Global Annual Freezing and Thawing Indices, Version 1

The total annual freezing and thawing indices are defined as the
cumulative number of degree-days when air temperatures are below and
above zero degrees Celsius. The total annual freezing index has been
widely used to predict permafrost distribution; estimate the
maximum thickness of sea, lake, and river ice, and the maximum depth of
ground-frost penetration; and classify snow types. The annual total
thawing index has been used to predict permafrost distribution and to
estimate the maximum depth of thaw in frozen ground. Both total
freezing and thawing indices are important parameters for engineering
design in cold regions.

Data coverage is global. The data set contains the total annual freezing and thawing indices with a spatial resolution of 0.5 degrees
latitude by 0.5 degrees longitude. Two data files are available, for
the freeze and thaw indices respectively, in flat binary format. Each
file is approximately 1 MB in size. The total annual freezing and
thawing indexes were calculated based upon the monthly mean air
temperature by Legates and Willmott (1990).