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The European Centre for Medium-range Weather Forecasts (ECMWF) 4D-Var data assimilation system has been modified to allow the direct assimilation of Principal Component (PC) scores derived from spectra measured by the Infrared Atmospheric Sounding Interferometer (IASI). Testing of a prototype system where 165 IASI radiances are replaced by just 20 PC scores shows significant computational savings with no detectable loss of skill in the resulting analyses or forecasts. Indeed in some respects the assimilation of PC scores leads to marginal improvements over the traditional radiance-based assimilation. [ABSTRACT FROM AUTHOR]

The article discusses a study that presents a quality assessment of the Infrared Atmospheric Sounding Interferometer (IASI) carbon monoxide (CO) profiles retrieved by the two different retrieval algorithms SOFRID and FORLI. It indicates that SOFRID and FORLI showed biases no higher than 13%compared to the MOZAIC reference set. It found discrepancies between the two IASI products and MOZAIC.

Retrieval products for temperature, water vapour and ozone have been obtained from spectral radiances measured by the Infrared Atmospheric Sounding Interferometer flying onboard the first European Meteorological Operational satellite. These products have been used to check the consistency of the forward model and its accuracy and the expected retrieval performance. The study has been carried out using a research-oriented forward-inverse methodology, called '-IASI, that the authors have specifically developed for the new sounding interferometer. The performance of the forward-inversion strategy has been assessed by comparing the retrieved profiles to profiles of temperature, water vapour and ozone obtained by co-locating in space and time profiles from radiosonde observations and from the European Centre for Medium-Range Weather Forecasts analysis. Spectral residuals have also been computed and analyzed to assess the quality of the forward model. Two versions of the highresolution transmission molecular absorption database have been used, which mostly differ for ozone absorption line parameters, line and continuum absorption of both CO2 and H2O molecules. Their performance has been assessed by inter-comparing the results, and a consistent improvement in the spectral residual has been found when using the most updated release. [ABSTRACT FROM AUTHOR]

A retrieval algorithm that uses a statistical strategy based on dimension reduction is proposed. The methodology and details of the implementation of the new algorithm are presented and discussed. The algorithm has been applied to high resolution spectra measured by the Infrared Atmospheric Sounding Interferometer instrument to retrieve atmospheric profiles of temperature, water vapour and ozone. The performance of the inversion strategy has been assessed by comparing the retrieved profiles to the ones obtained by colocating in space and time profiles from the European Centre for Medium-Range Weather Forecasts analysis. [ABSTRACT FROM AUTHOR]