Tropical SNO comparisons of AIRS and CrIS calibration for windows

摘要

AIRS on EOS-Aqua and CrIS on Suomi NPP are two hyperspectral infrared sounders with similar capabilities and orbits, so there is a great opportunity to compare their absolute calibration while they are both in orbit. This insures that long-term climate record can be created by concatenating the two instrument records. There are significant differences in instrument architecture which may lead to subtle differences and complicate attempts to combine the records. We use Tropical Simultaneous Nadir Observations (TSNOs), cases where both instruments are looking nearly at the same place at the same time, to explore the differences. Due to the presence of cold clouds and clear hot desert surface, the data cover a brightness temperature range from 190 K to 340 K. We concentrate on the differences between the mean of the two instruments using atmospheric window channels as function of brightness temperature in 20-K wide bins. With the currently available AIRS and CrIS official calibrated data, radiometric differences as large as 0.3 K are seen at the extreme temperatures. These differences may be reduced in future releases of the AIRS and CrIS calibration.