Climate Change Sensitivity Evaluation from AIRS and IRIS Measurements

Outgoing longwave radiation (OLR) measurements over a long period from satellites provide valuable information for climate change. Due to the different coverage, spectral resolution and instrument sensitivities, the data comparisons between different satellites could be problematic and possible artifacts could be easily introduced. In this paper, we illustrate the method and procedures when we compare different satellite measurements by using the data taken by Infrared Interferometric Spectrometer (IRIS) in 1970 and by Atmospheric Infrared Sounder (AIRS) from 2002 to 2010. We use the spectra between 650 cm(-1) and 1350 cm(-1) for nadir view footprints in order to match the AIRS and IRIS measurements. Most of the possible sources of error or biases, which include the errors from spatial coverage, spectral resolution, spectra frequency shift due to the field of view, sea surface temperature uncertainty, clear sky determination, and spectra response function (SRF) symmetry, can be corrected. Using the correct SRF is extremely important when comparing spectra in the high slope spectral regions where possible large artifacts could be introduced.