あい風の正体

あい風という風が、日本海沿岸の各地で知られている。あい風はそれぞれの地の地形や気象で決まる局地的な風であり、風向も同じではない。しかし、各地のあい風には、A)海から幸せを運ぶ好ましい風、および、B)北前船のノボリの順風、という二つの共通な特徴がある。あい風の風向が、北海道から、東北、北陸、山陰と南下するにつれて、北寄りから東寄りの風にかわる事実は、特徴AとBによって説明される。あい風の典型例として、石狩のあい風が調べられた。石狩のあい風は、江戸時代初期、おそらく300年以上前から始まった物資の輸送や人々の交流、移住の歴史の中で、特徴AとBに沿うように生まれ、育まれてきた。石狩のあい風は、春、夏、秋に吹くさわやかな北寄りの風であるが、気象学的には、典型的な海風であることが、気象データの解析とドップラーライダーの観測から明らかにされた。AIKAZE is a wind which has been known at various regions along the coast of the Japan Sea. Its nature as a local wind depends on the geographical feature and climate at each place, and its blowing direction is different. But two common characteristics are noted in each AIKAZE,i.e.,A)favorable wind bringing about happiness from sea,and B)wind suitable for KITAMAE ship to sail south smoothly. A and B give reasonable grounds to understand the fact that the direction of AIKAZE changes from northerly wind at Hokkaido to easterly wind at Hokuriku and San-in regions. The history of AIKAZE at Ishikari goes back to the early years of the Edo period, roughly 300 years ago. It was concluded that AIKAZE at Ishikari has originated and developed through the long period of products transport and immigration in accordance with the characteristics A and B. AIKAZE at Ishikari is characterized as a crisp northerly breeze which blows in spring,summer,and autumn. Analyses of meteorological data and Doppler Lidar measurements showed that AIKAZE is a typical sea breeze blowing from the Bay of Ishikari

Air Bubble Formation in Ice Crystals

International Conference on Low Temperature Science. I. Conference on Physics of Snow and Ice, II. Conference on Cryobiology. (August, 14-19, 1966, Sapporo, Japan

Dynamical Behaviors of Snow Particles in the Saltation Layer

A photographic technique was developed to analyze dynamical behaviors of saltating particles in blowing snow. Each photograph taken with this technique can give information of trajectories of flying snow particles as well as their velocities and accelerations at each height. The analyses have shown that horizontal drag the surrounding air flow exerts on saltating particles is of Stokes type and the drag coefficient C_D can be represented as C_D=N/Re where Re is the Reynolds number and N is numerical constant ranging from 0.6 to 9. As for vertical motions a substantial downward force was found to act on a snow particle at the time of both its ascent and descent; Ascending snow particles did not reach the maximum height ^2/2g where υ_0 and g are respectively the initial vertical velocity and the acceleration of gravity, and the maximum heights measured were smaller than those calculated by taking account of drag due to the surrounding air

Power spectral analysis of snow densities at Mizuho Station, Antarctica

Power spectrum analyses were made of layer-to-layer variations of densities of core-samples recovered by drilling at Mizuho Station, Antarctica. The power spectra computed by the maximum entropy method show twenty-seven cyclic changes of snow deposition mode and consequently of climatic circumstances. The periods of the climatic changes are estimated to range from 6.1 to 389.4 years

Adhesion shear theory of ice friction at low sliding velocities, combined with ice sintering

Adhesion and shear deformation of ice have been traditionally considered to be responsible for ice friction at sliding velocities lower than about 10–2 m/s, but the simple mechanism cannot explain the recent finding that the ice–ice friction coefficient increases with decreasing sliding velocity. This article proposes an improved adhesion shear theory, which takes account of junction growth of asperities at the sliding ice interface due to sintering. At lower sliding velocities and higher homologous temperatures, contacts of ice asperities develop resulting in the increase of friction force

Measurements of Air Permeability and Elastic Modulus of Snow and Firn Drilled at Mizuho Station, East Antarctica

Air permeability and elastic modulus were measured for firn samples prepared from a 20-m pit and cores drilled to the depth of 147.5m at Mizuho Station in East Antarctica. Air permeability decreased and elastic modulus increased with increasing depth or density. Two distinct changes were found at densities of 550 and 730kg・m^, i.e. at porosities of 0.40 and 0.20,in the plots of air permeability and elastic modulus against density or porosity. The former change is explained by the alteration of the densification mechanicism from mechanical packing to plastic deformation of ice particles, and the latter by the attainment of an optimum configuration of ice bonding for air permeation and mechanical strength. Observed results are compared with the theoretical air permeability of an ideal snow, to which all polar snows are considered to approach in a long ageing period under high hydrostatic pressure and high homologous temperature. It is suggested that the optimum state, which is reached at the density of 730kg・m^ or the porosity of 0.20,is that of snow in which air channels are mainly located at intersections of grain boundaries and some 30 percent of them are unblocked

Densification rates of snow at polar glaciers

The densification process of snow at polar glaciers is explained as a pressure sintering phenomenon, and the strain rates of snow densification obtained from density-depth relationships at two polar sites are discussed in terms of pressure sintering parameters. It is found that the power law and diffusional creep mechanisms are important at shallower and deeper depths respectively than the depth of air bubble close-off