Northern Hemisphere Seasonal and Intermittent Frozen Ground Areas 1901-2001
This data set contains monthly values of the total exposed land area of seasonally frozen ground and annual values for intermittently frozen ground in the Northern Hemisphere. Seasonally frozen ground is defined as the near-surface soil that experiences freeze for more than 15 days per year, while intermittently frozen ground experiences fewer than 15 days of freeze per year. The values were calculated based upon the monthly mean air temperature from the 1901-2002, 0.5 deg. global land temperatures from the University of East Anglia Climate Research Unit (Mitchell and Jones, 2005) using the technique described by Zhang, et al. (2003).
Two ASCII files are available. One file contains monthly values of seasonally frozen ground area in square kilometers for 1901-2001. The other file contains annual values of intermittently frozen ground area. Data are available via FTP.
The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.
T. Zhang, J. Smith. 2006. Northern Hemisphere Seasonal and Intermittent Frozen Ground Areas 1901-2001. [indicate subset used]. Boulder, Colorado USA: National Snow and Ice Data Center.