Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 25 , Issue 4-6
Showing 1-6 articles out of 6 articles from the selected issue
  • H. Arakawa
    1947 Volume 25 Issue 4-6 Pages 45-47
    Published: November 05, 1947
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    The present writer has made an extensive and laborious study on the transformation of the equatorial air-mass moving from the Southern Hemisphere in the Far East. He has plotted dry and pseudo-wet-bulb temperatures for the individual Batavia flights.(1) In table I, he gives a brief resumé of 57 soundings used in this paper and the frequencies of the stability up to 30_??_mm Hg Level. It conforms well with the usual expectations of equatorial maritime air, being quite wet and unstable. For example, 78% cases are latent unstable, 4% cases psudo-unstable, and only 19% cases stable in the dry season (May-Oct.); 87% cases are latent unstable, 10% cases pseudo-unstable and only 3% cases stable in the rainy season (Nov.-April). Thus the instability is more pronounced in rainy season than in dry season.
    The mean values of greatest realisable energy up to 300mm Hg level for rainy and dry season are as follows:- rein_??_ season: 0.352 joule/g dry season: 0.205 joule/g (Nov.-april) (May-Oct.) From the same data the present writer has worked out for rainy season and dry season separately, as seasonal variations may affect the values of characteristic properties of air masses to a considerable extent. In table II, only readings taken during ascent at intervals of every 1km above M. S. L. have been included.
    When the Northern Hami sphere is summer, during the passage of the equatorial air from Batavia to Manila(1), Hong-Kong(2) or Nanking(3), there are definite increases in temperature and humidity at a_??_l heights above the surface. These results cited in table III indicate that while over China Sea or southern sea of Japan(4) the equatorial air is warmed at the surface, resulting in strong convection and through mixing.
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  • H. Arakawa
    1947 Volume 25 Issue 4-6 Pages 47-49
    Published: November 05, 1947
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    It has been pointed out that the mixing ratio may be computed from the formula: where W is the mixing ratio expressed in grams per kilogram of dry air, e, the vapor pressure, and p, the pressure of air. It is wellknown that the mixing ratio is one of the most conservative quantities that can be used for purpose of airmass identification, and the mixing ratio is constant in an adiabatic process. Thus it is quite eyident that the relation between pressure and vapor pressure in an adiabatic displacement of an unsaturated particle is as follows: where e is the vapor pressure of the particle at the pressure p, and e' is the vapor pressure it assumes at the pressure p' Thus we have an important relation as follows: If we now specify that the particle, originally at the vapor pressure e and the pressure p', be compressed to 1000_??_mb pressure, we have where E is the vapor pressure, which the particle assumes at this pressure 1000mb, and we shall call E as the potential vapor-pressure. The potential vapor-pressure is als_??_ constant in an adiabatic process. By definition it is clear that where E is the original potential vapor-pressure of the particle at the pressure P and the vapor pressure e, and E' is the potential vapor-pressure it assumes at the pressure p' and the vapor pressure e'. By means of Eq. (1) it can be easily shown that E=E' Thus proposition is proved.
    After vapor pressure h_??_s been determined, the potential vapor-pressure, E, is calculated by means of the formula (2). A slide rule is most convinient for this computation. (Table giving the factor 1000/p may also be constructed to facilitate this computation.) It can be shown that potential temperature and potential vapor pressure can be used for the purposes of air mass identification. These two quantities can also be used in isentropic analysis and synoptic weather science.
    For example, in any adiabatic chart, the lines of constant potential vapor pressure are identical with the lines of equal values of the humidity mixing ratio, and they may be called as the dew-point lines. This fact facilitates the computation of the dew-point lines. Further, when an element of air is set in motion in dry adiabatic process, the dr_??_ adiabatic through the dry-bulb temperature, the saturated adiabatic through the wet-bulb temperature and the dew-point line through the dew-point in any adiabatic chart, all meet in a point at the condensation level.
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  • I. Imai
    1947 Volume 25 Issue 4-6 Pages 49-55
    Published: November 05, 1947
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    It is very important, for the problem of ice formation, to investigate theoretically the paths of the fog particles near a cylindrical body exposed to wind. But it is fairly difficult to solve the equations of motion analytically, and the exact solution looks like to be obtainable only by numerical integration, say Runge-Kutta's method, starting from thg point at infinity.
    The author has found that the solution at sufficient distance from the body can be obtained by asymptotic expansion of x, y, u and v in terms of t, and the troubles of calculations are markedly reduced by taking the starting points of integration far nearer to the body.
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  • K. Takeda
    1947 Volume 25 Issue 4-6 Pages 55-57
    Published: November 05, 1947
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    The wind direction is observed by measuring the variation of the electric resistance due to the wind. A special device is undertaken for the proportionality between the reading of the measuring instrument and the variation of the wind direction, and to avoid sudden jumps in the reading at the endsof the resistance. Two wires are necessary.
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  • Y. Kato, T. Oguti
    1947 Volume 25 Issue 4-6 Pages 57-59
    Published: November 05, 1947
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    The investigation was made for the purpose of studying weather the change of the electrical conductivity of atmosphere concerned with the changes of the weather condition or not.
    The diurnal variation of the electrical conduetivity of atmosphere is remarkable and takes maximum value in the midnight and minimum in the morning. The former is considered to be due to the inversion of air temperature and the latter, to the upward air current and the generation of radiation fog.
    The value of the electrical conductivity of atmosphere, specialy that of negative ion, becomes maximum in case of, the low pressure or the front.
    The value of the electrical conductivity of atmosphere becomes minimum at the time of the generation of haze.
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  • S. Ogiwara
    1947 Volume 25 Issue 4-6 Pages 60-67
    Published: November 05, 1947
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    In the preceding investigations we have not touched with the temperature of cloud or rain drops, which is however very important on the evaporation. As the rate of fall of cloud and fog particles is very small we can assume the temperature and humidity of the surrounding air as constant through the fall. Therefore we can regard the rate of evaporation of them as stationary. By comparing the incoming and outgoing heat of particles their temperature was given as T0=T_??_+q(C0-C_??_) where, T_??_: air temperature; C0, C_??_, k, a: same as in the “Studies on Evaporation IV”; l: heat of vaporisation; λ: thermal conductivity of the air; α=μ0/2k; α=c_??_μ0/2λ μ0: rate of fall of the particle; Cμ: specific heat of the air at constant pressure; _??_: density of the air. The value of q is 2.48×106_??_2.24×106 for a=0_??_60μ and _??_o the temperature of cloud and fog particles is nearly the same as the wet bulb temperature of the surrounding air.
    As regards rain drops, however, only in the special case or in the stationary state its temperature is expressed by the same formula as that of cloud, the value of q being 2.24×106. In the non-stationary state its temperature changes as the drop falls in the air and so it depends on the temperature and humidity distributions of the atmosphere. Some example were shown diagrammatically in Fig. 3 and 4. Lastly the author calculated the increase of humidity of the atmosphere by the evaporation of rain drops and confirmed that fog or cloud can be not rarely formed by the evaporation of rain drops.
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