Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 67 , Issue 4
Showing 1-15 articles out of 15 articles from the selected issue
  • Tadanori Sei, Takehiko Gonda
    1989 Volume 67 Issue 4 Pages 495-502
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Polyhedral ice crystals are grown on a growth substrate at a low air pressure of 40Pa at -7, -15 and -30°C at relatively low supersaturations. The measurements of the normal growth rates of ice crystals versus supersaturation and in situ observations of ice crystal surfaces are carried out. It is inferred that the {0001} and {1010} faces of ice crystals grown under these conditions grow by the mechanism proposed by Burton, Cabrera and Frank (BCF mechanism). The habit change of ice crystals with temperature is equivalent to the temperature dependence of the condensation coefficient al of the {0001} and {1010} faces. In this paper, the formation mechanism of non-hexagonal snow crystals observed in the upper atmosphere and in Antarctica is discussed.
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  • Masahito Ishihara, Hitoshi Sakakibara, Zenji Yanagisawa
    1989 Volume 67 Issue 4 Pages 503-520
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The characteristics and structure of mesoscale snow clouds generated in the western Hokuriku District of Japan is examined, mainly through Doppler radar data. These clouds were produced in the convergence zone between the land-originated local wind (land breeze) and the northwesterly monsoon flow. This convergence zone was located in a convective mixed layer over the relatively warm sea, producing mesoscale snow bands found along the coast.
    The snow bands periodically appeared in synoptic situations during which the northwesterly monsoon was not intense and moderately cold air existed in the lower troposphere. They occurred at an interval of 3-4 days and brought about moderate snowfall to the coastal regions. Their horizontal scale was approximately 100km×20km with a lifetime of 1.0-1.5 hours classified them as meso-β scale phenomena. The land breeze circulation was produced by a thermal contrast between the warm sea and the cold mountainous land. The cold gravity current associated with the circulation flowed downward toward the sea. The current was modified by the relatively warm sea surface and converged with the northwesterly monsoon flow 10-30km offshore, producing the snow bands.
    The snow bands exhibited a marked evolution from the growing stage to the decaying stage, as they moved from the sea to the coast. The successive production of the snow bands resulted from the coupling of three air flows, the northwesterly monsoon, the land breeze and the low-level outflow originating from the anvil-like cloud at the rear of the snow bands. The low-level convergence between the monsoon flow and the land breeze resulted in the development of the snow bands in the growing stage. The pumping of land breeze air into the updraft of the snow bands caused the land breeze front to retreat toward the coast, accompanied by the snow bands. The low-level outflow from the decaying snow bands acted as a trigger or a seed for the formation of a new snow band. The dissipation of the snow band and the extinction of the updraft pumping allowed the front to advance offshore again.
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  • Noboru Sato, Katsuhiro Kikuchi
    1989 Volume 67 Issue 4 Pages 521-528
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The correlation among the gohei twins, seagull and spearhead-type crystals, which are typical polycrystalline snow crystals of low temperature types, was discussed based on a number of microphotographs taken in the polar regions and obtained in laboratory experiments. The crystal structure of the spearhead type was determined, that is, the angle between the c-axes is 116° and the supplementary angle of intersection of two prism planes is 31°. The spearhead-type crystal is the twin whose twinning plane is {1013}, and corresponds to the gohei twin whose tip angle is 54°. It is one wing of the seagull-type crystals of the inside bend from the center. The other wing of the seagull-type crystals of the inside bend from the center grows from the boundary of the mother crystal of the spearhead-type crystal, and has the same crystal structure as the mother crystal. There is another snow crystal of the seagull-type, the seagull type of the outside bend from the center, which has an angle between two wings of about 130°. The structure of their wings is the same as the spearhead-type snow crystals. This may be a penetration twin of the spearhead-type snow crystals. The formation mechanisms of gohei twins and spearhead crystals are considered based on a cubic structure model and the rotation of an ice crystal lattice about <0001> axis on the basal face.
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  • Masanori Yamasaki
    1989 Volume 67 Issue 4 Pages 529-540
    Published: 1989
    Released: October 19, 2007
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    Employing an implicit representation scheme for cumulus convection (Yamasaki, 1986), numerical experiments are performed to study tropical cyclone formation in the intertropical convergence zone. Fine resolution grid of 40km is used in the tonal belt where the sea surface temperature is relatively high while two areas having a coarse grid resolution of 120km are located to the north and the south. Cyclic conditions are imposed in the tonal direction. Initially, buoyancy perturbations are added to a resting atmosphere or an easterly flow having a horizontal shear is applied so that vertical motion (and convection) may be initiated. No external disturbances such as subtropical highs are taken into account.
    Results of the numerical experiments indicate that convection and larger-scale circulations such as tropical disturbances and meridional Hadley circulations interact in a cooperative way. As a result, they are maintained or formed repeatedly over a long period of time. Some weak disturbances or vortices which are created by convective activity develop to become tropical depressions and tropical cyclones. In many respects results obtained in this study are consistent with those from the model of explicit cumulus convection (Yamasaki, 1983, 84).
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  • Eiji Ohtaki, Osamu Tsukamoto, Yoshiharu Iwatani, Yasushi Mitsuta
    1989 Volume 67 Issue 4 Pages 541-554
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Atmospheric fluctuations of carbon dioxide, humidity and temperature were simultaneously measured over the ocean, 255m off the coast line of the Sea of Japan in October, 1986 and 1987, and in August, 1988. The power spectral density of carbon dioxide followed approximately a -5/3 power law in the high frequency ranges. This frequency dependency of carbon dioxide fluctuations is basically similar to those of temperature and humidity. The cospectrum of carbon dioxide and vertical wind velocity had negative components for the whole frequency ranges analyzed, representing a downward transport of carbon dioxide by the turbulent eddies over the ocean. The carbon dioxide flux due to the mean flow showed positive, and its value was about twice that of the turbulent eddy flux. This means that the flux direction of carbon dioxide over the ocean is mainly controlled by the transport direction of fluxes of sensible heat and latent heat. The upward flux of carbon dioxide may occur when the air layer over the ocean is in unstable stratification. It is noted that the total flux of carbon dioxide, which is the summation of the turbulent eddy flux term and the mean flow flux term, increased with increasing fluxes of sensible heat, laten t heat and momentum over the ocean.
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  • Masato Shinoda
    1989 Volume 67 Issue 4 Pages 555-564
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
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  • Shigeki Mitsumoto
    1989 Volume 67 Issue 4 Pages 565-574
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The slope wind circulation was investigated by a laboratory experiment using a temperaturecontrolled water tank, the bottom of which consists of a PLAIN and a SLOPE. The following results were obtained:
    (1) A cellular convection occurs on the plain with the rise of the surface temperature of the plain and the slope, as was seen in the laboratory experiment on the land- and sea-breeze circulation (Mitsumoto et al., 1983). However, it does not occur on the slope. The flow along the slope has a smooth periodical variation. The thermal boundary layer on the slope is thinner than that on the plain. The phase of the temperature variation on the plain delays upward, while the phase on the slope is constant and the same as that of the surface temperature.
    These results are explained using the solution of a simple linear theory corresponding to the case in which the surface temperature of an infinitely long slope varies periodically.
    (2) The total flow circulation in the whole slope-plain system is quite complicated. The upslope flow constitutes a circulation with the height comparable to the slope height, while the downslope circulation is restricted in a lower region with a second circulation above it. The counter-flows to the main flows along the slope have a tendency to maintain their directions throughout one period, adapting themselves to the alternating stage by changing their roles in the total flow system. Such a conservation of the flow direction produces a residual flow in this laboratory model.
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  • Hiroyuki Iwasaki, Takao Takeda
    1989 Volume 67 Issue 4 Pages 575-586
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The behavior of cumulonimbus-cloud groups in a slow-moving long-lasting cloud cluster was studied mainly by the analysis of satellite data and PPI radar data. The cloud cluster exhibited multi-scale structure in satellite infrared imagery. It contained one or several large meso-ß scale (50-200km) cold regions of very low TBB and each cold region was composed of several small meso-ß scale (20-50km) portions whose TBB were lower by a few degrees than ambient clouds. The latter portions corresponded to a deep cumulonimbus-cloud group (Cb group).
    The cloud cluster remained almost stationary for several hours in its developing stage over the ocean. During this stage, Cb groups showed three characteristic sorts of behavior as constituents of the cloud cluster. First, a new Cb group formed to the west side of a pre-existing eastward-moving one. The replacement of Cb groups occurred several times in the stationary cloud cluster. Secondly, Cb groups moved slowly in the first half of its life, in other words, .before the appearance of a new Cb group to its west side. As a result of this behavior, the cloud cluster was maintained and moved slowly. This case-study suggests that a cloud cluster can remain stationary over the ocean without any clear orographic effect. The third feature is that the convective activity of coexisting Cb groups changed in phase with time.
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  • Yoshinobu Nikaidou
    1989 Volume 67 Issue 4 Pages 587-604
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The relationship between precipitation over the tropical western Pacific and sea level pressure of the subtropical high to the south of Japan was investigated by making use of the global spectral model. Two experiments in 4-month numerical integration starting from the initial value on 1 May 1984 without and with an SST warm anomaly of 1.5°C over the tropical western Pacific were examined. In both integrations, the subtropical high with a barotropic structure was formed around Japan in midsummer.
    Clear positive correlation was found between sea level pressure of the subtropical high and precipitation over the tropical western Pacific in the case of the integration with the SST anomaly. The relationship between the subtropical high and the tropical western Pacific could be also ascertained by EOF analyses of the precipitation. The EOF analyses indicate a close relationship of precipitation among the middle latitudes around Japan, the subtropics and the tropics over the western Pacific more clearly in the integration with the SST anomaly than without the SST anomaly. This relationship of precipitation has a resemblance in many respects to the intraseasonal PJ (Pacific-Japan) oscillation found by Nitta (1987), which is the north-south oscillation of cloud amount over the West Pacific and the Far East.
    It was also found in the integration with the SST anomaly that Rossby waves propagate along a great circle from the south of the Japan Islands to the west coast of North America, accompanied by an increase in precipitation over the tropical western Pacific. The wave propagation is similar to the phenomena reported by Nitta (1987). It took about 5 days for Rossby waves to propagate from Japan to North America. The increase in precipitation over the tropical western Pacific in the experiment caused not only the northeastward propagation of Rossby waves but also the westward propagation of fluctuations in precipitation along the south Asian monsoon region.
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  • Tomoaki Ose, Tatsushi Tokioka, Koji Yamazaki
    1989 Volume 67 Issue 4 Pages 605-619
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    This paper studies how the Hadley circulation is affected by a different treatment of penetrative cumulus convections with the use of the Meteorological Research Institute model (MRI•GCM) under the framework of the Arakawa-Schubert penetrative cumulus parameterization and the aqua planet condition. The present experiments clearly show that a cumulus parameterization adopted in a GCM widely controls low latitude climate.
    When the occurrence of deep penetrative cumuli is suppressed, precipitation increases at all latitudes with a remarkably concentrated peak at the equator. The Hadley circulation intensifies and shrinks in the latitudinal direction in addition to the decrease of vertical static stability in low latitudes. Similar results are obtained in the experiments with an axially symmetric GCM. Though change of momentum and heat transports by large scale eddies contributes to the shrink of the Hadley circulation, a large scale eddy process is not essential to the circulation's change. The concentrated precipitation around the equator is responsible for the strong Hadley circulation. On the other hand, the narrow Hadley circulation is explained by the change of the mid-latitude precipitation peak.
    Latitudinal concentration of precipitation around the equator is closely connected with the activity of deep penetrative cumuli. When they are active, they transport water vapor upward from the planetary boundary layer, and the precipitation rate is very close to the local surface evaporation rate. Precipitation is distributed rather broadly in the meridional direction in this case. On the other hand, when deep penetrative cumuli are suppressed, the lower part of the troposphere becomes more humid and the Hadley circulation accumulates water vapor around the equator and maintains a concentrated peak of precipitation there.
    The suppression of the AS cumuli accompanies the decrease of cumulus friction. The Hadley cell weakens by 15% and shrinks by 2° in the meridional direction through the removal of cumulus friction.
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  • Toshiro Inoue
    1989 Volume 67 Issue 4 Pages 621-637
    Published: 1989
    Released: October 19, 2007
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    Cloud covers for six cloud types have been studied over the tropical Pacific Ocean from split window data of the advanced very high resolution radiometer (AVHRR) on board NOAA-9 during the period January 11 to February 9, 1987. Six cloud types, including cirrus clouds and low-level cumulus/stratocumulus clouds which were hard to detect without visible data, are classified by the radiative properties of the 10μm window region. Comparisons between cloud types classified by the split window method and visible data show consistency in optical thickness. Cumulus-type clouds classified by the method indicate higher reflectivity than cirrus-type clouds.
    The thirty-day mean cloud cover defined in 2.5° latitude/longitude areas over the tropical Pacific for total cloudiness, total optically thin clouds (cirrus-type clouds), . optically thick high-level clouds (cumulonimbus-type cloud) and optically thick low-level clouds (cumulus/stratocumulus-type clouds) have coverage of 54%, 31%, 6% and 9%, respectively. It is found that cirrus-type clouds are the major cloud over the tropics. Another feature is that cumulonimbus-type clouds occupy only about 46% within the so-called high-level cloud (colder than -20°C) defined by single infrared data.
    Cloud features over the western Pacific and the eastern Pacific divided along 150°W, show significant differences. The total cloudiness over the western Pacific ocean area was 61%, and 41% over the eastern Pacific. Cumulonimbus-type cloud and cirrus-type cloud appear over the western Pacific twice as often as over the eastern Pacific. In contrast, cloud cover of cumulus/stratocumulus-type clouds over the eastern Pacific is twice as much as over the western Pacific.
    The spatial distribution of high cloud amount area of cumulonimbus-type cloud over the western Pacific shows overall correspondence to a warmer sea surface temperature (SST)(>29°C) area, while the distribution of high cloud amount area of cumulus/stratocumulus-type clouds is confined to over the cooler SST (<27°C) area. It is reconfirmed that deep convection over the tropics is likely to occur over the warm (>26°C) ocean area from the scatter diagram of SST derived from the split window data and cloud cover of cumulonimbus-type cloud, and also from the scatter diagram of SST and mean brightness temperature of cumulonimbus-type cloud.
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  • Kozo Ninomiya
    1989 Volume 67 Issue 4 Pages 639-658
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The cloud distribution over the East Asia and the northwestern Pacific, during the pre-Baiu, Baiu and post-Baiu periods of 1979 are studied in relation to the large-scale circulations.
    The distribution of the following cloud systems is studied;
    1) major cloud system including deep convective clouds (MCS-CON),
    2) major cloud system of layer and shallow convective clouds (MCS-LAY),
    3) cloud system including deep convective clouds (CS-CON), and
    4) cloud system of layer and shallow convective clouds (CS-LAY).
    The following features are found in the present study;
    (1) The area and period of the largest Baiu precipitation coincide with the area and period of most frequent MCS-CON's occurrence. This indicates that MCS-CON is the most important cloud system in the production of Baiu precipitation.
    (2) During the pre-Baiu period, CS-LAY's cover is large over southern China. With the rapid change in the static stability from the convectively stable to the unstable condition, CS-LAY's cover decreases around the end of May, and CS-CON'S cover increases.
    (3) During the pre-Baiu period, a zone of MCS-CON results from the passage of polar frontal depressions in the vicinity of Japan.
    (4) The large-scale circulations change rapidly around the beginning of June. The polar jet stream shifts northward. The Baiu ridge and Baiu trough form in this period. A zone of MCS-CON associated with the Baiu frontal depressions forms along the NW∼N rim of the Pacific subtropical anticyclone which grows and shifts westward in June.
    (5) During the Baiu period, the Baiu trough cloud zone exists apart from the Baiu frontal cloud zone in the 130∼150° area. The Baiu trough cloud zone is located 1000∼1500km north of the Baiu frontal cloud zone.
    (6) Large cover of CS-LAY and a convectively stable condition are seen over the northwester Pacific throughout the pre-Baiu and Baiu period.
    (7) During the peak Baiu period, the Baiu frontal cloud zone attains its maximum extension and maximum cloud cover. The notable regional (W to E) difference is seen in the Baiu frontal cloud zone. The western part of the cloud zone (over China), which forms in the proximity of the Baiu trough, is characterized by CS-CON, strong convectively unstable conditions and very weak baroclinicity. The central part of the cloud zone (in the vicinity of Japan), which forms along NW∼N rim of the Pacific anticyclone, is characterized by MCS-CON, weak convectively unstable conditions and fairly strong baroclinicity. The eastern part of the cloud zone (over the NW Pacific) is characterized by MCS-LAY, convectively stable condition and strong baroclinicity.
    (8) Around the end of July, the Baiu ridge and the Baiu trough weaken. The height and thermal fields change into a zonal pattern with weak meridional gradient. The pacific anticyclone shifts northward. The Baiu frontal cloud zone shifts northward, and the cloud cover decreases.
    (9) The zone of MCS-CON is the essential part of the Baiu frontal cloud zone. The zone of MCSCON forms under the coexistence of weak convectively unstable conditions and moderately strong baroclinicity in the lower troposphere. The aforementioned condition is seen only in the peak Baiu period in the 120∼150° region.
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  • Mitsuo Mizuma
    1989 Volume 67 Issue 4 Pages 659-676
    Published: 1989
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A numerical model of the land and sea breeze which is based on the spectral method is proposed. This spectral model provides the diurnally cyclic solution without daily trends corresponding to the diurnally cyclic thermal boundary condition. The model takes the dependence of the eddy exchange coefficient on the atmospheric stability into account. In order to obtain the convergent solution properly by an iterative process, some elaboration is devised in the numerical aspects. Although the present model assumes a flat terrain and uniform field in the direction parallel to the coastline, the model simulates well the observed features of the land and sea breeze if observational sites satisfy the topographic conditions assumed in the model. It is evident from numerical experiments with the present model that the strength of land and sea breezes increases linearly with the temperature contrast between land and sea. Experiments with larger temperature contrast do not always provide the convergent solution for narrower land and/or sea configurations. Inclusion of the stationary components for the spectral model generates the feature of the land and sea breeze superposed on the stationary horizontal convection. However, the experiment with the present spectral model, when including the stationary components, results in divergence of the iterative process for a much smaller amplitude of temporal variation of the prescribed ground surface temperature than does the experiment excluding the stationary components.
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  • Tsuyoshi Nitta
    1989 Volume 67 Issue 4 Pages 677-681
    Published: 1989
    Released: October 19, 2007
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    Convective activity, low-level winds and sea surface temperature associated with a twin cyclone developed in tropical western Pacific during May 1986 were analyzed in connection with the initiation of the 1986-87 El Nino. The westerly bursts over the equator were greatly intensified, corresponding to the development of the twin cyclone resulting in an eastward expansion of the warm surface water toward the dateline. This event, together with other intraseasonal variations of convection, seems to provide favorable conditions for the 1986-87 El Nino onset.
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  • Kazuo Saito
    1989 Volume 67 Issue 4 Pages 683-690
    Published: 1989
    Released: October 19, 2007
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