Radial heat transports through a rotating fluid annulus, from outer warm wall to inner cold wall, are measured for both the Hadley and the Rossby regimes. Special attention is paid to the dependence on the viscosity of experimental fluid. As the viscosity increases, the behavior of heat transport in the Hadley regime becomes considerably different from what has been known by several experiments with water. For example, when the viscosity becomes 80 or 100 times larger than that of water, the heat transport (expressed by Nusselt number) near zero angular velocity increases as the angular velocity increases, and it is almost constant for moderate and large angular velocity. Further, we shall present also how the viscosity affects the transition between the (upper)Hadley and the Rossby regimes.
The properties of wave disturbances in the Trades are examined theoretically using a primitive equation model. The model is two-dimensional, nonlinear, and time-dependent. It incorporates the effects of condensation heating due to cumulus convection and nonconvective rain. Numerical integrations of the model show the development of two wave types. One wave type is a slowmoving synoptic disturbance while the other type is a fast-moving wave whose nature is not entirely understood. The structure, phase speed, and preferred wavelength of the waves are discussed. The integrations also show that condensation heating due to cumulus convection alone produces only extremely weak disturbances; condensation heating from nonconvective rain is necessary for the generation of large-amplitude disturbances.
In the previous paper [Iwashima (1973)], it has been shown that, by means of the time-filter method, the ultra-long wave in the atmosphere is generally separated into the two parts, i.e. travelling and quasi-stationary parts, and that the latter part of the ultra-long wave is usually associated with an amplitude-change. In the present paper the energy equations for both parts of the wave are derived, and applied to an energetical study on the 1967/68 stratospheric sudden warming. From an analysis before separating the wave into the travelling and quasi-stationary parts, it is shown that the energy processes are similar to the results obtained by Reed et al. (1963), Julian and Labitzke (1963), etc.. Separating the each ultra-long wave into the quasi-stationary part and the travelling one, we can obtain the respective energy processes. Some of the results are summarized as follows : i) At the the warming stage, the kinetic energies of the quasi-stationary and travelling ultralong waves of wavenumber two [KS(2) and KT(2)] increase, and especially the increment of the former part is remarkable. ii) The increase (or decrease) of KS(2) is mainly due to that of the energy transfer from the troposphere through the so-called pressure-interaction term of the quasi-stationary part of wavenumber two BGS(2). iii) Increasing of KS(2) during the warming stage is also controlled by the energy transfer from the travelling waves of the various wavenumbers. iv) The available potential energies of both parts of wavenumber one increase during the warming stage. These are mainly converted from the zonal available potential energy.
The forcing of the second-order zonally-averaged wind and temperature fields due to the quasiresonant growth of planetary waves in a two-layer model is considered. Dissipation in the form of linear drag and Newtonian cooling is allowed for. Calculations are made in a mid-latitude β-plane channel bounded by two vertical walls. The linear or first order solution is constrained so as to not transport momentum meridionally. Three neutral modes in the adiabatic two layer model are brought to resonance separately by adjusting the basic zonal flow configuration. For a dissipation time scale of 2 days, the quasi-resonant enhancement of the response is negligible. A time scale of 4 days is used. For resonance involving the two layer equivalent of the Rossby wave, the strong westerly zonal flow configuration causes most of the second order effects to be confined to the lowest few scale heights, where a slow easterly acceleration of the zonal flow occurs. A second resonance associated with weak westerlies surmounted by moderate westerlies leads to a very rapid high level easterly acceleration lasting about two weeks. A final resonant wind configuration with easterlies above westerlies is associated with very rapid temperature rises near the pole. Calculations suggest that the quasi-resonant enhancement of the planetary wave-zone flow interaction resulting from certain basic flow configurations might be the explanation of the stratospheric warming. It is hypothesized that the timing of warmings is determined by how well tuned the zonal flow structure is in the sense that appreciable secondorder effects will result in response to small influxes of planetary-wave energy from below. Furthermore, it is suggested that the subsequent evolution of a warming into a full scale warming depends on the ability of the zonal flow configuration to evolve through a series of tuned or resonant states.
As a step to study the ensemble effect of cumuli on larger scale disturbances, the development of an averaged cumulus convection is numerically simulated by using the model based on the 2-column model devised by Asai and Kasahara (1967). Two cases are taken up. In the first case, the radius of the inner cloud column is fixed during the calculation regardless to the development of the cloud. The effect of the drag force of the condensed water droplets on the motion is specifically estimated. It is shown that the effect of the drag force suppresses considerably the maximum height of cloud top, the maximum value of vertical velocity and the maximum anormalies of other meteorological field variables such as potential temperature, water vapor and liquid water. However, the life time of the convection remains unaltered. If we assume that all the condensed liquid water is instantaneously taken out of the atmosphere by precipitation, the life time is a little shortened and the vertical eat transport is more or less decreased. In the second case, the inner cloud column is allowed to change its radius according to development of the cloud. Although the same effect of the drag force as in the first case is also incorporated in this case, the changeability of radius of inner cloud column results in the increase of thermal activity of the convection, even overcoming the suppressing effect due to the drag force. The life time in this case is a little larger than in the first case. In each case, the total heat transport per unit area during forty minutes is calculated as ameasure of the thermal activity of convection. For several horizontal scales calculated, themaximum values of the heat transport are attained at almost similar values of the ratio of the radius of inner cloud column to that of the whole column in both cases.
his paper presents mean maps of upper tropospheric temperature and constant-pressure height fields constructed from SIRS (Satellite Infrared Spectrometer) data for the period June-July 1969.These tropical Atlantic data were gathered for both clear and cloudy atmospheres. Temperature analyses at seven pressure levels above 500mb revealed generally cooler temperatures over the continental areas and warmer temperatures over the ocean. Constant-pressure height profiles indicated lower values over the continents in contrast to higher values over the ocean. With increasing cloud amount, the area of high height values shrank while areas of low height values expanded and became more dominant, suggesting a profound influence of cloud cover on the constant-pressure height profiles. The scatter diagrams of height versus percent cloud cover in the instrument field of view also suggest that increases in percent cloud cover and greater cloud thickness are related to decreases in height of all constant-pressure surfaces above and below cloud top levels.
The bulk thermodynamical property of the cumulus convections within the small area (about 4×(100km)2) over the Kuroshio region is studied analytically by means of the atmospheric heat energy budget in February 1968. The situations of cumulus convections in the area are classified from the PPI radar observa tions into three categories, i.e., the situation of “echo cluster”, “weak echo” and “no echo”. The statistics of the mean vertical velocity (ω), individual changes of temperature and mixing ratio of water-vapor (δ1T/δt and δq/δt) and the horizontal convergence of water vapor (∇Vq) indicate the characteristic bulk thermodynamic property for each category of the echo situation. The bulk property of “echo cluster” is characterized by the strong upward motion, large positive value of δT/δt and large negative value of δq/δt in the middle troposphere and large negative value of ∇Vq in the lower atmosphere. The bulk property for the situations of “weak echo” and “no echo” are characterized by the weak downward motion, small positive value of δT/δt, δq/δt and ∇Vq. The structure of the disturbances of synoptic and medium-scale associated with the echo cluster are also studied by analysing the time series data of aerological observations.
The generation of available potential energy by sensible heating is studied for the cyclogenetic regions along the east coasts of Asia and North America for a data period of four Decembers and four Januarys. Radiosonde data are used to prepare daily cross sections oriented perpendicular to the Asian and North American coasts. From the cross sections daily values of the efficiency factors are calculated. The bulk aerodynamic method is used to estimate the daily sensible heat flux over the ocean near Shionomisaki, Japan and Cape Hatteras, U.S.A. Using the efficiency factors and sensible heat flux, total mean generation estimates of 3.85 watts/m2 near Shionomisaki and 1.66 watts/m2 near Cape Hatteras are obtained. The larger value for Asia is due to the larger efficiency factor values found along the east coast of Asia. Estimates of the frictional dissipation of kinetic energy in the two areas are also made. Near Cape Hatteras the mean generation by sensible heating exceeds the frictional dissipation, while near Shionomisaki the frictional dissipation somewhat exceeds the generation.
It has been attempted to observe the subsynoptic scale turbulent kinetic energy with high resolution upper-air wind profiles. After filtering out the characteristic large-scale profile, the remaining disturbance part of the observed profile is deemed subsynoptic scale in nature. It is then subject to a direct harmonic analysis for the portion of the atmosphere above 5, 000m in height to examine the distribution of variances over harmonic numbers. It is suggested that the major portion of the subsynoptic scale turbulent energy seems to be contained in the variances from the harmonic analysis of the isolated component of the wind profiles. Examination of obtained variance spectra indicates that they can be grouped in a number of characteristic types according to the concentration of kinetic energy in certain harmonic number ranges. It is suggested that this is related to the flow of kinetic energy from large to small scales or vice versa through subsynoptic scale ranges. Those subsynoptic scale components of kinetic energy in the upper and mid troposphere are also examined in relation to the Richardson number.
Using drop-freezing technique, suspensions of different cements as well as of certain calcium compounds have been tested. The suspensions have also been tested after they have aged for given time periods. The study, besides pointing out that the threshold temperature of cement is around -5° to -6°C, has suggested that hydration could be the contributory cause for their ice nucleating behaviour. A special category of ice nucleants, having a transitory ice nucleating property, has been identified for the first time.
Experiments show that for small specimens of pure ice corona discharges can be sustained at temperatures greater than a critical value, Tc, as a result of the flow of current through the ice surface. However, at a well defined temperature (Tc=-18±1°C) corona is extinguished because the surface conductivity σs is insufficient to support the corona current. A model of current flow through the ice surface is then used to calculate as at the temperature Tc; a maximum value of about 2×10-9ohm-1 was obtained. Ice specimens whose surface were deliberately doped to give a higher value of σs were found to possess lower threshold temperatures Tc.