Papers in Meteorology and Geophysics
Online ISSN : 1880-6643
Print ISSN : 0031-126X
ISSN-L : 0031-126X
Volume 29 , Issue 4
Showing 1-4 articles out of 4 articles from the selected issue
  • Junichi Shiino
    1978 Volume 29 Issue 4 Pages 157-194
    Published: December 15, 1978
    Released: December 11, 2012
    A numerical study of precipitation development in cumulus clouds with the use of an Eulerian one-dimensional cloud model which consists of the vertical equation of motion, the mass continuity equation, the thermodynamic equation and the parameterized cloud microphysics for liquid and solid water substances is presented. Especially the differences between warm cumulus and ice-bearing cumulus clouds are investigated. Condensed water substance is classified into three components, cloud droplets (cloud water), raindrops (precipitation water) and frozen raindrops (solid water).
    The parameterized liquid phase processes include condensation of w ater vapour, autoconversion of cloud droplets to raindrops, collection of cloud droplets by raindrops and evaporation of cloud droplets and raindrops. The ice phase processes include heterogeneous glaciation of raindrops, riming, sublimation of water vapour, melting of frozen raindrops, evaporation of frozen raindrops and evaporation of melting frozen raindrops.
    The main results obtained are as follows: 1) The model presented here simulates fairly well some qualitative characteristics of ice-bearing cumulus clouds as observed by Byers and Braham (1949) and others, Especially the inclusion of the time and temperature dependent glaciation process results in a more realistic simulation of the phase change of water substance.2) In warm cumulus the maximum rain intensity appears only once, whereas in ice-bearing cumulus cloud a secondary maximum rain intensity is observed when the major glaciation occurs in a relatively warmer supercooled temperature region. Although the stimulation of cloud growth is expected by including the ice phase in the model, the maximum rain intensity, the total amount of rainfall at the ground surface and the precipitation efficiency are all larger in magnitude in warm cumulus than in ice-bearing cumulus cloud. These results are qualitatively not inconsistent with the work by Koenig and Murray (1976) and their caution, explained in the article, is borne out by the results of our present study.3) According to the sensitivity analyses of the model for various atmospheric conditions, there may be optimum values of lapse rate of temperature and surface temperature for the occurrence of the most intense rainfall and the largest amount of total rainfall under a given humidity distribution. A cumulus cloud with a larger horizontal size causes stronger rain intensity and a larger amount of rainfall.4) Cloud physical processes exert great influence on the development of cumulus clouds. Generally speaking, a cumulus cloud with cloud physical parameters with a sense of faster production of precipitation water causes earlier initiation of the maximum rain intensity and the lifetime of such a cloud is shorter and the precipitation efficiency is larger but the maximum rain intensity is rather affected by the thermodynamic structure of the environmental atmosphere. Limitations of the model are also discussed.
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  • Akio Yoshida
    1978 Volume 29 Issue 4 Pages 196-203
    Published: December 15, 1978
    Released: December 11, 2012
    The activity of pre-existing conjugate faults system is considered in relation to the regional stress field. Fault movement is assumed to be like a stick slip, and the magnitude of effective shear stress on each fault surface is compared.
    It is derived that neither of the two faults is more a ctive provided the coefficient of friction on the faults ti has not changed from the coefficient of inner friction at the time the conjugate faults system had been formed, even if the stress field has changed since then. When p>p0, the fault which makes a smaller angle to the maximum pressure axis is more easily activated, and when p<p0, the reverse is deduced.
    The residual stress field after the activity of either of the con j u gate faults is also considered and the relation between the principal axes of initial stress field and those of the residual stress field is obtained. From the result it is concluded that, when u>u0, the very fault which activates first is more active successively, but when p<u0, there is a possibility that the conjugate faults move one another.
    Although this is still a preliminaly research, th e above formulated idea is applied to the Matsushiro earthquake swarm and the seismicity of the Izu Peninsula. It is found that the fault motion associated with these activities can be explained by this idea. But further study will be required for applications of this theory to geology.
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  • Tomoshige Suda, Masami Wada
    1978 Volume 29 Issue 4 Pages 205-215
    Published: December 15, 1978
    Released: December 11, 2012
    The results of Chree analysis of c osmic ray nucleonic intensity from a number of stations with epochs at the crossing of IMF sector boundary are presented together with those of IMF and solar wind parameters. Agreement in time variations among stations is excellent. There are Forbush type decreases just after the boundary whose time profile is similar to those found at the time of ssc. The variation spectrum of the former is, however, harder than that of the latter. The variations depending on the polarity change are divided into two components: an asymmetric and a symmetric variation about the boundary, of which some characteristics are investigated.
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  • Muneyasu Kano, Masaatsu Miyauchi, Masashi Suzuki
    1978 Volume 29 Issue 4 Pages 217-224
    Published: December 15, 1978
    Released: December 11, 2012
    We constructed spectral pyranometers that can measure the spectral global radiation properly Using these pyranometers the simultaneous measurements of global radiations in the infrared, infrared to visible and infrared to ultraviolet (entire spectral) regions were carried out to examine the relations between the global radiations in the infrared, visible and ultraviolet regions and the global radiation in the entire spectral region. It was found that the global radiations in the infrared, visible and ultraviolet regions SI, Sv, and Su can be estimated with enough accuracy from the global radiation in the entire spectral region S by the following equation SK=AKS+BKSn+1 (K=I, V, U)where n is a numerical constant.
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