New version of the OSI SAF Sea Ice Concentration Climate Data Record

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Click here to look at quicklooks : http://osisaf.met.no/p/ice_reproc_daily_twoimg.php

OSI-450 is the second major version of the OSI SAF Global Sea Ice Concentration Climate Data Record (SIC CDR v2.0). The first version 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. A table reports an overview of the main differences and similarities between OSI-450 and OSI-409.

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 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.

Input data

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).

OSI-450 (like OSI-409) 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.

OSI-450 also use the global 3-hourly fields from ECMWF's ERA-Interim (Dee et al., 2011), which are accessed from the MARS archive. The following prognostic variables are taken from the ERA-Interim files and collocated with satellite swath data: 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 Product User Manual. Each step of the processing is presented in full details in the Algorithm Theoretical Basis Document.

File format and content

The data record 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 record

The sea ice concentration data record can be downloaded at this anonymous FTP server:

ftp://osisaf.met.no/reprocessed/ice/conc/v2p0.

The files are also served by a number of other protocols (THREDDS, OpenDap, WMS,...) here:

http://thredds.met.no/thredds/osisaf/osisaf_cdrseaiceconc.html.

Before you access the files, please note below the section about user registration.

Documentation

More technical details about the data record can be found in the Product User Manual and the Algorithm Theoretical Basis Document.

Validation results can be found in the Validation Report.

Associated ESA CCI data record from AMSR-E and AMSR2 data

A global sea ice concentration data record is released by the ESA CCI Sea Ice project (http://esa-seaice-cci.org). It uses the same algorithms (and processing chain) as OSI-450, but processes the AMSR-E (2002-2011) and AMSR2 (2012-onwards) satellite sensors. Prospective users are invited to visit the ESA CCI Data Portal to access the data.

Citation

This data record should be referred as the EUMETSAT OSI SAF global sea ice concentration data record (SMMR/SSMI/SSMIS) 10.15770/EUM_SAF_OSI_0008

All intellectual property rights of this product belong to EUMETSAT. The use of this product is granted to every interested user, free of charge. If you wish to use this product, EUMETSAT’s copyright credit must be shown by displaying the words “Copyright © 2017 EUMETSAT”.