ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-7971-2009 IASI temperature and water vapor retrievals – error assessment and validation Pougatchev N. 1 August T. 2 Calbet X. 2 Hultberg T. 2 Oduleye O. 2 Schlüssel P. 2 Stiller B. 3 Germain K. S. 4 Bingham G. 1 Space Dynamics Laboratory, North Logan, Utah, USA EUMETSAT, Darmstadt, Germany German Meteorological Service, Meteorological Observatory, Lindenberg, Germany Integrated Project Office, Silver Spring, Maryland, USA 25 03 2009 9 2 7971 7989 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/9/7971/2009/acpd-9-7971-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/7971/2009/acpd-9-7971-2009.pdf

The METOP-A satellite Infrared Atmospheric Sounding Interferometer (IASI) Level 2 products comprise retrievals of vertical profiles of temperature and water vapor. The error covariance matrices and biases of the most recent version (4.3.1) of the L2 data were assessed, and the assessment was validated using radiosonde data for reference. The radiosonde data set includes dedicated and synoptic time launches at the Lindenberg station in Germany. For optimal validation, the linear statistical Validation Assessment Model (VAM) was used. The VAM uses radiosonde profiles as input and provides optimal estimate of the nominal IASI retrieval by utilizing IASI averaging kernels and statistical characteristics of the ensembles of the reference radiosondes. For temperature temperatures above 900 mb and water retrievals above 700 mb, level expected and assessed errors are in good agreement. Below those levels, noticeable excess in assessed error is observed, possibly due to inaccurate surface parameters and undetected clouds/haze.

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