Suomi-NPP CrIS/VIIRS Radiometric Intercomparison Study

The joint NASA/NOAA Suomi National Polar-Orbiting Partnership (Suomi NPP) is a satellite instrument suite that was launched on 28 October 2011. We compare measurements from two instruments that reside on Suomi NPP—the Cross-Track Infrared Sounder (CrIS) and Visible Infrared Imaging Radiometer Suite (VIIRS). CrIS provides Earth view radiances in three spectral bands (650-1095 cm-1, 1210-1750 cm-1 and 2155-2550 cm-1 at 0.625 cm-1 spectral resolution) at 30 cross-track positions, each with a 3x3 array of observations. VIIRS observes 22 imaging and radiometric bands covering 0.41 to 12.5 microns.

For this study, we focus on four VIIRS radiometric bands, M13 (4.05 um), M15 (12.01 um), M16 (10.45 um) and I05 (11.45 um), that fall within the spectral range of CrIS. CrIS and VIIRS observations are co-located and the VIIRS radiances that fall within a given CrIS footprint are spatially averaged. The CrIS measurements are spectrally integrated over the VIIRS channel SRFs to create a one-to-one matchup for each of the four VIIRS bands within each CrIS footprint.

These data provide a strong quality assurance metric for long-term CrIS/VIIRS analysis, producing over 11 million co-located radiance observations on a daily basis. We can characterize the results versus time, field-of-regard, field-of-view, scene brightness temperature and orbit phase. Analysis spanning more than seven years of observations show agreement between the instruments to within 100 mK, with a mean trend of less than a few mK per year.