Preprints
https://doi.org/10.5194/amt-2020-179
https://doi.org/10.5194/amt-2020-179

  14 Sep 2020

14 Sep 2020

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Estimation of the error covariance matrix for IASI radiances and its impact on ozone analyses

Mohammad El Aabaribaoune1, Emanuele Emili1, and Vincent Guidard2 Mohammad El Aabaribaoune et al.
  • 1CECI, Université de Toulouse, Cerfacs, CNRS, Toulouse, France
  • 2CNRM, Météo France, Toulouse, France

Abstract. In atmospheric chemistry retrievals and data assimilation systems, observation errors associated with satellite radiances are chosen empirically and generally treated as uncorrelated. In this work, we estimate inter-channel error covariances for the Infrared Atmospheric Sounding Interferometer (IASI) and evaluate their impact on ozone assimilation with the chemical transport model MOCAGE (MOdèle de Chime Atmospheric à Grand Echelle). The method used to calculate observation errors is a diagnostic based on the observation and analysis residual statistics already adopted in numerical weather prediction centers. We used a subset of 280 channels covering the spectral range between 980 and 1100 cm−1 to estimate the observation error covariance matrix. We computed hourly 3D-Var analyses and compared the resulting O3 fields against ozonesondes and the measurements provided by the Microwave Limb Sounder (MLS).

The results show significant differences between using the estimated error covariance matrix with respect to the empirical diagonal matrix employed in previous studies. The validation of the analyses against independent data reports a significant improvement especially in the tropical stratosphere. The computational cost has also been reduced when the estimated covariance is employed in the assimilation system.

Mohammad El Aabaribaoune et al.

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Mohammad El Aabaribaoune et al.

Mohammad El Aabaribaoune et al.

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Short summary
This work aims to use correlated IASI errors in the ozone band within a chemical transport model assimilation. The validation of the results against ozone observations from ozonesondes, MLS, and OMI instruments has shown an improvement of the ozone distribution. The computational time was also highly reduced. The surface sea temperature was also improved. The work aims to improve the quality of the ozone prediction which is important for air quality, climate, meteorological applications.