Papers in Meteorology and Geophysics
Online ISSN : 1880-6643
Print ISSN : 0031-126X
ISSN-L : 0031-126X
Volume 38, Issue 2
Displaying 1-5 of 5 articles from this issue
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  • Toshio Fujita
    1987 Volume 38 Issue 2 Pages 67-76
    Published: 1987
    Released on J-STAGE: March 09, 2007
       On the basis of many observational experiments on the phase relationship between wave-induced air flows and underlying swell waves, a hypothetical model for air flows is constructed, and an equation for the momentum flux through wave-induced perturbations is derived. It is found that there exists a layer with upward momentum transfer near the sea surface and a downward flux over it. Consequently, the jet-shaped departure from the logarithmic wind profile found in our observations (1983) is well simulated by the model.
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  • Nobuo Hamada
    1987 Volume 38 Issue 2 Pages 77-156
    Published: 1987
    Released on J-STAGE: March 09, 2007
       The first half of this study is dedicated to correcting the misconception that the seismometrical data obtained by the earlier seismological station network are so poor in quality that they are not available for the modern method of analysis. In the course of the study, one of the best methods to locate hypocenters using these old data was established. In the latter part of this study, we investigated seismicity associated with several destructive earthquakes which occurred in the inland area of Honshu during the period from the 1930's to the 1970's. On the basis of the examination of seismicity, common characteristics related to the faulting process of these earthquakes and the long-term variation of seismic activity around the focal area were discussed.
       Important conclusions derived from the review of the history of our seismological observation are as follows:
       1) In spite of the gradual improvement of the network with temporary setbacks due to the social crises brought about by World War II, we could not find any distinct heterogeneity in the quality and the quantity of the observational data from the early 1930's to the late 1960's. This implies that it is possible, for all practical purposes, to apply the same data processing techniques to all the data.
       2) Evaluation of earthquake location capability in the inland area for every five years in the period from 1926 to 1984 shows that most earthquakes of magnitude 4.2 or more could be located, from the early 1930's to the present, if we supplement yet unprocessed but still available data in some periods, especially during and immediately after the War. From the late 1950's, most events of magnitude 3.8 or more can be located if we re-examine all the data before 1975. This estimation will be useful for discussing the long-term variation of seismicity.
       3) Since the early days of seismological observation, with respect to the earthquake location accuracy, hypocenter location using P and S arrivals has always been superior to that using S-P interval times. This latter often resulted in large location errors especially for large earthquakes which often have multiple focal processes.
       4) Hypocenter location errors for earthquakes in the 1960's estimated from travel time residuals are two to three times, and those for earthquakes in the 1940's are three to four times, larger than the present level. Most of epicenter location errors for inland earthquakes in the 1940's are estimated to be within 10km.
       5) Judging from the earthquake location errors, it may be possible to recognize the double seismic zone in the Kanto district from the data of the 1930's and the 1940's, if we reexamine them.
       6) A joint hypocenter determination method (JHD) using mean travel time residuals as station corrections is successfully applied to the aftershocks of old earthquakes. This means that the time keeping of the old network is good enough to deduce the travel time anomaly originated in the inhomogeneous crustal structures.
       Results of the re-examination of seismicity associated with the destructive earthquakes occurring in the inland area of Honshu during the period from 1930 to 1970 are as follows:
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  • Tsugunobu Nagai
    1987 Volume 38 Issue 2 Pages 157-169
    Published: 1987
    Released on J-STAGE: March 09, 2007
       Energetic protons, alpha particles, and electrons are measured with the Space Environment Monitor (SEM) on the Geostationary Meteorological Satellite (GMS, GMS-2, and GMS-3) “Himawari”. SEM on GMS-2 and GMS-3 (GMS) has six (seven) channels P1-P6 (P7) for protons with energies of 0.8-100 MeV (1.2-500MeV), five channels A1-A5 for alpha particles with energies of 8-370 MeV (9-370 MeV), and one channel EL for electrons with energies of > 2 MeV. However, the P1 channel is contaminated by pile-up electrons so that the proton response in the P1 channel is masked. The P2 and A1 channels from GMS provide data of good quality, but other channels from GMS respond to sunlight. Failure of detectors causes trouble in some data sets.
       Solar particle events (SPE's) are observed in the P2-P6 (P7) and A1-A5 channels. Some events show a sharp rise and a gradual decay of the particle fluxes, but most events show a gradual rise and a further gradual decay of the particle fluxes. The differential energy spectral index in the SPE's is around 3 for both protons and alpha particles. The flux behavior seen in the A1 channel is quite similar to that seen in the P2 channel. The long-term trend of high energy particle ejection from the sun during the Solar Cycle 21 could be monitored with the A1 and P6 channels, which were noise-free throughout the whole period. SPE's frequently occurred in 1978-1979 and 1981-1982. SPE's in 1980 were not large and were less energetic, although the sunspot number and the solar flare number were quite high. After 1983, SPE's were less frequent, but there occurred several large and energetic SPE's. Therefore, the long-term trend in the high energy particle ejection from the sun is quite different from that in the sunspot number.
       The EL and P1 channel response is largely due to energetic particles trapped in the earth's magnetic field. The fluxes from these channels show substorm-induced variations. Characteristics of these substorm-induced flux variations depend highly on local time. The flux levels in these channels diminish just after the onset of high geomagnetic activities and then they rapidly increase above the pre-storm level. Finally, the fluxes gradually decrease to the normal level. The high flux level generally corresponds to the high geomagnetic activity. The fluxes from these channels show a clear 27-day recurrent pattern in 1983-1986, which can be recognized in the geomagnetic activities. The fluxes in the EL and P1 channels can be used as a monitor of geomagnetic activities.
       Thus the GMS/SEM provides excellent data bases on the high energy particle ejection from the sun, the cosmic ray intensity, the geomagnetically trapped particle flux level and others. This is valuable for the study of the Solar-Terrestrial relationship.
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  • Takayo Matsuo
    1987 Volume 38 Issue 2 Pages 171-179
    Published: 1987
    Released on J-STAGE: March 09, 2007
       Collision experiments were made on tilting and fluttering disks in a vertical wind tunnel to evaluate the effects of falling attitude and fluttering motion on the riming of snow particles. Two disks of the same diameter were supported at the ends of needles inserted in the tunnel. One was tilted or given fluttering motion, and the other was set horizontal as a reference disk. Impact was given to the disks with water droplets at various air speeds. The collection efficiency of the tilted or fluttering disk was estimated in comparison with the reference disk.
       The results showed that the effects of tilting and fluttering motion on the collection efficiency of the disks for droplets depend largely on the inertia of impacting droplets. For small inertia of droplets, the collection efficiency was increased by tilting. Small droplets around a cutoff point were collected more by tilting. The fluttering motion did not affect the collection efficiency except for a case of strong fluttering motion. This result could be explained in terms of deformation of air flow near the disk due to tilting or strong fluttering motion.
       For large inertia of droplets, the collection efficiency was decreased by tilting, but was not affected by fluttering motion. This result could be interpreted by the decrease in the effective cross section of the disk against the airstream due to tilting.
       The collection efficiency of the rear disk surface for droplets was decreased by tilting and was slightly increased by fluttering motion.
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  • Kunihiko Kodera
    1987 Volume 38 Issue 2 Pages 181-185
    Published: 1987
    Released on J-STAGE: March 09, 2007
       An index to the bad rice harvest, Icd, in the Tohoku district, northern part of Japan, is defined according to Hatake's table. A comparison between Icd and annual growth rate of the tree-ring of a zelkova felled in Yamagata shows that the large variation of Icd reflects the change of natural weather conditions.
       Bad harvest years are objectively defined using Icd, and superposed epoch analysis is applied to the study of the relationship between bad harvest and solar activity. The results show an increase of bad rice harvest about one year after the sunspot minimum. The growth rate of the zelkova also has a small maximum around the sunspot minimum.
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