1986 Fiscal Year Final Research Report Summary
Relation between the freezing index calculated from air temperature and the frost penetration depth
| Project/Area Number |
60460236
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
自然地理学
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| Research Institution | Hokkaido University |
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Principal Investigator |
SEIITI Kinosita Professor, Institute of Low Temperature Science, Hokkaido Univ, 低温科学研究所, 教授 (20001638)
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| Co-Investigator(Kenkyū-buntansha) |
FUKUDA Masami Associate Professor, Institute of Low Temperature Science, Hokkaido Univ, 低温科学研究所, 助教授 (70002160)
HORIGUCHI Kaoru Associate Professor, Institute of Low Temperature Science, Hokkaido Univ, 低温科学研究所, 助教授 (60001658)
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| Project Period (FY) |
1985 – 1986
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| Keywords | Frozen Ground / Frost Action / 寒令 |
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| Research Abstract |
The ground freezes, when its surface is exposed to cold air. Then the frost penetration depth D cm is obtained by an empirical formula :
D = <alpha> <root(F)> , where F゜C・day is the freezing index, that is, the cumulative degreedays of the daily mean air temperature below 0゜C. The value of <alpha> usually ranges widely from 1 to 5. The coverage of the ground surface with vegetation or snow decreases D. Also the heaving of the ground surface decreases D, according to another empirical formula: D = <D_0> (1 - a <gamma> ), where <D_0> is the value of D when the surface does not heave; <gamma> is the heave ratio (the ratio of the heave amount to D); and a is the decrease coefficient.
First, analytical calculation was made to obtain <D_0> and a of the second formula assuming the Stephan model (the temperature gradient is linear within the frozen zone and the temperature is 0゜C throughout the unfrozen zone).
Secondly, from the calculation of field data collected during several winters a was found to range widely from 0.2 to 1.3, having a tendency to decrease with an increase in heave ratio.
Thirdly, mathematical analysis was made of the temperature of the ground surface, using various meteorological data above the ground surface. As a result, a new method was proposed for precise calculation of D when the surface does not heave.
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