Inter-Compariosn of NPP/CrIS with AIRS and IASI

The Cross-track Infrared Sounder (CrIS) on the newly-launched Suomi National Polar-orbiting Partnership (Suomi NPP) and future Joint Polar Satellite System (JPSS) is a Fourier transform spectrometer that provides soundings of the atmosphere with 1305 spectral channels, over 3 wavelength ranges: LWIR (9.14 - 15.38 μm); MWIR (5.71 - 8.26 μm); and SWIR (3.92 - 4.64 μm). An accurate spectral and radiometric calibration is fundamental for CrIS radiance Sensor Data Records (SDRs). In this study, through inter- and intra-satellite calibration efforts, we focus on assessment of NPP/CrIS post-launch radiometric and spectral calibration. The purpose of this study is to use inter-calibration technologies to quantify the CrIS calibration bias and uncertainties of CrIS.

We will compare CrIS hyperspectral radiance measurements with the Atmospheric Infrared Sounder (AIRS) on NASA Earth Observing System (EOS) Aqua and Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A and -B to examine spectral and radiometric consistence and difference among three hyperspectral IR sounders. The newly-launched CrIS on Suomi NPP, combined with AIRS and IASI, provide the first-ever inter-calibration opportunity because three hyperspectral IR sounders can observe the Earth and atmosphere at the same spectral regions from different satellites. We will directly compare CrIS with AIRS and IASI at orbital crossing points of satellites occurring at high latitudes, the so-called simultaneous nadir overpasses (SNO). The CrIS, AIRS, and IASI spectra will be processed at common grids and then the spectral differences will be determined. In addition, an accurate collocation algorithm has been developed to collocate high spatial resolution measurements from the Visible Infrared Imager Radiometer Suite (VIIRS) within each CrIS Field of View (FOV). In order to reduce the comparison uncertainties, the VIIRS radiances will be used to identify the uniform scenes for comparison. Finally, the comparison for CrIS FOVs will be performed at the different CrIS FOVs to further check the spectral and radiometric consistency among different CrIS FOVs.