Effect of self-apodization correction on Cross-track Infrared Sounder radiance noise.

Self-apodization correction increases noise of the radiance spectra measured by the Cross-track Infrared Sounder (CrIS) in three spectral bands. It also increases noise correlation between spectral channels. The degree of the noise effect depends on the spectral resolution, channel frequency, and detector position in the 3×3 detector grids on the focal planes. The effect is relatively small when CrIS is operated in the normal spectral resolution mode, but can reach to the level of a 76% noise increase and 52% noise correlation in high-frequency channels of the shortwave-band spectra from the corner detectors when CrIS is operated in the full spectral resolution mode. The noise impact of the Hamming apodization applied to CrIS spectra is also discussed.