Selection of IASI channels for use in numerical weather prediction

TitleSelection of IASI channels for use in numerical weather prediction
Publication TypeTechnical memorandum
Date Published07/2007
Secondary TitleECMWF Technical Memoranda
AuthorCollard, A

IASI (Infrared Atmospheric Sounding Interferometer) is an infrared Fourier transform spectrometer flying on the MetOp satellite series starting in October 2006. It measures the radiance emitted from the Earth in 8461 channels covering the spectral interval from 645-2760cm-1 at a resolution of 0.5cm-1 (apodised). The high volume of data resulting from IASI presents many challenges, particularly in the areas of data transmission, data storage and assimilation. The simplest methods for reducing the data volume are spatial sampling and channel selection. The issue of channel selection is discussed and a selection of 300 channels suitable for tranmission to NWP centres is examined, where the primary aim is the improvement of the temperature, humidity, ozone and carbon dioxide state vectors. The channel selection method takes account of redundancy, the effect of interfering species and robustness against the choice of assumed background error covariance and atmospheric state.

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