The Japanese 55-year Reanalysis (JRA55) is used as an auxiliary dataset for SMOS sea ice thickness retrieval for both Level 3 and Level 4 products.

On 24 January 2024, the JRA55 reanalysis dataset ended, and was replaced with the Japanese Reanalysis for Three Quarters of a Century (JRA-3Q) providing a high-quality homogeneous reanalysis dataset that covers the previous 75 years.

A preliminary comparison of JRA55 and JRA-3Q temperature and its impact on the Level 3 SMOS sea ice thickness product has been carried out by Alfred Wegener Institute (AWI) and is shown in the image below.

The comparison indicates a temperature difference of up to 5K in some regions of the Arctic, which is caused by the update of sea-ice and snow schemes in JRA-3Q.

Considering the impact of the new reanalysis dataset, the entire SMOS Level 3 and Level 4 archive will be reprocessed at the end of the winter season in April 2024 with JRA-3Q to assure a consistent long-term SMOS sea ice thickness dataset.