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    The ASSET intercomparison of ozone analyses: Method and first results

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    Authors
    Geer, A.J.
    Lahoz, W.A.
    Bekki, S.
    Bormann, N.
    Errera, Q.
    Eskes, H.J.
    Fonteyn, D.
    Jackson, D.R.
    Juckes, M.N.
    Massart, S.
    Peuch, V.-H.
    Rharmili, S.
    Segers, A.
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    Discipline
    Earth and related Environmental sciences
    Subject
    atmospheric modeling
    atmospheric transport
    atomic absorption spectroscopy
    data assimilation
    error analysis
    general circulation model
    interferometer
    Kalman filter
    mesosphere
    ozone
    ozone depletion
    ozonesonde
    performance assessment
    stratosphere
    troposphere
    Audience
    Scientific
    Date
    2006
    Metadata
    Show full item record
    Description
    This paper aims to summarise the current performance of ozone data assimilation (DA) systems, to show where they can be improved, and to quantify their errors. It examines 11 sets of ozone analyses from 7 different DA systems. Two are numerical weather prediction (NWP) systems based on general circulation models (GCMs); the other five use chemistry transport models (CTMs). The systems examined contain either linearised or detailed ozone chemistry, or no chemistry at all. In most analyses, MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) ozone data are assimilated; two assimilate SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) observations instead. Analyses are compared to independent ozone observations covering the troposphere, stratosphere and lower mesosphere during the period July to November 2003. Biases and standard deviations are largest, and show the largest divergence between systems, in the troposphere, in the upper-troposphere/lower-stratosphere, in the upperstratosphere and mesosphere, and the Antarctic ozone hole region. However, in any particular area, apart from the troposphere, at least one system can be found that agrees well with independent data. In general, none of the differences can be linked to the assimilation technique (Kalman filter, three or four dimensional variational methods, direct inversion) or the system (CTM or NWP system). Where results diverge, a main explanation is the way ozone is modelled. It is important to correctly model transport at the tropical tropopause, to avoid positive biases and excessive structure in the ozone field. In the southern hemisphere ozone hole, only the analyses which correctly model heterogeneous ozone depletion are able to reproduce the near-complete ozone destruction over the pole. In the upper-stratosphere and mesosphere (above 5 hPa), some ozone photochemistry schemes caused large but easily remedied biases. The diurnal cycle of ozone in the mesosphere is not captured, except by the one system that includes a detailed treatment of mesospheric chemistry. These results indicate that when good observations are available for assimilation, the first priority for improving ozone DA systems is to improve the models. The analyses benefit strongly from the good quality of the MIPAS ozone observations. Using the analyses as a transfer standard, it is seen that MIPAS is ∼5% higher than HALOE (Halogen Occultation Experiment) in the mid and upper stratosphere and mesosphere (above 30hPa), and of order 10% higher than ozonesonde and HALOE in the lower stratosphere (100hPa to 30hPa). Analyses based on SCIAMACHY total column are almost as good as the MIPAS analyses; analyses based on SCIAMACHY limb profiles are worse in some areas, due to problems in the SCIAMACHY retrievals.
    Citation
    Geer, A.J.; Lahoz, W.A.; Bekki, S.; Bormann, N.; Errera, Q.; Eskes, H.J.; Fonteyn, D.; Jackson, D.R.; Juckes, M.N.; Massart, S.; Peuch, V.-H.; Rharmili, S.; Segers, A. (2006). The ASSET intercomparison of ozone analyses: Method and first results. , Atmospheric Chemistry and Physics, Vol. 6, Issue 12, 5445-5474, DOI: 10.5194/acp-6-5445-2006.
    Identifiers
    uri: https://orfeo.belnet.be/handle/internal/4485
    doi: http://dx.doi.org/10.5194/acp-6-5445-2006
    scopus: 2-s2.0-33749174946
    Type
    Article
    Peer-Review
    Yes
    Language
    eng
    Links
    NewsHelpdeskBELSPO OA Policy

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