@article{oai:obihiro.repo.nii.ac.jp:00000679,
 author = {原田, 裕介 and 土谷, 富士夫 and 武田, 一夫 and 宗岡, 寿美},
 issue = {4},
 journal = {雪氷, Journal of the Japanese Society of Snow and Ice},
 month = {Jul},
 note = {application/pdf, 北海道東部地域の1定点（帯広畜産大学構内)で， 1981 ~2006年度冬期に土の凍結深と積雪深の観測を実施し，積雪下の土の凍結融解特性を分析した。その結果，年最大凍結深は，26冬期に5~55cmと年毎に大きく異なった。凍結深は，積雪深に影響され，積雪深が20cmに達するまでの積算寒度の平方根に比例することを確認した。一方，凍土の融解は，地中からの熱流の影響もあるが，根雪期間完了ごろに地表面から急速に進行する。そして，3月下旬から5月上旬までに凍土は完全に消失した。 この凍土が消失する深さは，根雪期間完了日から凍土消失日までに降雨や表土の再凍結がなければ，その聞の積算暖度の平方根に比例することが示された。これらの関係を用いて，帯広測候所の気温と積雪深データから196 1 ~ 1980年度の最大凍結深や凍土消失日の予測結果を加え，46冬期の長期特性を考察した。初冬の積雪の増加，最深積雪の増加，1991年以降の凍結指数減少などにより，最大凍結深は減少し，凍土消失日は4月中旬から上旬へ早まる， この半世紀の傾向が明らかになった。, Observations of frost and snow depths were conducted at the Obihiro University site located in eastern Hokkaido，Japan，from November 1981 to April 2007，and the characteristics of ground freezing and thawing under snow cover were analyzed. The results indicated that the annual maximum frost depth ranged from 5 to 55cm during the 26 winters. Frost depth is inftuenced by seasonal changes in snow depth，and it was confirmed that it is proportional to the square root of the freezing index when snow depth reaches 20cm. The thawing of frozen ground starts from the surface at the seasonal end of snow cover and finishes from late March to early May （last frost day) A linear relationship was found between the vanishing frost depth and the maximum frost depth. Further，the vanishing frost depth was found to be proportional to the square root of the thawing index. Based on these findings，the seasonal maximum frost depth，vanishing frost depth，and last frost day were calculated using meteorological data from 1961 to 1980 obtained :from Obihiro Meteorological Observatory. Taken together， we can conclude that the annual maximum frost depth has decreased in Ihe last half century and that the last frost day has shifted frorn mid to early April.},
 pages = {241--251},
 title = {長期観測に基づく積雪下の土の凍結融解特性},
 volume = {71},
 year = {2009}
}