Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 60 , Issue 2
Showing 1-21 articles out of 21 articles from the selected issue
  • Masanori Yoshizaki
    1982 Volume 60 Issue 2 Pages 607-619
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The stability of finite-amplitude baroclinic waves in a two-layer channel flow is investigated by using the generalized Landau equiation which describes temporal and spatial modulations of finite-amplitude waves in a weakly non-linear regime. We first obtain a plane wave solution of the generalized Landau equation and then examine its stability with respect to sideband perturbations.
    A finite-amplitude wave of wavenumber α in a supercritical state is stable if α satisfies the inequality L±2(α±-αc)2>(α-αc)2, where αc;denotes the critical wavenumber at the linearly marginal state while α+ and α-(α+>α-) are wavenumbers on the neutral curve at a prescribed supercritical state. The coefficient L±2 is 1/3 when the beta effect is absent, while it is generally greater than 1/3 when the beta effect is present.
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  • Masanori Yoshizaki
    1982 Volume 60 Issue 2 Pages 620-637
    Published: 1982
    Released: October 19, 2007
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    By using a two-layer channel model, the stability and behaviours of finite-amplitude baroclinic waves are investigated in the moderately non-linear regime. Two methods which are applicable to the moderately non-linear regime are adopted. One is the method in which steady wave solutions are first obtained and then their stabilities are examined with respect to various perturbations. The other is the numerical method in which time integrations of a grid model are performed as an initial value problem. We obtain many interesting results, although we treat some cases with particular values of non-dimensional parameters except the vertical shear U. The main results are summarized as follows: (1) The stability of steady finite-amplitude baroclinic waves is determined mostly by the sideband instability. (2) The dominant wavenumber seen in a finite-amplitude state is different from that predicted by the linear theory. (3) The beta effect reduces the stable region of finite-amplitude baroclinic waves in the (α, U)-plane, where a is wavenumber. (4) The wavenumber realized in the finiteamplitude state for given values of parameters depends on the initial conditions. Such a hysteresis phenomenon in wavenumber selection is seen when the stable region contains more than two wavenumbers. (5) Both wavenumber and amplitude vacillations are simulated by numerical experiments. The sideband instability can produce such time-dependent motions. The mechanism of vacillations produced by this instability is different from those proposed by Lorenz (1963) and Pedlosky. (1976, 1977).
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  • Takio Murakami, Akimasa Sumi
    1982 Volume 60 Issue 2 Pages 638-648
    Published: 1982
    Released: October 19, 2007
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    Some of the characteristic features of the Southern Hemisphere summer monsoon were investigated by using twice-daily, objectively analyzed wind data at 850 and 200mb for December 1978 to February 1979, over an expanded WMONEX region (90°E-140°W, 30°N-30°S).
    In January, the extent of the Southern Hemisphere monsoon is probably denoted by a zone of strong 850mb equatorial westerlies that extends along about 10°S from the northeastern Indian Ocean (100°E), across the Indonesian Seas and New Guinea, to the western South Pacific (180°). The eastern end of the Southern Hemisphere monsoon trough is characterized by a major low-level (850mb) convergent center and an upper-level (200mb) anticyclonic system associated with pronounced divergence.
    In the immediate vicinity of the Southern Hemisphere monsoon trough (15°S), the divergence effect was the main factor in low-level disturbance development. Conversely, between the equator and 10°S, disturbances developed by receiving vorticity from the zonal mean flow via barotropic nonlinear interactions.
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  • Takio Murakami, Akimasa Sumi
    1982 Volume 60 Issue 2 Pages 649-671
    Published: 1982
    Released: October 19, 2007
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    The onset of the 1978-79 Southern Hemisphere summer monsoon at around 23 to 27 December was initiated by a series of events that occurred away from the Indonesia-Australia region. Low-level monsoon westerlies were first established over the western South Pacific (160°E-170°W, 0°-10°S) in response to the intensification of the tradewinds over the North Pacific and cross-equatorial northerlies near 170°E. The monsoon became fully established with the westward expansion of this low-level westerly regime into the Indonesian-Arafura Sea region.
    The western South Pacific was also a key area for the initiation of the "break" monsoon that prevailed from around 8 to 17 February. The initial phase shift from a westerly ("active") to a predominantly easterly ("break") regime occurred over this region as a result of vorticity advection due to northerly divergent winds (low-level Hadley circulation) and planetary boundary layer friction effects.
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  • Ernest C. Kung, Taher A. Sharif
    1982 Volume 60 Issue 2 Pages 672-681
    Published: 1982
    Released: October 19, 2007
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    Meteorological variables which likely are associated with the initiation and maintenance of the Indian summer monsoon are examined in a regression analysis. Consequently, a longrange forecasting scheme for the monsoon onset date in southwestern India and the total seasonal rainfall in central India is formulated. The regression forecasting scheme involves five predictors for the onset date and six predictors for the rainfall. These predictors include upper air parameters at 100, 200 and 700mb over India and Australia and the sea surface temperature in the Indian region. The forecast experiments for the period1958-77show the predicted onset dates and seasonal rainfall to be very close to the recorded dates and rainfall. Various aspects of the forecasting scheme are discussed.
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  • Richard H. Johnson
    1982 Volume 60 Issue 2 Pages 682-690
    Published: 1982
    Released: October 19, 2007
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    Observations from the International Winter Monsoon Experiment (Winter MONEX) have been analyzed to determine the nature of the vertical motion field within mesoscale deep convective systems that occurred during December 1978 over the southern portion of the South China Sea. Vertical motion has been computed using rawinsonde data from a nearly equilateral triangle (∼400km on a side) of Soviet research vessels situated off the north coast of Borneo.
    It has been found that over the South China Sea to the north of Borneo a diurnal cycle of convective activity occurs throughout December. During its mature stage the convection is characterized by a deep (from near 500mb to ∼l00mb) lightly-precipitating stratiform cloud layer of mesoscale (∼200-400km) dimension. Using triangle-computed vertical velocities and an assumption that the clear environment surrounding clouds is subsiding at a rate just sufficient to offset net radiational cooling to space, it has been determined that within mesoscale clouds upward motion occurs with, on the average, a peak vertical velocity in the very high troposphere near 250mb (10km) of ∼12cm s-1. Beneath the mesoscale cloud systems downward motion is observed with a peak near 650mb or 3.5km of ∼3cm s-1.
    Comparison is made with vertical motion reported in mesoscale convection in other tropical and midlatitude regions. Because the mesoscale cloud systems cover large areas, they probably contribute in an important way to synoptic-scale atmospheric mass, heat and moisture budgets in the near equatorial winter monsoon region.
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  • Kunihiko Hozumi, Toshio Harimaya, Choji Magono
    1982 Volume 60 Issue 2 Pages 691-699
    Published: 1982
    Released: October 19, 2007
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    Small cumulus clouds over the ocean were observed photographically using air liners in the periods of AMTEX '74 and '75. These photographs were analyzed to determine the size distributions of cumulus clouds as a function of cloud amount by the trigonometric method. It was found that the size distributions are represented by the exponential distribution N=a⋅exp(-bD), where N is the number concentration and D is the diameter. The coefficients a and b are expressed exponentially as functions of cloud amount.
    The flatness of convective cells were also analyzed. It was shown that the cell diameter has a linear relation to its depth, and that the cell flatness has a linear relation to the reciprocal of its depth.
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  • Choji Magono, Kunihiko Hozumi
    1982 Volume 60 Issue 2 Pages 700-708
    Published: 1982
    Released: October 19, 2007
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    It was observed that cumulus clouds over the East China Sea near Miyako Island, Japan rotated around the horizontal axis in the winter season of 1975. The rotation occurred in cumulus clouds only in their developing stage. The direction of rotation is determined by the sign of vertical wind shear in the cloud level. That is, the moving cumulus clouds made mostly a retrogressive rotational motion when the sign of vertical wind shear was negative. Occasionally when the sign of wind shear was positive, they made a progressive rotation. When the strength of wind shear was smaller than 1.0×10-3/s, clouds conserved their usual convectional motion.
    The circular speeds in the descending portions of rotating clouds were much higher than those in the ascending portions. These properties of rotational motions of clouds suggested that the rotational motion is related not only to the vertical shear but to the convectional motion of cumulus clouds.
    Based on the results of observation and calculation, it was concluded that the rotational motion of fair weather cumulus clouds was caused by the composition of the convective motion and the vertical wind shear stress in the cloud level.
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  • Kikuro Tomine, Shigeo Abe
    1982 Volume 60 Issue 2 Pages 709-716
    Published: 1982
    Released: October 19, 2007
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    Large truncation errors are frequently found in the calculation of the pressure gradient force in the sigma coordinate systems for the domain with steep slopes. It is pointed out that the errors result from the use of hydrostatic equation in the calculation of pressure gradient force. Thus we propose the use of not the first order but the higher order approximation of the geopotential height in the calculation of the pressure gradient force. We adopt here a polynomial function of log p to represent the geopotential height Φ on each pressure level. The pressure gradient force between the two adjacent grid points i and i+ 1 is represented as the difference between the two geopotentials Φi and Φi+1 which are given by the polynomial functions on the same pressure level. It is found that the errors in the calculation of the pressure gradient force by this method are considerably smaller than that shown by previous workers.
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  • Hisao Ohno
    1982 Volume 60 Issue 2 Pages 717-725
    Published: 1982
    Released: October 19, 2007
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    An analysis and a forecast of tropopause height using a linear regression equation and empirical formulas with large scale meteorological variables obtained by objective analysis and a numerical prediction model for the northern hemispherical aviation weather service is discussed.
    Selected variables in the regression equations for the analysis and the forecast of the tropopause height were the geopotential heights, the stabilities of upper troposphere and the 500mb vorticity. The multiple correlation coefficients of analysis regression equations were about 0.87 and those of forecasting regression equations were about 0.85 except winter cases. The multiple correlation coefficients of the winter forecast remained around 0.65. It is found that observed tropopause heights considerably deviated from the analyzed and forecast values in the tropical and cold cutoff cyclone regions. In those regions the heights derived from the regression equations were modified by the empirical formulas. By this modification, resulting forecast error decreased to less than 20mb except in winter.
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  • Masanori B. Okamoto, Kosei Iwase
    1982 Volume 60 Issue 2 Pages 726-738
    Published: 1982
    Released: October 19, 2007
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    An index of gross feature of several climatic time series is given by a total of its hard limiting series obtained by level-crossing to the original time series. Under admitting a weak concordance between the paired hard limiting series, a distinguished cold period "Maunder minimum" or a warm period can be interpreted by the above index series.
    For a pair of random variable at any two time points, an unbiased estimator of correlation is given by a certain function of level, under the condition that a pair of random variable follows to a bi-variate normal distribution with known mean values and variances. An optimum level for the estimation of correlation is discussed by the criterion of minimum variance under the statistical optimality condition; the variance of estimator is explicitly given by a function of such a bi-variate correlation and level of crossing.
    Autocorrelation of index series can be also expressible by an integral form which is a function of such a correlation and level of crossing.
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  • Yukio Gocho
    1982 Volume 60 Issue 2 Pages 739-757
    Published: 1982
    Released: October 19, 2007
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    Relations among some characteristics of rainfall over the reference area of about 4, 000 km2 around the Suzuka mountains and meteorological conditions are statistically studied. The elements mainly analyzed are 6 hour precipitations at about 50 points in the area and the serological data at Hamamatsu both of which cover 463 days in total (every day) during three successive warm seasons (1972-1974) and also 87 heavy rainfall days in total with the maximum daily precipitations not less than 100mm in the area during 11 years (1967-1977).
    For about half of the heavy rainfall days, the maximum daily precipitation occurred in the neighbourhood of Mt. Gozaisho, a peak of the mountains; it can be said that the orographic effect on the observed rainfall in this area is significant. The importance of winds in the lower and middle troposphere for the rainfall is mainly pointed out. In about half of the cases having a southerly wind component in the lower troposphere. rain falls over the area. As the winds become strong, the rate of occurrence of rainfall tends to increase and rainfall area tends to widen. In most of the cases with a weak wind, precipitation is small, though intense rain with a total maximum of about 100mm falls occasionally.
    The maximum frequency of rainfall occurs in the cases of southeasterly and southwesterly winds, in which average convective stabilities are nearest to neutral and most unstable respectively.
    The maximum precipitation in the neighbourhood of the ridge appears frequently in the cases with wind direction from nearly southeast in the lower layer. The other maxima appear on the whole frequently over the windward sides of the ridge for the wind directions, especially around southeast and southwest, in the lower layer. Though there are the maxima also on the leeward sides, those are considerably near to the ridge. These tendencies become distinct in the cases with large rainfall areas and large maxima.
    Correlation between 6 hour precipitation on the ridge and wind speed in the lower layer (900mb) is high in the wind direction from southeast or around there. One of the reasons why the precipitation, especially daily precipitation, is generally large on mountains, would be because rain with not so high intensity continues for a long time at least as long as nearly southeasterly strong wind is prevalent, though there are some exceptions.
    When winds across the mountains flow from Ise Bay in the lower layer, the points of maximum precipitation tend to shift northward along the mountains according to the increase of southerly wind component. Further, in those cases, the points of maximum precipitation tend to shift eastward according to the increase of the vertical change of wind direction (ordinarily winds veer with the altitude).
    When winds flow from Ise Bay in the lower layer, the correlation coefficient between wind speed and maximum precipitation is generally positive. The rate of increase of the precipitation with wind speed tends to become large according to the increase of southerly wind component. Concerning the dependence of rainfall on convective stability, the rate of increase tends to become large according to the lowering of the stability, but rain can fall considerably heavily under any condition of stability, probably except in the case of high stable state. Furthermore, the more unstable the states become, the more frequent the cases with smaller rainfall areas are; while the more stable, the more frequent the cases with larger ones.
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  • Tadao Aoki
    1982 Volume 60 Issue 2 Pages 758-764
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Based on the work of Aoki (1980) an accurate and computationary fast method has been developed for the clear radiance retrieval in the case where the AVHRR picture data cannot be used because of, e.g., the limitation on the computation time. The present method has been applied to the observed radiance data by NOAA-6 meteorological satellite. It has been shown that the present method without the usage of the AVHRR data is slightly worse in accuracy than the method with using the AVHRR data but highly accurate than the current method of McMillin.
    A new type of the hardware system for the vertical sounding from satellite has been proposed, slightly modifying the current TIROS-N type sounding instruments.
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  • Akiyoshi Mita
    1982 Volume 60 Issue 2 Pages 765-776
    Published: 1982
    Released: October 19, 2007
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    Light absorption properties of inhomogeneous spherical particles, each consisting of absorbing core and nonabsorbing shell, were investigated using the theory of light scattering from a coated sphere. The absorbing core was assumed to be made of either carbon soot or hematite (Fe2O3), both of which are considered to be important substances in determining the absorptivity in the visible region of atmospheric aerosols. The absorption properties of polydisperse systems in which these inhomogeneous particles are distributed by the power law size distribution were also investigated.
    The absorption cross section of spherical soot and hematite particles can increase by a factor of about two when they become coated with concentric spherical shells of nonabsorbing substances having real refractive indices 1.33-1.53. This enhancement of absorption occurs for soot particles of any size. For hematite particles, however, in some cases the nonabsorbing coating acts to reduce the absorption cross section in the region where the particle size is comparable to the wavelength of light. It is shown that the imaginary part of the effective refractive index for polydisperse systems composed of absorbing and nonabsorbing substances becomes somewhat larger when the absorbing component occurs as mixed particles coated with nonabsorbing substances.
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  • Kikuo Okada, Kenji Isono
    1982 Volume 60 Issue 2 Pages 777-786
    Published: 1982
    Released: October 19, 2007
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    Trends in visibility in the urban atmosphere and their relation to the change in consumption of fossil fuels were studied. The data of visibility observed at Nagoya Local Meteorological Observatory at 0900 JST during the period 1945-1977 were used in analysis. According to the relation between the extinction coefficient calculated from visibility in Nagoya and consumption of fossil fuels in the Tokai district including Nagoya, the trends in visibility in the urban atmosphere over Nagoya were closely related to the amount of aerosols originated from the combustion of fossil fuels. It is suggested that the causes of the recovery of visibility after about 1960 were the application of control techniques to the sources of particulate matter and the change in fuel usage from coal to oil. On the basis of the difference in visibility or extinction coefficient as a function of relative humidity between 1960 and 1973, it is suggested that the amount of insoluble matter in aerosols decreased in recent years as a result of the change in fuel usage from coal to oil.
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  • Sadamu Mochizuki
    1982 Volume 60 Issue 2 Pages 787-796
    Published: 1982
    Released: October 19, 2007
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    In the maritime atmosphere near the land, natural radon and its daughters dispersed from land to over ocean are found gradually to attain their radioactive equilibrium with time lapse after they left land sources.
    Radioactive equilibrium is found to be established at the distance 100∼150km from the land, at least in winter season. Farther off from the distance about 150km from the land, radioactive equilibrium will get deviation mode from their equilibrium state.
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  • Masahiro Kajikawa
    1982 Volume 60 Issue 2 Pages 797-803
    Published: 1982
    Released: October 19, 2007
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    Free-fall pattern of early snow flakes, which were composed of two to six crystals, were observed by a stereophotogrammetric method.
    The considerable part (about 80%) of analysed snow flakes showed the fall pattern of spiral type or rotation type. On the other hand, the stable motion (the fall pattern without horizontal movements) was only observed in the small number of snow flakes composed of two crystals. Whether those snow flakes show the stable motion or not depend on Reynolds number of mean vertical motion, the combined state and the ratio of sizes of two component crystals.
    The nondimensional frequency and the period of spiral motion increased in proportion to Reynolds number and the nondimensional amplitude of spiral path, respectively. Moreover, the displacement velocity of spiral axis increased proportionally to the falling velocity of early snow flakes.
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  • Tateki Mizuno, Osayuki Yokoyama, Akira Yasuraoka
    1982 Volume 60 Issue 2 Pages 804-818
    Published: 1982
    Released: October 19, 2007
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    Vertical diffusion from a ground level line source was estimated using the structure model of the atmospheric boundary layer proposed by Yokoyama et al. (1977a, b, c). The two-dimensional differential equation of diffusion was computed numerically for stationary and horizontally homogeneous conditions. Making the equation dimensionless, we showed that the characteristic spread (Zσ) divided by the height of the boundary layer (h), is a function of two dimensionless lengths, χ/Reh and z0/h, in the mixing and neutral layers (χ: downwind distance from the source, Re: the quantity formed from the characteristic scale of wind speed, eddy diffusivity and the height of the boundary layer, z0: the roughness length of the ground surface.) In the stable layer, another dimensionless length, h/L (L: Monin-Obukhov length), is needed in addition to the above two parameters.
    From the relationship between Zσ/h and χ/Reh, it may be shown that in the mixing layer, Zσ is a function of traveling time of the smoke. In the neutral and stable layers, however, Zσ is independent of the mean wind speed and depends only on the downwind distance from the source.
    As for the computed concentrations, vertical spread Zσ in the mixing layer increases rapidly in the early stage of the diffusion and tends to vary slowly when the upper part of the layer affects the diffusion. Profiles of vertical concentration in the mixing layer are nearly exponential when Zσ/h«1 and approach a Gaussian distribution gradually with an increase in the downwind distance. On the other hand, in the stable layer, these profiles are nearly Gaussian even at short downwind distances and become more rounded at long distances. The estimated vertical spread Zο and concentrations at the ground surface are discussed, comparing them with diffusion experiments and the Pasquill-Gifford chart.
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  • Y. Dokiya, Y. Sugimura, K. Hirose
    1982 Volume 60 Issue 2 Pages 819-820
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
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  • K. Sahashi, R. J. Francey
    1982 Volume 60 Issue 2 Pages 821-823
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
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  • H. Kondo, K. Saito, Y. Manuiya, M. Hara
    1982 Volume 60 Issue 2 Pages 824-829
    Published: 1982
    Released: October 19, 2007
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