An approach to cross-calibrating multi-mission satellite data for the open ocean

Abstract

Synchronous observations with similar illumination-observation and meteorological conditions are critical components of cross-calibration analysis. This study outlines data quality control criteria for obtaining the stable synchronous data needed for developing and evaluating a cross-calibration algorithm. With image data from the Visible Infrared Imaging Radiometer (VIIRS) and Medium Resolution Spectral Imager II (MERSI II), we developed a cross-calibration algorithm using 35 image pairs of four ocean gyres, and we evaluated the data using 11 image pairs of the global ocean. We found that our new algorithm provided well-calibrated MERSI II reflectance at the top-of-atmosphere. The coefficients of determination (R2) were greater than 0.89, and the mean absolute percent difference (MAPD) varied from 1.13% to 8.37% in the visible bands, which was significantly superior to an algorithm developed from a data set constrained by existing data quality controls. When the satellite data were preprocessed with the new cross-calibration algorithm, the MERSI II instrument provided inter-mission remote sensing reflectance for the North Pacific Gyre that was consistent with the VIIRS instrument. Furthermore, we derived consistent estimates of remote sensing reflectance and backscattering coefficients (bb) from VIIRS and the cross-calibrated MERSI II reflectance data for four typically turbid coastal waters. The VIIRS bb coastal images had special distribution patterns, such as tongue-shaped plumes and mesoscale eddies, which accurately reappeared in the MERSI II images. The inter-mission MAPD values varied from 16%–24% for the coastal waters. This uncertainty level was much lower than the bb data quantified from the original MERSI II data with no cross-calibration. Our results suggest that our data quality control criteria provide good quality synchronous data for cross-calibration analysis. MERSI II could provide good ocean color products for oceanic communications after cross-calibration, even though the radiance calibration for the original MERSI II reflectance data are imperfect.