Evaluating a new homogeneous total ozone climate data record from GOME/ERS‐2, SCIAMACHY/Envisat, and GOME‐2/MetOp‐A

Koukouli, M. E.; Lerot, Christophe; Granville, J.; Goutail, Florence; Lambert, Jean-Christopher; Pommereau, Jean‐Pierre; Balis, D.; Zyrichidou, I.; Roozendaël, Michel Van; Coldewey‐Egbers, Melanie; Loyola, Diego; Labow, G. J.; Frith, S. M.; Spurr, Robert; Zehner, Claus

doi:10.1002/2015jd023699

Cited by 39 publications

(45 citation statements)

References 56 publications

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“…To assess the quality of these new products, extensive validation work was carried out by comparison with co-located ground-based reference measurements, obtained with direct-sun instruments such as Dobsons and Brewers, and with ZSL-DOAS instruments such as the Système d'Analyse par Observation Zénithale (SAOZ). This validation work is already published, Koukouli et al (2015), and it is not the purpose of the present paper to reproduce these results.…”

Section: Total Ozone Column Validation As a Topical Case Studymentioning

confidence: 43%

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Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

et al. 2015

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Abstract. Comparisons with ground-based correlative measurements constitute a key component in the validation of satellite data on atmospheric composition. The error budget of these comparisons contains not only the measurement errors but also several terms related to differences in sampling and smoothing of the inhomogeneous and variable atmospheric field. A versatile system for Observing System Simulation Experiments (OSSEs), named OSSSMOSE, is used here to quantify these terms. Based on the application of pragmatic observation operators onto high-resolution atmospheric fields, it allows a simulation of each individual measurement, and consequently, also of the differences to be expected from spatial and temporal field variations between both measurements making up a comparison pair. As a topical case study, the system is used to evaluate the error budget of total ozone column (TOC) comparisons between GOME-type direct fitting (GODFITv3) satellite retrievals from GOME/ERS2, SCIAMACHY/Envisat, and GOME-2/MetOp-A, and ground-based direct-sun and zenith-sky reference measurements such as those from Dobsons, Brewers, and zenith-scattered light (ZSL-)DOAS instruments, respectively. In particular, the focus is placed on the GODFITv3 reprocessed GOME-2A data record vs. the ground-based instruments contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). The simulations are found to reproduce the actual measurements almost to within the measurement uncertainties, confirming that the OSSE approach and its technical implementation are appropriate. This work reveals that many features of the comparison spread and median difference can be understood as due to metrological differences, even when using strict colocation criteria. In particular, sampling difference errors exceed measurement uncertainties regularly at most mid-and high-latitude stations, with values up to 10 % and more in extreme cases. Smoothing difference errors only play a role in the comparisons with ZSL-DOAS instruments at high latitudes, especially in the presence of a polar vortex due to the strong TOC gradient it induces. At tropical latitudes, where TOC variability is lower, both types of errors remain below about 1 % and consequently do not contribute significantly to the comparison error budget. The detailed analysis of the comparison results, including the metrological errors, suggests that the published random measurement uncertainties for GODFITv3 reprocessed satellite data are potentially overestimated, and adjustments are proposed here. This successful application of the OSSSMOSE system to close for the first time the error budget of TOC comparisons, bodes well for potential future applications, which are briefly touched upon.

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Section: Total Ozone Column Validation As a Topical Case Studymentioning

confidence: 43%

“…The TOC validation work performed within ESA's O 3 CCI and reported by Koukouli et al (2015) represents a topical application of such comparisons. Consequently, the research presented here is based on the same co-located data sets, or subsets thereof.…”

Section: Satellite and Ground-based Data: Origin Uncertainties And mentioning

confidence: 99%

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

et al. 2015

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“…Both absolute agreement and long-term stability are excellent with respect to the ground reference for almost all latitudes Koukouli et al, 2015) and well within the Global Climate Observing System (GCOS) target requirements (Mason and Simmons, 2011). A small number of outliers were found mostly related to sampling differences that could not be completely eradicated (see Figs.…”

Section: Gtomentioning

confidence: 99%

Total ozone trends from 1979 to 2016 derived from five merged observational datasets – the emergence into ozone recovery

et al. 2018

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“…In this study, two different TOC products from GOME-2/MetOp-A (GOME-2A) were used for the validation of IASI TOCs from FORLI: (1) GOME-2 TOC data that have been generated as part of the EU-METSAT Ozone Monitoring and Atmospheric Composition Satellite Application Facility (O3M SAF) with the GOME Data Processor (GDP) operational algorithm, which is an iterative differential optical absorption spectroscopy (DOAS) air-mass factor fitting algorithm and uses the ozone absorption features in Huggins band between 325 and 335 nm Hao et al, 2014); and (2) GOME-2 TOC data generated as part of the ESA Ozone Climate Change Initiative (O3-CCI) with the GOME-type Direct Fitting (GODFIT) algorithm Lerot et al, 2014) and publicly available at http://www.esa-ozone-cci.org. The GOME-2 O3M SAF and CCI TOC products have been validated using ground-based measurements (e.g Hao et al, 2014;Koukouli et al, 2012Koukouli et al, , 2015Loyola et al, 2011), which has shown an overall agreement within 1 % in most situations. Note that in this section (and in Sect.…”

Section: Comparison With Gome-2 Retrievalsmentioning

confidence: 99%

“…The Dobson and Brewer stations considered in this paper and the criteria used for the selection of the stations have been extensively used in a series of validation papers of satellite total O 3 measurements (e.g., Weber et al, 2005;Balis et al, 2007a, b;Koukouli et al, , 2015. For the comparisons with IASI TOCs from FORLI, only direct sun observations are used as those are the most reliable for both the Dobson and the Brewer spectrophotometers, the latter offering an accuracy of about 1 % at moderate solar zenith angles (e.g., Kerr, 2002).…”

Section: Comparison With Ground-based Spectrophotometer Datamentioning

confidence: 99%

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

et al. 2016

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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 30 km) shows that on average IASI with FORLI processing underestimates O 3 by ∼ 5-15 % in the troposphere while it overestimates O 3 by ∼ 10-40 % in the stratosphere, depending on the latitude. The largest relative differences are found in the tropPublished by Copernicus Publications on behalf of the European Geosciences Union. 4328A. Boynard et al.: Seven years of IASI ozone retrievals from FORLI ical tropopause region; this can be explained by the low O 3 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 to cover a larger spectral range using the latest HITRAN spectroscopic database (HITRAN 2012) and implementing numerical corrections. The assessment of the new O 3 product with the same set of observations as that used for the validation exercise shows a correction of ∼ 4 % for the TOC positive bias when compared to the UV ground-based and satellite observations, bringing the overall global comparison to ∼ 1-2 % on average. This improvement is mainly associated with a decrease in the retrieved O 3 concentration in the middle stratosphere (above 30 hPa/25 km) as shown by the comparison with ozonesonde data.

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Evaluating a new homogeneous total ozone climate data record from GOME/ERS‐2, SCIAMACHY/Envisat, and GOME‐2/MetOp‐A

Cited by 39 publications

References 56 publications

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

Total ozone trends from 1979 to 2016 derived from five merged observational datasets – the emergence into ozone recovery

Seven years of IASI ozone retrievals from FORLI: validation with independent total column and vertical profile measurements

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