Proceedings Article | 3 August 2021
KEYWORDS: Calibration, Sensors, Climate change, Clouds, Temperature metrology, Spectroscopy, Spectral resolution, Spatial coherence, Modulation, Sun
Aqua-AIRS data have been available now for almost 20 years, Suomi-NPP CrIS for 9 years, and JPSS1 CrIS for 4 years. The three instruments satisfy nearly identical functional requirements, and are in very similar polar orbits. However, there are differences in the design, spatial scan pattern and sun-angle, in addition to absolute calibration differences. We compared AIRS, CrIS SNPP and CrIS JPSS data for the 1148 days between 20180217 and 20210430 for the 900 cm-1 channel under clear and random sampled tropical ocean, tropical land, and Arctic conditions. Although JPSS and SNPP are identical designs, the difference between JPSS and SNPP are as large as the differences relative to AIRS. For the day and night tropical ocean at typically 295K and for night tropical land and under the Arctic conditions (265K typical), averaged over all scan angles, detector elements and time, AIRS, JPSS and SNPP agree within 100 mK. Under Antarctic and Antarctic conditions, the difference between JPSS and AIRS and SNPP and AIRS are on average 200 mK, but with a much larger summer/winter correlated pattern. For clear tropical day (318K), AIRS is 500 mK warmer than JPSS, but 150 mK colder than SNPP. The three instruments find 40% fewer clear cases at night than during the day. With JPSS we find 3% fewer clear cases than with AIRS, 9% more than with SNPP day and night. Differences seen in the past three years in the AIRS, SNPP and JPSS data are calibration artifacts. Unless corrected in the construction of merged AIRS/SNPP/JPSS and follow-on time series, they will complicate the interpretation of trends potentially related to climate change.
