freezing index

(Also called "coldness sun.") As used by the U. S. Army Corps of Engineers, the number of Fahrenheit degree-days (above and below 32°F) between the highest and lowest points on the cumulative degree-days time curve for one freezing season.

For a critical review of the topic see Sakari Tuhkanen (1980). "The freezing index is used as a measure of the combined duration and magnitude of below freezing temperatures occurring during any given freezing season. The index determined for air temperatures at 4.5 feet above the ground is commonly designated as the air freezing index, while that determined for temperatures immediately below a surface is known as the surface freezing-index." (from Glossary of Arctic and Subarctic Terms 1955).
Compare thawing index.
Tuhkanen, S. 1980. Climatic parameters and indices in plant geography. Acta phytogeographica Suecica. 67. Svenska Vaxgeografiska Sallekapet, Uppsala, . 105 pp.
Arctic, Desert, Tropic Information Center (ADTIC) Research Studies Institute 1955. Glossary of Arctic and Subarctic Terms. ADTIC Pub. A-105, Maxwell AFB, AL, . 90 pp.