Verification of the GSICS GEO-LEO Inter-Calibration Products with GEO-GEO Collocation Data

The Global Space-based Inter-Calibration System (GSICS) geostationary (GEO) vs. low earth orbit (LEO) inter-calibration correction products have been routinely generated for years at NOAA to improve and harmonize the data quality of the operational GOES satellite for a better global weather monitoring, prediction and climate change studies. In this study, the collocated GOES-13 and GOES-15 Imager infrared (IR) data are used to validate the GSICS GEO-LEO Imager inter-calibration correction products. To compensate the impact of difference in the spectral response function (SRF) on the GSICS corrected GEO radiance, two radiative transfer models (RTM) with different atmospheric profiles are used to simulate the relations between the two GEO radiance values. The results of GEO-GEO inter-calibration shows that the mean Tb difference between GOES-13 and GOES-15 is less than 0.2K(Ch2), 0.65K(Ch3), 0.08K(Ch4) and 0.35K(Ch6). The two RTM models with different atmospheric profiles have significantly different impacts on the Tb difference at the two absorptive channels, Ch3 and Ch6, indicating that the impact of different optical path is not well addressed in this study. Future study should apply the double difference using the RTM as transfer to compensate for the SRF and viewing/optical path difference at each collocated pixel.