Abstract
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 - 15.38um); MWIR (5.71 - 8.26um); and SWIR (3.92 - 4.64 um). 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 and systems to quantify the CrIS calibration bias and uncertainties of CrIS. First, 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 computed. Secondly, inter-sensor calibration between sounders and imagers on the same satellite such as CrIS and the Visible Infrared Imager Radiometer Suite (VIIRS) will also be performed. We will compare CrIS spectrally-averaged radiances with the spatially-averaged collocated radiances from the VIIRS IR channels. A precise collocation of CrIS and VIIRS will be carried out by considering the change of CrIS field of views (FOVs) along all scan angles. Based on this, the FOV-by-FOV differences will be evaluated based on the VIIRS radiances.
Post-launch Radiometric and Spectral Calibration Assessment of NPP/CrIS by Comparing CrIS with VIIRS, 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 - 15.38um); MWIR (5.71 - 8.26um); and SWIR (3.92 - 4.64 um). 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 and systems to quantify the CrIS calibration bias and uncertainties of CrIS. First, 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 computed. Secondly, inter-sensor calibration between sounders and imagers on the same satellite such as CrIS and the Visible Infrared Imager Radiometer Suite (VIIRS) will also be performed. We will compare CrIS spectrally-averaged radiances with the spatially-averaged collocated radiances from the VIIRS IR channels. A precise collocation of CrIS and VIIRS will be carried out by considering the change of CrIS field of views (FOVs) along all scan angles. Based on this, the FOV-by-FOV differences will be evaluated based on the VIIRS radiances.