Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 2 2009 10.5194/acpd-9-8101-2009 http://www.atmos-chem-phys-discuss.net/9/8101/2009/ http://www.atmos-chem-phys-discuss.net/9/8101/2009/acpd-9-8101-2009.html http://www.atmos-chem-phys-discuss.net/9/8101/2009/acpd-9-8101-2009.pdf 8101 8119 2009-03-27 Intercomparison of integrated IASI and AATSR calibrated radiances S. M. Illingworth J. J. Remedios R. J. Parker EOS, Space Research Centre, Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK The mission objectives of the Infrared Atmospheric Sounding Interferometer (IASI) are driven by the needs of the Numerical Weather Prediction (NWP) and climate monitoring communities. These objectives rely upon the IASI instrument being able to measure top of atmosphere radiances accurately. This paper presents a technique and results for the validation of the radiometric calibration of radiances for IASI, using a cross-calibration with the Advanced Along Track Scanning Radiometer (AATSR). The AATSR is able to measure Brightness Temperature (BT) to an accuracy of 30 mK, and by applying the AATSR spectral filter function to the IASI measured radiances we are able to compare AATSR and IASI Brightness Temperatures. By choosing coincidental data points that are over the sea and in clear sky conditions, a threshold of homogeneity is derived. It is found that in these homogenous conditions, the IASI BTs agree with those measured by the AATSR to within 0.5 K, with a precision of order 0.04 K. These results indicate that IASI is likely to be meeting its target objective of 0.5 K accuracy. 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