Sensitivity tests for an ensemble Kalman filter for aerosol assimilation

N. A.J. Schutgens, T. Miyoshi, T. Takemura, T. Nakajima

    Research output: Contribution to journalArticle

    24 Citations (Scopus)

    Abstract

    We present sensitivity tests for a global aerosol assimilation system utilizing AERONET observations of AOT (aerosol optical thickness) and AAE (aerosol Ångstr̈om exponent). The assimilation system employs an ensemble Kalman filter which requires tuning of three numerical parameters: ensemble size ens, local patch size patch and inflation factor ρ. In addition, experiments are performed to test the impact of various implementations of the system. For instance, we use a different prescription of the emission ensemble or a different combination of observations.

    The various experiments are compared against one-another and against independent AERONET and MODIS/Aqua observations. The assimilation leads to significant improvements in modelled AOT and AAE fields. Moreover remaining errors are mostly random while they are mostly systematic for an experiment without assimilation. In addition, these results do not depend much on our parameter or design choices. It appears that the value of the local patch size has by far the biggest impact on the assimilation, which has sufficiently converged for an ensemble size of en sCombining double low line20. Assimilating AOT and AAE is clearly preferential to assimilating AOT at two different wavelengths. In contrast, initial conditions or a description of aerosol beyond two modes (coarse and fine) have only little effect. We also discuss the use of the ensemble spread as an error estimate of the analysed AOT and AAE fields. We show that a very common prescription of the emission ensemble (independent random modification in each grid cell) can have trouble generating sufficient spread in the forecast ensemble.

    Original languageEnglish
    Pages (from-to)6583-6600
    Number of pages18
    JournalAtmospheric Chemistry and Physics
    Volume10
    Issue number14
    DOIs
    Publication statusPublished - Jul 23 2010

    Fingerprint

    Kalman filter
    aerosol
    patch size
    assimilation
    test
    experiment
    inflation
    MODIS
    wavelength

    All Science Journal Classification (ASJC) codes

    • Atmospheric Science

    Cite this

    Sensitivity tests for an ensemble Kalman filter for aerosol assimilation. / Schutgens, N. A.J.; Miyoshi, T.; Takemura, T.; Nakajima, T.

    In: Atmospheric Chemistry and Physics, Vol. 10, No. 14, 23.07.2010, p. 6583-6600.

    Research output: Contribution to journalArticle

    Schutgens, N. A.J. ; Miyoshi, T. ; Takemura, T. ; Nakajima, T. / Sensitivity tests for an ensemble Kalman filter for aerosol assimilation. In: Atmospheric Chemistry and Physics. 2010 ; Vol. 10, No. 14. pp. 6583-6600.
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