The global sea ice concentration climate data record version 3

OSI-450-a is the third major version of the OSI SAF Global Sea Ice Concentration Climate Data Record (SIC CDR v3.0). OSI-430-a is the corresponding Interim CDR, an operational extension with a latency of 16 days.

OSI-450-a is a full reprocessing of sea ice concentration, with improved algorithms and an upgraded processing chain, covering the period 1978.10.01 to 2020.12.31. The sea ice concentration is computed from the SMMR (1978-1987), SSM/I (1987-2008), and SSMIS (2006-2020) instruments, as well as ECMWF ERA5.

The basic principles and methodologies that were the backbone of the previous version (OSI-450) are also on board OSI-450-a (e.g. atmospheric correction of brightness temperature with NWP re-analysis data, dynamic tie-points, uncertainties, etc.) but they were partly revisited through dedicated R&D in the OSISAF project and, notably, through the ESA CCI Sea Ice projects, whose contribution is acknowledged.

OSI-430-a extends OSI-450-a from 2021 onwards. It uses SSMIS data from NOAA CLASS, and preliminary daily updates of the ERA5 analysis from ECMWF (ERA5T). Otherwise, the same processing chain and algorithms are used for OSI-450-a and OSI-430-a, ensuring temporal consistency.

A new feature in this version is the so-called fasttrack stream of the ICDR. The nominal ICDR files are provided with a 16 days latency, while the fasttrack ICDR files are provided with 2 days latency.

More details of these data records are provided in the Product User Manual (PUM), Algorithm Theoretical Basis Document (ATBD) and Scientific Validation Report (SVR).