Author(s): K. Hirayama; S. Sakai; H. Sasaki
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Keywords: No Keywords
Abstract: Ice process of Lake Ogawara is observed for four winters from 1983-1986. The lake is located in Aomori Prefecture of Main island of Japan. The climate condition of the lake is rather mild; the average air temperature in January and February is only -2°C and the average freezing degree-day does not exceed 250°C-day. Complete ice cover is commonly formed. Water temperature of the lake reaches the freezing point in the middle of January and primary thin ice cover is initiated when air temperature drops. However, due to a strong western seasonal wind from Siberia the primary layer is broken and broken ice pieces are driven to the eastern shore. The complete ice cover is only attained when calm, cold condition is satisfied. A con dition to form a complete ic e cover i s analyzed. A \~ind stress on the ice sheet, which could cause a bending failu re of the sheet at the shore, is compared with an amount of ice growth in a day. Thus a necessary condition for initiation of complete ice cove r in lake Ogawara is obtained as a fun c tion of wind ve l oci ty and daily air temperature. This cr iteria gives a good co incidence with observations. The i ce cover of the lake consists of many layers of snow ice and s now s lush sandwiched b~tween them on an initia lly-formed black ice layer. Also a simulation model for the growth of ice cover after the formation of primary cove r is proposed. Computational res ults are favorably compared with fi~ld observation.
Year: 1992