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.
Three operational products are defined:
- Ice concentration (%) (Global)
- Ice edge: closed ice/open ice/open water (Global)
- Ice type: multi-year/first-year (Global)
In addition, several pre-operational or demonstration products are available. Those products require
more scientific and/or technical validation before they can be declared operational.
- Ice concentration from AMSR-E (%) (Global)
- Low Resolution Sea Ice Drift (NH)
Operational Sea Ice Products
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| OPERATIONAL |
Global Sea Ice Concentration |
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Title | OSI-401: SSM/I Sea Ice Concentration Maps on 10 km Polar Stereographic Grid |
| Description | The sea ice concentration product from the EUMETSAT OSI SAF. Ice concentration is computed
from atmospherically corrected SSM/I brightness temperatures, using a combination of state-of-the-art
algorithms. It is operational since 2005. |
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| Data used | SSM/I (DMSP F13, F15), ECMWF forecast for atmospheric correction |
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| Formats | HDF5, NetCDF, GRIB |
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| NRT access | FTP (last 31 days in HDF5 and GRIB), EUMETCast (GRIB) and alternative FTP (NetCDF) |
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| Archive | FTP (since 2005) and UMARF |
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| Documentation | Product User's Manual |
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| Links | Quicklooks NH, Quicklooks SH, Validation & monitoring |
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| Remarks | N/A |
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| OPERATIONAL |
Global Sea Ice Edges |
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| Description | The sea ice edge product from the EUMETSAT OSI SAF. Ice classes are assigned
from atmospherically corrected SSM/I brightness temperatures, using a Bayesian approach.
It is operational since 2005. |
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| Data used | SSM/I (DMSP F13, F15), ECMWF forecast for atmospheric correction |
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| Formats | HDF5, NetCDF, GRIB |
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| NRT access | FTP (last 31 days in HDF5 and GRIB), EUMETCast (GRIB) and alternative FTP (NetCDF) |
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| Archive | FTP (since 2005) and UMARF |
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| Documentation | Product User's Manual |
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| Links | Quicklooks NH, Quicklooks SH, Validation & monitoring |
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| Remarks | N/A |
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| OPERATIONAL |
Global Sea Ice Types |
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| Description | The sea ice type product from the EUMETSAT OSI SAF. Ice classes are assigned
from atmospherically corrected SSM/I brightness temperatures, using a Bayesian approach.
It is operational since 2005. |
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| Data used | SSM/I (DMSP F13, F15), ECMWF forecast for atmospheric correction |
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| Formats | HDF5, NetCDF, GRIB |
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| NRT access | FTP (last 31 days in HDF5 and GRIB), EUMETCast (GRIB) and alternative FTP (NetCDF) |
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| Archive | FTP (since 2005) and UMARF |
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| Documentation | Product User's Manual |
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| Links | Quicklooks NH, Quicklooks SH, Validation & monitoring |
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| 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. |
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Other Sea Ice Products
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| PREOPERATIONAL |
Low Resolution Sea Ice Drift |
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Zoom from map above |
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Title | OSI-405: Sea Ice Motion Maps with 48 hours span, on 62.5 km Polar Stereographic Grid |
| Description | The 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.
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| Data used | AMSR-E (37 GHz, EOS-Aqua), SSM/I (85 GHz, DMSP F15), ASCAT (Metop-A) |
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| Formats | NetCDF |
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| NRT access | FTP (last 31 days in NetCDF) |
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| Archive | FTP (since December 2009), HTTP and OPENDAP (from October 2006 to December 2009) |
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| Documentation | Product User's Manual |
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| Links | Quicklooks NH |
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| 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
May, 1st and September 30th do not contain any valid vector.
- The product would have to be extended to Southern Hemisphere before it can be declared as operational.
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|
| DEMONSTRATION |
Global Sea Ice Concentration from AMSR-E |
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Title | OSI-408: AMSR-E Sea Ice Concentration Maps on 10 km Polar Stereographic Grid |
| Description | The sea ice concentration product from the EUMETSAT OSI SAF. Ice concentration is computed
from atmospherically corrected AMSR-E brightness temperatures, using a combination of state-of-the-art
algorithms. Thanks to the higher resolution of the AMSR-E channels, this product allows for retrieving
enhanced details, particularly close to the ice edges.
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| Data used | AMSR-E (EOS-Aqua), ECMWF forecast for atmospheric correction |
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| Formats | HDF5 |
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| NRT access | FTP (last 31 days in HDF5) |
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| Archive | contact us |
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| Documentation | N/A |
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| Links | N/A |
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| Remarks |
- This product requires more technical validation before the processing chain can be declared operational.
An operational status is expected during 2010.
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The concentration product is currently based on passive microwave
data from SSM/I. A sea ice concentration algorithm has been established
as a smooth combination of two algorithms, the NASA/TEAM 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 NASA/TEAM 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 SSM/I brightness temperatures. The corrected
brightness temperatures are used in the ice concentration calculations as well
as in the multi sensor ice analysis.
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, SSM/I 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 background sea ice information from met.no's
operational Sea Ice Service in Tromsø.
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 opeational product uses SSM/I data. A new test product
which use SSM/I and QuikScat data is also available.
Contact
Contact person for OSI SAF Sea Ice products is Steinar Eastwood, met.no,
osisaf-manager[at]met.no.
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