The core partner data centres that are integrated in NorDataNet are listed in https://www.nordatanet.no/en/node/69. In addition to this NorDataNet harvests information on relevant datasets from a number of other data centres. The data centre responsible for the data presented is usually (but not always) listed in the discovery metadata. In essence NorDataNet is an aggregating service that combines information from a number of existing data centres.
Citation of data and service
If you use data retrieved through this portal, please acknowledge our funding source:
Research Council of Norway, project number 245967/F50, Norwegian Scientific Data Network.
Always remember to cite data when used!
Citation information for individual datasets is often provided in the metadata. However, not all datasets have this information embedded in the discovery metadata. On a general basis a citation of a dataset include the same components as any other citation:
author, title,
year of publication,
publisher (for data this is often the archive where it is housed),
edition or version,
access information (a URL or persistent identifier, e.g. DOI if provided)
All partner repositories of NorDataNet support Digital Object Identifiers (DOI), but not all datasets are minted. Whether or not minted depends often on source of the data (e.g. operational data are often yet not minted). However, all data centres support persistent identifiers according to local systems. The information required to properly cite a dataset is normally provided in the discovery metadata the datasets.
Brief user guide
The Data Access Portal has information in 3 columns. An outline of the content in these columns is provided above. When first entering the search interface, all potential datasets are listed. Datasets are indicated in the map and results tabulation elements which are located in the middle column. The order of results can be modified using the "Sort by" option in the left column. On top of this column is normally relevant guidance information to user presented as collapsible elements.
If the user want to refine the search, this can be done by constraining the bounding box search. This is done in the map - the listing of datasets is automatically updated. Date constraints can be added in the left column. For these to take effect, the user has to push the button marked search. In the left column it is also possible to specific text elements to search for in the datasets. Again pushing the button marked "Search" is necessary for these to take action. Complex search patterns can be constructed using logical operators identified in the drop down menu with and phrases embedded in quotation marks. Prefixing a phrase with '-' negates the phrase (i.e. should not occur in the results). Searches are case insensitive.
Other elements indicated in the left and right columns are facet searches, i.e. these are keywords that are found in the datasets and all datasets that contain these specific keywords in the appropriate metadata elements are listed together. Further refinement can be done using full text, date or bounding box constraints. Individuals, organisations and data centres involved in generating or curating the datasets are listed in the facets in the right column. The combination of search fields (including facets) is based on a logical "AND" combination of the fields, i.e. all conditions are fulfilled for the results provided.
Sea Ice Frequency charts display the percentage of ice-covered days of a given month over the last 30 years. These charts, available as GeoTIFF raster data, are derived from daily sea ice concentration data provided by the National Snow and Ice Data Center (NSIDC), USA. Ice frequency is defined as the frequency of occurence of sea ice concentration values equal or higher than 0.15. A value of 100% indicates areas where every single day of a given month sea ice concentrations were equal or higher than 0.15, while a value of 0% indicates areas where such sea ice concentrations have never been observed. A value of 0.5% indicates that sea ice concentrations were equal or higher than 0.15 during approximately 5 days within 30 years period for that particular month.
In addition to the raster files in GeoTIFF format vector polygon files, called isobands, are provided in ESRI Shapefile format. As polygons they represent the area, unlike the contour lines which represent the interval boundaries. To reduce the noise and improve the visual representation of the data we set the lower and upper threshold to 0.5% and 99.5% respectively. Please refer to the raster files for exact pixel values.
Reserved values
Several mask values are reserved in the raster dataset:
- -1 - Missing data
- -2 - Landmask
- -3 - Coastal areas
Coordinate reference system and extent
The dataset comes in the same geographic projection as the source NSIDC dataset: EPSG 3411 or “NSIDC Polar Stereographic North”. Please refer to https://nsidc.org/data/polar-stereo/ps_grids.html for the complete grid definition.
References
- Meier, W., F. Fetterer, M. Savoie, S. Mallory, R. Duerr, and J. Stroeve. 2017. NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration, Version 3. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: https://doi.org/10.7265/N59P2ZTG. [2017-07-04].
- Peng, G., W. Meier, D. Scott, and M. Savoie. 2013. A long-term and reproducible passive microwave sea ice concentration data record for climate studies and monitoring, Earth Syst. Sci. Data. 5. 311-318. https://doi.org/10.5194/essd-5-311-2013
Changelog
2024-01-17
- Added product for 1993-2022
2024-01-16
- Added product for 1992-2021
- Switched to NSIDC Sea Ice Concentration Climate Data Record version 4
2018-08-23
- Lower and upper boundaries in vector data set to 0.5% and 99.5% respectively
- Minimum and maximum extent shapefiles are not included anymore since the information is already provided in the isoband files
- Attribute name for ice frequency values in shapefile attribute table is changed from “value” to “ice_freq”
2018-07-02
This dataset update includes a major change where the new type of source data is used: (Sea Ice Concentration Climate Data Record, G02202-v3)[http://nsidc.org/data/G02202/versions/3]. Major changes:
- Transition to NSIDC G02202-v3 Sea Ice Concentration Climate Data Record dataset.
- Filling polar pole: we assume that the polar hole areas always contain sea ice concentrations above 15%. Therefore we set the values to 100%
- In contrast with the previous processing scheme we do not fill the missing days with the values from the preceding day in 1987. However the weight of each observation is maintained and the final occurence frequency values are not affected.