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Data Set ID:
G02130

Reconstructed North American Snow Extent, 1900-1993, Version 1

This data set contains reconstructed monthly North American snow extent values for November through March, 1900-1993. Investigators used a combination of satellite and station observations and based the reconstruction on linear regressions between the two types of observations. The data also includes standard errors of estimates as well as the observed values upon which the regressions were based.

Geographic Coverage

Parameter(s):
  • Snow/Ice > Snow Cover > Snow Extent
Spatial Coverage:
  • N: 49, S: 35, E: -60, W: -125

Spatial Resolution:
  • Varies
Temporal Coverage:
  • 1 December 1900 to 31 March 1993
Temporal Resolution: 1 month
Data Format(s):
  • ASCII Text
Platform(s) GROUND-BASED OBSERVATIONS, NOAA-11, NOAA-14, NOAA-4, NOAA-7, NOAA-9
Sensor(s): AVHRR, SURVEYING TOOLS, VHRR, VISUAL OBSERVATIONS
Version: V1
Data Contributor(s): Allan Frei, David Robinson
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.

Frei, A. and D. Robinson. 2002. Reconstructed North American Snow Extent, 1900-1993, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5000014. [Date Accessed].

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Overview

This data set contains reconstructed monthly North American snow extent values for November through March, 1900-1993. Station-based snow observations are available for dates since the early twentieth century but lack comprehensive spatial coverage. A remotely sensed product based on visible-band imagery provides more complete spatial coverage but has been available only since the early 1970s. Investigators used a combination of satellite and station observations and based the reconstruction on linear regressions between the two types of observations. Additionally, the data set includes standard errors of estimates and the observed values upon which the regressions were based.

Figure 1 shows the reconstructed time series for North American snow extent for February from 1900-1993. Red dots are observed values and blue bold lines are reconstructed values. The figure also shows reconstructed values ± 1 standard error (blue solid lines). Note that reconstructed values can underestimate the magnitude, but not the sign, of the variations.

Reconstructed snow extent time series for the Northern Hemisphere
Figure 1. Reconstructed time series for North American snow extent for February, 1900-1993

Since the reconstructed values of snow extent are based on regression, variability in extent is underestimated, and therefore the magnitude of some extreme extent values is underestimated. However, in no case during the satellite era, when both data sets were available, was the sign of the reconstructed deviation from the mean extent different than observed.

Detailed Data Description

Format

The data are in ASCII text format.

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File Size

8 Kb

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Spatial Coverage

The data set contains reconstructions of snow cover extent for North America.

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Temporal Coverage and Resolution:

The data span ranges from December 1900 to March 1993 and contains time series of reconstructed monthly snow extent.

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Parameter or Variable

The data consist of reconstructed monthly snow extent values, standard errors, and observed values (when available). All values are in units 106 km2.

Sample Data Record:

Year Nov-R Nov-SE Nov-Obs Dec-R Dec-SE Dec-Obs Jan-R Jan-SE Jan-Obs Feb-R Feb-SE Feb-Obs Mar-R Mar-SE Mar-Obs
1910 10.42 0.749 13.60 0.654 14.86 0.595 14.35 0.396 12.54 0.496
1911 11.72 0.749 13.87 0.654 14.34 0.595 14.25 0.396 12.64 0.496
1912 10.25 0.749 13.55 0.654 15.10 0.595 14.68 0.396 14.53 0.496

Abbreviations Key: 
R: Reconstructed values 
SE: Standard errors of the reconstructions; can be used as confidence limits 
Obs: Observed values upon which the reconstructions are based 

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Data Acquisition and Processing

The investigator generated a time series of reconstructed monthly snow cover extent based on linear regressions between station-based snow observations (from the Cooperative Weather Observer Program) and remotely sensed visible-band imagery (from the NOAA polar orbiting series of satellites). Additionally, the data set includes standard errors of snow cover estimates and the observed values upon which the regressions were based.

Frei et al. (1999) and Frei and Robinson (1999) describe the reconstruction method, along with its advantages and disadvantages.

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References and Related Publications

Contacts and Acknowledgments

Dr. Allan Frei 
Department of Geography, Hunter College 
City University of New York 
Rm 1006, North Building 
695 Park Avenue 
New York, NY 10021 
USA 
Telephone: 212-772-5322 
Fax: 212-772-5268 
E-mail: afrei@geo.hunter.cuny.edu

Dr. David A. Robinson 
Professor and Chair, Department of Geography 
New Jersey State Climatologist 
Rutgers University 
54 Joyce Kilmer Avenue 
Piscataway, NJ 08854-8054 
USA 
Telephone: 732-445-4741 
Fax: 732-445-0006 
E-mail: drobins@rci.rutgers.edu

Document Information

Document Authors

NSIDC Technical Writers

Document Creation Date:

October 2002

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