Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 54 , Issue 1
Showing 1-9 articles out of 9 articles from the selected issue
  • Tsuyoshi Nitta
    1976 Volume 54 Issue 1 Pages 1-14
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The atmospheric budgets of mass, heat and moisture are analysed for the first phase (February 14-28, 1974) of the Air-Mass Transformation Experiment (AMTEX). The analysed period is subdivided into three parts according to different synoptic situations. During the period in which a warm air enters the AMTEX area from the subtropicalregion, a strong inversion lies near 800mb and there is a downward motion with a maximum value near the inversion. An apparent heat sink and a moisture source of the large-scale motion system are found near the inversion base and total heat transports by subgrid-scale
    eddies are almost confined below the inversion base. The value of the total heat supply from the sea surface is estimated to be 400ly day-1. On the other hand during the period in which a cold-air outbreak occurs, a large amount of total heat energy more than 1, 000 ly day-1 is supplied from the sea surface. A large apparent heat source and a large apparent moisture source are found in the layer between the sea surface and 800mb. During the intermediate period between the previous two periods, the AMTEX area is affected by the traveling cyclones whose centers pass through to the north of the AMTEX area.
    Values of the total heat flux calculated by large-scale budgets agree quite well with those estimated independently by bulk aerodynamic computations.
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  • Masato Murakami
    1976 Volume 54 Issue 1 Pages 15-31
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Temporal fluctuations appearing in the summer monsoon over India are investigated by using the data of 1962. By the method of spectrum analysis, it is revealed that two major periodicities exist, at least, in the temporal fluctuation of the monsoon. One is the oscillation around 5 days period and the other is around 15 days pericd.
    The oscillation around 5 days period appears mainly in the range from the north Bay of Bengal through the monsoon trough region in northern India. The structure of the disturbance which causes this periodicity is examined by the method of cross spectrum analysis. The results show that the disturbance is a westward-moving one and its longitudinal wavelength is about 30°. This disturbance seems to represent the so-called monsoon low. The vertical structure of these monsoon lows indicates that their cyclonic circulation is prevailing in the lower troposphere and the axis of the trough slightly tilts westward. Moreover, the monsoon low is accompanied with a distinct warm core in the upper troposphere. In the lower levels, the amplitude of the temperature is mall and the disturbance is neither warmnor cold cored. It is also shown that the monsoon low has a steering level at the height around 500mb level.
    The oscillation around 15 days period is revealed to be in connection with the active/weak cycle of monsoon. The intense wind fluctuations associated with this cycle appear both in the upper and the lower troposphere, being in phase with each other. At the stage of active monsoon, it is revealed that the area with cyclonic circulation is formed over the Bay of Bengal. This cyclonic circulation is accompanied with cold temperature anomalies in the lower troposphere and warm anomalies in the upper levels. Besides, it is also shown that the depth of the moist layer over the Bay increases at this stage. These situations strongly suggest that the active monsoon condition over India is characterized by the enhanced convective activity over the Bay. Nearly opposite situations occur at the stage of weak monsoon and the anticyclonic circulation is formed over the Bay. The latitudinal shift of monsoon trough can be explained by superposing these two circulations on the distribution of the mean flow.
    The transition between the active and the weak stage is also investigated by applying the time-composite technique to the time series of surface pressure anomalies. At the stage of active monsoon, a large low pressure area is formed over the Bay of Bengal and the high pressure anomalies appear at the weak stage. By examining the time sequences of this transition, it is shown that a pair of high- and low pressure anomalies rotate clockwise over the wide area including the Bay of Bengal, Tibetan Plateau, whole Indian subcontinent and Indo-China. As for the nature of this rotation, it is suggested that the north-south standing oscillation between Tibetan Plateau and the Bay of Bengal together with the east-west one between Indo-China and the Indian continent can cause the clockwise rotation mentioned above. It is also discussed that these oscillations seem of reflect the temporal variations of the intensity of the mean meridional- and the mean zonal circulation cells respectively.
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  • Takao Takeda, Noriaki Moriyama, Yasunobu Iwasaka
    1976 Volume 54 Issue 1 Pages 32-41
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A case study is made for heavy rain which occurred in the area around Owase in the Kii Peninsula from the 9th to the 11th of September, 1971, using data from autographic raingauges with the aid of PPI radar photographs and the time variations of drop-size distribution and electric field intensity measured at Owase. Results of analysis show that travelling cumulonimbi produced heavy rain in Owase area, as if rainfall from it were amplified there, on account of the interaction with surrounding precipitating clouds of low top which formed only around Owase and in which the contribution of raindrops of 1 to 2mm in diameter to rainfall intensity was very large. It can be inferred that very efficient mechanism of rainfall formation was realized in Owase area as a result of the modification of cumulonimbus due to orographic effect. Mechanism of orographic enhancement of rainfall is discussed. Further it is pointed out that during the period of heaviest rain electric field intensity has the time variation of long time scale which does not reflect the passage of individual cumulonimbus travelling from the south with the interval of two to four hours successively.
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  • Toshio Harimaya
    1976 Volume 54 Issue 1 Pages 42-51
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Embryos of graupel particles were studied by the thin section technique under a polarization microscope and direct observation by picking graupel particles apart under a microscope. Snow crystals and a frozen drop were picked out from graupel particles. They were considered as embryos morphologically. And it was confirmed by numerical calculations that they satisfy the condition for the graupel growth. According to the embryo and falling behavior of graupel, the formation of graupel was classified and a few formation mechanisms were presented.
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  • Shigeru Moriyama
    1976 Volume 54 Issue 1 Pages 52-58
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Radiative-convective equilibrium of the Martian atmosphere is investigated by considering all the radiative effects on the atmospheric thermal structure, i.e., heating due to absorption of solar radiation by dust, infrared radiative cooling by dust and cooling by CO2-15μ band. Dust does play an important role on determining the thermal structure of the Martian atmosphere.
    The following results are obtained.
    i) The thermal structure of the Martian atmosphere indicates a very stable feature. And the temperature is higher in dusty atmosphere than that of dust-free case at upper level.
    ii) The Martian atmosphere in dustry case is immediately heated up by absorption of the solar radiation rather than by heat transport due to convection from the lower layers.
    iii) The diurnal temperature change in the middle and upper "troposphere" is supposed to be much larger than that for the dust-free case.
    iv) When the optical path length for the solar radiation is long, a strong inversion layer of large thickness appears at the fairly upper levels even in the daytime.
    v) Because of decrease of the solar energy transmitted to the surface, the surface temperature is supposed to be lower than that of dust-free case, under the condition of high solar elevation angles. On the other hand, because of green-house effect due to dust, it would be higher in the case of nighttime or of very low solar elevation angles.
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  • Masao Shiotani, Yoshimi Iwatani
    1976 Volume 54 Issue 1 Pages 59-67
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The present paper deals with horizontal space correlations and lateral scales of fluctuating wind velocities observed during strong winds for providing the knowledge of design wind velocity of a long suspension bridge. Five anemometers at height of 40m are located in a line of 190m along the coastline. Horizontal space correlation decreases nearly exponentially with increasing separation, but does not tend to zero within the maximum separation in most of observed cases, Integral scales of turbulence are about 60m in a lateral direction and becomes 2.54 times larger in a longitudinal direction. Turbulent eddies appear to be elongated in the direction of the wind. Lateral scales related to narrow frequency ranges are approximately represented by a linear function of inverse wave numbers in the range not exceeding about 500m. The convection velocity of the eddies is discussed in observed cases that wind directions are not perpendicular to the anemometer line.
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  • Ernest M. Agee
    1976 Volume 54 Issue 1 Pages 68-71
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
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  • Kozo Ninomiya
    1976 Volume 54 Issue 1 Pages 72-75
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
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  • Makoto Komabayashi
    1976 Volume 54 Issue 1 Pages 76-79
    Published: 1976
    Released: October 19, 2007
    JOURNALS FREE ACCESS
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