A new global sea ice concentration climate data record
OSI-450 is the second major version of the OSI SAF Global Sea Ice Concentration Climate Data Record (SIC CDR v2.0). OSI-430-b is the corresponding Interim CDR, an operational extension with a latency of 16 days. These datasets are now deprecated. Please use OSI-450-a/430-a instead.
OSI-450 is a full reprocessing of sea ice concentration, with improved algorithms and an upgraded processing chain, covering the period 1979 to 2015. The sea ice concentration is computed from the SMMR (1979-1987), SSM/I (1987-2008), and SSMIS (2006-2015) instruments, as well as ECMWF ERA-Interim data (Dee et al., 2011).
The basic principles and methodologies that were the backbone of the previous version (OSI-409) are also on board OSI-450 (e.g. atmospheric correction of brightness temperature with NWP re-analysis data, dynamic tie-points, uncertainties, etc.) but they were all revisited through dedicated R&D in the OSISAF project and, notably, through the ESA CCI Sea Ice projects, whose contribution is acknowledged.
OSI-430-b extends OSI-450 from 2016 onwards. It uses SSMIS data from NOAA CLASS, and operational analysis and forecast from ECMWF. Otherwise, the same processing chain and algorithms are used for OSI-450 and OSI-430-b, ensuring temporal consistency.
Input data
For OSI-450, the SMMR, SSM/I, and SSMIS data are all from the Fundamental Climate Data Record (FCDR) V3 (2016) from the EUMETSAT Climate Monitoring Satellite Application Facility (CM-SAF, DOI: 10.5676/EUM_SAF_CM/FCDR_MWI/V003).
The table below lists the satellite platforms used in OSI-450:
| Satellite | Start | End |
|---|---|---|
| Nimbus 7 SMMR | January 1979 | August 1987 |
| DMSP F8 SSM/I | July 1987 | December 1991 |
| DMSP F10 SSM/I | January 1991 | November 1997 |
| DMSP F11 SSM/I | January 1992 | December 1999 |
| DMSP F13 SSM/I | March 1995 | December 2008 |
| DMSP F14 SSM/I | May 1997 | August 2008 |
| DMSP F15 SSM/I | February 2000 | July 2006 |
| DMSP F16 SSMIS | November 2005 | December 2013 |
| DMSP F17 SSMIS | December 2006 | December 2015 |
| DMSP F18 SSMIS | March 2010 | December 2015 |
The table below lists the satellite platforms used in OSI-430-b:
| Satellite | Start | End |
|---|---|---|
| DMSP F16 SSMIS | January 2016 | on-going |
| DMSP F17 SSMIS | January 2016 | on-going |
| DMSP F18 SSMIS | January 2016 | on-going |
OSI-450 and OSI-430-b use all DMSP platforms (for SSM/I and SSMIS instruments) available at any time, taking advantage of the overlap of satellite missions. This strategy greatly reduces the occurrence of missing data in the final sea-ice concentration fields.
The following fields are accessed from ECMWF (ERA-Interim for OSI-450, and operational forecast for OSI-430-b): 10m wind speed, 2m air temperature, and total column water vapour. They are used for RTM-based corrections of the brightness temperatures.
More details are available from the PUM and the ATBD. Also, refer to Lavergne et al. (2019).
Algorithms and processing schemes
The processing steps can be divided in three main steps; Level 1 and 2, Level 3 and Level 4. An overview of these three steps is shown in the figure below, and the scope of each step is presented in full details in the ATBD.
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File format and content
The dataset is a collection of netCDF files with daily sea ice concentration products. There are separate files for the Northern Hemisphere and Southern Hemisphere grids.
Each file contains six variables (in addition to latitude, longitude, time, and other CF- related information):
- main (filtered) sea ice concentration (ice_conc)
- raw sea ice concentration values (raw_ice_conc_values)
- total uncertainty (total_standard_error)
- smearing uncertainty (smearing_standard error)
- algorithm uncertainty (algorithm_standard_error)
- status flag (status_flag)
All are netCDF-4 CLASSIC MODEL files, following the netCDF Climate and Forecast (CF) conventions for data layers, and the Attribute Convention for Data Discovery (ACDD) convention for metadata.
Download data set
The sea ice concentration data records can be downloaded at this anonymous FTP server:
- OSI-450: ftp://osisaf.met.no/reprocessed/ice/conc/v2p0
- OSI-430-b: ftp://osisaf.met.no/reprocessed/ice/conc-cont-reproc/v2p0
The files are also served by a number of other protocols (THREDDS, OpenDap, WMS,...) here:
- OSI-450: http://thredds.met.no/thredds/osisaf/osisaf_cdrseaiceconc.html
- OSI-430-b: http://thredds.met.no/thredds/osisaf/osisaf_crepseaiceconc.html
Before you access the files, please note below the section about user registration.
Data set history
- OSI-450: Released in Mai 2017, covers 1979-2015.
- OSI-450: Released in Mai 2019, covers 2016 onwards (16 days latency).
- OSI-450: New version released, OSI-450-a, should be used instead of OSI-450.
Documentation
More technical details about the data set can be found in the Product User Manual and the Algorithm Theoretical Basis Document.
Validation results can be found in the Validation Report.
Quicklooks
Quicklooks can be viewed in a browser tool. The tool can also be used to compare sea ice at two different dates in the data record, or compare sea ice in the new data record to that in the old data record. See this link.
Reference
OSI-450
EUMETSAT Ocean and Sea Ice Satellite Application Facility. Global sea ice concentration climate data record 1979-2015 (v2.0, 2017), [Online]. Norwegian and Danish Meteorological Institutes. doi: 10.15770/EUM_SAF_OSI_0008
OSI-430-b
EUMETSAT Ocean and Sea Ice Satellite Application Facility. Global sea ice concentration interim climate data record 2016 onwards (v2.0, 2019), [Online]. Norwegian and Danish Meteorological Institutes.
Lavergne, T., Sørensen, A. M., Kern, S., Tonboe, R., Notz, D., Aaboe, S., Bell, L., Dybkjær, G., Eastwood, S., Gabarro, C., Heygster, G., Killie, M. A., Brandt Kreiner, M., Lavelle, J., Saldo, R., Sandven, S., and Pedersen, L. T.: Version 2 of the EUMETSAT OSI SAF and ESA CCI sea-ice concentration climate data records, The Cryosphere, 13, 49-78, doi:10.5194/tc-13-49-2019, 2019.
Registration
We invite all users to register at our central web site https://osi-saf.eumetsat.int. By doing so, you can choose to get service messages about sea ice products, and we will be able to serve you better. We will also be able to better report on the use of our products.
Contact
Contact person for the OSI SAF Sea Ice Concentration Climate Data Records is Thomas Lavergne, MET Norway, osisaf-manager[at]met.no.
Associated ESA CCI data record from AMSR-E and AMSR2 data
A global sea ice concentration dataset was released by the ESA CCI Sea Ice project (https://climate.esa.int/en/projects/sea-ice/). It uses the same algorithms (and processing chain) as OSI-450, but processes the AMSR-E (2002-2011) and AMSR2 (2012-onwards) satellite sensors. See Lavergne et al. (2019).
Previous version of the SIC CDR
The first version of the OSI SAF SIC CDR was called OSI-409, and was initiated in 2006 through visiting scientist activities with the UK Met Office (Stark, 2008) and NSIDC (Meier, 2008). OSI-409 was extended at several occasions, using operational SSMIS and ECMWF data after 2009, but keeping the algorithms and processing chains unchanged. It is described in Tonboe et al. 2016.
