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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.
Data are available as an ASCII text file via FTP.
Citations for use of this data should read:
Brown, R. 2002. Reconstructed North American, Eurasian, and Northern Hemisphere snow cover extent, 1915-1997. Boulder, CO: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5V985Z6
Mr. Ross D. Brown
Meteorological Service of Canada
2121 Trans Canada Highway
Telephone: (514) 421-4772
Fax: (514) 421-4768
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 investigator acknowledges the following individuals and agencies:
The data are in ASCII text format.
The data set covers North America, North American mid-latitudes, Eurasia, and the Northern Hemisphere.
The data span ranges from January 1915 to December 1997.
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:
The data sets used to derive the time series were:
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 variation in North American (including Greenland) SWE (million km2)
Area-weighted mean snow depth (cm) over North America south of 60ºN
Data are available via FTP.
Please see Snow Data Sites for additional snow data.
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.
Frei, A. and D. Robinson. 2002. Reconstructed North American snow extent, 1900-1993. Boulder, CO: National Snow and Ice Data Center. Digital media.
Brown, R.D. 1997. Historical variability in Northern Hemisphere spring snow covered area. Annals of Glaciology 25: 340-346.
Brown, R.D. and R.O. Braaten. 1998. Spatial and temporal variability of Canadian monthly snow depths, 1946-1995. Atmosphere-Ocean 36: 37-45.
Easterling, D.R., P. Jamason, D. Bowman, P.Y. Hughes and E. H. Mason. 1997. Daily snow depth measurements from 195 stations in the United States. ORNL/CDIAC-95, NDP-059.
Frei, A., M.G. Hughes and D.A. Robinson. 1999. North American snow extent: 1910-1994. Int'l. J. Climatology 19: 1517-1534.
The following acronyms and abbreviations are used in this document .
|FSU||Former Soviet Union|
|SCE||Snow Cover Extent|
|SWE||Snow Water Equivalent|
15 October 2002