Data Set ID:

CanSISE Observation-Based Ensemble of Northern Hemisphere Terrestrial Snow Water Equivalent, Version 2

This data set is a daily gridded terrestrial snow water equivalent (SWE) dataset based on five component SWE products:

This is the most recent version of these data.

Version Summary:

Version 2 includes 32 new files: 30 "" files which provide the difference in meters SWE from the highest and lowest observation of the component data sets; two climatological files. The climatological files indicate the climatological SWE or climatological spread in SWE for the 30-year period. In Version 1, December 31 was incorrectly dropped during a leap year. The Version 2 data corrected this by removing Feb. 29 from all years and reprocessing. Other changes to the data and metadata include meeting CF (Climate and Forecast) conventions.

STANDARD Level of Service

Data: Data integrity and usability verified

Documentation: Key metadata and user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools

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Data Format(s):
  • NetCDF
Spatial Coverage:
N: 90, 
S: 0, 
E: 180, 
W: -180
Platform(s):AQUA, DMSP, Nimbus-7, TERRA, TIROS
Spatial Resolution:
  • 1 degree x 1 degree
Temporal Coverage:
  • 1 January 1981 to 31 December 2010
Temporal Resolution1 dayMetadata XML:View Metadata Record
Data Contributor(s):Lawrence Mudryk, Chris Derksen

Geographic Coverage

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.

Mudryk, L. R. and C. Derksen. 2017. CanSISE Observation-Based Ensemble of Northern Hemisphere Terrestrial Snow Water Equivalent, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].

Literature Citation

As a condition of using these data, we request that you acknowledge the author(s) of this data set by referencing the following peer-reviewed publication.

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Detailed Data Description


Data are in NetCDF-3 format.

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File and Directory Structure

Data are available via HTTPS in the directory. There are 62 files, two files per year between 1981-2010 and two files that are the daily average for the thirty-year period. The .nc file provides the SWE for 365 days of the year and the file provides the difference in meters of snow water equivalent (SWE) from the highest and lowest observation of the component data sets. All files contain six variables. Three of the variables are one-dimensional floating-point arrays: Time, Lat, and Lon. The lat_bnds and the lon_bnds are two-dimensional floating arrays. To maintain compliance with the Climate and Forecast (CF) metadata standard, the variable for SWE is SNW. SNW is a three-dimensional floating array. See Table 1 for a description of the variables in each file. The metadata for all files are CF (Climate and Forecast) compliant.

Table 1. Variable Description
Variable Long Name Number of Elements Description
Time Time 365 For individual year files, time is the number of days since Jan. 01, 1981. For the 1981-2010 climatological files, time is the number of days since Jan 01. Values range from 0 - 364, corresponding to a specific calendar date. There is no 29 February for any year in any file.
Lat Latitude (°) 90 Degrees north. Values range from 0 - 89.
lat_bnds Latitude bounds (°) 2 columns x 90 rows Minimum and maximum bounding latitudes for each latitude measurement from 0° to 90° within a range from -.5° to 1.5°.
Lon Longitude (°) 360 Degrees east. Values range from 0 - 359.
lon_bnds Longitude bounds (°) 2 columns x 360 rows Minimum and maximum bounding longitudes for each longitude measurement from 0° to 359° within a range from -.5° to 1.5°.
SNW Snow Water Equivalent (m) 360 columns x 90 rows Values range from 0.0 to ~1.5 m. There are 365 bands of SNW in each file, and each band is a 360 x 90 floating-point array. A value of 1.e+2Θf indicates missing data.
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File Naming Convention

The file naming convention for the files in this data set is explained in Table 2. The thirty-year climatological files follow the naming convention except for the year, which is a range of years instead of individual years.  See the examples below.

Naming Convention:

Example File Names:

Table 2. File Naming Convention
Variable Description
SWE Snow Water Equivalent
Blended5 Indicates that the data are a blend of five component SWE data sets
1x1daily Data are re-gridded on a 1x1 grid; temporal resolution is daily
xxxx Year of original data acquisition. The 1981-2010 files denote climatology.
spread Indicates that the values represent the difference in meters SWE from the highest and lowest observation of the component data sets
v2 Version 2 file
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File Size

Each file is 45.12 MB.

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The volume of the data set is 2.73 GB.

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Spatial Coverage

Northern Hemisphere:

  • Southernmost Latitude: 0.0°
  • Northernmost Latitude: 90.0°
  • Westernmost Longitude: -180.0°
  • Easternmost Longitude: 180.0°

Spatial Resolution

Spatial resolution is 1 degree x 1 degree.

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Temporal Coverage

The data set coverage is from 01 January 1981 through 31 December 2010.

Temporal Resolution

The data have a daily temporal resolution.

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The parameter of this data set is snow water equivalent.

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Sample Data

Figure. 1 shows a sample of the NetCDF plot of SWE for March 13, 1981 (day 72).

Figure 1. SWE for March 13, 1981

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Software and Tools

Software and Tools

For a list of resources for accessing NetCDF files, see NetCDF Software Tools .

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Data Acquisition and Processing

Data Processing Steps

 The following is the methodology used in processing the data:

  1. Acquired component data sets at native resolution, daily frequency, from 1981-2010
  2. Re-gridded to common 1 x 1 degree regular lon/lat grid (resolution of coarsest data product)
  3. Assessed temporal homogeneity in total Northern Hemisphere snow water mass over the 1981-2010 period 
  4. Calculated unweighted average (full spatial field for each day) of the five SWE data sets 
  5. Calculated spread (difference between maximum and minimum SWE) among the five products (full spatial field for each day)

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Sensor or Instrument Description
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References and Related Publications

Contacts and Acknowledgments

Lawrence R. Mudryk
University of Toronto
60 St. George Street
Toronto, ON Canada M4C1N5

Chris Derksen
Environment Canada
Gatineau, Quebec K1A 0H3 Canada


These data were generated through a grant from the Natural Science and Engineering Research Council (Canada): Environment Canada.

Document Information


January 2017


No technical references available for this data set.

How To

V0 Programmatic Data Access Guide
Data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) can be accessed directly from our HTTPS file system. We provide basic command line Wget and curl instructions for HTTPS file system downloads below. For questions about programmatic access to NSIDC... read more