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Sea Ice Products

An automatic analysis system, which derives sea ice products by combining satellite data from different sensors, has been developed and implemented for operational use.

Four operational products are defined:

  • Ice concentration (%) (Global)
  • Ice edge: closed ice/open ice/open water (Global)
  • Ice type: multi-year/first-year (Global)
  • Low Resolution Sea Ice Drift (Global)
These are defined as pre-operational because they switched to SSMIS on 19-01-2013 and are still under final validation.

One re-processed dataset is available:

Finally, some demonstrational products are available. Those products require more scientific and/or technical validation before they can be declared operational.

  • Medium Resolution Sea Ice Drift (NH)

Operational Sea Ice Products

OPERATIONAL Global Sea Ice Concentration
TitleOSI-401-a: SSMIS Sea Ice Concentration Maps on 10 km Polar Stereographic Grid
DescriptionThe sea ice concentration product from the EUMETSAT OSI SAF. Ice concentration is computed from atmospherically corrected SSMIS brightness temperatures, using a combination of state-of-the-art algorithms. It is operational since 2005.
Data usedSSMIS (DMSP F17), ECMWF forecast for atmospheric correction (SSM/I before 19-01-2013)
FormatsHDF5, NetCDF, GRIB
NRT accessFTP (last 31 days in NetCDF3, HDF5 and GRIB) and EUMETCast (GRIB).
ArchiveFTP (since 2005) and EUMETSAT Data Center
DocumentationProduct User's Manual
LinksQuicklooks NH, Quicklooks SH, Validation & monitoring
RemarksN/A
OPERATIONAL Global Sea Ice Edges
TitleOSI-402-a: Sea Ice Edge Maps on 10 km Polar Stereographic Grid
DescriptionThe sea ice edge product from the EUMETSAT OSI SAF. Ice classes are assigned from atmospherically corrected SSMIS brightness temperatures and ASCAT backscatter values, using a Bayesian approach. It is operational since 2005.
Data usedSSMIS (DMSP F17), ASCAT (Metop-A), ECMWF forecast for atmospheric correction (SSM/I before 19-01-2013)
FormatsHDF5, NetCDF, GRIB
NRT accessFTP (last 31 days in NetCDF3, HDF5 and GRIB) and EUMETCast (GRIB).
ArchiveFTP (since 2005) and EUMETSAT Data Center
DocumentationProduct User's Manual
LinksQuicklooks NH, Quicklooks SH, Validation & monitoring
RemarksN/A
OPERATIONAL Global Sea Ice Types
TitleOSI-403-a: Sea Ice Type Maps on 10 km Polar Stereographic Grid
DescriptionThe sea ice type product from the EUMETSAT OSI SAF. Ice classes are assigned from atmospherically corrected SSMIS brightness temperatures and ASCAT backscatter values, using a Bayesian approach. It is operational since 2005.
Data usedSSMIS (DMSP F17), ASCAT (Metop-A), ECMWF forecast for atmospheric correction (SSM/I before 19-01-2013)
FormatsHDF5, NetCDF, GRIB
NRT accessFTP (last 31 days in NetCDF3, HDF5 and GRIB) and EUMETCast (GRIB).
ArchiveFTP (since 2005) and EUMETSAT Data Center
DocumentationProduct User's Manual
LinksQuicklooks NH, Quicklooks SH, Validation & monitoring
Remarks
Note that during Arctic summer season (May-September) the ice type product is dubious because melting of the ice surface obscures the ice type signals.
PRE-OPERATIONAL Sea Ice Emissivity
TitleOSI-404: The near 50GHz global sea ice emissivity
Description The sea ice surface emissivity is representative for the near 50 GHz channels used for temperature sounding of the atmosphere using satellite radiometers such as SSMIS and AMSU.
Data usedSSMIS brightness temperatures at 19v, 37v and 37h
FormatsNetCDF
NRT accessFTP (last 31 days in NetCDF)
ArchiveFTP (coming soon)
DocumentationProduct User's Manual, Validation Report, ATBD
LinksQuicklooks NH,Quicklooks SH (coming soon)
Remarks
  • The emissivity is combined with the surface effective temperature, sometimes called the skin temperature, in the radiative transfer equation. Model simulations indicate that the snow-ice interface temperature or alternatively the 6 GHz brightness temperature is a closer proxy for the 50 GHz effective temperature than the snow surface or air temperature
OPERATIONAL Low Resolution Sea Ice Drift

Zoom from map above
TitleOSI-405-a: Sea Ice Motion Maps with 48 hours span, on 62.5 km Polar Stereographic Grid
DescriptionThe low resolution sea ice drift product from the EUMETSAT OSI SAF. Ice motion vectors with a time span of 48 hours are estimated by an advanced cross-correlation method (the Continuous MCC, CMCC) on pairs of satellite images. Several single-sensor products are available, along with a merged (multi-sensor) dataset.
Data usedSSMIS (85 GHz, DMSP F17), ASCAT (Metop-A)
FormatsNetCDF3
NRT accessFTP (last 31 days in NetCDF)
ArchiveFTP (since December 2009), HTTP and OPENDAP (from October 2006 to December 2009)
DocumentationProduct User's Manual, Validation Report
LinksQuicklooks NH, Validation and Monitoring
Remarks
  • Due to high atmospheric Liquid Water Content and to ice surface melting, it is not possible to track ice motion during Arctic summer, from the channels we are processing. Accordingly, the NH product files distributed between 30th April and 1st October do not contain any valid vector. Similar, the SH product fieles distributed between 31st October and 1st April do not contain any valid vector.
Operational Medium Resolution Sea Ice Drift

Zoom from map above
TitleOSI-407: Sea Ice Motion Maps with 24 hours span, on 20.0 km Polar Stereographic Grid
DescriptionThe Medium resolution sea ice drift product from the EUMETSAT OSI SAF. Ice motion vectors with a time span of 24 hours are estimated by a maximum cross-correlation method (MCC) on pairs of satellite images. Input data are ~1km Infra Red or Visible data from the AVHRR instrument on board the METOP satellite.
Data usedAVHRR channel 2 and channel 4 (Metop-A VIS and TIR respectively)
FormatsNetCDF
NRT accessFTP (last 31 days in NetCDF)
ArchiveFTP (coming soon)
DocumentationProduct User's Manual, Validation Report
LinksQuicklooks NH (coming soon)
Remarks
  • Due to pronounced cloud cover during summer, and occasional during winter periods, the daily data coverage can be very sparse.
  • The mr ice drift production is based on TIR data during winter and VIS data during summer, with an overlapping period in spring and autumn.

Other Sea Ice Products

REPROC DATASET Global Sea Ice Concentration reprocessing dataset (1978-2009)
TitleOSI-409: Global Sea Ice Concentration reprocessing dataset (1978-2009)
DescriptionThe reprocessed sea ice concentration dataset of the EUMETSAT OSI SAF, covering the period from October 1978 to October 2009 (SMMR and SSM/I). Ice concentration is computed from atmospherically corrected SSM/I brightness temperatures, using a combination of state-of-the-art algorithms and dynamic tie-points. The dataset includes error-bars for each grid cell (uncertainties). Version 1 of the dataset was released early 2010. Version 1.1 of the dataset, with longer temporal coverage was released late 2011.
Data usedSMMR and SSM/I, ECMWF re-analysis and forecast for atmospheric correction
FormatsNetCDF
Access DataFTP (whole dataset)
DocumentationProduct User's Manual, Validation report
LinksQuicklooks (single day), Quicklooks (compare 2 days)
Remarks WARNING: There is a bug in the uncertainty estimates in v1 of the data set. This bug has no effect on the maps of sea ice concentration. A new improved v1.1 dataset was made available in November 2011, with more accurate uncertainty estimates.

Use of this dataset should be acknowledged by referring to:
EUMETSAT Ocean and Sea Ice Satelitte Application Facility. Global sea ice concentration reprocessing dataset 1978-2009 (v1.1, 2011), [Online]. Norwegian and Danish Meteorological Institutes. Available from http://osisaf.met.no.

Sea Ice concentration analysis

The concentration product is currently based on passive microwave data from SSMIS. A sea ice concentration algorithm has been established as a smooth combination of two algorithms, Bristol algorithm and the Bootstrap frequency mode algorithm. To ensure an optimum performance over both marginal and consolidated ice, and to retain the virtues of each algorithm, the Bristol algorithm is given very little weight at low concentrations, while the opposite is the case over high ice concentrations. The algorithm is run on brightness temperatures corrected using the Numerical Weather Prediction (NWP) model based correction scheme and using the SAF monthly tiepoint set.

Atmospheric corrections

Contamination arising from atmospheric water vapour content and wind roughening of the open water surface is a problem. Using a radiative transfer model and input data from the ECMWF (European Center for Medium Range Weather Forecast) NWP-model weather an atmospheric correction is computed and applied to the SSMIS brightness temperatures. The corrected brightness temperatures are used in the ice concentration calculations as well as in the multi sensor ice analysis.

Multi sensor analysis of ice edge and ice type

A tool for combining various data sources containing uncertain information is given by the Bayesian approach. By this, several measured parameters can be combined to yield an optimal estimate taking into account the uncertainties involved in the various data sources. We obtain an estimate of the most probable ice class, and also of the uncertainty of this estimate.

A multi sensor analysis system using several sensors to analyse sea ice classes has been built. This system has been developed on SSM/I, scatterometer and AVHRR data. At present, SSMIS and ASCAT data is used operationally. The analysis system is implemented for ice edge analysis defining three classes: open water, open ice and closed ice. The basic step in building the analysis system was to derive the probability distributions for each ice class and given the measured quantity. To obtain this statistical knowledge of the average and the scatter of the expected measurement values, large sets have been collocated with satellite data from areas with know ice properties.

In a similar way an algorithm for sea ice type analysis, distinguishing between first year and multi year ice has been developed and implemented. The operational product uses SSMIS and ASCAT data.

Contact

Contact person for OSI SAF Sea Ice products is Steinar Eastwood, met.no, osisaf-manager[at]met.no.

   
       
     

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