AIRS and Full-Resolution CrIS: Comparison Using Tropical Simultaneous Nadir Observations

Abstract:

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 any attempt 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. Differences are explored as a function of wavelength, day vs. night, land vs. ocean, and different levels of cloudiness. Differences unique to the design of each instrument are seen. With the currently available AIRS L1c and CrIS CCAST calibrated data radiometric differences as large a 0.3K are seen. These differences need to be corrected or at least flagged to prevent them from becoming artifacts in a long-term climate record.