Abstract
The Cross-track Infrared Sounder (CrIS) on the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite, combined with the Atmospheric Infrared Sounder (AIRS) on NASA Earth Observing System (EOS) Aqua and Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A and –B, provided four hyperspectral infrared sounders on orbit. These four hyperspectral infrared sounders observe the Earth and atmosphere at the same spectral regions from different satellites, and provide soundings of the atmosphere. Given hyperspectral infrared measurements from the four different instruments, the fundamental question is whether there any radiometric and spectral calibration differences among them? This study will address this question by evaluating radiometric and spectral consistency of radiance measurements from these four hyperspectral infrared sounders.
First, we will directly 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 at orbital crossing points of satellites occurring at high latitudes, the so-called simultaneous nadir overpasses (SNO). The common collocation algorithm will be used to pair the spectra from different instruments. The CrIS, AIRS, and IASI spectra will be processed at common grids and then the spectral differences will be computed.
Secondly, the Visible Infrared Imager Radiometer Suite (VIIRS) can serve as a transfer radiometer to indirectly compare CrIS with AIRS and IASI. We will first compare spectrally-averaged radiances from CrIS, AIRS, and IASI with the spatially-averaged collocated radiances from the VIIRS IR channels. The CrIS-VIIRS, AIRS-VIIRS, and IASI-VIIRS inter-calibration results will be further compared to indirectly check the consistency of CrIS, IASI, and AIRS. A precise collocation of CrIS/AIRS/IASI with VIIRS will be developed to characterize the shape of field of views (FOV) of hyperspectral sounders. In addition, the out-of-band signals will be carefully addressed to reduce comparison uncertainties due to the spectral coverage of different hyperspectral sounders.
Radiometric and Spectral Consistency of Hyperspectral Infrared Sounders
The Cross-track Infrared Sounder (CrIS) on the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite, combined with the Atmospheric Infrared Sounder (AIRS) on NASA Earth Observing System (EOS) Aqua and Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A and –B, provided four hyperspectral infrared sounders on orbit. These four hyperspectral infrared sounders observe the Earth and atmosphere at the same spectral regions from different satellites, and provide soundings of the atmosphere. Given hyperspectral infrared measurements from the four different instruments, the fundamental question is whether there any radiometric and spectral calibration differences among them? This study will address this question by evaluating radiometric and spectral consistency of radiance measurements from these four hyperspectral infrared sounders.
First, we will directly 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 at orbital crossing points of satellites occurring at high latitudes, the so-called simultaneous nadir overpasses (SNO). The common collocation algorithm will be used to pair the spectra from different instruments. The CrIS, AIRS, and IASI spectra will be processed at common grids and then the spectral differences will be computed.
Secondly, the Visible Infrared Imager Radiometer Suite (VIIRS) can serve as a transfer radiometer to indirectly compare CrIS with AIRS and IASI. We will first compare spectrally-averaged radiances from CrIS, AIRS, and IASI with the spatially-averaged collocated radiances from the VIIRS IR channels. The CrIS-VIIRS, AIRS-VIIRS, and IASI-VIIRS inter-calibration results will be further compared to indirectly check the consistency of CrIS, IASI, and AIRS. A precise collocation of CrIS/AIRS/IASI with VIIRS will be developed to characterize the shape of field of views (FOV) of hyperspectral sounders. In addition, the out-of-band signals will be carefully addressed to reduce comparison uncertainties due to the spectral coverage of different hyperspectral sounders.