Validation Methodology for the OSI SAF Sea Ice Concentration Data Records

In the context of the OSI SAF Visiting Scientist Activities (VSA) Program, Roberto Saldo from the Technical University of Denmark (DTU) in Lyngby, Denmark, worked on the implementation of a new validation methodology for the OSI SAF sea ice concentration (SIC) climate data records (CDRs) and the validation of the OSI SAF SIC CDRs version 3. The work was initiated in December 2021 and completed with the successful release of the new sea ice concentration CDRs in November 2022. The work was supervised by Fabrizio Baordo and Matilde Brandt Kreiner (DMI).

Objectives and framework of the study

For the validation of the new version 3 of the OSI SAF Global Sea Ice Concentration CDRs it was decided to change the quality assessment method for the future OSI SAF sea ice concentration data records, so that the primary method for assessment is a direct comparison against high-quality 0% and 100% SIC reference data (SIC0 and SIC1). This primary evaluation methodology is independent of and more temporally consistent than the comparison to manually made ice charts, that has been used as the primary assessment method in OSI SAF up until now. Roberto Saldo from DTU has set up the validation of sea ice CDRs currently operated in the ESA CCI+ project and as part of this AS activity, he assisted OSI SAF scientists in implementing the methodology at DMI, as DMI is responsible for the quality assessment and validation of OSI SAF sea ice concentration CDRs. The CCI+ project has worked in parallel to the development of the OSI SAF CDRs (2019-2022) and this AS activity, along with a close coordination of the CCI+ and OSI SAF SIC activities ensures that the OSI SAF and CCI+ CDRs are complementary and that their performances can be compared.

Figure: Map of the location of SIC0 (blue) and SIC1 (green) reference data in the Northern Hemisphere (left) and Southern Hemisphere (right) that is used in the comparison with OSI SAF CDR and ICDR products. The location of the SIC0 data are fixed, but their use in the comparison is seasonally dependent. The SIC1 data locations vary spatially and over time and the map shows the sum of all locations where SIC1 data is used throughout the comparison from 2007 to 2020.

Report conclusions

The work has led to the setup of a new and more suitable validation methodology for the OSI SAF SIC CDRs. The results from the new validation method assess the CDR stability and is more easily used to diagnose the SIC algorithms and therefore foster improvements. The VSA  work has had a direct impact on the successful release of the OSI SAF SIC CDR v3 products (OSI-450-a, OSI-430-a, OSI-458) in October 2022.

Benefits for the SAF

• This work has been beneficial to OSI SAF and to DMI that wished to adopt and implement the ESA-CCI validation methodology for the upcoming OSI SAF SIC CDRs. 
• The work has implications for the quality assessment of all upcoming OSI SAF SIC CDRs.

Report on this study

Validation Methodology  for the OSI SAF Sea Ice Concentration Data Records

Authors

Roberto Saldo, Technical University of Denmark (DTU)

Fabrizio Baordo and Matilde Kreiner, Danish Meteorological Institute (DMI)