Northern Hemisphere Seasonal and Intermittent Frozen Ground Areas 1901-2001, Version 1

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.