Exploring the Inter-Field-of-Regard Radiance Differences of NPP/CRIS

The Cross-Track Infrared Sounder onboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite provides precious measurements of the hyper-spectral infrared radiances emitted from the Earth surface and its atmosphere, covering 1305 spectral channels, over 3 bands: LWIR (9.14 - 15.38 μm); MWIR (5.71 - 8.26 μm); and SWIR (3.92 - 4.64 μm). These measurements are sampled by a 3-by-3 array of sensors for each band and each unit is called a field-of-view (FOV). Each scan of the S-NPP CrIS is made of 30 Field of Regards (FOR) and each FOR is composed by nine FOVs. The inter-FOV consistency is a critical issue for weather forecasting, trace gas retrieval, climate change studies and other applications.

The operational sensor data record (SDR) since April 2012 is analyzed. To remove the limb effect, only the data of two nadir views, i.e. FOR 15 and 16, are used. We selected a long-wave window channel (900 cm-1), a mid-wave upper-level water vapor channel (1500cm-1) and a short-wave window channel (2500cm-1) in the investigation. The cloud contamination, day/night difference and latitudinal difference are considered. It is found that the average inter-FOV difference for window channels is less than 0.1 K in general.