Spectral calibration in hyperspectral sounders

Abstract

It is widely accepted that the knowledge of the frequencies of the spectral response functions (SRF) of the channels of hyperspectral sounders at the 10 parts per million (ppm) of frequency level is adequate for the retrieval of temperature and moisture profiles and data assimilation for weather forecasting. However, SI traceability and knowledge at the 1 ppm level and better are required to separate artifacts in the knowledge of the SRF due to orbital and seasonal instrument effects from diurnal and seasonal effects due to climate change. We use examples from AIRS to discuss a spectral calibration that uses the SI traceable upwelling radiance spectra to achieve an absolute accuracy of 0.5 ppm.