Using S-NPP VIIRS as a Transfer Radiometer to Inter-compare GOES-R ABI and Himawari-8 AHI
ABI and AHI both have 16 spectral channels in the visible and infrared spectrum, which is a significant increase in the number of spectral channels in comparison to heritage instruments. The two instruments have similar spectral bands with two main differences: ABI includes a 1.38 µm channel (for cirrus cloud detection), while this channel is replaced with a 0.51 µm channel (green band – to produce color composite imagery) on AHI. Given the instrument similarities and the planned launch of Himawari-8 one year ahead of GOES-R, an opportunity exists to leverage early AHI on-orbit data for GOES-R Calibration/Validation risk mitigation and post-launch readiness.
Toward this initial goal the radiometric differences between each channel must be well characterized, quantified and inter-compared. To assess the consistency in the future observations of ABI and AHI we propose to use the well calibrated Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) as a transfer radiometer to perform such inter-comparisons. S-NPP VIIRS is a new generation instrument with several similar spectral channels to ABI and AHI and within the field-of-view of both geostationary instruments.
This preliminary effort compared the publicly released Spectral Response Functions (SRF), using typical hyperspectral target spectra from space-based Infrared Atmospheric Sounding Interferometer (IASI) and the airborne-based Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), to assess the theoretical radiometric biases between the instruments. Preliminary results suggest there may be large biases between ABI and AHI in a few channels. Good agreements are expected for several other channels.
The current effort establishes a baseline for future comparisons between these systems, as well as an opportunity to collaborate and coordinate with the JMA. The theoretical radiometric characterization of these technologically advanced systems facilitates the ability to leverage AHI and S-NPP VIIRS to be used as risk mitigation assets for ABI post-launch support. This effort fosters continuity for the global earth observing system which ultimately heightens our collective ability to address future extreme weather and climate events.