Fusion of VIIRS and CrIS observations to generate MODIS-like infrared absorption band radiances at VIIRS spatial resolution: version 2 fusion radiance product, part I: pixel-level uncertainty
AbstractWe present the latest refinements to construct additional infrared spectral band radiances for the Visible Infrared Imaging Radiometer Suite (VIIRS) through fusion with hyperspectral measurements from the Cross-track Infrared Sounder (CrIS). The resulting VIIRS+ CrIS Fusion Radiance (FSNRAD) products have been created to provide a path for legacy products from Terra and Aqua to SNPP and NOAA-20 and -21 low Earth orbit platforms. This approach addresses a key limitation of VIIRS—the absence of IR absorption bands available on the Moderate Resolution Imaging Spectroradiometer (MODIS)—by reconstructing MODIS-like radiances at the native VIIRS spatial resolution (750 m) for full VIIRS swaths. The algorithm is now implemented as a NASA operational product, version 2 FSNRAD. An analogous fusion framework using Aqua MODIS and the Atmospheric Infrared Sounder is employed to assess performance and quantify uncertainty. Differences between MODIS+ AIRS fusion radiances and observed MODIS measurements are analyzed across 12 infrared bands to estimate pixel-level uncertainties for each VIIRS+ CrIS FSNRAD band. Results from simultaneous nadir overpasses with Aqua MODIS indicate biases typically below 0.5 K for all bands. Beyond reproducing MODIS-like channels, the method enables customized spectral band construction and reduces detector–detector radiometric differences, supporting improved retrievals and emerging remote sensing applications.
