The Global Space-based InterCalibration System (GSICS) for GOES-R and JPSS

The WMO Space Programme GSICS program currently includes participation from the United States (NOAA, NASA, NIST), Europe (CNES/France, EUMETSAT), China (CMA), Japan (JMA) ,Korea (KMA) and India (ISRO). These agencies have agreed to take steps to ensure better comparability of satellite measurements made by different instruments and to tie these measurements to absolute standards. The direct benefit of improved satellite observations will be improved weather and climate assessments and predictions. Satellite intercalibration is vital for reducing measurement uncertainty and to optimally integrate data from different observing systems: a) to generated blended products, b) to improve weather forecasting data assimilation and c) to generate long-term climate data records from multiple sensors. The GSICS activities are currently focused on the intercalibration of operational satellites from United States, Europe, China, Japan, Korea and India using high quality operational and research instruments as a reference.

At NOAA, GSICS activities will include the intercomparisons of GOES-R, JPSS, and MeTOP sensors. For example, GSICS has established the EUMETSAT Infrared Atmospheric Sounding Interferometer (IASI) as a reference instrument, along with NASA's Atmospheric InfraRed Sounder (AIRS) – because direct intercomparisons of those two instruments showed differences within 0.1 K with no appreciable trend over nearly four years of collocations. For JPSS, GSICS, primarily at NOAA/NESDIS STAR and CIMSS, will intercompare the Cross-track InfraRed Sounder (CrIS) with AIRS and IASI to determine the accuracy and stability of CrIS. The Visible/Infrared Imager Radiometer Suite (VIIRS) instrument on board NPP and JPSS satellites will be intercompared with NASA's MODIS, ESA's MERIS and ATSR instruments, and stable Earth targets such as the Antarctic DOME-C site and some deserts. The Ozone Mapping and Profiler Suite (OMPS) will be intercompared with EUMETSAT's GOME-2 and other high quality ozone sensors, and the Advanced Temperature Microwave Sounder (ATMS) will be intercompared with AMSU/MHS instruments. For GOES-R, GSICS will intercompare the Advanced Baseline Instrument (ABI) with IASI and AIRS and newly established reference instruments, including NASA's new CLARREO on-board traceable reference visible and infrared sensors. In summary, GSICS will assess the accuracy and stability of JPSS and GOES-R sensors. If appreciable biases and trends are found, GSICS will generate correction coefficients allowing users to adjust impacted instruments measurements to the quality of established reference instruments. An overview of the GSICS program, intercomparisons of current instruments as surrogates for future JPSS and GOES-R instruments, and examples of applications of correction coefficients will be presented.