Atmos. Chem. Phys. Discuss., 10, 22725-22764, 2010
© Author(s) 2010. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The use of IASI data to identify systematic errors in the ECMWF temperature analysis in the upper stratosphere
G. Masiello1, M. Matricardi2, and C. Serio1
1DIFA, University of Basilicata, Potenza, Italy
2ECMWF, Shinfield Park, Reading, UK

Abstract. Since data from the Infrared Atmospheric Sounding Interferometer (IASI) became available in 2007, a number of papers have appeared in the literature which have reported relatively large discrepancies between IASI spectra and forward calculations in the centre of the CO2 Q-branch at 667 cm−1. In this paper we argue that these discrepancies are primarily due to errors in the temperature profiles used in the forward calculations. In particular, we have used temperature profiles from the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis to demonstrate that for the case study considered in this paper, these profiles are affected by systematic errors of the order of 7–10 K at the level of the stratopause. To derive the magnitude and the spatial location of the systematic errors in the temperature profile, we have carried out forward/inverse calculations for a number of clear-sky, daytime, IASI tropical soundings over the sea. The forward calculations have been performed using atmospheric state vectors which have been obtained either from the direct inversion of the IASI radiances or from space-time co-located profiles derived from radiosonde observations and from the ECMWF analysis. To rule out any effect due to the accuracy of the forward model, we have performed the forward calculations using two independent models. The sensitivity of the temperature biases to the variability of the CO2 profile and to spectroscopy errors has also been studied.

Citation: Masiello, G., Matricardi, M., and Serio, C.: The use of IASI data to identify systematic errors in the ECMWF temperature analysis in the upper stratosphere, Atmos. Chem. Phys. Discuss., 10, 22725-22764, doi:10.5194/acpd-10-22725-2010, 2010.
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