An Emerging ESDR: Multi-Platform Hyperspectral Infrared Radiances fromEOS-AIRS, S-NPP/JPSS CrIS, and METOP IASI

Space-based measurements of high-spectral resolution infrared (IR) radiances of the earth began in Sept. 2002 with the NASA EOS-AQUA AIRS instrument. The CrIS instrument on NASA's Suomi-NPP platform supplements this record in the 1:30 polar orbit, starting in 2012, and may continue for 15 years under the NOAA/NASA JPSS Program. The first of three IASI hyperspectral sounders on EUMETSAT's METOP platforms (9:30 orbit) started operation in July 2007, followed by the 2nd IASI on METOP-2 in early 2013. Development of a follow-on instrument (IASI-NG) for post METOP-3 is well underway.

These instruments are sensitive to the atmospheric temperature and humidity profile, surface temperature and emissivity, and minor gases (CO₂, O₃, CO, CH₄, N₂O, CFCs, HNO₃, etc.) They also have high sensitivity to clouds, especially long-wave cloud radiative forcing. The National Research Council has recommended the development of a hyperspectral IR radiance climate data set as a climate benchmark. We present here evidence that supports the use of the existing hyperspectral sounders for generation of these ESDRs and eventually CDRs. The large spatial and temporal overlap between these sensors has provided a rich data-set for inter-calibration studies that are used to characterize the accuracy of a combined ESDR radiance product.

We will discuss the stability of each instrument, and inter-calibration differences (with error estimates). In addition, we have developed robust, non-statistical approaches for converting the AIRS spectral radiances into equivalent CrIS radiances, a key step in development of a long-term consistent radiance record. Finally, several examples of robust decadal changes in the earth's atmosphere using AIRS will be discussed and compared to ERA and MERRA re-analysis products (temperature, water vapor, cloud forcing). Finally, we will review the challenges involved in creating an ESDR from 3 different instruments and institutions/countries.