The process of getting data has improved!  Click the Download Data tab below to view all options for retrieving data. Read all about the new layout here.
Data Set ID:
NSIDC-0046

Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice Extent, Version 4

This data set is generated from brightness temperature data derived from the following sensors: SMMR, DMSP -F8, -F11 and -F13, SSM/Is, and SSMIS. The data are provided in the polar stereographic projection at a grid cell size of 25 x 25 km. This product is designed to provide a consistent time series of sea ice concentrations, the fraction or percentage of ocean area covered by sea ice, spanning the coverage of several passive microwave instruments.

This is the most recent version of these data.

Version Summary:
  • Temporal coverage was extended to 29 June 2014.
  • The projection changed to EASE-Grid 2.0, 720 x 720, at 25.000000 km
  • Sensor change over dates:
    • SMMR to SSM/I: 1987-07-03
    • SSM/I F08 to F11: 1991-12-09
    • SSM/I F11 to F13: 1995-05-08
    • SSM/I F13 to SSMIS F17: 2008-01-01
  • EASE-Grid Land Mask Source: Same as Version 3.1, regridded to EASE-Grid 2.0 (Brodzik et al. 2012).
  • Sea Ice data set used: 1978-10-23 to present: Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data.
Parameter(s):
  • Sea Ice > Ice Extent
  • Snow/Ice > Snow Cover
Data Format(s):
  • Binary
Spatial Coverage:
N: 90, 
S: , 
E: 180, 
W: -180
Platform(s):DMSP, DMSP 5D-2/F11, DMSP 5D-2/F13, DMSP 5D-2/F8, DMSP 5D-3/F17, GOES, GOES-7, Nimbus-7
Spatial Resolution:
  • 25 km x 25 km
Sensor(s):SMMR, SSM/I, SSMIS, VAS
Temporal Coverage:
  • 23 October 1978 to 31 December 2017
  • 3 October 1966 to 23 October 1978
Version(s):V4
Temporal Resolution7 dayMetadata XML:View Metadata Record
Data Contributor(s):Richard Armstrong, Mary Brodzik

Geographic Coverage

Download Via HTTPS: An Earthdata Login account is required to access these data.

Once you have logged in, you will be able to click and download files via a Web browser. There are also options for downloading via a command line or client. For more detailed instructions, please see Options Available for Bulk Downloading Data from HTTPS with Earthdata Login.

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Brodzik, M. J. and R. Armstrong. 2013. Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice Extent, Version 4. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/P7O0HGJLYUQU. [Date Accessed].

Back to Top

Collapse All / Open All

Detailed Data Description

Snow cover extent for this data set is based on the NOAA/NCDC Climate Data Record (CDR) of Northern Hemisphere (NH) Snow Cover Extent (SCE) by D. Robinson (2012) and regridded to the EASE-Grid. The NOAA/NCDC CDR of Northern Hemisphere Snow Cover Extent data were derived from the manual interpretation of AVHRR, GOES, and other visible-band satellite data (Helfrich et al. 2007). Sea ice extent is regridded to EASE-Grid from Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data.

Format

Data are stored in flat binary files with arrays of 720 columns by 720 rows of 1-byte unsigned integers. Each data file contains one array.

Background color on
Data Granularity

Data files represent weekly Northern Hemisphere snow cover and sea ice extent.

Background color on
File and Directory Structure

Data are available on the HTTPS site in the https://daacdata.apps.nsidc.org/pub/DATASETS/nsidc0046_weekly_snow_seaice/ directory. Within this directory there are four folders: browse, data, metdata, and stats. Figure 1 shows an image of the directory structure.

FTP directory image
Figure 1. FTP Directory Structure
Background color on
File Naming Convention

Weekly Data, Browse, and Metadata Files

Weekly data and browse files are named according to the following convention, and as described in Tables 1a and 1b:

EASE2_N25km.snowice.yyyymmd1-yyyymmd2.vVV.bin

EASE2_N25km.snowice.yyyymmd1-yyyymmd2.vVV.png

Where:

Table 1a. File Naming Convention for Weekly Data, Browse, and Metadata Files
Variable Description
EASE2_N25km Indicates this is an EASE-Grid 2.0 Northern Hemisphere 25 km file
snowice Indicates this is a snow and ice file
yyyymmd1 4-digit year, 2-digit month, and 2-digit day of month indicating the beginning of the NOAA week (d1)
yyyymmd2 4-digit year, 2-digit month, and 2-digit day of month indicating the end of the NOAA week (d2)
vVV Version number (v04)
.bin Indicates this is a binary data file
.png Indicates this is a PNG browse file

Metadata for each weekly data file is provided in an ASCII text file. The naming convention for this file varies only slightly from the above convention, for example:

EASE2_N25km.snowice.metadata.yyyy-yyyy.vVV.txt

Where:

Table 1b. File Naming Convention for Metadata Files (cont.)
Variable Description
metadata Indicates this is a metadata file
yyyy-yyyy Indicates 4-digit start and end years, such as 1966-2010
.txt Indicates this is an ASCII text file

Monthly Climatology Files

Monthly climatology files containing probability of occurrence, average extent, or variance data are named according to the following conventions, and as described in Table 2:

EASE2_N25km.parm.cli.mm.yyyy-yyyy.vVV.bin

EASE2_N25km.parm.cli.yyyy-yyyy.vVV.png

EASE2_N25km.parm.cli.yyyy-yyyy.vVV.ps

Where:

Table 2. File Naming Convention for Monthly Climatology Files
Variable Description
EASE2_N25km Indicates this is an EASE-Grid 2.0 Northern Hemisphere 25 km file
parm Parameter (sno, ice)
cli Climatology file (frq: frequency/probability of occurrence; avg: average extent; var: variance)
mm 2-digit month
yyyy-yyyy Indicates 4-digit start and end years, such as 1966-2005
vVV Version number (v04)
.bin Indicates this is a binary data file
.png Extension indicating a PNG file (viewable in any Web browser)
.ps Extension indicating a color PostScript file (viewable in any Web browser)
Background color on
File Size

Data files are approximately 508 KB each. The browse image files are approximately 22 to 23 KB each.

Background color on
Spatial Coverage

Northern Hemisphere

Spatial Resolution

Source data are regridded to a Northern Hemisphere of 25 km resolution with Version 2.0 EASE-Grid.

Projection and Grid Description

Data are gridded using EASE-Grid 2.0 (Brodzik et al. 2012), which is defined with the WGS 84 ellipsoid rather than the spherical Earth model in the original EASE-Grid. The grid is 720 columns by 720 rows (0,719). For a detailed comparison between the two versions of EASE-Grid, refer to the EASE-Grid Data Versions page.

Background color on
Temporal Coverage

Snow cover data are provided from 03 October 1966 through 23 October 1978, and combined snow cover and sea ice extent from 23 October 1978 through 31 December 2017.

Weekly sea ice extent was derived from an average of three or four sea ice source files for the SMMR time period. Weekly sea ice extent was derived from an average of seven ice source files for the SSM/I–SSMIS time period.

Temporal Resolution

Each file represents weekly data corresponding with the weekly NOAA/NCDC snow cover extent CDR data. A week is defined here as seven days.

Missing Data

No files exist for the following weeks:

  • Four weeks spanning 01 July – 28 July 1968
  • 21 weeks spanning 02 June – 26 October 1969
  • 12 weeks spanning 05 July – 26 September 1971

Files for the following weeks have no ice information:

  • All weeks prior to 23 October 1978
  • Five weeks spanning 07 December 1987 – 10 January 1988
Background color on
Parameter or Variable

Parameter Description

Snow Cover Extent

Binary, indicating snow or no snow

Sea Ice Extent

Binary, indicating presence or absence of sea ice when sea ice concentration is greater than 15 percent in a majority of a given week's sea ice files. The 15 percent ice concentration isopleth is a conventionally accepted cutoff for the ice edge (Johannessen et al. 1996).

Unit of Measurement

Binary presence or absence of snow or sea ice

Parameter Source

Parameter Range

Weekly Data

Data files contain a binary array of unsigned byte (8-bit) data with the following data values:

Table 3. Parameter Values
Data Value Parameter
0 Snow-free land
1 Snow-covered land
2 Sea ice
3 QC sea ice: pixel set to sea ice via QC during regridding
4 QC ocean: pixel set to open ocean via QC during regridding
5 QC snow: pixel set to snow via QC during regridding
6-252 Not used
253 Unclassifiable water due to mask mismatches
254 Corner pixels (outside Northern Hemisphere)
255 Open ocean
Metadata for Weekly Data

The metadata for each weekly data file is consolidated in one ASCII text file. Figure 2 shows a sample of the metadata file, which displays information such as pixel counts for two weekly data files in September 2008.

Figure 2. Sample of the Metadata File EASE2_N25km.snowice.metadata.1966-2010.v04.txt.
Monthly Probability of Occurrence

Monthly probability of occurrence is the percentage of time in a given month that each pixel was either snow or sea ice. Data in these files are 1 byte values, ranging from 0 to 100 percent.

Monthly Average Extent

Monthly average extent is the binary value for each pixel, indicating 50 percent or greater probability of occurrence of snow or sea ice. Data are 1 byte values of 0 (probability of occurrence was less than 50 percent) or 1 (probability of occurrence was greater than or equal to 50 percent).

Monthly Variance

Monthly variance is the snow or sea ice probability of occurrence for each pixel, calculated as shown in Equation 1:

Equation 1

Where:

i = 1966 through current processing year for snow or 1978 through current processing year for ice
n = number of years
= snow or sea ice probability of occurrence for data in this month for the period of record
 = snow or sea ice probability of occurrence for data in this month for year i

Data are 1-byte values, ranging from 0 to 26, representing variances of 0.0 (least variance, i.e. always or never snow or ice covered) to 0.26 (most variance).

Background color on
Sample Data Images

Sample data images are shown in Figures 3 through 6. Click on the thumbnail images for high-resolution images.

Sample image of snow cover and sea ice extent
Figure 3. Snow Cover and Sea Ice Extent Data for One Week
12 month average probability
Figure 4. Twelve-month Average Probability of Occurrence for Sea Ice
Extent Data
Sample image of snow and ice variance
Figure 5. Twelve-month Variance for Snow Cover and Sea Ice Extent
Sample image of snow and ice average over twelve months
Figure 6. Twelve-month Average of Snow Cover and Ssea Ice Extent
Background color on
Quality Assessment

NSIDC observed and manually inspected selected files in this data set, and performed spot checks against the original hand-drawn NOAA/NESDIS snow charts and the original sea ice data. Please refer to the Quality Control Summary for more information about quality control procedures at NSIDC.

Background color on

Software and Tools

Table 4 lists the software and tools that are available for this data set. Tools are accessible via direct FTP.

Table 4. Tools for this Data Set
Tool Type Tool File Name Description Access
Geocoordinate EASE2_N25km.lats.720x720x1.double
EASE2_N25km.lons.720x720x1.double

(Located within gridloc.EASE2_N25km.tgz)		 These are geolocation files containing double-precision (8-byte) floating point arrays (720 columns x 720 rows) representing latitude or longitude at the center of each cell in the EASE2_N25km grid. Cells in the grid that are not in the Northern Hemisphere are designated with the value -999.0. FTP
EASE2_N25km.gpd This is a Northern Hemisphere grid parameter definition file that contains projection and grid resolution information specifying a 25 km grid resolution in EASE-Grid 2.0. FTP
easeconv.pro

(Located within easeconv-0.3.tgz)		 Easeconv.pro is an IDL program containing routines to convert between latitude/longitude and row/column coordinates. FTP
Region Mask EASE2_N25km.LOCImask_land50_coast0km.720x720.bin This is the EASE-Grid 2.0 land-ocean-coastline-ice (LOCI) mask (Brodzik et al. 2012); it contains a flat, binary array (dimensions 720x720 pixels) of 1-byte unsigned integers. See the EASE-Grid 2.0 Land-Ocean-Coastline-Ice Masks Derived from Boston University MODIS/Terra Land Cover Data documentation for more information. FTP
Background color on

Data Acquisition and Processing

Data Source

Snow Data

The snow data used for Version 4 are from the recently released NOAA/NCDC Climate Data Record (CDR) of Northern Hemisphere (NH) Snow Cover Extent (SCE). The snow cover extent CDR uses an improved algorithm to produce pseudo-weekly snow charts from the daily, 24 km IMS product (NOAA/NESDIS/OSDPD/SSD 2004; Ramsay 1998; Helfrich et al. 2007). The snow cover extent CDR corrects spatial inconsistencies in snow-covered cells between the original weekly product and the pseudo-weekly data, primarily in mountainous regions, including the Himalayas, during specific months of the year. For data during the 1970s and early 1980s, the snow cover extent CDR also eliminates cells from the weekly data that were previously identified as patchy snow. D. Robinson and colleagues have determined that the early, coarser product depicted too much snow cover in these areas (personal communication to M. J. Brodzik, 23 December 2012). Robinson's statistical comparisons indicate that these adjustments are small, influencing previously published assessments of continental snow extent variability, by at most a few percent in several years in the late 1970s and early 1980s. Recent analysis of the snow cover extent CDR indicates a 95% confidence interval uncertainty in snow cover extent of plus or minus 3–5% during Northern Hemisphere spring for 1966–2010 (Brown and Robinson 2011).

Sea Ice Data

The sea ice data set used for Version 4 is the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data.

Background color on
Derivation Techniques and Algorithms

The majority of data values were derived via nearest-neighbor interpolation from the respective source grids. Pixels with QC data values were determined by more complex algorithms as described in the Quality Control Summary and in the Processing Steps in the following section of this document.

Background color on
Processing Steps
  1. Define an EASE-Grid 2.0 Northern Hemisphere land/ocean/permanent ice mask.
  2. Identify source land mask mismatches with the EASE-Grid 2.0 Northern Hemisphere land mask.
  3. Define EASE-Grid 2.0 sea ice climatology mask.
  4. Combine sea ice data for the given week and regrid sea ice from source grid (polar stereographic projection) to EASE-Grid 2.0 via nearest-neighbor interpolation.
  5. Set one-neighbor category mismatch pixels to QC sea ice if at least one of the surrounding eight source grid pixels was sea ice.
  6. Set two-neighbor category mismatch pixels to QC sea ice if at least one of the surrounding twenty-four source grid pixels was sea ice.
  7. Set the others category mismatch pixels to unclassifiable water.
  8. Set all regridded open ocean pixels above 83 degrees north latitude to QC sea ice.
  9. Set all regridded sea ice pixels outside the defined sea ice climatology mask area to QC ocean.
  10. Regrid digitized snow extent data from source (polar stereographic projection) grid to EASE-Grid 2.0 via nearest-neighbor interpolation.
  11. Set lower latitude snow neighbor category mismatch pixels to QC snow if at least one of the adjacent lower latitude source grid pixels was snow.
  12. Set any snow neighbor category mismatch pixels to QC snow if any of the adjacent source grid pixels were snow.

The EASE-Grid land-ocean-coastline-ice (LOCI) mask was derived from the Boston University version of global 1 km land cover from MODIS 2001 (Knowles 2004), courtesy of K. Knowles, National Snow and Ice Data Center.

NSIDC used American National Standards Institute (ANSI) C and Research Systems' Interactive Data Language (IDL) Version 8.2 to develop software for this data set.

Background color on
Version History

Table 5 summarizes the cumulative differences between versions of this product.

Table 5. Version History Summary
  • Version 1
  • Version 2
  • Version 3
  • Version 3.1
  • Version 4
  • Version 4.1
Version 1
NSIDC Data Use Recommendations
Projection, Dimensions, and Spatial Resolution EASE-Grid
721 x 721
25.067525 km
Temporal Coverage 1971-01-04 to 1995-09-03
Missing Weeks
  • 1972-12-18 to 1972-12-24 
    (1 week)
Weeks with 
No Ice
  • All weeks prior to 1978-10-23
  • 1984-08-13 to 1984-08-19 
    (1 week)
  • 1986-03-31 to 1986-04-13 
    (2 weeks)
  • 1987-12-07 to 1988-01-10 
    (5 weeks)
Weeks with Incomplete Ice
  • 1979-06-04 to 1979-06-17 
    (2 weeks)
  • 1990-10-22 to 1990-10-28 
    (1 week)
  • 1991-12-16 to 1991-12-29 
    (2 weeks)
Sensor Changeover Dates
  • SMMR to SSM/I F08: 1987-08-03
  • SSM/I F08 to F11: 1991-12-30
  • SSM/I F11 to F13: n/a (no F13 data in V1)
For details regarding sensors, refer to the SMMR, SSM/I, and SSMIS Sensors page.
Sea Ice Data Set Used N/A
Ice Climatology Static climatology, a "best guess" at likely sea ice locations, bounded by lat/lon boxes
Polar Stereographic Maps Earth Model Spherical, would have caused slight errors in regridded ocean/ice locations; the model error would cause geolocation errors of up to 8 km, which would result in errors of at most one pixel when sea ice was regridded using nearest-neighbor to the NL EASE-Grid
EASE-Grid Land Mask Source Original NSIDC EASE-Grid mask, all of Greenland was mapped to QC snow.
Manual Snow Chart Corrections
  • 1978-03-20
  • 1983-03-21
  • 1983-07-11
  • 1984-05-07
  • 1987-03-16
  • 1987-04-20
  • 1991-12-02
Version 2
NSIDC Data Use Recommendations
Projection, Dimensions, and Spatial Resolution EASE-Grid
721 x 721
25.067525 km
Temporal Coverage 1966-10-03 to 2001-06-24
Missing Weeks
  • 1968-07-01 to 1968-07-28 
    (4 weeks)
  • 1969-06-02 to 1969-10-26 
    (21 weeks)
  • 1971-07-05 to 1971-09-26 
    (12 weeks)
Version 1 included snow charts for these weeks, but D. Robinson removed them from Version 2 as a result of his most recent reanalysis. He does not recommend using the Version 1 files to fill in this gap (Robinson, personal communication).
Weeks with 
No Ice		 Same as Version 1
Weeks with Incomplete Ice
  • 1979-06-04 to 1979-06-17 
    (2 weeks)
  • 1990-10-22 to 1990-10-28 
    (1 week)
Sensor Changeover Dates
  • SMMR to SSM/I F08: 1987-08-03
  • SSM/I F08 to F11: 1991-12-09
  • SSM/I F11 to F13: 1995-05-08
Sea Ice Data Set Used N/A
Ice Climatology Monthly climatology, derived from historical record of SMMR and SSM/I sea ice data from 1978 to 1999
Polar Stereographic Maps Earth Model Elliptical, this is the correct Earth model for the input sea ice data
EASE-Grid Land Mask Source Original NSIDC EASE-Grid mask, all of Greenland was mapped to QC snow.
Manual Snow Chart Corrections
  • 1967-12-11
  • 1983-03-21
  • 1983-07-11
  • 1984-05-07
  • 1987-03-16
Version 3
NSIDC Data Use Recommendations NSIDC believes that those time periods using the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data should replace previous versions and updates using near-real-time and preliminary sea ice input data. Extensive quality-control, reducing the number of pixels misclassified as sea ice due to weather effects and/or coastal contamination as well as the long-term calibrated time-series extending back to the SMMR era makes this input data a higher quality product.
Projection, Dimensions, and Spatial Resolution EASE-Grid
721 x 721
25.067525 km
Temporal Coverage 1966-10-03 to 2005-06-05
Missing Weeks Same as Version 2
Weeks with 
No Ice
  • All weeks prior to 1978-10-23
  • 1987-12-07 to 1988-01-10 
    (5 weeks)
Weeks with Incomplete Ice None
Sensor Changeover Dates
  • SMMR to SSM/I: 1987-07-13
  • SSM/I F08 to F11: 1991-12-09
  • SSM/I F11 to F13: 1995-05-08
Sea Ice Data Set Used
Ice Climatology Monthly climatology, derived from historical record of SMMR and SSM/I sea ice data from 1978 to 2003
Polar Stereographic Maps Earth Model Same as Version 2
EASE-Grid Land Mask Source EASE-Grid land-ocean-permanent ice mask derived from BU-MODIS land cover (Knowles 2004)
Manual Snow Chart Corrections Rutgers corrected all previously noted irregularities. However, a
previously undetected irregularity was found and manually corrected in the chart for 1972-04-03.
Version 3.1
NSIDC Data Use Recommendations Users already making use of the original v03 data would not likely see significant changes in the overlap period in the new data because the processing differences are small. New users of these data are recommended to use v03.1 files for the overlap period 27 December 2003 to 05 June 2005. 

NSIDC believes that those time periods using the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data should replace previous versions and updates using near-real-time and preliminary sea ice input data. Extensive quality control, reducing the number of pixels misclassified as sea ice due to weather effects and/or coastal contamination as well as the long-term calibrated time-series extending back to the SMMR era makes this input data a higher quality product.
Projection, Dimensions, and Spatial Resolution EASE-Grid
721 x 721
25.067525 km
Temporal Coverage 2003-12-27 to 2007-06-24 (v3.1 files whose dates overlap v3.0 dates should replace them.)
Missing Weeks Same as Version 3
Weeks with 
No Ice		 Same as Version 3
Weeks with Incomplete Ice Same as Version 3
Sensor Changeover Dates Same as Version 3
Sea Ice Data Set Used
Ice Climatology Same as Version 3
Polar Stereographic Maps Earth Model Same as Version 3
EASE-Grid Land Mask Source Same as Version 3
Manual Snow Chart Corrections During data set quality control procedures, NSIDC noted a NOAA pixel at the western end of Baffin Island that became snow-free beginning with the week of 31 May to 06 June 1999, and that remained snow-free for the remainder of the current time series (through May 2005).
Version 4
NSIDC Data Use Recommendations NSIDC believes the improvements to the snow CDR data and the update to EASE-Grid 2.0 represent the best available analyses and presentation of these data sets, and warrant the complete reprocessing of this product. Refer to the Data Source section of this document. Users of previous versions are recommended to move to Version 4 data.
Projection, Dimensions, and Spatial Resolution EASE-Grid 2.0
720 x 720
25.000000 km
Temporal Coverage 1966-10-03 to 2014-06-29
Missing Weeks Same as Version 3.1
Weeks with 
No Ice		 Same as Version 3.1
Weeks with Incomplete Ice Same as Version 3.1
Sensor Changeover Dates
  • SMMR to SSM/I: 1987-07-03
  • SSM/I F08 to F11: 1991-12-09
  • SSM/I F11 to F13: 1995-05-08
  • SSM/I F13 to SSMIS F17: 2008-01-01
Sea Ice Data Set Used
Ice Climatology Same as Version 3.1, regridded to EASE-Grid 2.0 (Brodzik et al. 2012)
Polar Stereographic Maps Earth Model Same as Version 3.1
EASE-Grid Land Mask Source Same as Version 3.1, regridded to EASE-Grid 2.0 (Brodzik et al. 2012)
Manual Snow Chart Corrections Rutgers corrected all previously noted irregularities. However, NSIDC has discovered an irregularity in one file starting 03 April 1972
(EASE2_N25km.snowice.19720403-
19720409.v04.bin); a number of pixels in the Great Lakes region are showing a snow-free pattern. This has been reported to Rutgers.
Version 4.1
NSIDC Data Use Recommendations The input data to this data set, Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data, NSIDC-0051, was updated causing a minor update, 4.1, to this data set. The temporal coverage for this data set was also updated to 31 December 2015. Users of previous versions are recommended to move to Version 4.1 data.
Projection, Dimensions, and Spatial Resolution EASE-Grid 2.0
720 x 720
25.000000 km
Temporal Coverage 03 October 1966 to 31 December 2015
Missing Weeks Same as Version 3.1
Weeks with 
No Ice		 Same as Version 3.1
Weeks with Incomplete Ice Same as Version 3.1
Sensor Changeover Dates
  • SMMR to SSM/I: 1987-07-03
  • SSM/I F08 to F11: 1991-12-09
  • SSM/I F11 to F13: 1995-05-08
  • SSM/I F13 to SSMIS F17: 2008-01-01
Sea Ice Data Set Used
Ice Climatology Same as Version 3.1, regridded to EASE-Grid 2.0 (Brodzik et al. 2012)
Polar Stereographic Maps Earth Model Same as Version 3.1
EASE-Grid Land Mask Source Same as Version 3.1, regridded to EASE-Grid 2.0 (Brodzik et al. 2012)
Manual Snow Chart Corrections Rutgers corrected all previously noted irregularities. However, NSIDC discovered an irregularity in one file starting 03 April 1972
(EASE2_N25km.snowice.19720403-19720409.v04.bin); a number of pixels in the Great Lakes region are showing a snow-free pattern. This was reported to Rutgers.
Background color on
Limitations of the Data

These data are most appropriate for large area studies. Users should note that source grid snow pixels range in size from approximately 16,000 km2 to 42,000 km2, and source grid ice concentration pixels range in size from approximately 485 km2 to 664 km2.

Background color on
Known Problems with the Data

Pixels with values of unclassifiable water are undetermined because of mismatches between the various source and target land masks.

Background color on

References and Related Publications

Brodzik, M. J., B. Billingsley, T. Haran, B. Raup, M. H. Savoie. 2012. EASE-Grid 2.0: Incremental but Significant Improvements for Earth–Gridded Data Sets. ISPRS International Journal of Geo–Information 1(1):32-45. doi:10.3390/ijgi1010032.

Brodzik, M. J. and K. Knowles. 2011. EASE-Grid 2.0 Land Cover Classifications from Boston University MODIS/Terra Land Cover Data. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/doi:10.5067/XR8523MC24TB.

Brodzik, M. J., and K. Knowles. 2011. EASE-Grid 2.0 Land-Ocean-Coastline-Ice Masks Derived from Boston University MODIS/Terra Land Cover Data. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/doi:10.5067/VY2JQZL9J8AQ.

Brodzik, M. J. 1997. EASE-Grid: A Versatile Set of Equal-Area Projections and Grids. Boulder, Colorado USA: National Snow and Ice Data Center.

Brown R. D., and D. A. Robinson. 2011. Northern Hemisphere Spring Snow Cover Variability and Change over 1992–2010 Including an Assessment of Uncertainty. The Cryosphere 5:219–229, www.the-cryosphere.net/5/219/2011/doi:10.5194/tc-5-219-2011.

Cavalieri, D. J., J. Crawford, M. Drinkwater, W. J. Emery, D. T. Eppler, L. D. Farmer, M. Goodberlet, R. Jentz, A. Milman, C. Morris, R. Onstott, A. Schweiger, R. Shuchman, K. Steffen, C. T. Swift, C. Wackerman, and R. L. Weaver. 1992. NASA Sea Ice Validation Program for the DMSP SSM/I: Final Report. NASA Technical Memorandum 104559. 126 pp.

Cavalieri, D. J., P. Gloersen, and W. J. Campbell. 1984. Determination of Sea Ice Parameters with the NIMBUS–7 SMMR. Journal of Geophysical Research 89(D4):5355-5369.

Dewey, K. F. and R. Heim, Jr. 1981. Satellite Observations of Variations in Northern Hemisphere Seasonal Snow Cover. NOAA Technical Report NESS 87. 83 pp.

Dewey, K. F. and R. Heim Jr. 1982. New Data Base: A Digital Archive of Northern Hemisphere Snow Cover. Presented at Western Snow Conference, April 19–23. Reno, NV, 9 pp.

Estilow, T.W., A. H. Young & D.A. Robinson. 2015. A long-term Northern Hemisphere snow cover extent data record for climate studies and monitoring. Earth System Science Data, 7, 137-142, http://dx.doi.org/10.5194/essd-7-137-2015

Gloersen, P., W. J. Campbell, D. J. Cavalieri, J. C. Comiso, C. L. Parkinson, and H. J. Zwally. 1992. Arctic and Antarctic Sea Ice, 1978 - 1987: Satellite Passive Microwave Observations and Analysis. NASA SP–511.

Helfrich, S. R., D. McNamara, B. H. Ramsay, T. Baldwin, and T. Kasheta. 2007. Enhancements to, and Forthcoming Developments in the Interactive Multisensor Snow and Ice Mapping System (IMS). Hydrological Processes 21(12): 1576–1586.doi:10.1002/hyp.6720.

Johannessen, O. M., M. W. Miles, E. Bjørgo. 1996. Global Sea Ice Monitoring from Microwave Satellites. In IGARSS '96. 1996 International Geoscience and Remote Sensing Symposium. Remote Sensing for a Sustainable Future, ed. T. I. Stein, Vol. II: 932–934. Piscataway, NJ: Institute of Electrical and Electronics Engineers, Inc.

Knowles, K. 2004. EASE-Grid Land-Ocean-Coastline-Ice Masks Derived from Boston University MODIS/Terra Land Cover Data. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/doi:10.5067/YR21Q0Q8IPR6.

Knowles, K. 1993. Points, Pixels, Grids, and Cells: A Mapping and Gridding Primer. Boulder, Colorado USA: National Snow and Ice Data Center.

NOAA/NESDIS/OSDPD/SSD. 2004. IMS Daily Northern Hemisphere Snow and Ice Analysis at 4 km and 24 km Resolution. Boulder, Colorado USA: National Snow and Ice Data Center.

Ramsay, B. H. 1998. The Interactive Multisensor Snow and Ice Mapping System. Hydrological Processes 12:1537-1546.

Robinson, David A.; Estilow, Thomas W.; and NOAA CDR Program. 2012. NOAA Climate Data Record (CDR) of Northern Hemisphere (NH) Snow Cover Extent (SCE), Version 1. [indicate subset used]. NOAA National Centers for Environmental Information. doi: http://dx.doi.org/10.7289/V5N014G9 [access date].

Robinson, D. A., A. Bamzai, and B. Ramsay. 2001. Evaluating Northern Hemisphere Snow Cover During the Satellite Era: Variations in Extent and Associations with Temperature. Proceedings of the 12th Symposium on Global Change and Climate Variations. Albuquerque, New Mexico USA, American Meteorological Society, 36–39.

Robinson, D. A. 2000. Weekly Northern Hemisphere Snow Maps: 1966–1999. 12th Conference on Applied Climatology, Asheville, NC, American Meteorological Society, 12–15.

Robinson, D. A. and A. Frei. 2000. Seasonal Variability of Northern Hemisphere Snow Extent Using Visible Satellite Data. Professional Geographer 51: 307–314.

Robinson, D. A., J. D. Tarpley and B. Ramsay. 1999. Transition from NOAA Weekly to Daily Hemispheric Snow Charts. Proceedings of the 10th Symposium on Global Change, Dallas, TX, American Meteorological Society, 487–490.

Robinson, D. A., K. F. Dewey, and R. R. Heim, Jr. 1993. Global Snow Cover Monitoring: an Update. Bulletin of the American Meteorological Society 74:1689–1696.

Swift, C. T. and D. J. Cavalieri. 1985. Passive Microwave Remote Sensing for Sea Ice Research. EOS 66(49):1210–1212.

RELATED DATA COLLECTIONS

Contacts and Acknowledgments

Richard Armstrong
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309–0449 USA

Mary Jo Brodzik
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309–0449 USA

Acknowledgments: 

The National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA) provided funding for the production of this data set.

Document Information

DOCUMENT CREATION DATE

January 1997

DOCUMENT REVISION DATE

January 2013
September 2007
January 2005 
March 2002

No technical references available for this data set.

How To

How do I import EASE-Grid 2.0 snow cover and sea ice data into ArcGIS?
This document describes how to import  EASE-Grid 2.0 data files into ArcGIS, using Northern Hemisphere EASE-Grid 2.0 Weekly Snow Cover and Sea Ice Extent, Version 4 data as an example. These steps were tested with ArcGIS 10 on a Windows platform.  1. Rename data file Data files from... read more
Access complete Knowledge Base

Questions? Please contact:
NSIDC User Services
Phone: 1 303 492-6199
Email: nsidc@nsidc.org