Papers in Meteorology and Geophysics
Online ISSN : 1880-6643
Print ISSN : 0031-126X
ISSN-L : 0031-126X
Volume 34 , Issue 2
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  • Hitoshi Sakakibara
    1983 Volume 34 Issue 2 Pages 61-73
    Published: 1983
    Released: March 13, 2007
    JOURNALS FREE ACCESS
       A cold-frontal precipitation system which passed over the Kanto district was studied using surface observation data at meteorological observatories and AMEDAS stations, and those by the Tsukuba radar. The precipitation system was found to be affected by a small low and by mesoscale orography to the west of Kanto. The small low which was originally associated with a short-wave trough below 500 mb was enhanced by surface heating. As the low developed, it organized warm southerly winds which were responsible for active convections near the surface cold front. Convective clouds occurred near the surface cold front, moved to the cold air side, and dissipated over the cold air. After the low passed the Kanto district, the southerly winds over the district disappeared and the convective rain near the surface cold front stopped.
       During the passage of the cold front over the central part of the Japan Islands, the cold air behind the front was dammed up by the mesoscale orography and went round. The advance of the surface cold front over the Kanto district was slower than that to the north and to the southwest of the district.
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  • Tsutomu Takashima
    1983 Volume 34 Issue 2 Pages 75-81
    Published: 1983
    Released: March 13, 2007
    JOURNALS FREE ACCESS
       The reflection matrix of radiation just above the ocean surface is derived in a form suitable for the use of adding method. The air-water interface is separated by a ruffled surface, whose angular dependent reflection and transmission properties are calculated based on a Gaussian distribution of wave slopes (Cox and Munk, 1956). At present, the ocean is assumed to be vertically inhomogeneous, and its bottom to absorb all incident radiation. Polarization is included in the derivation of the equation. The reflection matrix of radiation thus derived enables us the computations of space radiance at the top of the atmosphere. The tiresome computation due to the polarity effect of radiation is overcome by the present method. Finally a sample computation is carried out in a scalar form.
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  • Hirofumi Okamura, Ichiro Isozaki
    1983 Volume 34 Issue 2 Pages 83-94
    Published: 1983
    Released: March 13, 2007
    JOURNALS FREE ACCESS
       Seasat-1 has a wind-measuring scatterometer (SASS) which is designed to measure globally the ocean surface wind vectors (accuracy ±2m/s and ±20°) independent of day or night, and in all weather conditions. The technique of SASS has its physical base mainly in the Bragg scattering of microwaves by capillary waves on the ocean (λω∼1 cm). Normalized radar cross section (σ°) of the ocean is proportional to the capillary wave amplitude which is proportional to a wind speed 19.5 m height over the sea surface in neutral stability. We can derive the wind direction, too, from some different azimuthal σ° measurements, since σ° is anisotropic.
       Data of revolution numbers 693 and 700 in SASS IGDR contain the sea surface wind observations of Typhoon Carmen (T7811). We can see by GMS that the SASS swaths are almost rain-free. So it is assumed that σ° is almost free from attenuation by the atmosphere, and that a comparison between SASS data and ground truth gives the evaluation for the SASS algorithm. Here is a study of SASS data in comparison with the winds by a two-layer baroclinic model for the marine boundary layer. The comparison is not a direct verification of SASS data, because there are some assumptions and boundary conditions in this model. However we can indirectly evaluate the significance of the data in the ocean where we can not make any observations of a typhoon region.
       The most significant result obtained is that a SASS wind speed is somewhat stronger than a surface truth wind from 5 to 15 m/s wind speed region. It is suggested that the SASS algorithm is too sensitive to wind speed, especially in this wind speed region. And the result of this study gives support to that of the GOASEX workshop reports.
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  • Toshio Mori, Makoto Kawamura, Kou Ohchi, Yoshiaki Mizuno
    1983 Volume 34 Issue 2 Pages 95-104
    Published: 1983
    Released: March 13, 2007
    JOURNALS FREE ACCESS
       The Kushibiki fault, which runs northwest-southeast and dips southwest, is an active fault in the western part of the Kanto plane, Japan. Earth resistivity by direct current method, self-potential gradient and geomagnetic total intensity are measured in this area.
       Analyses of the Schlumberger and Wenner soundings show that the resistivity structure in the fault zone in striking contrast to the surrounding layers. The relatively high resistivity layer of 300 to 500 ohm-m is restricted to the fault zone, and the layer dips more steeply southwest in the center than at the edge. A very low resistivity layer of 10 ohm-m or less appears at a depth of about 100 m outside of the fault zone, but in the fault zone the layer appears at a depth of 10 to 30 m just under the highly resistive layer.
       An anomalous field of geomagnetic total intensity in the range of 60 to 100 nT is found along the fault with a width of about 100 m. The distributions of the self-potential gradients on the two lines across the fault do not support the theory that the anomalous magnetic field originates in a current generated by a streaming potential. So the origin is considered to be magnetized bodies. It can be explained that the high resistivity layer in the fault zone is magnetized to an intensity of 1.5×10-3emu/cc, whereas the magnetization of the surroundings is 5×10-4emu/cc.
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