Intercalibration of Infrared Window Channels of FY-3A Instruments against AIRS/Aqua Data

This work addressed the intercalibration of the infrared window channels of InfraRed Atmospheric Sounder (IRAS), Visible and InfraRed Radiometer (VIRR) and MEdium Resolution Spectral Imager (MERSI) aboard Chinese second generation polar-orbiting meteorological satellite FengYun 3A (FY-3A) with high spectral resolution data acquired by the Atmospheric InfraRed Sounder (AIRS) aboard Aqua. A North Pole study area was selected according to the instruments' viewing geometry. The FY-3A L1 data and AIRS/Aqua 1B Infrared geolocated and calibrated radiances (AIRIBRAD) in July of 2008 or 2009 were used in this work. A sub-pixel registration method was developed and applied to the satellite images to improve the intercalibration accuracy. The co-located measurement pairs were picked out with absolute Viewing Zenith Angle differences less than 5°(|VZA|<;5°), absolute Viewing Azimuth Angle differences less than 90^o(|VAA|<;90°), and absolute time differences less than 15 min (|ΔT|<;15'). The results show that the FY-3A measurements were linearly related to the convolved AIRS/Aqua measurements with high correlation coefficients and calibration discrepancies exist between FY-3A and AIRS channels, especially for MERSI channel 5.