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Accurate weather prediction requires a detailed knowledge of the state of the atmosphere from which a forecast model can predict the future weather. Much of our understanding of the state of the atmosphere comes from remote sensing observations from satellite instruments.

The Infra-Red Atmospheric Sounder Interferometer ( IASI) is a thermal infrared sounder operating on the European Metop satellite. It measures the thermal infrared radiation leaving the planet at around 8461 spectral channels.

Current use of these data in numerical weather prediction models is conservative in that only a few hundred channels are used and those sensitive to the land surface or clouds are often rejected. This conservative utilisation of  IASI data has nevertheless had a significant impact on the accuracy of weather forecasting. It is expected that the current  IASI satellite will have follow on missions in both polar and geostationary orbit in the future for many years to come.

This project aims to use the ARIES instrument operated on the  FAAM BAe146 research aircraft to develop novel techniques that will allow us to use more of the data from IASI and other space based sounders. Within the Observations Based Research section of the Met Office we have developed Principal Component based radiative transfer codes that allow us to model full spectrum  IASI data in the presence of clouds and over any surface. These techniques are being validated against in-situ data gathered by the  FAAM BAe146 aircraft with a view ultimately allowing these techniques to be used within the Unified Model.

Key Aims

• Improved understanding of infrared radiative transfer over land and in the presence of clouds and aerosols
• Development of Principal Component based radiative transfer models that allow the fast simulation of 1000's of spectral channels.
• Development and testing of variational data assimilation techniques that allow greater use of infrared sounder data in numerical weather prediction models.
• Validation of the performance of space based infrared sounders.

Current Projects

• JAIVEx – a joint UK/US project aimed at calibration and validation of the  IASI satellite instrument.
• VACAR - a UK-based campaign to gather airborne data to allow development and testing of novel techniques to use hyperspectral sounding data over land and in the presence of clouds.