thawing index
Link: http://w3id.org/permafrost/v/ipaglossary/t0355
Within: IPA Permafrost Glossary
Definition: The cumulative number of degree-days above 0°C for a given time period.
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thawing index
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indice de dégel fr |
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| Comment |
Four main types of air thawing indices have been used: 1. approximate thawing index - calculated from the mean monthly air temperatures for a specific station without making corrections for negative degree-days (T < 0°C) in spring and fall (Boyd, 1973, 1979); 2. total annual thawing index - calculated by adding all the positive mean daily temperatures (°C) for a specific station during a calendar year (Harris, 1981); 3. seasonal thawing index - calculated as the arithmetic sum of all the positive and negative mean daily air temperatures (°C) for a specific station during the time period between the lowest point in the spring and the highest point the next fall on the cumulative degree-day time curve (Huschke, 1959); 4. design thawing index - calculated by taking the average of the seasonal thawing indices for the three warmest summers in the most recent 30 years of record. If data for 30 years are not available, then the index is based on the warmest summer in the latest 10-year period of record (U.S. Army/Air Force, 1966). The total annual thawing index has been used to predict permafrost distribution, and the design thawing index is commonly used in engineering design to estimate the maximum depth of thaw in frozen ground. A surface (ground, pavement, etc.) thawing index differs from the air thawing index (see n-factor).
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https://doi.org/10.4224/20386561
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