Journal of the Meteorological Society of Japan. Ser. II
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Volume 49A
Showing 1-33 articles out of 33 articles from the selected issue
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  • K. Miyakoda, R. W. Moyer, H. Stambler, R. H. Clarke, R. F. Strickler
    Volume 49A (1971) Pages 521-536
    Released: February 18, 2015
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     A general circulation model with the global grid system proposed by Kurihara was used to make a two-week forecast. The general characteristics of the model are: 9 vertical levels, a grid interval of approximately 220 km, orography, land-sea distribution, radiation, water vapor and convective adjustment. Data were collected from various regional data centers, and the maps were analyzed manually. The predicted results are compared with independent predictions for each hemisphere, using a hemispheric model of stereographic mapping, and also compared with observed data, where available. On the whole, the model’s performance was somewhat inferior to that of a hemispheric model with comparable physics and grid resolution, due to excessive truncation error. Yet some advantage of the global prediction over the hemispherical predictions was recognized, particularly in the tropics and also in the middle latitudes. For example, it predicted the latitudinal position of the subtropical jet more correctly.
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  • Yoshio Kurihara
    Volume 49A (1971) Pages 537-544
    Released: February 18, 2015
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     The variation of temperature of an atmosphere at rest with latitude and time is invest’gated. The heating of an air column which is due to short-wave and long-wave radiation is estimated by simple parameterization. A condition of heat balance is assumed at the earth’s surface to evaluate sensible heat flux there.
     An analysis of the equation shows that the heat capacity and the properties of the long-wave radiation of the atmosphere determine the time lag between variations in temperature and insolation. In the numerical integration, extreme temperatures at middle latitude occurred about one month after the solstices. In the equatorial region, two maxima and two minima appeared in the temperature variation. The lowest temperat,ure in the polar region took place in spring because of the winter polar night.
     A comparison of the results of the integration with the observed variation demonstrates the importance of the meridional transport of energy in the atmosphere and ocean. This comparison also suggests the importance of the storage of energy in the ocean and land.
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  • Isamu Hirota
    Volume 49A (1971) Pages 545-552
    Released: February 18, 2015
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     An examination is made of the response of forced Rossby waves to the time change of mean zonal wind and to external heating using quasi-geostrophic and β-plane approximations. Results from the numerical time integration of the linearized potential vorticity equation under several assumed external conditions are compared with steady-state solutions.
     Four cases were studied for the effects of time change of mean zonal wind and thermal forcing; it was found that the “maximum response time scale” (the period at which the wave amplification becomes maximum) has a significant linear relationship to the wave amplitude of the steady-state solution in the uppermost layer.
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  • M. Aihara, H. Imai
    Volume 49A (1971) Pages 553-563
    Released: February 18, 2015
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     Stability properties of planetary-scale motions in a baroclinic zonal current are studied numerically by means of a simple primitive equation system. Mathematical technique used is a form of the method of the initial value which is employed after Brown, Jr. (1969). Some special devices and extensions are made so as to make it applicable to the primitive equation model.
     It is concluded that all waves are unstable and move always eastward. Results are compared with those of the multi-layer geostrophic model.
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  • Yukio Kikuchi
    Volume 49A (1971) Pages 564-572
    Released: February 18, 2015
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     In order to obtain some information concerning the relationship between the blocking action and the effects of mountains and land-sea distribution, numerical experiments were performed with four models. One of these models includes both the effects of mountains and land-sea distribution, two models contain one or the other and the remaining model neither of them.
     The statistical analysis of the results thus obtained leads to the following conclusions:
     1. Even in the case including neither the effects of mountains nor land-sea distribution, blocking action occurs and its behaviour is very similar to that observed in the actual atmosphere.
     2. The duration period of blocking action in the model atmosphere is remarkably short compared to that in the actual atmosphere. However, there is a tendency for the duration period to become somewhat longer if the effect of mountains is included in the model.
     3. The most frequent existence of blocking highs in the areas from 150°E eastward to 150°W (including Alaska) and from 30°W eastward to 30°E (including the Atlantic) results from the effect of mountains. An additional incorporation of the effect of land-sea distribution contributes to yielding the result that the blocking highs are more frequently bound in the area from 30°E eastward to 150°E (including the Eurasian Continent) than in the area from 150°W eastward to 30°W (including the North American Continent).
     4. It is not likely that the effects of mountains and land-sea distribution play a major role in bringing about the fact that blocking highs exist most frequently in the latitudinal belt between 50°N and 70°N in the actual atmosphere.
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  • Akira Kasahara
    Volume 49A (1971) Pages 573-594
    Released: February 18, 2015
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     Real global data of seven levels (surface pressure, geopotential heights for 700, 500, 300, 200, 100, and 70 mb) analyzed by Baumhefner for the period of 15-19 J anuary 1958 (IGY) are used to evaluate the transports of angular momentum, water vapor, and energy due to mean meridional circulation and eddy motions. Since only mass fields are analyzed, a technique is used to claim the fields of wind and water vapor. With the aid of a six-layer general circulation model developed at the National 'Center for Atmospheric Research (NCAR), short-range forecasts are made from analyzed initial mass fields with geostrophic wind as an initial condition. A climatological zonal mean specific humidity distribution for January is assumed as the initial field for water vapor. It is found that the wind and water vapor fields evolving after 24 hours of time integration appear to be usable for the evaluation of various transport quantities.
     The computed mean and eddy transports of momentum, water vapor, and energy are compared with those of various observational sources and of a simulated January starting from an isothermal atmosphere with the NCAR general circulation model. It is shown that the values of various transport quantities for the January 1958 case in the Northern Hemisphere are in reasonable agreement with those of other sources. However, the values of transport quantities in the Southern Hemisphere are underestimated due to weak wave activity. The weakness of eddy motions in the Southern Hemisphere is presumably attributed to difficulty in the initial data analysis owing to sparsity of observation stations in the Southern Hemisphere.
     In this study, we intend to demonstrate that the diagnostic analyses of the mean and eddy transports of various meteorological quantities can be performed from basic data sets with the use of a general circulation model as the means of imposing dynamical constraints among meteorological variables.
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  • Y. Masuda
    Volume 49A (1971) Pages 595-612
    Released: February 18, 2015
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     A 3-layer non-geostrophic balanced model is constructed and the results of a numerical prediction applied over the Northern Hemisphere are examined.
     In this model, a generalized “balance” relation is assumed between wind and pressure fields. The equation of change of water vapour is treated explicitly. The nonadiabatic effects, such as the effects of latent heat due to condensation by large-scale motion and the sensible heat transfer from the sea surface, are taken into account. The vertical motion due to large-scale topography and the surface friction layer are also considered in a crude manner and treated as a lower boundary condition for the so-called ω-equation.
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  • Hiroshi Itoo, Yoshinori Isono
    Volume 49A (1971) Pages 613-627
    Released: February 18, 2015
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     This preliminary report describes a model of 5 days forecast now being developed. The model uses the primitive equations which are expressed by the Cartesian coordinates on the stereographic projection plane and by the σ-coordinate in the vertical.
     Physical processes involved in the model are almost similar to those in the operational forecast model at JMA, except for some differences in the parameterization of physical processes. A case of numerical experiment of four days forecast is analysed.
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  • Takashi Nitta
    Volume 49A (1971) Pages 628-637
    Released: February 18, 2015
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     Starting from a set of meteorological data, the response of a dynamical model to the artificially produced imbalance in the mass field is pursued by making use of the pseudo-forecast initialization procedure. A three-level primitive equation model in the a-coordinate system is used as the computational model.
     The imbalance is produced over a subdomain located near the center of the whole region as follows:
     Case A : The surface pressure is replaced within the subdomain by its area average over the same subdomain.
     Case B: The same as case A, but for the geopotential height at the middle level of the troposphere.
     Case C: A constant value (i.e., 5°C) is added to the temperature field at the lowest level.
     Case D: The same constant value is added to the temperature fields at all the information levels.
     As the wind field, the geostrophic wind is used, which is estimated from the geopotential height with the variable Coriolis parameter.
     During the iterative calculation mutual adjustment toward the quasi-geostrophic equilibrium is expected to take place between the mass and velocity fields.
     For the imbalance extending throughout the total air column (cases A and D), the recovery of the pattern from the unbalanced state to the original one was rapid and sufficient. The result may be explained by the essential role of the external inertiogravitational wave in the adjustment procedure. When it is deep, the imbalance is rapidly dissolved by the external mode because of the fast phase speed of the high frequency wave. The adjustment is then mostly performed under the initiative of the velocity field. Thus the restoration to the original pattern is sufficient.
     On the other hand, for the imbalance located within the air column (cases Band C), ffie convergence to the original was slow and worse than in the previous cases. In the latter cases, the internal mode of the gravity-inertia wave played the main role. Thus the adjustment procedure was dull, and initiative was given neither to the mass field nor to the wind field to yield a different state of balance from the original.
     Although the implications of the present experiment are limited, the result may be applicable to the processing of asynoptic data in weather analysis and may account for the influence of erroneous meteorological information upon numerical prediction.
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  • Tadashi Ozawa
    Volume 49A (1971) Pages 638-647
    Released: February 18, 2015
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     For the numerical analysis and initialization in the ASIA Region, a comparative study was made of the stream line, vorticity and vertical velocity patterns according as analysed by a quasi-geostrophic, a linearized balance and a generalized balance, models with 300km coarse mesh and 150km fine mesh, respectively, As a results, it seems that in 300km coarse mesh the analysed pattern by a generalized balance model corresponds better to the synoptic situations of the observed pattern than those of the other two models, and in 150km fine mesh the analysed pattern by a linearized balance model represents better the observed pattern involving medium scale disturbances than those of the other two models.
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  • S. Matsumoto, K. Ninomiya
    Volume 49A (1971) Pages 648-662
    Released: February 18, 2015
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     Msoscale and medium-scale structures of the Baiu front are studied for the case of July 8, 1969, on which special observations including aerial and ground-base mesoscale upper air soundings were being operated by the Severe Rainstorms Research Project. Within the region of a synoptic scale cyclone generated on the Baiu frontal zones, a medium-scale structure is found which is further decomposed into mesoscale rain bands in the vicinity of the cold front part of that cyclone. A finer structure is also depicted in a low-level jet stream which often appears in the Baiu season particularly at a time of heavy rainfall.
     Based on wind, temperature and relative humidity field analyses, some dynamical considerations and numerical experiments are made on the generation of the low-level jet stream and relevant vertical circulation.
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  • K. Ninomiya, T. Akiyama
    Volume 49A (1971) Pages 663-677
    Released: February 18, 2015
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     On July 04, 1969, severe precipitation took place over the Japan Islands with the passage of medium-scale disturbances along the Baiu front. The structure and the process of the development of the disturbance are analysed in detail by using the data of the Severe Rainstorms Research Project and satellite cloud pictures.
     The satellite and radar pictures show that the disturbance is accompanied by a well organized medium-scale cluster of convective clouds. Detailed analyses of rawinsonde data inside the disturbance revealed that the deepening of the surface pressure is deeply related to the formation of a mid-tropospheric warm core accompanied by a significant field of convergence in the lower troposphere. The high humidity in the warm core and the intense precipitation suggest that the formation of the walm core is due to the process of so-called convective warming, i.e. the release of latent heat and the upward transport of heat energy caused by cumulus convections. The formation of the convergence field is due to the increase of low-level wind velocity over the intense rainfall area. The active cumulus convections in the sheared westerly transport the momentum downward and therefore work to increase the low-level wind velocity.
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  • K. Gambo
    Volume 49A (1971) Pages 678-690
    Released: February 18, 2015
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     The Rossby and gravity waves are discussed on a rotating sphere. The YanaiMaruyama waves observed in the Tropical Pacific are considered as the so-called tidal motion of the second kind k=4 and n=4 or n=6, where k is the wave number in the longitudinal direction and n is the order of the latitudinal eigenfunction. In case where k=4 and n=4, the equivalent depth h is estimated as h∼O (10 m) if we assume that the period of disturbances is about 5 days and the disturbances are confined to the neighbourhood of the equator. On the other hand we have h∼O (1 km) in case where k=4 and n=6 and the disturbance becomes a global one. The results of numerical computation in case where k=4 and n= 6 are shown.
     As the mutual interaction of disturbances between middle latitudes and tropics, the simple consideration whether the disturbances are external or internal on the horizontal plane is put in the discussion when the zonal current has a horizontal shear.
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  • Masanori Yamasaki
    Volume 49A (1971) Pages 691-698
    Released: February 18, 2015
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     The properties of Rossby waves in the surface boundary layer in the low latitudes are studied by the use of a very simplified model. It is shown that concentrated frictional convergence takes place at latitudes where the absolute value of the Coriolis parameter is equal to the frequency of Rossby wave. The frictional convergence associated with the vorticity field is also discussed.
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  • T. Murakami
    Volume 49A (1971) Pages 699-717
    Released: February 18, 2015
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     A linearized form of the primitive equations of motion on an equatorial, β-plane is used to demonstrate that tropical Rossby waves can be distinguished from inertiogravity waves by the difference of their phase speed, provided the meridional scale of disturbances considered is of the order of 1,000 km and the pressure scale, of the order of 1,000 mb. Based upon this, a scale analysis is then made to modify the nonlinear primitive equations of motion so that the modified equations do not contain the possibility of inertio-gravity motions. We obtain a balance-barotropic system for largescale disturbances in a dry tropical atmosphere. This system is exactly the same as that Charney (1963) proposed.
     An attempt is then made to combine the balance-barotropic tropical system with the quasi-geostrophic extratropical system. This combined system requires the streamfunction to be specified first. The geopotential and divergence (vertical velocity as well) fields can be determined by the system as a function of prescribed streamfunction. These fields thus determined are compared with analytical Rossby solutions in linearized primitive equations of motion. An accuracy of simulating Rossby waves is examined as an initial value problem.
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  • M. Yoshitake
    Volume 49A (1971) Pages 718-725
    Released: February 18, 2015
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     The Blasius equation for a flat plate in uniform laminar flow is solved approximately in a closed form. This solution is simple but in good agreement with the exact solution found by numerical integration. Some applications of this solution are undertaken.
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  • Taketo Maruyama
    Volume 49A (1971) Pages 726-735
    Released: February 18, 2015
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     Two kinds of equatorial waves are predominantly observed during the Line Islands Experiment (March-April, 1967),. The one is mixed Rossby-gravity waves in the layer of 25-35 mb where the basic westerlies weaken with height. The other is Kelvin waves in the layer of 40-80 mb where the basic westerlies strengthen with height. The vertical convergence of the westerly momentum due to Kelvin waves may well contribute to the acceleration of the basic westerlies.
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  • Hiroshi Matano, Mitsuru Sekioka
    Volume 49A (1971) Pages 736-743
    Released: February 18, 2015
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     The process by which a tropical cyclone is transformed into an extratropical cyclone in middle latitudes is considered from several aspects in selected typical examples. It is proposed that there are three aspects to the extratropical transformation of the tropical cyclone in relation to outbreaks of cold air over the continent.
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  • Katsuyuki Ooyama
    Volume 49A (1971) Pages 744-756
    Released: February 18, 2015
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     On the assumption that cumulus clouds can be represented by independent buoyant elements, a general theory is developed for parameterization of cumulus convection illlarge-scale weather systems. No specific method ready for application is yet proposed, except for a simple application to tropical disturbances. The main purpose of this study is to propose a basic theoretical structure of parameterization, so that further investigations, both observational and analytical, can be integrated to produce better practical methods.
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  • Tomio Asai, Isao Nakasuji
    Volume 49A (1971) Pages 757-765
    Released: February 18, 2015
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     Stability properties of an unstably stratified parallel flow with vertical and horizontal shears are investigated by solving numerically a system of perturbation equations. Horizontal shear as well as vertical shear tends to suppress thermal instability. Stabilizing influence of the shear on perturbations is more efficient as the wavelength in the longitudinal direction is shorter, while the longitudinal roll perturbation is free from the stabilizing effect of the shear. A longitudinal roll convection may thus be most favorable for development.
     Conversion between the kinetic energy of the basic flow and that of the perturbation is found besides conversion of potential to kinetic energy. A longitudinal perturbation which is of the preferred mode is associated with horizontal and vertical transports of momentum to decrease the shear which result in transforming the kinetic energy of the flow into that of the perturbation.
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  • Yoshikazu Sasaki
    Volume 49A (1971) Pages 766-773
    Released: February 18, 2015
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     A brief summary of the recent studies made by the author and his students on one topic of the variational method is given. The topic concerns the low-pass filters and band-pass filters adopted in the variational formalisms.
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  • M. Magata, K. Nishida
    Volume 49A (1971) Pages 774-783
    Released: February 18, 2015
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     Several computational problems are discussed using simple numerical models, such as irregular appearance of errors, nonlinear computational instability, aliasing errors, conservation of the physical quantity and boundary conditions. It is also shown in the advective equation that the character of solution of the differential equation is essentially different from that of its difference equation.
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  • Arnt Eliassen
    Volume 49A (1971) Pages 784-789
    Released: February 18, 2015
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     The system under study is an Ekman boundary layer in a circular vortex bounded by a plane horizontal surface which rotates around the axis in an absolute sense. It is found that the vertical motion forced by a turbulent Ekman layer near the axis will tend to zero with the radius. In contrast, it is known from the Greenspan-Howard theory that the vertical motion is constant near the axis in the laminar case. Implications for the spin-up mechanism and for the structure of typhoons are pointed out.
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  • H. Wada, E. Kitahara
    Volume 49A (1971) Pages 790-797
    Released: February 18, 2015
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     A classification of monthly and 5-day mean 500 mb height patterns is carried out for the period 1946-19'10, by the use of the zonal index anomalies in the four quadrants of the Northern Hemisphere. The patterns are classified into three types, two foundamental circulation types, Z and M, and a sub-circulation type S. These are further classified into subdivisions, that is, 10 fundamental types and 6 sub-types. The model patterns for these types are constructed by making use of the composite maps.
     Some relationships between the typical patterns of the Northern Hemisphere and the recent climate in the world are studied, by using the result of this classification. It is found that the frequency and presistence of patterns in each type have a close relation to the features of climate in the world and that the new set of types is very useful for a study of the climatic change in Japan and also for practical long-range forecasting. In this paper, the patterns in the Northern
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  • Takeo Yamamoto
    Volume 49A (1971) Pages 798-812
    Released: February 18, 2015
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     Through an investigation of various historical records on climate written from the beginning of the XVII to the end of the XIX century, it is tried to connect the climatic change in the recent instrumental observation age to that of the historical times in Japan. It is concluded that the J apanese climate passed through a “little ice age” around 1750 to 1850. The mean January air temperature in the first half of the XIX century and the mean July air temperature from 1751 to 1850 are estimated as 1°-2°C lower than the present normal and the summer climate is concluded to have been pluvial, judging from the frequency of flood occurrences and their unprecedented scale. On the basis of the data of recent meteorological observations, it is concluded that the “little ice age” was caused by the weakening of the subtropical high and the southward retreat of the climatic zone.In this paper, the patterns in the Northern
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  • Tetsuya T. Fujita
    Volume 49A (1971) Pages 813-820
    Released: February 18, 2015
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     July 14, 1969 was selected from BOMEX Period IV as the day of detailed analysis of cloud velocity fields over the northern tropical Atlantic Ocean. A total of 375 low-cloud velocities were obtained between ITCZ and 34N and 70 velocities between ITCZ and the equator. These velocities are found to be very useful in understanding circulation patterns over a vast region of water where little synoptic data is available. Over 170 high-cloud velocities were computed mostly in the area of cloud clusters. It was found that a field of high-cloud divergence existed over practically each of large cloud clusters in the ITCZ and an easterly wave appearing on this day. Motion of dust clouds from Sahara was also computed by using an accelerated movie technique. It is concluded that ATS III picture sequences can be analyzed independently from conventional synoptic and/or network data so that the computed velocities of clouds, dust, and propagating waves can be used as supplementary data to past and future tropical experiments.
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  • Keitaro Mohri
    Volume 49A (1971) Pages 821-823
    Released: February 18, 2015
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     A remarkable inversion layer was observed in the middle troposphere at Sapporo 15th June 1970. Temperature at 400-mb was 13°C warmer than that at 500-mb in the inversion layer. It is shown that, as a result of cross-section analysis, this strong inversion in the middle troposphere was a phenomenon associated with a cold dome which passed over north Japan at this time.
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  • Choji Magono
    Volume 49A (1971) Pages 824-835
    Released: February 18, 2015
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     The localization phenomena of snowfalls in the winter monsoon season were studied from various points of view, namely cloud physics, laboratory experiment, radar meteorology and the satellite meteorology.
     The results of the study are summarized as follows:
     1. Snowfalls can occur over the Sea of Japan without any upglide effect by mountains.
    2. The localization of snowfalls is produced by the convergence of snow clouds, because falling snow crystals are considered to be transported nearly horizontally by wind.
    3. A meso-scale front is formed by two meso-scale air-masses, and a series of mesoscale cyclones is formed along the meso-scale front.
    4. The formation mechanism of meso-scale cyclones may be explained by the classical model given by Bjerkness.
    5. The orographic effect on the movement of snow clouds is considerably stronger than usually expected.
    6. The snowfall is localized on an area where the wind speed is decreasing.
     Actual examples of the localization of a result of the orographic effect.
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  • Kenji Isono, Kunimoto Iwai
    Volume 49A (1971) Pages 836-844
    Released: February 18, 2015
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     Ice crystals were grown in air at pressures lo\ver than 10-1 Torr in a cryostat. It was found that at pressures lower than 10-1 Torr ice crystals grew in spherically symmetric form with facets of higher indices and then the facets of lower indices developed. These ice crystals were transparent and facets were specular. Even at high supersaturation, neither skeletal, nor edge growth were observed. The measured growth rates indicate that the growth of the ice crystals was not controlled by diffusion of water vapor in air, but by the free molecular influx onto surfaces of the ice crystals.
     The sublimation coefficient of ice was determined at temperatures between -50°C and -ll0°C; Its values were about 0.07 at temperatures between -50°C and -80°C and below -83°C increased with decreasing temperature to 0.4 at -110°C, which is nearly equal to the temperature at the level where noctilucent clouds are often observed.
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  • A. Ono
    Volume 49A (1971) Pages 845-858
    Released: February 18, 2015
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     Evidence is presented that small regular ice crystals found in maritime cumulus clouds with summit temperature warmer than -10C were formed in clouds near the sampling level. Their concentrations were far larger than those usually observed for natural ice nuclei, so that it is supposed that they were the secondary products and the primary ice crystals growing on natural ice nuclei could be multiplied many times in the course of the formation of small regular ice crystals. Their sizes, concentrations and microphysical conditions of occurrence support the hypothesis that they were formed when ice fragments were thrown off from water drops freezing after accreting on ice crystals.
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  • Giichi Yamamoto, Masayuki Tanaka, Kimio Arao
    Volume 49A (1971) Pages 859-865
    Released: February 18, 2015
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     Secular variation of atmospheric turbidity is estimated from direct solar radiation measurements at several stations in Japan using the method proposed by the present authors. Estimated results show that while the atmospheric turbidity did not change appreciably before 1950, it began to increase year after year in the last two decades not only in large cities but also in rural regions. As a result, the present amount of aerosols over Japan is about twice as large as that of the prewar days and the increasing trend of turbidity is likely to continue in the future. It is also shown that the general pattern of the seasonal variation of turbidity has changed from the pattern with maximum in spring to that with maximum in summer.
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  • Ysohinari Nakagawa, Paul Swarztrauber
    Volume 49A (1971) Pages 866-875
    Released: February 18, 2015
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     A numerical study of non-axisymmetric hydromagnetic model of the solar cycle is described. The medium is assumed incompressible and confined between two differentially rotating spherical shells, then the basic equations of hydromagnetic are integrated. It is shown that magnetic activity develops near the heliographic latitude 30°. However, it is found that the present model leads eventually to axisymmetric flows and magnetic fields in the presence of viscosity and magnetic diffusivity due to the axisymmetric boundary conditions. The improvements of the model and the direction of future investigations are discussed.
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  • Koji Hidaka
    Volume 49A (1971) Pages 876-883
    Released: February 18, 2015
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