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Data Set ID:
G02131

Reconstructed North American, Eurasian, and Northern Hemisphere Snow Cover Extent, 1915-1997, Version 1

This data set contains time series of monthly snow cover extent (SCE) for North America, Eurasia, and the Northern Hemisphere from 1915 to 1997, based on snow cover reconstruction and NOAA satellite data. In addition, the data set contains time series of annual variation in areally-averaged monthly snow depth and (SWE) for the North American grid domain used to derive the snow cover index.

Geographic Coverage

Parameter(s):
  • Snow/Ice > Ice Depth/Thickness > Snow Depth
  • Snow/Ice > Snow Cover > Snow Extent
  • Snow/Ice > Snow Water Equivalent
Spatial Coverage:
  • N: 90, S: 0, E: 180, W: -180

Spatial Resolution:
  • Varies
Temporal Coverage:
  • 1 January 1915 to 31 December 1997
Temporal Resolution: 1 month
Data Format(s):
  • ASCII Text
Platform(s) NOAA-4
Sensor(s): VHRR
Version: V1
Data Contributor(s): Ross Brown
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.

Brown, R. D. 2002. Reconstructed North American, Eurasian, and Northern Hemisphere Snow Cover Extent, 1915-1997, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5V985Z6. [Date Accessed].

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Overview

This data set contains time series of monthly snow cover extent (SCE) for North America, Eurasia, and the Northern Hemisphere from 1915 to 1997, based on snow-cover reconstruction and NOAA satellite data. The reconstruction method used in situ snow depth and daily climate data from the U.S., Canada, China, and the former Soviet Union (FSU) to generate a monthly snow-cover index, which was closely related to satellite-derived estimates of SCE in certain months. Brown (2000) describes the method, which may be more robust than SCE reconstruction based on statistical methods, such as those found in Brown, 1997; Frei et al., 1999.

In addition, the data set contains time series of annual variation in area-averaged monthly snow depth and estimated snow water equivalent (SWE) for the North American grid domain that was used to derive the snow cover index. These provide additional insights into secular changes in snow cover over North America since SCE and depth variations are not always positively correlated.

The ability to reconstruct SCE via the snow index method is closely constrained by the spatial distribution of in situ data. For North America, six months (November - April) were reconstructed, but only three months (October, March, April) could be generated for Eurasia.

Detailed Data Description

Format

The data are in ASCII text format and reside in one data file: time_series_sce_swe.txt.

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File Size

18 KB

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Spatial Coverage

The data set covers North America, North American mid-latitudes, Eurasia, and the Northern Hemisphere.

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Temporal Coverage

The data span ranges from January 1915 to December 1997.

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Parameter or Variable

Parameter Description:

The data set consists of three time series of monthly snow cover extent based on snow cover reconstruction and NOAA satellite data. The reconstruction method used in situ snow depth and daily climate data from the U.S., Canada, China, and the FSU to generate a monthly snow cover index that was calibrated with NOAA satellite-derived estimates of SCE over the 1972-1992 period.

The time series are as follows:

  • Historical variation in NA monthly snow cover extent, 1915-1997 (Nov - April)
  • Historical variation in Eurasian monthly snow cover extent, 1922-1997 (Oct, March, April)
  • Historical variation in NH SCE, 1922-1997 (March, April)

The data sets used to derive the time series were:

  • North America - in situ and reconstructed daily snow depths (1915-1992)
  • Eurasia - reconstructed monthly snow cover from daily climate data (1915-1993)
  • NOAA weekly snow cover extent (1972-1997)

The data set also includes two time series of annual variability in area-weighted monthly snow depth and SWE for the North American grid domain used to derive the snow cover index. SWE was estimated by applying mean monthly density values derived from an analysis of Canadian snow course data.

  • Historical variability in area-weighted (monthly) mean snow depth over North American mid-latitudes, 1915-1992 (Nov - April)
  • Historical variability in area-weighted (monthly) mean (estimated) SWE over North American mid-latitudes, 1915-1992 (Nov - April)

Sample Data Record:

Historical variation in North American (including Greenland) SCE (million km2)

Year Jan Feb Mar Apr Nov Dec
1915 17.405 17.034 15.379 12.066 12.347 16.261
1916 17.796 17.577 16.493 13.128 12.068 16.648
1917 17.770 17.467 16.974 14.293 11.486 17.308

Area-weighted mean snow depth (cm) over North America south of 60ºN

Year Jan Feb Mar Apr Nov Dec
1915 9.9 14.6 13.5 4.5 3.7 7.6
1916 17.2 23.1 29.3 15.6 3.4 8.0
1917 15.7 23.2 27.5 19.6 2.5 9.4
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Data Acquisition and Processing

The investigator generated a monthly snow cover index using a reconstruction method that used in situ snow depth and daily climate data from the U.S., Canada, China, and the FSU.

Brown (2000) describes the method for reconstructing snow cover extent, as well as gridding and data analysis methodology. Reconstruction of monthly snow cover extent was possible only in certain months due to the spatial distribution of the in situ data used to derive the snow cover index.

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References and Related Publications

Contacts and Acknowledgments

Mr. Ross D. Brown 
Meteorological Service of Canada 
2121 Trans Canada Highway 
Dorval, QC 
Canada 
H9P 1J3 

Telephone: (514) 421-4772 
Fax: (514) 421-4768 
E-mail: Ross.Brown@ec.gc.ca

Acknowledgments: 

The investigator acknowledges the following individuals and agencies:

  • Drs. David Robinson and Allan Frei for support and fruitful discussions
  • Dr. Pavel Groisman for supplying updated daily climate data from the FSU and for invaluable advice on correcting sources of inhomogeneity in the data
  • The National Climatic Data Center for making the U.S. daily snow depth data set freely available
  • The National Snow and Ice Data Center for the historical daily snow depth data set for the FSU

Document Information

Document Author

NSIDC Technical Writers

Document Creation Date

15 October 2002

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