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    Validation of GOMOS ozone precision estimates in the stratosphere

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    Authors
    Sofieva, V.F.
    Tamminen, J.
    Kyrölä, E.
    Laeng, A.
    Von Clarmann, T.
    Dalaudier, F.
    Hauchecorne, A.
    Bertaux, J.-L.
    Barrot, G.
    Blanot, L.
    Fussen, D.
    Vanhellemont, F.
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    Discipline
    Earth and related Environmental sciences
    Subject
    altitude
    climate modeling
    error analysis
    estimation method
    geophysical method
    ozone
    stratosphere
    uncertainty analysis
    Audience
    Scientific
    Date
    2014
    Metadata
    Show full item record
    Description
    Accurate information about uncertainties is required in nearly all data analyses, e.g., inter-comparisons, data assimilation, combined use. Validation of precision estimates (viz., the random component of estimated uncertainty) is important for remote sensing measurements, which provide the information about atmospheric parameters by solving an inverse problem. For the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument, this is a real challenge, due to the dependence of the signal-to-noise ratio (and thus precision estimates) on stellar properties, small number of self-collocated measurements, and growing noise as a function of time due to instrument aging. The estimated ozone uncertainties are small in the stratosphere for bright star occultations, which complicates validation of precision values, given the natural ozone variability. In this paper, we discuss different methods for geophysical validation of precision estimates and their applicability to GOMOS data. We propose a simple method for validation of GOMOS precision estimates for ozone in the stratosphere. This method is based on comparisons of differences in sample variance with differences in uncertainty estimates for measurements from different stars selected in a region of small natural variability. For GOMOS, the difference in sample variances for different stars at tangent altitudes 25–45 km is well explained by the difference in squared precisions, if the stars are not dim. Since this is observed for several stars, and since normalized χ2 is close to 1 for these occultations in the stratosphere, we conclude that the GOMOS precision estimates are realistic in occultations of sufficiently bright stars. For dim stars, errors are overestimated due to improper accounting of the dark charge correction uncertainty in the error budget. The proposed method can also be applied to stratospheric ozone data from other instruments, including multi-instrument analyses.
    Citation
    Sofieva, V.F.; Tamminen, J.; Kyrölä, E.; Laeng, A.; Von Clarmann, T.; Dalaudier, F.; Hauchecorne, A.; Bertaux, J.-L.; Barrot, G.; Blanot, L.; Fussen, D.; Vanhellemont, F. (2014). Validation of GOMOS ozone precision estimates in the stratosphere. , Atmospheric Measurement Techniques, Vol. 7, Issue 7, 2147-2158, DOI: 10.5194/amt-7-2147-2014.
    Identifiers
    uri: https://orfeo.belnet.be/handle/internal/2844
    doi: http://dx.doi.org/10.5194/amt-7-2147-2014
    scopus: 2-s2.0-84904365919
    Type
    Article
    Peer-Review
    Yes
    Language
    eng
    Links
    NewsHelpdeskBELSPO OA Policy

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