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Dataset Title:  Sea Ice Extent and Concentration V2, NOAA/NSIDC, Arctic, 25km, 1850-Onward,
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Institution:  NOAA NSIDC   (Dataset ID: nsidcSeaIceConc1850)
Information:  Summary ? | License ? | FGDC | ISO 19115 | Metadata | Background (external link) | Files | Make a graph
Dimensions ? Start ? Stride ? Stop ?  Size ?    Spacing ?
 time (UTC) ?      2016    30 days 10h 29m 36s (uneven)
  < slider >
 latitude (degrees_north) ?      240    -0.25 (even)
  < slider >
 longitude (degrees_east) ?      1440    0.25 (even)
  < slider >
Grid Variables (which always also download all of the dimension variables)
 seaice_conc (Sea Ice Concentration (Percent), 1) ?
 seaice_source (Source of Sea Ice Concentration Data, 1) ?
 gridcell_area_2d (Grid Cell Area, km^2) ?

File type: (more info)

(Documentation / Bypass this form) ?
(Please be patient. It may take a while to get the data.)


The Dataset Attribute Structure (.das) for this Dataset

Attributes {
  time {
    Int32 _ChunkSizes 512;
    String _CoordinateAxisType "Time";
    Float64 actual_range -3.7855728e+9, 1.5134256e+9;
    String axis "T";
    String calendar "julian";
    String coverage_content_type "coordinate";
    String ioos_category "Time";
    String long_name "Time";
    String standard_name "time";
    String time_origin "01-JAN-1970 00:00:00";
    String units "seconds since 1970-01-01T00:00:00Z";
  latitude {
    String _CoordinateAxisType "Lat";
    Float32 actual_range 30.125, 89.875;
    String axis "Y";
    String coverage_content_type "coordinate";
    String ioos_category "Location";
    String long_name "Latitude";
    String standard_name "latitude";
    String units "degrees_north";
    Float32 valid_max 90.0;
    Float32 valid_min 30.0;
  longitude {
    String _CoordinateAxisType "Lon";
    Float32 actual_range 0.125, 359.875;
    String axis "X";
    String coverage_content_type "coordinate";
    String ioos_category "Location";
    String long_name "Longitude";
    String standard_name "longitude";
    String units "degrees_east";
    Float32 valid_max 360.0;
    Float32 valid_min 0.0;
  seaice_conc {
    Int32 _ChunkSizes 1, 240, 1440;
    String _Unsigned "false";
    Float64 colorBarMaximum 100.0;
    Float64 colorBarMinimum 0.0;
    String colorBarPalette "KT_ice";
    String comment "Values are percent-concentration from 0 to 100.  Sentinel value of 120 in the concentration field indicates land";
    String coverage_content_type "physicalMeasurement";
    String ioos_category "Ice Distribution";
    String long_name "Sea Ice Concentration (Percent)";
    Byte missing_value 120;
    String short_name "Concentration";
    String standard_name "sea_ice_area_fraction";
    String units "1";
  seaice_source {
    Int32 _ChunkSizes 1, 240, 1440;
    String _Unsigned "false";
    String colorBarContinuous "false";
    Float64 colorBarMaximum 19.0;
    Float64 colorBarMinimum 0.0;
    String colorBarNSections "19";
    String colorBarPalette "nsidc_seaIceSource";
    String coverage_content_type "referenceInformation";
    String ioos_category "Other";
    String long_name "Source of Sea Ice Concentration Data";
    Byte missing_value 0;
    String name_source_00 "Land";
    String name_source_01 "Satellite passive microwave";
    String name_source_02 "Danish Meteorological Institute";
    String name_source_03 "Dehn";
    String name_source_04 "NAVO yearbooks";
    String name_source_05 "AARI";
    String name_source_06 "Hill";
    String name_source_07 "Whaling Records - Complete Sea Ice";
    String name_source_08 "Whaling Records - Partial Sea Ice";
    String name_source_09 "Whaling Records - No Sea Ice";
    String name_source_10 "DMI yearbook narrative";
    String name_source_11 "ACSYS";
    String name_source_12 "Walsh and Johnson";
    String name_source_13 "JMA charts";
    String name_source_14 "Kelly ice extent grids";
    String name_source_15 "Landmask correction fill";
    String name_source_16 "Change-of-landmask ocean";
    String name_source_17 "Analog fill - spatial";
    String name_source_18 "Analog fill - temporal";
    String short_name "Seaice Source";
    String standard_name "source";
    String units "1";
  gridcell_area_2d {
    Float64 colorBarMinimum 0.0;
    String colorBarPalette "KT_amp";
    String coverage_content_type "physicalMeasurement";
    String ioos_category "Other";
    String long_name "Grid Cell Area";
    String short_name "Grid_Cell_Area";
    String standard_name "cell_area";
    String units "km^2";
    String _NCProperties "version=2,netcdf=4.6.3,hdf5=1.10.5";
    String cdm_data_type "Grid";
    String citation "";
    String comment 
"The data provided by PolarWatch are the gridded subset of the data package provided by NSIDC. Additional regional and arctic-wide ice extent, ice area, masks and ancillary data are available in the zip package from NSIDC at the source_url link. 

            The V2.0 extent and area values are slightly higher than those derived from V1.0. To create V1.1, inconsistencies in the V1.0 land mask were addressed by applying an -- if ever land, always land-- rule to grid cells. This had the effect of slightly expanding the land mask, so that the area covered by ocean cells, and thus the area that could contain sea ice, was proportionally reduced. The improved V2 land mask leaves more ocean cells in which ice may occur. In total, about 450,000 sq km of coastal ocean are added. V2.0 ice extent and area differ from extent and area derived using V1.0, simply because the V1.0 and V2.0 land areas are not the same. This difference is greatest in the winter months, when ice reaches a greater expanse of coastline. Most of the higher V2.0 extent and area values are the result of the changed land mask, with the change in input CDR source data version being an additional factor in the satellite era. There is a seasonal effect in the change attributable to the improved land mask. Metadata were alter to be in compliance with CF and ACDD standards.";
    String contributor_email ",,";
    String contributor_name "John E. Walsh, William L. Chapman, Florence Fetterer, J. S. Stewart";
    String contributor_role "investigator, investigator, investigator, investigator";
    String Conventions "CF-1.6, ACDD-1.3";
    String creator_email ",,";
    String creator_name "John E. Walsh, William L. Chapman, Florence Fetterer, J. S. Stewart";
    String creator_type "group";
    String dataset_doi "";
    String date_created "2019-09-03T00:00:00Z";
    String date_issued "2019-09-03T00:00:00Z";
    Float64 Easternmost_Easting 359.875;
    Float64 geospatial_lat_max 89.875;
    Float64 geospatial_lat_min 30.125;
    Float64 geospatial_lat_resolution 0.25;
    String geospatial_lat_units "degrees_north";
    Float64 geospatial_lon_max 359.875;
    Float64 geospatial_lon_min 0.125;
    Float64 geospatial_lon_resolution 0.25;
    String geospatial_lon_units "degrees_east";
    String history 
"Apr 19 2020: netCDF modified via nco tools to expand dimension of the grid_cell_area variable for compatability with ERDDAP: ncap2 -s gridcell_area_2d[time,latitude,longitude]= Gridcell_Area, Jan 27 2020: downloaded zip package including netCDF file from
    String id "g10010";
    String infoUrl "";
    String institution "NOAA NSIDC";
    String instrument "SSM/I, visual observations";
    String keywords "1850, Earth Science > Cryosphere > Sea Ice > Ice Extent, Earth Science > Cryosphere > Sea Ice > Sea Ice Concentration, Earth Science > Oceans > Sea Ice > Ice Extent, historical, NSIDC, sea ice concentration";
    String keywords_vocabulary "GCMD Science Keywords";
    String license 
"The data may be used and redistributed for free but is not intended
for legal use, since it may contain inaccuracies. Neither the data
Contributor, ERD, NOAA, nor the United States Government, nor any
of their employees or contractors, makes any warranty, express or
implied, including warranties of merchantability and fitness for a
particular purpose, or assumes any legal liability for the accuracy,
completeness, or usefulness, of this information.";
    String metadata_link "";
    String naming_authority "data/org.nsidc";
    String NCO "netCDF Operators version 4.7.9 (Homepage =, Code =";
    Float64 Northernmost_Northing 89.875;
    String platform "DMSP, ships";
    String publisher_email "";
    String publisher_name "NOAA NMFS SWFSC ERD and NOAA NESDIS CoastWatch PolarWatch";
    String publisher_type "institution";
    String references "Walsh, J. E., W. L. Chapman, F. Fetterer, and J. S. Stewart. 2019. Gridded Monthly Sea Ice Extent and Concentration, 1850 Onward, Version 2. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi:";
    String release_date "February 28, 2019";
    String source "microwave satellite observations, visual observations";
    String sourceUrl "";
    Float64 Southernmost_Northing 30.125;
    String summary "Observations from historical sources are the basis of this monthly gridded sea ice concentration product that begins in 1850. In 1979, these sources give way to a single source: concentration from satellite passive microwave data. The historical observations come in many forms: ship observations, compilations by naval oceanographers, analyses by national ice services, and others. Monthly sea ice concentration is given in a 1/4 degree latitude by 1/4 degree longitude grid. In addition to the concentration array, for each month a corresponding source array indicates where each of 16 possible sources is used.";
    String time_coverage_end "2017-12-16T12:00:00Z";
    String time_coverage_resolution "P1M";
    String time_coverage_start "1850-01-15T12:00:00Z";
    String title "Sea Ice Extent and Concentration V2, NOAA/NSIDC, Arctic, 25km, 1850-Onward, Monthly";
    String version "2.0";
    Float64 Westernmost_Easting 0.125;


Using griddap to Request Data and Graphs from Gridded Datasets

griddap lets you request a data subset, graph, or map from a gridded dataset (for example, sea surface temperature data from a satellite), via a specially formed URL. griddap uses the OPeNDAP (external link) Data Access Protocol (DAP) (external link) and its projection constraints (external link).

The URL specifies what you want: the dataset, a description of the graph or the subset of the data, and the file type for the response.

griddap request URLs must be in the form{?query}
For example,[(2002-06-01T09:00:00Z)][(-89.99):1000:(89.99)][(-179.99):1000:(180.0)]
Thus, the query is often a data variable name (e.g., analysed_sst), followed by [(start):stride:(stop)] (or a shorter variation of that) for each of the variable's dimensions (for example, [time][latitude][longitude]).

For details, see the griddap Documentation.

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