Radiometric Calibration of the Solar Backscatter Ultraviolet Sounder and Validation of Ozone Profile Retrievals

The Solar Backscatter Ultraviolet Sounder (SBUS) is one of the 11 main payload instruments onboard Feng Yun-3 (FY-3), the second generation of Chinese polar orbit meteorological satellites. This paper presents the results of SBUS instrument calibration, and data and product validation during the prelaunch and postlaunch periods. Topics include the instrument prelaunch calibration and characterization, in-orbit monitoring, validation of the ozone profiles retrieved from the FY-3 SBUS measurements, and an application of the retrievals to monitoring the 2011 Arctic ozone depletion. For the prelaunch calibration of SBUS, the estimated uncertainty of laboratory calibration is approximately 4.7%. The in-orbit solar irradiance measurements indicate that the diffuser reflectivity degraded approximately 15% for the 252-nm channel, and 3% to 5% for the other 11 channels during a 12-mo period. Using ozone vertical profiles retrieved from National Oceanic and Atmospheric Administration Solar Backscatter Ultraviolet (SBUV)/2s as a "truth," the initial comparison of ozone profiles between FY-3 SBUS and SBUV/2s finds that the relative percent bias of the FY-3 SBUS with the SBUV/2 results is good. The averaged differences range over to ±7% for FY-3A SBUS and ±6% for FY-3B SBUS. The SBUS ozone profile retrievals reveal that the spring 2011 Arctic ozone depletion mainly resulted from a sharp ozone decrease in the upper troposphere to lower stratosphere, which accounts for 70% to 80% of the total ozone loss.