Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 32 , Issue 5-6
Showing 1-7 articles out of 7 articles from the selected issue
  • K. Oouchi
    1954 Volume 32 Issue 5-6 Pages 119-128
    Published: May 25, 1954
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    The author studied theoretically the process of freezing of supercooled water, on the basis of the following assumptions:
    (1) Free energy of an interface between ice and water is, for every molecule of water in contact with the interface, expressed by α-kTlog 2,
    where α=1/2{(inner energy of water per molecule) - (inner energy of ice per molecule)}=1/2 {(evaporation heat of ice per molecule) - (evaporation heat of water per molecule) } k=Boltzmann constant, and T=temperature.
    (2) Freezing begins with the formation of an ice bud of hexagonal prism in shape whose main axis is perpendicular to the nuclear surface, and the bud is to be formed on a plane surface of a solid “ freezing nucleus ” in supercooled water.
    (3) The ice bud sprouts at such portions of the nuclear surface as the molecules in the base of the ice prism can adhere to. An ice molecule can adhere to an atom of the nuclear surface only in the case where the displacement along the nuclear surface between to molecule and the atom is less than 12 per cent of lattice constant of ice. The radius of the ice prism should grow to that of this adhesion domain which can be calculated from both lattice structures and lattice constants for each of the nuclear surface and the base of the ice prism.
    Starting from these assumptions, the author calculated the following quantities:
    (i) the increase in the free energy, _??_F, caused by the formation of the ice bud;
    (ii) the temperature at which the ice bud of a given size will be formed, to satisfy either of the equations, where l means the radius of the ice bud in a number of molecular layers, and x the length of the ice bud in a number of molecular layers;
    (iii) the nucleation rate of the ice bud in a water droplet;
    (iv) the maximum radius of the ice bud determined by the lattice structure of the nuclear surface, -the critical freezing temperature which is characteristic of each nuclear substance.
    Calculated values of temperature agree well with the critical temperatures of ice crystal formation observed in the expansion chamber (-41°C, -32°C etc.), and also with the temperatures of freezing beginning in supercooled water droplets with various sorts of nuclei (AgI, PbI2, CdI2, NaNO3, CuI, NH4I, KI, NaCl, MgO, NaF, CdO, I2, CsI), obtained by many investigators. “-41°C” is thought to be the temperature at which an ice bud, consisting of 6 molecules or 24 molecules, forms in a droplet of supercooled water. “-32°C” is thought to be the eutectic point of a thin layer of NaCl solution, which is enveloped by newly condensed water and which envelops the freezing nucleus of NaCl crystal.
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  • T. Ôkita, K. Kimura
    1954 Volume 32 Issue 5-6 Pages 129-142
    Published: May 25, 1954
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    When dense steam fog occurred along the rivers in Asahikawa, Hokkoidô, in winter, the fog was seeded with the silver iodide nuclei by means of a new type silver iodide generator and the growth of ice crystals in the fog was observed.
    Various forms of ice crystals were produced, and among them plates were most predominant. A relatively small number of columns and capped columns were also found. Many steller crystals were formed on March 14, when the weather conditions were supposed to be favorable for the growth of these crystals.
    The observed size showed a good agreement with the value predicted by Houghton within about 150 m from the generator, but at larger distances from the generator the size became smaller than the predicted one. This probably suggests that larger crystals had fallen upon the ground through the shallow fog layer before they were carried to distant places.
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  • Y. Ogura, K. Miyakoda
    1954 Volume 32 Issue 5-6 Pages 143-159
    Published: May 25, 1954
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    The three-dimensional diffusion of minute particles emitted from a point source is discussed in close connection with the energy spectrum of the isotropic and homogeneous turbulence, and it is shown that the feature of the diffused cloud near the source is controlled solely by the energy spectrum in the intermediate wave-number range.
    Moreover, an approximate representation for statistical quantities which appear frequently in the turbulence theory is presented.
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  • Y. Ogura, K. Miyakoda
    1954 Volume 32 Issue 5-6 Pages 160-166
    Published: May 25, 1954
    Released: February 05, 2009
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    The spectrum of the pressure fluctuations in isotropic turbulence is theoretically studied on the basis of an assumption that the joint probability distribution of turbulent velocities is normal, making use of an approximate representation for the interrelation between the longitudinal velocity correlation and the velocity spectrum. The three-dimensional pressure spectrum _??_*(k) thus derived is: _??_*(k) _??_ k-7/3 for the intermediate wave-number range and _??_*(k)_??_k2 for the low wave-number range, corresponding to the velocity spectra F*(k) _??_ k-5/3 and F*(k) _??_ k, respectively. These theoretical results are compared with the pressure spectra observed in the westerlies zone of middle latitudes with fairly good agreement.
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  • M. MARUYAMA, K. HAMA
    1954 Volume 32 Issue 5-6 Pages 167-174
    Published: May 25, 1954
    Released: February 05, 2009
    JOURNALS FREE ACCESS
  • 1954 Volume 32 Issue 5-6 Pages 182a
    Published: 1954
    Released: February 05, 2009
    JOURNALS FREE ACCESS
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  • 1954 Volume 32 Issue 5-6 Pages 182b
    Published: 1954
    Released: February 05, 2009
    JOURNALS FREE ACCESS
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