Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 29 , Issue 1
Showing 1-4 articles out of 4 articles from the selected issue
  • G. Yamamoto, A. Miura
    1951 Volume 29 Issue 1 Pages 1-13
    Published: 1951
    Released: February 05, 2009
    Opacity at Sendai was investigated following the lines of researches of Wright and Simpson. The obtained results are as follows:
    1. The values of opacity at Sendai toward N direction at noon are practically independent of relative humidity when the latter values are smaller than 50% but they increase rapidly with humidity when the values of humidity exceed 50%. This relation, is well explained if we assume, following Simpson, that change of opacity is due to acid nuclei which change their sizes with relative humidity. If, for instance, H2SO4 nuclei only are assumed as acid nuclei, we have, as their number and hygroscopic constant, N=190, Q=16×10-15 respectively. Or as the concentration of H2SO4 we have 3.04×10-11g/cc. However, the opacity-humidity relation at Sendai may also be explained by assuming that sea-salt nuclei as well as acid nuclei are effective to opacity. In this case, we have for NaCl, which is taken to represent sea-salt nuclei, N=85, Q=10×10-15 and the concentration of NaCl=5.1×10-12g/cc. and for H2SO4, which is taken to represent acid nuclei, N=130, Q=18×10-15 and the concentration of H2SO4=2.34×10-11g/cc.
    2. Next the relation between opacity and lapse rate of temperature is studied. The obtained result is the well established relation that opacity descreases according as lapse rate increases. This relation was hitherto explained that nuclei concentrate in the lower atmosphere in stable case causing bad visibility, and that they scatter high up in unstable air which cause good visibility, We have, however, shown that lapse rate and relative humidity have good negative correlation and in stable air nuclei have generally large sizes due to increased humidity. So that the increase of opacity in stable air will be caused not only by the increase of numbers of nuclei in the lower layer but also by the increase of sizes of nuclei. And it is shown that the latter effect is rather more predominant than the former effect in causing change of opacity with lapse rate.
    3. The relation between opacity and wind velocity was then examined and the well known relation, that opacity decreases with increase of wind velocity, was ascertained. It is, however, shown that for each group of data in which H>70% or H<70%, the values of opacity are independent of values of wind velocity. So that it may be concluded that number of nuclei effective for opacity in the air will not change appreciably with change of wind velocity in usual case. And the opacity-wind velocity relation obtained may ba explained by the change of sizes of nuclei with wind velocity, since wind velocity has good negative correlation with relative humidity.
    4. Opacity at each wind direction was then examined. It was shown that at Sendai opacity is large when wind blows from SE, or NE, or SW and it is small when wind blows from NW. Large opacity for SW wind will probably be due to the local effect of city of Sendai. And large opacities for NE and SE winds and small opacity for NW wind will be due to the effects of different air masses, which cover Sendai when respective wind is blowing. Because it is probable that Pm air mass corresponding to NE wind and Tm air mass corresponding to SE wind will contain large amounts of nuclei, whereas Pc air mass corresponding to NW wind will contain small amounts of nuclei.
    5. As to the seasonal variation of opacity at Sendai it was shown that opacity is generally large in summer having its maximum in July and is generally small in winter, its minimum occurring in October and in March intervened with secondary maximum of December.
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  • E. Inoue
    1951 Volume 29 Issue 1 Pages 14-19
    Published: 1951
    Released: February 05, 2009
    The vertical structure of wind near the ground is assumed to be composed of the mean flow and many ranks of vertical turbulons. At a certain height z there are the largest vertical turbulons which are coupled with the mean flow. They take the energy from the mean flow, and give it to turbulons of smaller size at that height. This rate of energy transfer is represented by the relations K (dU/dz)2_??_W3/_??_z, K_??_W_??_z. where _??_z denotes the diameter of the largest vertical turbulon and is thought to be proportional to the height z. Moreover, the vertical velocity W of the largest vertical turbulon is deduced to be independent of height. Thus the logarithmic law for the vertical distribution of wind velocity is obtained.
    The largest turbulon is thought obviously nonisotropic, but turbulons of smaller scale may be conceived to be locally isotropic. Then the spectral function of vertical turbulon energy is also deduced to obey the negative five-thirds power law.
    The thickness of the laminar sub-layer is obtained as the limiting length of application of this turbulent boundary layer theory, and is given by z0_??_ν/V*, where V* means the friction velocity and is proportinal to W. Thus z0 is known to correspond to the particular case of the diameter of the smallest turbulon.
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  • T. Ando
    1951 Volume 29 Issue 1 Pages 20-27
    Published: 1951
    Released: February 05, 2009
    1. Warm air is flowing as a jet stream in the upper and lower layer when a typhoon is approaching. This jet stream height is of maximum vertical velocity.
    2. The jet stream proceeds some hundreds kilometers ahead the typhoon, and causes heavy rainfall. The rainfall amount is controlled by the mixing ratio at the jet stream height.
    3. Typhoon rain consists of two kinds, one is vortical in nature and the other moves north as a wave-like disturbance.
    4. The rainfall due to the wave-like disturbance is proportional to the net time change of eu, where e is the vapour tension and u the horizontal velocity, which shows that this rainfall is due to the line of convergence.
    The vortical rainfall occurs at the place of vorticity accumulation and moves with vorticity.
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  • H. Hatakeyama, K. Utikawa
    1951 Volume 29 Issue 1 Pages 28-33
    Published: 1951
    Released: February 05, 2009
    The atmospheric potential gradient was observed at the summit of Mt. Fuji (3778m), 5.5 go (2800m), Tarobo (1290m) and Gotemba (460m), each during two or three days in August, 1947, and January, 1948. The polonium-collector was attached to the opposite side of the Shimizu's unifilar electrometer made by the Institute of Physical and Chemical Research and it was mounted on the top of the tripod. The visual observation was made hourly or half-hourly to investigate the diurnal variation of the atmospheric potential gradient.
    According to the observational results, the ordinary semidiurnal variation (i. e. two maxima and two minima) prevails at Gotemba, and at Tarobo the diurnal variation is not so conspicuous, whereas at 5.5 go and at the summit the potential is greater through the daytime and smaller in the night. Thus it was made clear that the large semi-diurnal variation of the atmospheric potential gradient has the local character not only in the geographical locality but also in the vertical extent in the free atmosphere.
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