Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 60 , Issue 1
Showing 1-50 articles out of 52 articles from the selected issue
  • Barry Saltzman, Chung-Muh Tang
    1982 Volume 60 Issue 1 Pages 1-15
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A brief review is given of a series of analytical studies by the authors demonstrating the effects of second order nonlinear and nongeostrophic processes on the evolution of an amplifying two-level baroclinic wave. It is shown that many of the finite amplitude properties of the waves observed in the atmosphere and ocean can be deduced. However, in these studies the feedback between the altered basic state and the lower order (primary) wave field is neglected so that the waves grow in an unrealistic exponential manner without reaching saturation (i.e., occlusion). In order to demonstrate the saturation effects of feedbacks between the static stability and baroclinicity (vertical wind shear) variations and the growing primary wave, a heuristic semi-numerical algorithm is developed that, in principle, can be coupled with the previous analytical studies. It is found that for a typical initial basic state, and in the absence of friction and barotropic wave-wave and wave-mean flow interactions, the time scale for the development of an occluded state is about 10days for the atmosphere and 2 months for the ocean. In both cases the effects of baroclinicity variations are much more important than static stability variations in bringing the wave to saturation. Because friction is neglected the ultimate decay of the occluded wave cannot be represented.
    Download PDF (1868K)
  • Tu-cheng Yeh, Mai-tsun Li
    1982 Volume 60 Issue 1 Pages 16-23
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    It is shown in this paper that the development of most of the atmospheric weather systems, large-scale or small-scale, consists of three stages, namely the adjustment stage (called geostrophic adjustment for large-scale motions), the developing stage and the quasisteady stage. There are three time scales corresponding to these three stages of development, the time scale for the adjustment stage being shortest, that for the developing stage being much longer and that for quasi-steady stage being longest. The physical processes in the development of these three stages are related to the evolution of the potential vorticity field.
    It is further shown in this paper that similar to the scale effect in large-scale motion with a critical scale L0=c/ƒ, there is also a critical scale L0'=c/Ω for meso-scale motion, where c is the speed of gravity wave;ƒ, the Coriolis parameter and Ω, the characteristic value of absolute vorticity of the wind. Under certain assumptions, a critical scale L0"=[u2/g/ρ∂ρ/∂z]1/2 can also found for motions of cumulus scale, where u and ρ are the characteristic velocity and density of the atmosphere respectively. The roles of L0' and L0" in meso-scale and cumulus-scale motions are similar to that of L0 for large-scale motions.
    Download PDF (978K)
  • Qing-Cun Zeng
    1982 Volume 60 Issue 1 Pages 24-31
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The evolution and interaction of quasi-geostrophic disturbances and zon barotropic atmosphere on a rotating sphere are investigated by integral properties as well as by the WKB method. The results obtained by these two methods are in full agreement and supplement with each other. Two concepts, the available zonal energy and rotational adaptation, are introduced. It is indicated that the atmospheric motion on a rotating sphere always keeps some anisotropy, and can become a completely zonal flow under favorable conditions. Developing (decaying) disturbance superimposed on zonal flow or ultra-long wave enlarges (shortens) its size, i.e., local wave length, provided the jet is moderate and satisfies the stable condition. Developing (decaying) disturbances transfer angular momentum out from (into) the jet region; and weaken (strengthen) both the jet and its shear. At the same time, the propagation of developing (decaying) disturbance decelerates (accelerates).
    Download PDF (867K)
  • Andrei S. Monin
    1982 Volume 60 Issue 1 Pages 32-36
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Study of synoptic processes in the ocean and development of methods for their prediction becomes one of the burning problems of ocean hydrodynamics. The comparison to the atmospheric processes and the disclosure of similarities and differences may help in speeding up the solution of this problem. The essence of the phenomenologic model of the general atmospheric circulation is given in brief. A description is presented of the differences in the origin of the large-scale currents in the ocean and the atmosphere, in density stratification and in dependent processes. Typical horizontal scales, motion velocities and lifetimes of synoptic disturbances in the ocean and the atmosphere are discussed. Different mechanisms of generation are considered, and a brief classification of synoptic motions in the ocean is given. A complexity of the wave field in the ocean is shown to be due to a great variety and a wide distribution of wave generation mechanisms, weak attenuation and on an ability of reflecting from the coasts.
    Download PDF (729K)
  • Michael E. McIntyre
    1982 Volume 60 Issue 1 Pages 37-65
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Ever since Matsuno's pioneering numerical simulations of the stratospheric sudden warming there has been little reason to doubt that this spectacular natural phenomenon is essentially dynamical in origin. But theoretical modelling, and the use of satellite observations, are only just reaching the stage where there seem to be prospects of understanding stratospheric warmings in some detail and forecasting them reasonably well. An informal discussion of recent progress is given, and suggestions are made for future work, including a way of avoiding spurious resonances in mechanistic numerical models in which tropospheric motions are prescribed a priori.
    Download PDF (4766K)
  • Richard S. Lindzen, Takehiko Aso, David Jacqmin
    1982 Volume 60 Issue 1 Pages 66-77
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The linearized response of the atmosphere to thermal and orographic stationary wave forcing is examined with a high resolution (1km vertical resolution, 1.5° latitude resolution) primitive equation model. It is found that the response to thermal forcing (but not orographic forcing) is sensitive to small changes in the basic distribution of wind and temperature. This suggests that anomalies in stationary waves can occur even without changes in forcing.
    Download PDF (1252K)
  • Rong-hui Huang, K. Gambo
    1982 Volume 60 Issue 1 Pages 78-92
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The standing waves responding to forcing by the Hemispheric topography are investigated by means of a quasi-geostrophic, steady state, 34-level model, with Rayleigh friction, the effect of Newtonian cooling and the horizontal kinematic thermal diffusivity included in a spherical coordinate system.
    The results computed by this model show that the topography at high latitude, such as Greenland Plateau, plays an important role in the standing planetary waves responding to forcing by the Hemispheric topography, and the anomaly of standing waves is connected with a zonal mean wind at the surface at 70°-85°N in winter. The computed results show also that the standing waves responding to forcing by the Hemispheric topography can be propagated vertically and laterally toward the region of larger refractive index, i.e., toward the region of weaker westerly winds at low latitudes.
    The amplitudes are maxima at 38km height, 60°N for wave number 1, and at 27km height, 60°N for wave number 2. In addition, they have secondary peaks in the upper troposphere at 20°-30°N. This may be considered as one of reasons for the formation of standing waves in the upper troposphere at low latitudes.
    Download PDF (1843K)
  • Rong-hui Huang, K. Gambo
    1982 Volume 60 Issue 1 Pages 93-108
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The response of a Hemispheric model atmosphere to forcing by the Hemispheric topography and the stationary heat sources in winter was examined. In this computation the model described in Part I of this paper is used.
    The computed results show that the amplitude of standing wave responding to forcing by stationary heat sources at high latitudes, for zonal wave number 1, is larger than that forced by stationary heat sources at middle latitudes. The results also show that the amplitude of standing waves for zonal wave number 1 responding to forcing by the Hemispheric stationary heat sources is larger than that responding to forcing by the Hemispheric topography. In these computations, the role of refractive index square of standing waves for zonal wave number 1 or 2 is discussed in relation with the propagation of standing waves from the lower troposphere at middle and high latitudes toward the upper stratosphere at high latitudes or the upper troposphere at low latitudes.
    The momentum, heat and Eliassen-Palm fluxes due to standing waves computed by this model, are qualitatively in good agreement with the observed results.
    Download PDF (7499K)
  • David J. Karoly, Brian J. Hoskins
    1982 Volume 60 Issue 1 Pages 109-123
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The ideas of ray tracing from geometrical optics and wave propagation in a slowly varying medium are used to study the propagation of plaentary waves in the atmosphere. Kinematic wave theory is applied to wave solutions of the linearised quasi-geostrophic potential vorticity equation on the sphere. An index is defined for planetary wave propagation in the vertical-meridional plane and it is shown that wave activity is refracted towards larger values of this index.
    Ray solutions for stationary planetary waves are calculated for simple basic states and for basic states representative of Northern Hemisphere summer, autumn and winter conditions. The results agree with those from observational and numerical model studies of stationary planetary waves in the atmosphere. It is shown that the sphericity of the Earth and the curvature of the zonal flow are important factors determining the propagation of planetary waves.
    Download PDF (1833K)
  • Karin Labitzke
    1982 Volume 60 Issue 1 Pages 124-139
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The variability of the stratospheric winters is investigated.Monthly mean 30-mbar temperatures over the North Pole which are available for a 26-year period, have been grouped according to the phase of the equatorial QBO at the 50-mbar level, following a suggestion of Holton and Tan (1980).It is shown that the winters are"relatively undisturbed, cold" with an enhanced tendency for the development of a pronounced "normal wave 2 pattern" when the equatorial winds at the 50-mbar level are from the west.Major midwinter warmings seem not to take place in this category, except near the sunspot maxima. In contrast, during the "easterly" phase of the equatorial QBO there is a tendency for an enhanced development of height-wave 1 already in early winter, which leads often to the development of a major warming during midwinter and hence to a generally warmer polar region.
    Download PDF (1834K)
  • James R. Holton, Hsiu-Chi Tan
    1982 Volume 60 Issue 1 Pages 140-148
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Monthly mean Northern Hemisphere geopotential heights and temperatures on the 10, 30, 50, 100, and 300mb surfaces for a 16 year period (1962-1977) are composited with respect to the phase of the equatorial quasi-biennial oscillation (QBO) at 50mb for the winter months (November-March). The composited fields show zonally symmetric seesaw oscillations in both heights and temperatures with negative (positive) anomalies in polar regions and positive (negative) anomalies in midlatitudes during the westerly (easterly) phase of the equatorial QBO.
    Latitude-height cross sections of the zonal mean geostrophic wind for the 10-300mb layer indicate that during the westerly (easterly) phase of the equatiorial QBO at 500mb the polar night jet is stronger (weaker) than normal and the ttopospheric midlatitude jet is slightly weaker (stronger) than normal.
    Similar composites for zonal wavenumbers 1 and 2 and composites of the Eliassen-Palm flux show some indication of a QBO in stratospheric planetary waves, but the signal is surprisingly small considering the large amplitude QBO in the polar night jet.
    Download PDF (1063K)
  • John M. Wallace, Fong-Chiau Chang
    1982 Volume 60 Issue 1 Pages 149-155
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Interannual vartability of the Northern Hemisphere polar vortex at the 30mb during 21 winter seasons is examined making use of two indices which may be viewed as measures of the intensity of the vortex. The signature of stratospheric warmings is clearly evident in time series of the indices, but these events account for only part of the interannual variability. Alleged relationships between the intensity of the wintertime stratospheric polar vortex and the phase of the equatorial stratospheric quasi-biennial oscillation and the tropical tropospheric Southern Oscillation are examined, making use of the same indices. Both relationships show up quite distinctly in our analysis but neither one is consistent with the anomalies in the intensity of the polar vortex during all winters.
    Download PDF (818K)
  • Yoshikazu Hayashi
    1982 Volume 60 Issue 1 Pages 156-171
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Space-time spectral analysis methods and their applications to large-scale atmospheric waves are reviewed.
    Space-time spectral analysis resolves transient waves into eastward and westward moving components and is mathematically analogous to rotary spectral analysis which resolves twodimensional velocity vectors into clockwise and anticlockwise components. Space-time spectral analysis can also resolve transient waves consisting of multiple wavenumbers into standing and traveling wave packets. Space-time energy spectra are governed by space-time spectral energy equations which consist of linear and nonlinear energy transfer spectra.
    Space-time spectra can be estimated by either the lag correlation method, direct Fourier transform method or the maximum entropy method depending on the length of the time record. By use of the modified space-Fourier transform these spectra can be estimated correctly from polar-orbiting satellite data which are sampled globally at different hours of the day.
    Space-time spectral analysis has been extensively applied to data generated by GFDL general circulation models to determine the wave characteristics, structure and energetics of transient planetary waves, to verify the model with observations and to clarify their generation mechanisms by means of controlled experiments.
    Download PDF (2194K)
  • Taketo Maruyama
    1982 Volume 60 Issue 1 Pages 172-182
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Vectors showing cloud movements observed by the geostationary meteorological satellite "Himawari" (0°, 140°E) were studied with the use of a spectral analysis for the period from May 1978 to December 1980. A large-scale upper tropospheric zonal wind oscillation with a period of 30-50 days was detected. Its amplitude is 3 m•s-1 on the average over the equator. The oscillation appeared to originate in the equatorial region and to behave like a standing oscillation with an antinode region near 110-120°E and a node region at 150-160°E or further eastern. The oscillation was found to be in an active stage from April 1979 to June 1980, and inactive stage prior to March 1979 and after July 1980.
    Download PDF (1190K)
  • Takio Murakami, Yi-Hui Ding
    1982 Volume 60 Issue 1 Pages 183-196
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    During the early summer of 1979, massive changes occurred in the wind and temperature fields over extensive areas of the Eurasian continent north of 15°N. Among the areas, the most significant one is the Afghanistan-western Tibetan Plateau region which was characterized by an abrupt increase of 300mb temperature and intensification of 300mb anticyclone at around 4 June; i.e., about two weeks prior to the monsoon onset over India. At the sametime, the strong upper jet stream in the westerlies at 300mb exhibited a distinct northward shift from about 30°N to 35°-40°N and the easterlies at 700mb exhibited rapid establishment and intensification over extensive areas near 25°N. A similar northward shift of the 300mb jet stream also took place very far upstream (55°E) of the Tibetan Plateau on about 3 June. But, in contrast to Yin's early finding, this northward shift of the 300mb jet stream was not observed over the eastern Tibetan Plateau. Concurrently, rapid development of upper-tropospheric anticyclone and increase of temperature also occurred in association with the establishment of intense monsoon rains over the East China Sea-Japan region. The computations have shown that the increased temperature in these areas may be primarily caused by the adiabatic heating (-1.5°C per day).
    The above-described changes were also accompanied by rapid weakening and retrograding of a long-persistent blocking high over eastern Europe in May and rapid development of a prominent ridge system over central Siberia. In short, our study has not only shown that the Eurasian continent underwent drastic changes in the circulation and temperature fields during the transitional season from spring to summer of 1979, but also indicated that these large changes could exert some effects on the onset of the summer monsoon over south Asia and east Asia.
    Download PDF (8281K)
  • Takashi Sasamori, Jer-Heng Chen
    1982 Volume 60 Issue 1 Pages 197-205
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A statistical correlation analysis is made between the horizontal eddy heat flux across 60N at 850mb and the meridional gradient of the zonal mean temperature during the winter season. The high correlation between these variables, which was found by Madden (1975) in the stratosphere, is also maintained in the lower troposphere, where the forced stationary waves are coupled with transient waves to produce the quasi-periodic perturbation in the zonal mean temperature. The correlation is highest for the perutrbations with frequencies less than 0.1 cycle/day.
    The result of analysis suggests that the theory by Sasamori and Youngblut (1981) is a plausible mechanism which influences the winter circulation in middle and high latitudes with a dominant time period of about 20 days.
    Download PDF (1078K)
  • K. Gambo
    1982 Volume 60 Issue 1 Pages 206-214
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    It is shown that the spectral density of vorticity of transient ultra-long waves in the frequency domain is proportional to the minus second power of the frequency in middle latitudes in winter season. In order to explain the physical background of the above result, the vorticity equation of transient ultra-long waves is examined if there is the possibility to rewrite: in the same form with Langevin's equation in Brownian motion. By making use of data in two winter seasons of 1971-1972 and 1975-1976, it is shown that the vorticity equation of ultra-long waves in middle latitudes in winter may be treated in the same way with Langevin's equation in Brownian motion.
    Download PDF (7328K)
  • Taroh Matsuno
    1982 Volume 60 Issue 1 Pages 215-226
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Using a quasi one-dimensional model, in which the latitudinal distributions of variables are assumed and only the vertical dependence is explicitly treated, the general circulation of the middle atmosphere interacting with internal gravity waves is treated. An ensemble of internal gravity waves with an isotropic spectrum are introduced at the lower boundary and their propagation in the prevailing zonal wind field are determined incorporating the effect of eddy viscosity, in the same way as done by Plumb and McEwan (1978). As the result of selective transmission due to the background wind effect, deceleration of the stratomesospheric wind system and generation of a reverse flow take place near and above the mesopause level, owing to the wave momentum flux. Results of numerical calculations are compared with those obtained by using the conventional Rayleigh friction.
    Download PDF (1630K)
  • Takehiko Satomura
    1982 Volume 60 Issue 1 Pages 227-244
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Using a channel model in a shallow water, we numerically consider characteristics of finite-amplitude gravity waves which were found to be unstable waves in a constant shear flow by the linear analysis. Numerical integration is performed at Froude number equals to five for both inviscid and viscous case. In the inviscid run, it is shown that the first appeared mode has the growth rate and the structure which are the same as those expected from the linear analysis. Energy budget shows that disturbances extract their energy from the additional part of the mean kinetic energy as in the linear analysis.
    In the viscous run (Re=3000), it is shown that disturbance energy reaches a quasisteady state. Energy budget shows that energy is supplied to the mean kinetic energy, converted to the eddy kinetic energy, and then dissipated by the viscosity acting on the disturbances. Momentum budget indicates that these gravity waves can mix the averaged momentum permanently.
    At a later stage of time integration, the disturbance energy oscillates. A linear stability analysis for the quasi-steady state is examined, and it shows that the oscillation is produced by unstable sub-harmonics.
    Shape of disturbance depth near the boundaries and change of mean depth are also discussed.
    Download PDF (1886K)
  • Yoshihisa Matsuda
    1982 Volume 60 Issue 1 Pages 245-254
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A steady state model on the four-day circulation in the Venus atmosphere proposed by Matsuda (1980) with use of two-layer model is examined by time integrations of a fivelayer model.
    By assuming infinite horizontal viscosity, it is shown that the fast zonal flow is gradually formed in the upper layer over 1, 000 days by the accumulation of angular momentum. This angular momentum is supplied to the lower atmosphere from a slowly rotating planet and is transported upward by meridional circulation.
    Stationary solutions are obtained for various values of three external parameters (i.e., horizontal diffusion time, latitudinal differential heating and planetary speed of rotation). Multiple equilibrium states appear in the system when the horizontal diffusion time (normalized by the vertical one) 8 is reduced to 10-2. The super-rotation rate as large as the observed one is realized in some solutions when 8 is reduced to 10-3. The parameter dependence of (multiple) equilibrium states in the present model is analogous to that obtained by the two-layer model in Matsuda (1980). By comparison between the equilibrium states obtained in these two models, the prediction on the stability of multiple equilibrium states (Matsuda (1980)) is verified; the state with the fast zonal flow and the state with the strong meridional cell are stable and the state having the characteristics intermediate between these two states is unstable.
    Finally, by assuming two different ways of external heating (sudden heating and gradual heating), it is examined which of the two stable states is attained as a final state; the sudden heating leads to the state with strong meridional cell, while the gradual heating to the state with fast zonal flow.
    Download PDF (1291K)
  • Edward N. Lorenz
    1982 Volume 60 Issue 1 Pages 255-267
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Low-order models (LOM's), which are systems of ordinary differential equations which have been simplified by extreme reduction of the number of dependent variables, are often capable of representing atmospheric processes in a qualitatively correct manner. With a LOM it is generally possible to obtain a much more extended time-dependent solution, or a much larger ensemble of solutions, than would be economically feasible with a larger model.
    A general procedure for constructing LOM's is described. A selection of LOM's is presented, to illustrate the many forms which these models may take and the many uses to which they may be put. The step-by-step construction of a LOM is illustrated with a model of the large-scale circulation of a moist atmosphere.
    Download PDF (1972K)
  • H. Flohn
    1982 Volume 60 Issue 1 Pages 268-273
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Near the equator and along some coasts cool water ascends, together with the thermocline. This paper discusses on this phenomenon, which plays an important role in climatic change. The observed facts indicate as follows: a) A positive correlation between equatorial sea surface temperature and atmospheric content of CO2 and H2O, b) a negative correlation between the intensity of trades and equatorial (plus coastal) sea surface temperature, c) a negative correspondence between the intensity of the trades and the latitude of the subtropical anticyclone at the both hemispheres, d) a negative correlation between the tropospheric temperature difference, equator minus pole, and the latitude of the subtropical anticyclone, and e) a negative correlation between global temperature changes and the tropospheric temperature difference, equator minus pole, which is caused by the snow-ice-albedotemperature feedback. A hypothetical hemispheric climatic feedback mechanism is, in the case of cooling after a cluster of volcanic eruptions: meridional temperature gradient will become greater, latitude of the subtropical anticyclones become lower, intensity of Hadley cell winds (trade) increases, equatorial sea surface temperature becomes cold, atmospheric content of CO2 and H2O becomes lower, thus resulting in further cooling. In the case of warming during a prolonged lull of volcanic activity, the tendencies mentioned above are opposite. This feedback mechanism changes drastically frequency and intensity of equatorial and coastal upwelling. Since the oceans are closed basin and the turnover time of thee deep ocean may be in the order of 500 years, the efficiency of the process is limited in the time of several centuries.
    Download PDF (790K)
  • Jia-cheng Zhang
    1982 Volume 60 Issue 1 Pages 274-281
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The atmospheric processes are usually presented through the phase of spatial waves and/or of temporal periods as units. Owing to the limited size of the Earth, temporal periods has more generality in identification of atmospheric processes with different dimensions. There are several categories of atmospheric periodicities different not only in dimension, but also in nature and causes of formation. That is the storeyed structure of atmospheric processes. For singling out the basical aspects of climatic processes in a given dimension, scale correspondence is an important working principle. Among the processes in different storeys there also exist close relationships. Generally speaking, the macro-phase is the background of micro-processes. A certain mutation of individual micro-process in its turn may imply some information about the transition of macro-phases. So the structural analysis of atmospheric processes gives the idea of their predictability in any time scale. That is the conditional quasi-predictability which would be beneficial to make the methodology of climate prediction more rationalized.
    Download PDF (1075K)
  • Jih-Ping Chao, Yu-Fu Guo, Ru-Nan Xin
    1982 Volume 60 Issue 1 Pages 282-291
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    By parameterizing various types of heat sources (sinks) a linear model of coupled oceanatmospheric system has been established. By means of frequency analysis it is shown that in this model there are two different types of waves, one corresponding essentially to the travelling Rossby wave in non-adiabatic atmosphere which has a period of several days, and the other is a slowly varying wave which are driven by anomaly heating in ocean. Evidently the existence of this short time-scale weather process presents difficulties for the long-range numerical weather forecasting, because the evolution of the long-range weather process of smaller amplitude will be distorted by the short-range weather process of large amplitude. In order to overcome these difficulties the travelling Rossby wave are filtered as a "noise" from the model of the long-range weather forecast. A simple method of filtering is given. Then a practical model for predicting the monthly mean anomalous fields of 500mb geopotential height and earth's surface temperature is given and the experimental results are reported. This tentative study shows that the filtering method mentioned in this paper may be a promising way for making long-range weather forecast.
    Download PDF (1120K)
  • K. Miyakoda, Jin-Ping Chao
    1982 Volume 60 Issue 1 Pages 292-308
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The feasibility of monthly and seasonal forecasts is considered. The gross features of departures of meteorological variables from climatology (anomalies) are the targets of forecasts, and the anomalies can be divided into two modes, i.e., free modes and forced modes. The free modes are the anomalies that are predicted under the specification of climatological external forcings for the surface temperature, that are free from the anomalous forcings, whereas the forced modes are the anomalies that correspond to the anomalous components of external forcings. The GCM (general circulation model) is, in some cases, capable of predicting the free mode at least one month ahead (particularly the most extraordinary blocking event in January, 1977), and is, in other cases, marginal. However, the capability could be increased further by improving the GCM. In addition, recent studies have revealed that there are growing evidences for the feasibility of prediction of forced modes over the United States through the teleconnection process from the sea surface temperature anomalies over the equatorial Pacific.
    Yet the GCM approach is expensive and may be limited in improving mathematical accuracy, to a satisfactory extent. As a remedy, the possibility of anomaly models are being investigated.
    Download PDF (2512K)
  • B. G. Hunt
    1982 Volume 60 Issue 1 Pages 309-318
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A hemispheric general circulation model set up for annual mean conditions has been used to investigate the consequences of varying the obliquity from 23.5° to 0° and 65°. Such obliquity values have been claimed to have occurred in past eras. The 0° obliquity climate is more vigorous than the existing climate, but also drier and colder at the surface at high latitudes. However, overall a slight warming of the troposphere occurred in the model. Two experiments were performed for 65° obliquity, both had low albedoes at high latitudes, while one had glacial albedoes at low latitudes. For annual mean conditions there was virtually no tropospheric latitudinal temperature gradient in the first experiment, and consequently greatly reduced mean zonal winds and baroclinic activity. The second experiment had minimum surface temperatures in the tropics, but still sufficiently high to prevent glacial conditions prevailing, and consequently a tropical easterly jet maintained by a "reversed Hadley cell"Other aspects such as the simulated hydrology, energy exchanges, etc. provide considerable enlightenment concerning climatic conditions at such extreme obliquity. It is concluded that the Earth's habitable zone would be reduced for both 0°and 65°obliquity. These experiments illustrate the considerable unexploited potential of general circulation models in evaluating hypothetical climatic states which have veen proposed at various times.
    Download PDF (1479K)
  • André Robert
    1982 Volume 60 Issue 1 Pages 319-325
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A semi-Lagrangian algorithm is associated with the semi-implicit method in the integration of the shallow water equations on a rotating sphere. The resulting model is unconditionally stable and can be integrated with rather large time steps. Truncation errors remain reasonably small with time steps 25 times as large as those used with explicit integration schemes.
    An analysis of the proposed method is performed and it indicates that the scheme is stable. Also, the results of a few integrations are presented and from these we conclude that the model is not very sensitive to the size of the time step provided that it does not exceed a value of the order of two or three hours.
    Download PDF (822K)
  • Fedor Mesinger, Robert F. Strickler
    1982 Volume 60 Issue 1 Pages 326-338
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Four cases of cyclogenesis in the Gulf of Genoa (so-called Genoa cyclogeneses) have been simulated using a high resolution prediction model. Integrations are performed for a 48 hour period, using observed boundary conditions, and for each case with and without mountains in the model.
    It is found that in two of these cases cyclogenesis happens irrespective of the presence of mountains. However, mountains have a strong modifying influence, in ridging at the surface to the northwest and to the southwest of the Alpine obstacle, and at mid-troposphere in ridging in central Europe north of the Alps.
    Of the two cases in which cyclogenesis does not happen without mountains, in one case a very realistic simulation of the surface development is obtained. In mid-troposphere, although simulated geopotential heights are even less than observed, the intensity of the cutoff process north of the Genoa region is not sufficiently realistic. It is suggested that, therefore, the problem is either in an insufficient intensity of blocking north of the obstacle, or in a process of a more large scale nature.
    Download PDF (1871K)
  • S. Matsumoto, K. Ninomiya, R. Hasegawa, Y. Miki
    1982 Volume 60 Issue 1 Pages 339-354
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Detailed analyses are made on a subsynoptic-scale cold vortex which caused the intense convective precipitation while it passed over Japan on 9-10 May 1980. This cold vortex was embedded in a large-scale trough and associated with a dome shaped cold air. The stable layer which bounded the cold dome was not distinct over the eastern part of the dome. The cold dome boundary was well defined, rather, by the horizontal temperature gradient. It is found from GMS imageries that the subsynoptic-scale cloud system relevant to the cold dome was located 1000km behind the cloud system associated with a synoptic cyclone and frontal system. This subsynoptic-scale cloud system was formed in the eastern quadrant of the dome-shaped cold air, while the precipitation was concentrated in the southern quadrant. The maximum precipitation intensity took place in coincidence with a rapid increase of aerial coverage of lower TBB values. Cumulus convections penetrated through the cold dome boundary and reached to the level of tropopause funnel.
    A forecast experiment is performed by using a fine-mesh primitive equation model, and some of characteristic features of the subsynoptic-scale cold vortex are well simulatedd if the reanalyzed fine structure is incorporated in the initial field.
    Download PDF (4095K)
  • T. Theodore Fujita
    1982 Volume 60 Issue 1 Pages 355-368
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    An approximate but accurate method of stereo-height computations from overlapping images of geosynchronous satellites is presented. The method was applied to determine the height of ITCZ clouds from GMS-1 and GOES West images. The cloud-top topography of severe thunderstorms over the United States was obtained from GOES East and West images along with IR temperature measurements by both satellites. It was found that the IR temperature is 5 to l0° warmer than the expected temperature of overshooting tops.
    It is suspected that the warm IR temperature is caused by the stratospheric cirrus located 1 to 3km above the anvil top, which was found repeatedly during the Lear Jet Experiment in 1971-1978. The cirrus is generated in the wake of overshooting tops as they sink violently into the anvil cloud. The radiometric characteristics of the cirrus uncouple the heighttemperature relationship at the overshooting height, resulting in an uncertainty that the cloud-top warming may mean either sinking cloud top and/or increasing cirrus.
    Download PDF (3425K)
  • Katsuyuki V. Ooyama
    1982 Volume 60 Issue 1 Pages 369-380
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Dynamically, the tropical cyclone is a mesoscale power plant with a synoptic-scale supportive system. By the early 1960's, the general structure and energetics of the system and basic components of the supportive mechanism were fairly well documented by the instrumented aircraft observation of hurricanes and through the diagnostic interpretation of the data. The prognostic theory which would have unified these basic findings in a dynamically coherent framework had a more difficult time emerging. When a viable theory finally emerged, a change in the theoretical perception of the problem was necessary. The parameterization of cumulus convection was an important technical factor in the reduction of a multiscale interaction problem to a mathematically tractable form. Nevertheless, it was the change in our perception of the basic problem and the re-arrangement of priorities that made the parameterization a tolerable substitute for real clouds. Even then, the validity and limitation of the new theory, known as CISK, were fully appreciated only through careful experiments with nonlinear numerical models. In the meantime, the mathematical simplicity of certain parameterization schemes enticed many to apply the schemes to other tropical disturbances, including the easterly wave, in the traditional idiom of linear stability analysis. More con fusion than enlightenment often ensued as mathematics overran ill-defined physics. With further advances in numerical modeling, the interest in tropical cyclone research shifted from conceptual understanding of an idealized system to quantitative simulation of the detail of real cyclones, and it became clear that the intuitive parameterization of whole clouds would have to be discarded. Now that some models have returned to explicit calculation of the cloud scale, one may wonder if all the exercises with parameterized convection were an unfortunate detour in the history of tropical cyclone modeling. The answer depends on one's philosophical view of "progress."
    Download PDF (1771K)
  • Yoshio Kurihara, Morris A. Bender
    1982 Volume 60 Issue 1 Pages 381-395
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A tropical cyclone has been simulated in a quadruply nested mesh model with finest grid resolution of about 5km. At the center of the vortex, a compact eye was maintained.
    Azimuthal means as well as asymmetry of the eye and the eye wall structure are described. The asymmetric features within the eye wall moved cyclonically at a much smaller rotation rate than the cyclonic wind within the eye wall. Roles of the mean radial-vertical circulation, the eddy motions and the diffusion effect in the maintenance of the mean structure are analyzed. In the analysis, attention is given to the balance between the wind and pressure fields and also to the budgets of relative angular momentum, heat and water vapor. The eddy motions caused a cooling and moistening effect in the eye which counterbalanced a warming and drying effect due to the mean sinking motion.
    Download PDF (2057K)
  • Robert A, Houze, Jr.
    1982 Volume 60 Issue 1 Pages 396-410
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The sensible heat budget of a large-scale area containing an idealized tropical cloud cluster is analyzed. The cluster is assumed to have spatial dimensions and precipitation rates typical of observed cloud clusters.
    In its early stages of development the idealized cluster consists of isolated deep precipitating convective cells, or "hot towers." A simple model using the assumed precipitation rates as input is employed to compute the condensation and evaporation rates and sensible heat fluxes associated with the precipitating hot towers. The condensation dominates the contribution of the hot towers to the large-scale heat budget, and the net effect of the towers is warming distributed through the full depth of the troposphere.
    In its mature stage of development, the idealized cluster contains not only convective towers but a widespread cloud shield interconnecting the towers. The cloud shield is dynamically and thermodynamically active, and processes associated with it also contribute significantly to the large-scale sensible budget. Stratiform precipitation falls from the cloud shield, and in the stratiform precipitatioi region, condensation occurs in mesoscale updraft aloft, evaporation occurs in a mesoscale downdraft at low levels and melting occurs in a middle-level layer. The condensation, evaporation and sensible heat transports associated with the mesoscale updraft and downdraft are determined from simple models using the cluster's assumed stratiform precipitation rate as input. The evaporation and melting in the stratiform precipitation region are also estimated from vertical profiles of radar reflectivity in real cloud clusters. The total effects of the stratiform precipitation processes on the largescale heat budget are warming of the middle to upper troposphere, where condensation in the mesoscale updraft is the dominant effect, and cooling in the lower troposphere, where melting and mesoscale downdraft evaporation dominate.
    The widespread cloud shield present in the mature and later stages of a cloud cluster's life cycle is also an important absorber and emitter of radiation. Radiative transfer models applied to tropical cloud shields show substantial heating effects in the middle to upper troposphere. These effects are nearly as important as the heating by convective towers and the heating and cooling associated with the stratiform precipitation processes.
    As the idealized cloud cluster progresses from early to mature stages of development, its net effect on the large-scale heat budget changes. As the cloud shield develops, the mesoscale updraft condensation and radiation reinforce the heating by convective towers aloft, while the mesoscale downdraft evaporation and melting counteract the convective-tower heating at low levels. Thus, the net heating by the cluster increases in the upper troposphere and decreases in the lower troposphere as the system develops. Large-scale upward motion, which is required to balance the large-scale heat budget against the effects of the cluster, is thus expected to increase aloft and decrease at low levels. Vertical motions deduced from large-scale wind observations in the tropics confirm this expectation. Thus, it is concluded that the mesoscale stratiform and radiative processes associated with the cloud shields of developing cloud clusters are sufficiently strong to alter the large-scale vertical motion field in the tropics.
    Download PDF (2448K)
  • Michio Yanai, Chung-Hsiung Sui, Jan-Hwa Chu
    1982 Volume 60 Issue 1 Pages 411-424
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The effects of cumulus convection on the large-scale vorticity budget are studied. The feasibility of parameterizing the cumulus effects is examined by relating the eddy correlation terms in the large-scale vorticity equation to the properties of cumulus ensembles. By introducing a spectral representation of a cumulus ensemble, a general expression for the cumulus effects is obtained. The expression reduces to a simple form when the fractional area coverage of cumulus clouds is very small and the mean cloud vorticity has the same order of magnitude as the mean vorticity of the environment. This approximate expression interprets the cumulus effects in terms of the detrainment of excess vorticity from the cumulus clouds, and of the vertical advection, the twisting and the stretching of the large-scale vorticity by cumulusinduced subsidence.
    The approximate expression is combined with a spectral model of a cumulus ensemble, using the budget equations for mass, moist static energy, water substance and vorticity of sub-ensembles. The model is then used to estimate the cumulus effects over the Marshall Islands area and the calculated, vertical profile is compared with the observed profile of the residual of the large-scale vorticity budget (the apparent vorticity source). Cases with and without downdrafts are tested. The calculations without downdrafts produce excessively large vorticity source immediately above the cloud base and above the 300mb level. The inclusion of downdrafts and of lateral detrainment in the sub-ensemble budget equations significantly improves the results, especially below 700mb.
    Download PDF (1665K)
  • Tomio Asai, Isao Nakasuji
    1982 Volume 60 Issue 1 Pages 425-431
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Numerical experiments are made to determine a preferred mode of cumulus convection in a conditionally unstable atmosphere. The model developed in the previous study (Asai and Nakasuji, 1977) is extended to deal with water vapor explicitly. The preferred mode of cumulus convection is regarded as the steady convection cell attained eventually after a random potential temperature disturbance is imposed initially. It is shown that the preferred scale of the convection cell and the preferred cloud coverage depend on mean vertical velocity, static stability and relative humidity. It is confirmed that the preferred cumulus convection minimizes the potential energy and consequently the mean temperature lapse-rate in the convective layer.
    Download PDF (714K)
  • H. A. Panofsky, Zhou Leyi
    1982 Volume 60 Issue 1 Pages 432-438
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Airflow characteristics in neutral conditions over two kinds of complex terrain are compared: on hill tops, and over land, downstream of water. In spite of the large differences in the dynamical characteristics, several similarities emerge: logarithmic wind profiles with large shear near the surface, in spite of vertically decreasing stress; weaker wind shears above, and agreement between surface stresses inferred from wind profiles with Reynolds stresses extrapolated downward. Also, in both cases, dissipation is locally balanced by mechanical energy production.
    Download PDF (821K)
  • Tetsuji Yamada
    1982 Volume 60 Issue 1 Pages 439-454
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A simplified second-moment turbulence closure model, which has been reasonably well tested in various geophysical problems, is used to simulate effects of a tall tree canopy on air circulations in the atmospheric boundary layer. Qualitative simulation of a canopy flow, with nearly constant and low wind speeds in a canopy, but large wind shears near a treetop, and unstable (stable) temperature layers within a canopy during the night (day) are all satisfactory. Strong couplings between the mean and turbulence variables are obvious when simulations performed with and without a canopy in the model are compared with one another.
    Download PDF (1984K)
  • O. Yokoyama, M. Gamo, S. Yamamoto, M. Hayashi
    1982 Volume 60 Issue 1 Pages 455-460
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Spectra of the turbulence fluctuations of the vertical wind component and temperature vary with height in the atmospheric boundary layer. This vertical change of the spectra can be expressed in terms of the vertical change of the dissipation rate of kinetic energy ε and variance of the temperature fluctuation and mean wind speed. Here, relations expressing the vertical change of the spectra are derived using the similarity hypothesis proposed by
    Yokoyama et al. (1979). The vertical profile relation for the spectra is compared with observed spectra normalized by q0 and u*0 which have been estimated by using their vertical profile relations, and relatively good agreement between the derived relations and observations has been obtained. As an application of the temperature spectrum relation, the refractive index structure parameter, CT2, which is proportional to echo intensity of the SODAR sound, is derived. The shape of the theoretical profile of CT2 fit the observations, well.
    Download PDF (709K)
  • J. Kondo, T. Sate
    1982 Volume 60 Issue 1 Pages 461-471
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    From simultaneous measurements of the friction velocity u*(=√-uw) and the mean wind profile in the atmospheric surface layer, the von Karman constant was determined to be 0.39. The constant is not a fixed value but has a range with a standard deviation of about 7%. This property may be inherent in the nature of the atmospheric turbulence. Before the field observations, the aerodynamic characteristics of the sonic and cup anemometers were examined. In determining the present von Karman constant, errors due to these characteristics were corrected.
    Download PDF (1234K)
  • D. H. Lenschow
    1982 Volume 60 Issue 1 Pages 472-480
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Mean and turbulence variables of reactive trace species in the atmospheric boundary layer can be modified by chemical reactions. These effects are illustrated with results obtained from an aircraft instrumented with a fast-response ozone sensor. The ozone variance budget was estimated for one case in which production of variance by chemical reactions seems probable. Another example shows thin laminae of ozone concentration considerably different from adjacent layers in the turbulent inversion layer at the top of the boundary layer. Again, chemical reactions seem the most plausible explanation. Vertical profiles of reactive species may also be modified in the surface layer if their reaction time is of the order of a hundred seconds. These effects of chemical reactions may be useful in studying sources and sinks of trace species in the boundary layer.
    Download PDF (1186K)
  • G. I. Marchuk
    1982 Volume 60 Issue 1 Pages 481-485
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The paper deals with the Industrial Effluent Optimization problem which becomes of ever increasing concern to scientists and engineers. To solve the optimization task the writer uses principal and conjugate equations of air transportation and diffusion of substances. The author presents the disturbance theory, which gives the possibility of estimating sensitivity of functional to deviations of model entrance parameters.
    Download PDF (532K)
  • John Mason
    1982 Volume 60 Issue 1 Pages 486-499
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    This paper reviews recent researches in the Meteorological Office designed to elucidate how the physical processes involved in the development of radiation fog interact to deter mine its formation, growth and dissipation. The results of field measurements and computer models are combined to illustrate the delicate balance that exists between radiative cooling of the air and droplets, conduction of heat from the soil, turbulent transport of heat and moisture within the fog and the deposition of droplets and dew on the ground. The clearance of fog by solar radiation and by the advection of a low-level cloud sheet is also investigated.
    Download PDF (2698K)
  • August H. Auer, Jr, John M. White
    1982 Volume 60 Issue 1 Pages 500-507
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A winter cyclone of average size, but strong intensity, was analyzed in detail to ascertain its kinematic features of a level of nondivergence at 550mb (-16°C) with upward vertical velocities of 6.5 cm sec -1. Calculations of a water balance were also made indicating a precipitation efficiency of approximately 80%. It was found that regions of maximum rate of condensate that occur near the level of nondivergence at temperature regimes near -15°C must be suspect for producing heavy snowfall episodes. This finding was collaborated by a mini-climatological study of 75 heavy snowfall episodes which depicted saturated ascent through the level of nondivergence at θe=304-309°K (i.e., 600-mb temperature of -13-15°C).
    Download PDF (1038K)
  • Tsutomu Takahashi
    1982 Volume 60 Issue 1 Pages 508-519
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    Electrification and precipitation mechanisms were studied in maritime shallow warm clouds around the island of Hawaii.
    Ion-drop interaction during drop evaporation is assumed to be the principal charge separation mechanism in warm clouds. During showers a negative potential gradient is observed at the ground, probably caused by negative ions transported from the cloud top to the ground by downdrafts.
    Giant nuclei do not contribute significantly to the initiation of warm rain. Most drop growth occurs near the cloud top where the updraft speed decreases with height. Raindrop formation near the cloud top is required to initiate rain beneath the cloud base. The rate at which raindrops form depends mainly on the humidity profile in the trade wind layer. The rainwater accumulation rate varies with the cloud type.
    Unsolved problems related to both cloud electrification and precipitation mechanisms are discussed to encourage future research in the tropics.
    Download PDF (2805K)
  • T. Kuroda
    1982 Volume 60 Issue 1 Pages 520-534
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    First we briefly review the experimental studies on growth forms and mechanisms of ice crystals from the vapour, i.e. snow crystals. Then we discuss why the basic habit of ice alternate three times with decreasing temperature: from plates (A) to columns (B) at -4°C, to plates (C) at -10°C, and to columns (D) at -20°C∼-35°C. The surface of ice just below 0°C is covered with a quasi liquid layer, whose thickness or coverage 9 decreases with falling temperature, and therefore the growth mechanism of a crystal face changes also as follows: I) Vapour-Quasi Liquid-Solid-Mechanism (∂<1), II) Adhesive Growth on a surface strongly adsorbed by H2O molecules themselves (0.02<∂<l), and III) Two Dimensional Nucleation Growth on a surface with low eigen adsorption (∂<0.02). The type of surface structure and consequently the growth mechanism depend on the surface orientation and temperature. Therefore the complicated habit change is caused mainly by the combination of surface growth mechanisms of the {0001}- and {1010}-face. Furthermore diffusion field surrounding a crystal contributes to the third habit conversion from plates (C) to columns (D) in dependence on supersaturation, and to the formation of the marked habits with extreme axis ratio (c/a»1, «1). Finally we discuss why the transition from polyhedral to skeletal to dendritic morphology occurs with increasing supersaturation. This morphological instability of polyhedral crystal is due to the inhomogeneity in supersaturation over its surface. In order to pursue the problem, we must self-consistently solve three dimensional diffusion field surrounding a polyhedral crystal and growth kinetics at the surface with supersaturation inhomogeneity.
    Download PDF (1996K)
  • Yoshinori Furukawa
    1982 Volume 60 Issue 1 Pages 535-547
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    On the basis of the three dimensional Coincidence-Site Lattice (CSL) concept and the formation of an ice germ with a cubic structure in nucleation process, structures and formation mechanisms of a variety of snow polycrystals in nature are systematically explained.
    When each component of poly initial-crystal, which is originated from a cubic ice germ and the subsequent growth in hexagonal structure on its { 111 } faces grows independently, snow polycrystals are formed as a "regular" assemblage of single crystals. While, under the conditions of low temperature and low supersaturation, growth of the initial-crystal may be controlled by a new growth mechanism in which a CSL boundary acts as a successive source of growth steps, so that the formation of snow polycrystals with a specific boundary as a crossed-plate crystal becomes more preferential.
    Download PDF (1999K)
  • Katsuhiro Kikuchi, Tatsuo Endoh
    1982 Volume 60 Issue 1 Pages 548-561
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    During the volcanic activities of the Mt. Usu volcano, Hokkaido Island, Japan, in August 1977, atmospheric electrical observations, especially atmospheric electric field strength (potential gradient), charges on volcanic ash particles together with spatial concentration and size of ash particles were carried out at the school grounds of Sobetsu Junior High School, Sobetsu Town. The township is located approximately 5km east-northeastward from the crater of Mt. Usu, and the observations were made from August 9 to August 15, 1977.
    Although the atmospheric electric field strength showed undisturbed values from a calm night to the early morning, immediately after a sea breeze commenced blowing in the morning the atmospheric electric field showed an abrupt negative shift and distinct changes were seen as shown in Figs. 3∼5 and 11, an the other hand, when the volcanic ash particles fell the atmospheric electric field changed violently to positive alternating to negative again and vice versa incessantly. The values of the electric field exceeded ±15, 000 V⋅m-1 when coagulated large ash particles fell. The inverse relationship between the polarities of the electric field and the net falling ash particle current held.
    In laboratory experiments with volcanic ash particles, relatively smaller ash particles were charged more negatively than larger ash particles. This came from friction. It is considered that our experimental results adequately explains the negative atmospheric electric field recorded in dust storms of volcanic ash swept away from the ground surface.
    Download PDF (7545K)
  • Y. Iwasaka, K. Nagaya, K. Okada, A. Ono
    1982 Volume 60 Issue 1 Pages 562-569
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    The size distribution function of aerosols in the lower atmosphere (_??_0km-2km)measured by the two-wavelength lidar technique is compared with the results determinedby an airborne optical particle counter. The comparison shows following facts, 1) The vertical changes of size distribution functions determined by the lidar techniqueshow good agreements with the results of the airborne particle counter in a qualitativesense.
    2) The parameter of γ in the size distribution function for aerosol radius R, n(R)=AR-γ can be fully accurately determined by the lidar measurements, but the estimation of the other parameter A contains some uncertainty.
    The remote sensing technique for the size distribution, function should contribute to the study of aerosol growth process, aerosol transformation process, aerosol transport process due to air motion in lower atmosphere, and so on.
    Download PDF (1041K)
  • Kuo-Nan Liou, Kristi L. Gebihart
    1982 Volume 60 Issue 1 Pages 570-582
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    A number of numerical experiments have been carried out to investigate the climatic effects of the cirrus cloud thickness and location in various atmospheric conditions on the thermal equilibrium temperature of the earth's atmosphere. While the convective adjustment program utilized follows the procedures outlined previously by Manabe and his associates, several new endeavors for treating the transfer of solar and infrared radiation through semitransparent and nonblack clouds are incorporated into the radiative-convective progarm. The numerical program is developed in such a manner that the solar and infrared radiative properties of cirrus can be carefully treated in conjunction with the temperature profile determination. We show that the presence of a 0.1km thin cirrus with an infrared emissivity of 0.45 and a solar reflectivity of 0.08 heats the atmosphere by as much as 20°K regardless of the cloud location. However, the influence of thick clouds depends strongly on their atmospheric location. The presence of low thick ice clouds will cool the atmosphere significantly, a conclusion shared by several investigators. A composite thermal equilibrium temperature profile is constructed using the climatological water vapor and ozone profiles and cloud parameters for the tropical atmosphere. Comparison with the climatological temperature profile in the tropics reveal a close agreement (within 1°K) in the troposphere and about l0°K difference in the stratosphere. Using the tropical data, we show that increasing the cirrus cloud cover by 10% at the expense of the clear column will warm the surface temperature by about 0.2°K.
    Download PDF (1693K)
  • S. Twomey, T. Cocks
    1982 Volume 60 Issue 1 Pages 583-592
    Published: 1982
    Released: October 19, 2007
    JOURNALS FREE ACCESS
    In the near-infrared region, liquid water (and ice) absorb weakly, causing a dependence of spectral cloud reflectance on the mean radius of the droplets. Provided optical thickness is known or can be inferred, measurements of reflectance would seem to be capable of yielding some microphysical information, providing a remote sensing technique for cloud microphysics. The present paper compares measured and computed spectra for clouds for which both spectral reflectance and in situ drop-size and and liquid-water measurements were made. Some as yet unresolved disparities were encountered between the various measurements, and these need to be resolved before remote sensing is attempted.
    Download PDF (1401K)
feedback
Top