Reprocessing of Suomi NPP SDR Data for Weather and Climate Applications

Since the successful launch of Suomi NPP (SNPP) satellite on 28 October 2011, the JPSS ground Interface Data Processing Segment (IDPS) has being constantly upgraded to incorporate the latest changes in instrument calibration tables, sensor/environmental data record (SDR/EDR) algorithms, quality flags, etc. These changes in SNPP real-time data, which are distributed to operational centers and user communities, can be manifested as sudden jumps in radiances and retrieved products. If the SNPP mission-up-to-date data are used to detect the atmospheric and environmental anomalies, the artefacts caused by instrument calibration updates and algorithm changes could be taken as the physical anomalies. Moreover, if the IDPS-generated real-time data are used by NWP centers for their global and regional reanalysis, the NWP data assimilation system needs to be updated for quality control and bias correction in order to handle the IDPS data jumps. A new initiative is developed in 2016 to reprocess the SDR and EDR data from the entire SNPP mission lifetime for the following goals: 1) understanding SNPP instruments’ in-orbit performance and SDR anomalies; 2) obtaining the user experiences and recommendations for further improvements in SNPP data quality; 3) developing the improved and advanced cal/val algorithms for reprocessing applications; and 4) evaluating the impacts of the reprocessed SNPP data for weather and climate applications. A preliminary analysis shows that the quality of SNPP SDR data is significantly improved after reprocessing. Specifically, the OMPS reflectance time series is more stable than the real-time products generated from JPSS IDPS. ATMS radiances at sounding channels have smaller biases and are mostly less than 0.2 K with respect to the “on-orbit-truth” from the GPS RO simulations. The spectral calibration of CrIS radiances is reduced to less than 3 ppm and the CrIS systematic noise is reduced by minimizing the ring effect arising from the interferometric Fast Fourier Transformation. The reprocessing of the VIIRS reflective solar band (RSB) calibration coefficients has improved the radiometric accuracy and corrected the sudden changes that occurred in 2014. The sudden jumps and the discontinuity in VIIRS Day and Night Band (DNB) radiometric gain are also corrected through updating the Relative Spectral Response (RSR) function in the initial algorithm. The reprocessed RSB and DNB calibration coefficients improved and ensured a high quality VIIRS SDR products in the early lifetime of 2012.