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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:
- GlobSnow combined SWE product (passive mircowave/ground-based weather station, version 2)
- ERA-Interim/Land reanalysis SWE product
- MERRA reanalysis SWE product
- Crocus SWE data set: output from the Crocus snowpack model, driven by ERA-Interim meteorology (Brun et al. 2013)
- GLDAS SWE product (version 2) (Rodell et al. 2004; Rodell and Beaudoing 2013)
Version 2 includes 32 new files: 30 ".spread.nc" 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.
Geographic Coverage
Spatial Coverage: |
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Spatial Resolution: |
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Temporal Coverage: |
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Temporal Resolution: | 1 day |
Parameter(s): |
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Platform(s) | AQUA, DMSP, NIMBUS-7, TERRA, TIROS |
Sensor(s): | AMSR-E, MODIS, SMMR, SSM/I, TOVS |
Data Format(s): |
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Version: | V2 |
Data Contributor(s): | Lawrence Mudryk, Chris Derksen |
Metadata XML: | View Metadata Record |
Data Citation
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. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.5067/96ltniikJ7vd. [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.
Mudryk, L. R. et al. 2015. Characterization of Northern Hemisphere Snow Water Equivalent Datasets, 1981–2010, Journal of Climate. 28. 8037-8051. http://dx.doi.org/10.1175/JCLI-D-15-0229.1
Detailed Data Description
Data are in NetCDF-3 format.
Data are available via HTTPS in the https://daacdata.apps.nsidc.org/pub/DATASETS/nsidc0668_swe_ensemble_v2
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 .spread.nc
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.
Variable | Long Name | Number of Elements | Description |
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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. |
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:
SWE_Blended5_1x1daily.xxxx.v2.nc
SWE_Blended5_1x1daily.xxxx.spread.v2.nc
Example File Names:
SWE_Blended5_1x1daily.1981.v2.nc
SWE_Blended5_1x1daily.1981.spread.v2.nc
SWE_Blended5_1x1daily.1981-2010.v2.nc
SWE_Blended5_1x1daily.1981-2010.spread.v2.nc
Variable | Description |
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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 |
Each file is 45.12 MB.
The volume of the data set is 2.73 GB.
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.
The data set coverage is from 01 January 1981 through 31 December 2010.
Temporal Resolution
The data have a daily temporal resolution.
The parameter of this data set is snow water equivalent.
Figure. 1 shows a sample of the NetCDF plot of SWE for March 13, 1981 (day 72).

Software and Tools
For a list of resources for accessing NetCDF files, see NetCDF Software Tools .
Data Acquisition and Processing
The following is the methodology used in processing the data:
- Acquired component data sets at native resolution, daily frequency, from 1981-2010
- Re-gridded to common 1 x 1 degree regular lon/lat grid (resolution of coarsest data product)
- Assessed temporal homogeneity in total Northern Hemisphere snow water mass over the 1981-2010 period
- Calculated unweighted average (full spatial field for each day) of the five SWE data sets
- Calculated spread (difference between maximum and minimum SWE) among the five products (full spatial field for each day)
See the following web pages for descriptions of the instruments used to gather the data:
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
DOCUMENT CREATION DATE
January 2017
DOCUMENT REVISION DATE
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