isotopic GCM LMDZ, accounting for the effects of spatiotemporal sampling and instrument sensitivity. We find that LMDZ reproduces the spatial patterns in the lower and mid troposphere remarkably well. However, it underestimates the amplitude of seasonal variations in isotopic composition at all levels in the subtropics and in midlatitudes, and this bias is consistent across all data sets. LMDZ also underestimates the observed meridional isotopic gradient and the contrast between dry and convective tropical regions compared to satellite data sets. Comparison with six other isotope-enabled GCMs from the SWING2 project shows that biases exhibited by LMDZ are common to all models. The SWING2 GCMs show a very large spread in isotopic behavior that is not obviously related to that of humidity, suggesting water vapor isotopic measurements could be used to expose model shortcomings. In a companion paper, the isotopic differences between models are interpreted in terms of biases in the representation of processes controlling humidity. TCCON measurements at Wollongong and Darwin are supported The mid-infrared FTIR retrievals have been performed in the framework of the project MUSICA (http://www. imk-asf.kit.edu/english/musica), which is funded by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement 256961. This work was supported by NASA Energy and Water-cycle Study (07-NEWS07-0020) and NASA Atmospheric Composition program (NNX08AR23G). We thank all reviewers for their fruitful comments.

International audience; We use a three-dimensional atmospheric model to study the airglow emissions from molecular oxygen in the Martian atmosphere. We estimate the O2 Herzberg I and II, the Chamberlain, and the Infrared Atmospheric band emissions from different sets of kinetic parameters available in the literature. As expected, the enhanced production of atomic oxygen during daytime leads to stronger emissions at 12 hour local time than at 00 hour local time. Nevertheless, at night, the strongest emissions are found in the subtropics and around the terminator where the photochemistry of atomic oxygen is more active. Among the simulated emissions, we find that the Infrared Atmospheric emission is the most intense, as expected, and has maximum intensity reaching a few megarayleighs over the poles during the equinoctial seasons, and an average intensity over the equatorial latitudes of 50 kilorayleighs. We investigate the impact of different levels of water and dust content on airglow and we observe that the airglow structure is modulated by variations in the background atmospheric conditions. Moreover, comparisons of the emission with observations from instruments on board Mars orbiters and with ground-based measurements from Earth allow us to validate the consistency of our airglow model. Finally, we observe that the emission profiles from all band systems show structures; a double-layer profile is very frequent, and is representative of the vertical distribution of the current measurements of O2 nightglow. This paper emphasizes the advantage of using three-dimensional global circulation models for the diagnostic of O2 photochemistry in CO2-dominated atmospheres.

International audience; Launched on March 1st, 2002 on-board the polar orbiting ENVISAT satellite, the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) mid-infrared FT spectrometer performed limb emission measurements at high spectral resolution (0.025 cm-1) for about two years. Due to too frequent anomalies observed in the Interferometer Drive Unit, operations were suspended in March 2004 and finally resumed, in January 2005, in a new reduced resolution (0.01 cm-1) mode. Operational level 2 products for the complete set of target species (i.e. geo-located vertical profiles of Temperature and volume mixing ratio of H2O, O3, HNO3, CH4, N2O and NO2) were obtained during MIPAS full resolution mission, from July 6th, 2002 to March 26th, 2004. In this timeframe, several research groups involved in the ESA programme for geophysical validation of the ENVISAT Atmospheric Chemistry Instruments and in related national activities, carried out a variety of ground-based observations (ozone soundings, FT-IR, microwave radiometers, lidars) of the ozone vertical distribution and of in situ and remote sensing measurements from high altitude platforms, in close spatial and temporal coincidence with MIPAS overpasses. As a result, a comprehensive database of correlative measurements became available for a first inter-comparison of MIPAS O3 profiles with various datasets from coincident observations. A co-ordinated effort was finally conducted to bring together the individual outcomes of the different validation activities and to better exploit their redundant and complementary information. In the latter phase, special attention was paid to rigorous selection and use of correlative data, by adopting stringent coincidence criteria and by giving top priority to homogeneous and reliable validation data sources. Here we report a brief overview of the validation of MIPAS O3 data versions 4.61 and 4.62 (fully equivalent for validation purposes) by ground-based, balloon/aircraft and satellite measurements and discuss in details the resulting quality assessment of MIPAS O3 retrieved profiles.

International audience