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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.
The figure above shows the reconstructed time series for North American snow extent, February, 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.
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.
Data are available as ASCII text files via FTP.
Citations for use of this data should read:
Frei, A., and D. Robinson. 2002. Reconstructed North American snow extent, 1900-1993. Boulder, CO: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5000014
Dr. Allan Frei
Department of Geography, Hunter College
City University of New York
Rm 1006, North Building
695 Park Avenue
New York, NY 10021
Dr. David A. Robinson
Professor and Chair, Department of Geography
New Jersey State Climatologist
54 Joyce Kilmer Avenue
Piscataway, NJ 08854-8054
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
The data are in ASCII text format.
The data set contains reconstructions of snow cover extent for North America.
The data span ranges from December 1900 to March 1993 and contains time series of reconstructed monthly snow extent.
The data consist of reconstructed monthly snow extent values, standard errors, and observed values (when available).
R: Reconstructed values
SE: Standard errors of the reconstructions; can be used as confidence limits
Obs: Observed values upon which the reconstructions are based
All values are in units 106km2
Data are available via FTP.
Please see Snow Data Sites for additional snow data.
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.
Brown, R. 2002. Reconstructed North American, Eurasian, and Northern Hemisphere snow extent, 1915-1997. Boulder, CO: National Snow and Ice Data Center. Digital media.
Frei, A. and D. A. Robinson. 1999. Northern Hemisphere snow extent: regional variability 1972-1994. International Journal of Climatology 19: 1535-1560.
Frei, A., D. A. Robinson and M. G. Hughes. 1999. North American snow extent: 1900-1994. International Journal of Climatology 19: 1517-1534.
Robinson, D. A. 1993. Historical daily climatic data for the United States. Proceedings of the Eighth Conference on Applied Climatology. Anaheim, CA. American Meteorological Society: 264-269.
Robinson, D. A., K. F. Dewey and R. R. J. Heim. 1993. Global snow cover monitoring: an update. Bulletin of the American Meteorological Society 74(9): 1689-1696.
Robinson, D. A. and A. Frei. 1999. Seasonal variability of Northern Hemisphere snow extent using visible satellite data. Professional Geographer 52(2): 307-315.
17 October 2002