Papers in Meteorology and Geophysics
Online ISSN : 1880-6643
Print ISSN : 0031-126X
ISSN-L : 0031-126X
Volume 41 , Issue 2
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  • Kiyotaka Shibata
    1990 Volume 41 Issue 2 Pages 43-61
    Published: 1990
    Released: October 20, 2006
       To account for the experimental characteristic of the Platinum electric resistance thermometer that it does not follow a first order system in usual meteorological conditions, the indicial response of a model for the electric resistance thermometer is obtained by analytically solving its thermal diffusion equation. The model is so simplified as to be composed of three infinite concentric cylinders, i.e., protector sheath, filling material and electric resistance element. The theoretical indicial response is evaluated for various model thermometers with different properties in the filling material. The major results are as follows: (1) over a certain Fourier number the indicial response can be approximated with one term of the exponential function C exp (-t/λ) including two parameters, coefficient C (>1) and exponent λ; (2) when the Biot number is small, the response speed hardly depends upon the inner structure. It becomes, however, sensitive to the thickness and thermal properties of the filling material as the Biot number increases; (3) the thermal properties of protector sheath and electric resistance element have little effect on the response speed, so long as the filling material is thermally insulating.
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  • A study on the causes of anomalous changes in the earth-potential observed at Izu-Oshima
    Mituko Ozima
    1990 Volume 41 Issue 2 Pages 63-82
    Published: 1990
    Released: October 20, 2006
       It has been so far impossible to prove that a given anomalous change in the earth-potential is due to a specific tectonic activity. However, we can correlate these two phenomena after we have eliminated all other possible causes such as meteorological or artificial disturbances.
       From our experiences of the observation of the earth-potential at the Magnetic Observatory, we can derive an empirical rule that rectangular changes in the earth-potential are caused by artificial disturbances. In our observation using telegraphic facilities at Mito, the author found that one of the several types (including rectangular ones) of artificial disturbances was caused by the leakage current from the electric trains on the Hitachi Electric Railway, which occurs in conjunction with certain meteorological phenomena.
       Uyeda et al. reported that the anomalous changes of the telluric potential observed at Izu-Oshima Island using telegraphic facilities are possibly precursors of earthquake swarms off the east coast of the Izu-Peninsula. The fact, however, that almost all their “signals” appear from 6 to 22 o'clock implies that those “signals” are of man-made origin. The author claims that those anomalous changes are not related with earthquakes but are caused by the precipitation and the telephone exchange repeaters at the observation station.
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