Detecting Climate Trends Using AIRS, IASI and CrIS High Spectral Resolution Brightness Temperature Spectra

Infrared brightness temperature observations from a satellite platform offers the ability to track minute trends in the monthly and seasonal brightness temperature anomalies given the high radiometric stability of the measurements. The high spectral resolution nature of the spectra offer the ability to track various climate relevant parameters such as window channels sensitive to surface temperature and clouds, channels with higher sensitivity to trace gases including CO2, CH4, SO2, HNO3, as well as channels sensitive only to upper tropospheric and stratospheric brightness temperature.

NASA's Atmospheric Infrared Sounder (AIRS) provides a data record that extends from its 2002 launch to the present. The Infrared Atmospheric Sounding Interferometer (IASI) onboard Metop- (A launched in 2006, B in 2012), as well as the Joint Polar Satellite System (JPSS) Cross-track Infrared Sounder (CrIS) launched in 2011, complement this data record. Next generation infrared sounders with similar capabilities will augment these measurements into the near future.

We have created a database of daily global observations, of the nadir-most field-of-views, for each of the instruments listed above. Seasonal trends can be distinguished from these measurements with greater than 1-sigma confidence given that both AIRS and IASI-A observations have existed for more than a decade. Subtle differences between comparable spectral channels for each of AIRS, IASI and CrIS can lead to significant differences in the observed upwelling brightness temperatures. We have taken the higher spectral resolution IASI (0.25 cm-1) data, subsampled to CrIS and AIRS spectral grids, respectively, to effectively compare data across the various platforms.