CMEMS Arctic MFC: Validation of thin sea ice

Validation based on satellite data from SMOS

Validation of the CMEMS ARC MFC results for the thickness of thin sea ice is performed using a dataset which is derived from observations from the Soil Moisture and Ocean Salinity (SMOS) satellite. The sea ice thickness data are produced using an emperical algorithm developped by Huntemann et al.. The algorithm takes advantage of data from the microwave radiometer onboard the SMOS satellite.

SMOS-based results for the thickness of thin ice are available from an OPeNDAP server at http://icdc.cen.uni-hamburg.de/thredds/aggregationSmosIcethicknessCatalog.html. SMOS processing was funded by EU project SIDARUS and data are obtained from http://www.meereisportal.de (grant: REKLIM-2013-04).

Results by bulletin date
April 2015
04-02
04-09
04-16
04-23
04-30

May 2015
05-07
05-14
05-21
05-28

June 2015
06-04
06-11
06-18
06-25

July 2015
07-02
07-09
07-16
07-23
07-30

August 2015
08-06
08-13
08-20
08-27

September 2015
09-03
09-10
09-17
09-24

October 2015
10-01
10-08
10-15
10-22
10-29

November 2015
11-05
11-12
11-19
11-26

December 2015
12-03
12-10
12-17
12-24
12-31

January 2016
01-07
01-14
01-21
01-28

February 2016
02-04
02-11
02-18
02-25

March 2016
03-03
03-10
03-17
03-24
03-31

April 2016
04-07
04-14
04-21
04-28

May 2016
05-05
05-12
05-19
05-26

June 2016
06-02
06-09
06-16
06-23
06-30

July 2016
07-07
07-14
07-21
07-28

August 2016
08-04
08-11
08-18
08-25

September 2016
09-01
09-08
09-15
09-22
09-29

October 2016
10-06
10-13
10-20
10-27

November 2016
11-03
11-10
11-17
11-24

December 2016
12-01
12-08
12-15
12-22
12-29

January 2017
01-05
01-12
01-19
01-26

February 2017
02-02
02-09
02-16
02-23

March 2017
03-02
03-09
03-16
03-23
03-30

April 2017
04-06
04-13
04-20
04-27

May 2017
05-04
05-11
05-18
05-25

June 2017
06-01
06-08
06-15
06-22
06-29

July 2017
07-06
07-13
07-20
07-27

August 2017
08-03
08-10
08-17
08-24
08-31

September 2017
09-07
09-14
09-21
09-28

October 2017
10-05
10-12
10-19
10-26

November 2017
11-02
11-09
11-16
11-23
11-30

December 2017
12-07
12-14
12-21
12-28

January 2018
01-04
01-11


Processing

We use results for the sea ice thickness and the uncertainty of these data, derived from the SMOS observations. Samples of these two fields are displayed below.

SMOS sea ice thickness SMOS sea ice thickness
SMOS sea ice thickness on 2017-03-09 Thickness uncertainty on 2017-03-09

Before the comparison of model results and SMOS-based observations is performed, we restrict the validation region by requiring that the uncertainty does not exceed either 1 m or 75% of the seaice thickness (see the description of Data quality on the L3C SMOS Sea Ice Thickness web page).

Next, the sea ice thickness bias and RMS difference between model results and observations are computed. Finally, the thickness distribution is categorized into pre-defined thickness classes, and the model/observation category match-up is displayed in contingency tables.

Validation based on satellite data from CryoSat-2

Validation of the CMEMS ARC MFC results for the thickness of thick sea ice is performed using a dataset which is derived from observations from the CryoSat-2 satellite, using observations from its SAR Interferometric Radar Altimeter (SIRAL) instrument. The sea ice thickness data set we use based on the SIRAL observations is provided by the Centre for Polar Observation and Modelling (CPOM), which also provides details and references on data processing that is applied.

CPOM provides access to the sea ice thickness results in an interactive interface. Data are available from CPOM under http://www.cpom.ucl.ac.uk/csopr/sidata.

Results by bulletin date
January 2017
01-12
01-19
01-26

February 2017
02-02
02-09
02-16
02-23

March 2017
03-02
03-09
03-16
03-23
03-30

April 2017
04-06
04-13
04-20
04-27

May 2017
05-04
05-11
05-18
05-25

June 2017
06-01
06-08
06-15
06-22
06-29

July 2017
07-06
07-13
07-20
07-27

August 2017
08-03
08-10
08-17
08-24
08-31

September 2017
09-07
09-14
09-21
09-28

October 2017
10-05
10-12
10-19
10-26

November 2017
11-02
11-09
11-16
11-23
11-30

December 2017
12-07
12-14
12-21
12-28

January 2018
01-04
01-11


Processing

We use results for the sea ice thickness, and the uncertainty of these data, derived from the CryoSat observations. The CryoSat data set consists of thickness data along the satellite tracks, aggregated over a 2-week period. Also provided are quality information represented by the standard deviation of these measurements. After discarding thickness values with standard deviations exceeding 75%, the thickness data are projected onto the TOPAZ grid prior to the model-data comparison.

Next, sea ice thickness results from TOPAZ simulations are averaged over the same 2-week period, and the region without data coveraged is masked. Based on the resulting set of observations and model results, basic statistical quantities are calculated, and maps of shaded contours for the products are plotted. Finally, the thickness distribution is categorized into pre-defined thickness classes, and the model/observation category match-up is displayed in contingency tables. Note that the tabulated dates above for the validation of the thick sea ice corresponds to the last day in the 2-week period under examination.

Region

Validation region

The present version of the coupled sea ice and ocean circulation model used in CMEMS's Arctic MFC covers the Arctic Ocean, the North Atlantic Ocean and adjacent ocean regions. The northern part is depicted in the figure to the left. Validation of sea ice thickness from model results is performed for the domain indicated by the blue region in the figure.

Note that the actual region for which the validation is performed varies from day to day due to limitations in the geographical coverage, and also due the screening of data resulting from regionally high estimated uncertainty in the observational product.

Finally, the temporal observational coverage is restricted seasonally. SMOS data are provided for the freeze-up season since the SMOS data poorly reproduce the sea ice thickness in the melting season. CryoSat data are discontinued during the season when meltponds affect the data. Thus, essentially, both products are available during winter, and not available during summer.

TOPAZ

The model results are produced with the TOPAZ ocean data assimilation model system. Presently, TOPAZ is run weekly with data assimillation one week prior to the bulletin date, followed by a one-week 100 member ensemble simulation ending on the bulletin date, and finally a 10 day deterministic forecast. TOPAZ was developed and is maintained by the Nansen Center.

TOPAZ results are available as aggregated, best estimates, and as a list of Bulletin dates with separate forecasts.