A numerical simulation was carried out to examine the mechanism of summertime ice formation at the Ice Valley in Milyang, Korea. The Ice Valley's ice is different from ordinary perennial cave ice in that the ice is formed at the surface of the talus, exposed to hot air during summer, and disappears during winter. The talus consists of sedimentation of large boulders about 100cm in diameter along the mountain slope and has sufficient open space between the boulders for cold air to penetrate during winter.
The author attempted to simulate the Ice Valley's ice based on a theory of convective ice formation. This theory explains ice formation by an effective drainage flow of cold air penetrating into the talus during winter, since the air temperature above is colder than the temperature of the talus. The wintertime ice may be preserved by the extremely stable stratification of the air within the talus until the next summer.
A numerical model was developed based on a system of the equation of motion for air, the continuity equation for air, and the thermodynamic energy equation for both air and talus. The physical processes considered in the model are: 1) buoyancy; 2) Rayleigh friction, 3) adiabatic heating; 4) Newtonian cooling; 5) diffusion of air; and 6) thermal conduction of the tales. The governing equation is integrated in time by controlling the air temperature from -5°C in winter to 25°C in summer to examine the ice distribution and the stream function in the talus.
The result of the simulation appears to support the theory of convective ice formation under suitable model parameters. We confirmed that cold air can penetrate deep into the talus to form ice in winter and that the wintertime ice is preserved untill the next summer. During winter, the penetration of the cold air starts from the top region of the talus, a moderate downward motion occurs inside the talus, and an upward motion dominates along the slope of the talus surface. Conversely, in summer a descending motion along the talus slope develops to create a typical cold air flow, as observed. A moderate ascending motion is induced inside the talus to compensate for the strong cold air descending motion. The Ice Valley's ice melts fast at the region of the warm air intake at the foot of the talus slope. Hence, the coldest region appears slightly above the foot of the talus slope, which is consistent with observations.
It was found in this study that the ice itself plays an important role in preserving wintertime coldness owing to its abundant solidification heat. Without the existence of ice, rocks in the talus alone are inadequate to maintain the freezing temperature during summer because of its their specific heat capacity. The results of this study suggest that the moisture supply from the underground water table at the bottom of the talus is a necessary condition to form the Ice Valley's ice.

抄録全体を表示

MIS 2における東アジアの風成塵供給源と卓越風を復元する目的で,中国,韓国,日本の計26地域から黄土,土壌,古土壌,泥炭を採取し,これらの堆積層中の微細石英 (〓20μm) の酸素空格子信号強度を測定した.タクラマカンの砂漠レスやツアイダムのワジ堆積物は6.2～8.2, 黄土は5.8～8.3, 韓国の土壌は6.0～7.7であり,黄土や韓国土壌が中国の乾燥地域やチベット高原起源の風成塵の影響を強く受けたことを示している.日本各地の土壌・泥炭の微細石英はMIS 2で4.5～12.7であり,そのうち5.8～12,7の値を示す微細石英が遠隔地から飛来した広域風成塵起源,数値の低いものは大陸棚などから吹き上げられた風成塵と推測された.日本列島のうち北部日本地域は>10で東アジア北部から北西季節風によって,中央-西南日本地域は黄土と同じ5.8～8.7で中国の乾燥地域やチベット高原から偏西風によって,与那国島は9.7で中国南部などからそれぞれ飛来した可能性が指摘された.

抄録全体を表示

The horse chestnut is distributed mainly in the heavy snowfall areas of eastern Japan. It is a deciduous broad-leaf tree which together with beech trees composes valley forests. Raw horse chestnuts (buckeyes) cannot be eaten raw because they contain bitter tannic components such as aloin and alkaloid. It is thought that the method for removing tannic acid from buckeyes was discovered in the latter half of the mid-Jomon period, when buckeyes were a staple food. The custom of eating buckeyes originally diffused from the east to the west in Japan, and presently it is moving from east Japan to Okuhida and its environs in Gifu prefecture and to Tajima and neighboring districts in Hyogo prefecture.
We studied regional differences in the processing of buckeyes in Japan in: 1) the San-Shin-En border range extending through Aichi, Nagano, and Shizuoka prefectures; 2) the Chichibu range area extending through Saitama, Gunma, and Yamanashi prefectures, and the Tokyo metropolitan area; and 3) the Minobu range area in Yamanashi prefecture, which was previously little studied.
In the San-Shin-En border range area people follow the ancient custom of gathering buckeyes and use traditional preservation methods. Thus we find chirikisebu (the custom of buying a mountain forest excluding the buckeyes), yoraidochi (the traditional system of gathering buckeyes and distributing them equally), and narikizeme (the traditional ceremony of breeding trees), and Jomon-type processing methods, including kozawashi (buckeyes processed in water and boiling bleaching in the Hida highland area) and farm-type processed buckeye cakes. It is clear that people in the San-ShinEn border range area have depended on the buckeye as a food source for a long time. The traditional method for removing the tannic acid from buckeyes (neriaku) in this area is excellent. Although in the past it was customary to peel buckeyes with the teeth, the people here now use a wooden tool (tochimuki) to peel them, which is called an anguri in this area. The southern part of the Shinano district is well known for using tochimuki-ishi (stone for peeling buckeyes), which is called a tataki-ishi or tenshi.
Jomon-type processed buckeye foods are found throughout the Chichibu range area, including tochizarashi (buckeyes processed with water and boiling bleaching in Otaki village). It is still customary to peel buckeyes with the teeth. The neriaku method is also used for removing tannic acid. Although the tochimuki is not found in this area, it is most advanced in the use of tochimuki-ishi.
Processed buckeye foods in the Minobu range area are the same as in the San-Shin-En border range areas in terms of the method of acid removal, but the people in the Minobu range area use tools for peeling buckeyes similar to those used in the southern Shinano district and the Chichibu range area.
The results of this study show that Jomon-type processed buckeye foods are more widely distributed throughout, Japan than previously thought. In addition, the two cultural elements of Jomontype processing and peeling buckeyes with the teeth can be thought of as one set in terms of distribution.
Although we cannot depend on field work to determine regional differences in processed buckeye foods, the study of ancient documents and literature will become more important in future studies of this type.

抄録全体を表示