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Volume 132, Issue 616 p. 935-957
Research Article

The assimilation of AIRS radiance data at ECMWF

A. P. Mcnally

Corresponding Author

A. P. Mcnally

European Centre for Medium-Range Weather Forecasts, Reading, UK

European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, Berkshire RG2 9AX, UKSearch for more papers by this author
P. D. Watts

P. D. Watts

European Centre for Medium-Range Weather Forecasts, Reading, UK

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J. A. Smith

J. A. Smith

European Centre for Medium-Range Weather Forecasts, Reading, UK

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R. Engelen

R. Engelen

European Centre for Medium-Range Weather Forecasts, Reading, UK

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G. A. Kelly

G. A. Kelly

European Centre for Medium-Range Weather Forecasts, Reading, UK

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J. N. Thépaut

J. N. Thépaut

European Centre for Medium-Range Weather Forecasts, Reading, UK

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M. Matricardi

M. Matricardi

European Centre for Medium-Range Weather Forecasts, Reading, UK

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First published: 10 January 2007
Citations: 209

Abstract

The development of an assimilation system for radiance data from the Atmospheric InfraRed Sounder (AIRS) is described, in particular the identification of cloud contamination, bias correction and the characterization of errors in the measured radiances and radiative-transfer model. The results of assimilation experiments are presented. These show that a conservative use of AIRS radiance data (in a system already extensively observed with other satellite data) results in a small, but consistent, improvement in the quality of analyses and forecasts. Larger impacts of AIRS are found in hypothetical experiments that test the use of radiances from only a single sounding instrument. In these, the use of AIRS is found to outperform the use of data either from a single Advanced Microwave Sounding Unit-A (AMSU-A) or from a single High-resolution InfraRed Sounder (HIRS). In this hypothetical context the relative forecast performance of each sensor is found to correlate with the size and vertical scale of increments caused by the assimilation of the radiances. Copyright © 2006 Royal Meteorological Society.