Inter-comparison of the longwave infrared channels of MODIS and AVHRR/NOAA-16 using simultaneous nadir observations at orbit intersections

Near nadir observations in the 11 gm and 12 gm bands of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the TERRA spacecraft and the Advanced Very High Resolution Radiometer (AVHRR) onboard the NOAA-16 spacecraft are collected at their orbit intersections, where both MODIS and AVHRR view the Earth and its atmosphere at the same location within 30 seconds in the Arctic region. Sample data with I km resolution from spatially uniform areas are taken for direct inter-comparison of the scene radiance and brightness temperatures at around 270 K. Then a pixel-by-pixel match between the MODIS and AVHRR observations is performed to evaluate their correlation at different scene temperatures. The results show that MODIS and AVHRR observations agree well (difference less than 0.3 K) for both the 11 gm and 12 gm bands, although their band correlation exhibits a slightly non-linear trend for scene temperatures greater than 285 K. The performance of MODIS is considered a good predictor of the performance of the National Polar-orbiting Operational Environmental Satellite System (NPOESS)/Visible Infrared Imager/Radiometer Suite (VIIRS), the future replacement of AVHRR. The direct comparison of MODIS and AVHRR observations is therefore considered a risk reduction study for VIIRS.