Inter-comparison of NOAA-21/NOAA-20/S-NPP VIIRS solar reflective bands (RSB) with PACE OCI and JPL EMIT hyperspectral observations

This study inter-compares NOAA-21, NOAA-20, and S-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) operational RSB SDRs with the NASA Plankton, Aerosol Cloud and Ocean Ecosystem (PACE) Ocean Color Instrument (OCI) and JPL Earth Surface Mineral Dust Source Investigation (EMIT) observations over well-established pseudo invariant calibration sites (PICS) over desert areas, including Algeria3, Algeria3, Arabia-2, Libyan-1, and Libyan-4. Time series of VIIRS visible and near infrared bands (VisNIR, M1-M5, M7, and I1-I2) top of atmosphere (TOA) reflectance were compared with matching PACE OCI observations from April 11, 2024 to October 15, 2024. Preliminary results suggest that S-NPP VisNIRs agree better with PACE OCI than NOAA-20 and NOAA-21. M1-M4, M7, and I1-I2 bias lower than OCI for all three VIIRS. Moreover, shorter wavelength bands (M1-M4) show large biases, and biases decrease as wavelengths increase. Bands M5, M7, and I1-I2 agree with OCI within 5% for majority of cases. VIIRS shortwave infrared bands (SWIR, M8, M10-M11, and I3) and VisNIR I-bands (I1-I2) were compared with co-located JPL EMIT observations (June -November 2023) over the desert sites. Preliminary results indicated VIIRS agree with EMIT within 3% in majority of cases. Meanwhile, larger uncertainty may exist in the VIIRS-EMIT inter-comparison results due to the limited cases available and the residual BRDF and atmospheric effects. Additional PACE OCI and JPL EMIT data over PICSs will be analyzed as additional observations become available in the future.