Properties of both a turbulent jet injected downward in a rotating fluid and the induced secondary circulation are investigated by means of laboratory experiments and a linear theory. The main results obtained by the laboratory experiments are summarized as follows: 1) The advancing velocity of the lower end of the jet is smaller than that in a static fluid. 2) A remarkable upward motion appears when the injection of the source fluid is stopped. 3) The secondary circulation induced by the jet does not penetrate far below the lower end. The structure of the induced secondary circulation can be qualitatively explained by the linear theory in which a two-dimensional laminar jet is assumed. The suppression of the vertical velocities is caused by the upward pressure gradient force which is generated by the entrainment of the rotating ambient fluid and is horizontally balanced with the centrifugal force acting on the swirling fluid particles as was considered by Barcilon (1967b) and Wilkins et al. (1971a). The existence of this pressure gradient force is consistent with 1) and 2). 3) indicates that the depression in the pressure near the nozzle cancels the high pressure near the lower end of the jet due to the divergence field so as to make the pressure perturbation far below the jet vanish.
The generation of the mean zonal wind in the lower thermosphere is discussed, based upon momentum transport by dissipating tidal waves, especially, the first mode of the solar diurnal tide (S11) and the second symmetric mode of the solar semidiurnal tide (S42). The amplitudes of tidal waves at the lower boundary are set to reasonable values which are obtained by the observations and the theoretical studies. The problem is solved numerically as the initial value problem as done by Miyahara (1978). It is shown that these dissipating tidal waves, especially, S11 mode can induce strong easterly (-66m/sec) in the lower thermosphere over the equator.
Orographical effects of a slope behind a flat plain on the land and sea breeze circulation are investigated using a numerical model with a simplified configuration of the lower boundary. It is found that (1) when the temperature at the slope surface varies with a diurnal period similarly to that at the plain surface, both the sea breeze and the land breeze are amplified and the alternation of the sea and the land breezes occurs earlier than the land and the sea breezes over a flat plain, and (2) when the slope works merely as a barrier, both the land and the sea breezes are reduced and the circulation domain is confined in the sea and the plain regions. The solution of linear differential equations for the unsteady slope wind is examined to make more clear the physical process in the above mentioned situation. The land and sea breeze in the former case is found to be modified by the slope wind which is stronger than and is in advance of the land and sea breeze over a flat plain. The land and sea breeze for the case with a slope varying its surface temperature is highly efficient in producing the available potential energy and converting it to the kinetic energy of the breeze.
Based on the grid-nesting method proposed by the present author (1974), a Movable, multi-Nested Grid scheme (hereafter, MNG) is formulated to apply to a three-level primitive equation model in the σ-coordinate system. The outermost grid size is 381km at 6°N and the mesh ratio for each inner subdomain is one half. The interface condition between different nets is the so called “two-way” interaction. The Euler-backward scheme is adopted for the time integration. The heating due to cumulus ensemble is represented in the same way as the circular symmetric heating function proposed by Harrison (1973). Several preliminary tests have been carried out to examine the computational characteristics of the scheme and to see how the present MNG method works with real data (T7609, T7617, T7709 and T7711) produced by the JMA operational objective analysis system. The grid values of the finer grid net are calculated by a cubic interpolation formula step by step, and analyzed values on the innermost grid are modified as a results of the superposition of the symmetric model typhoon which is specified by the observed diameter of typhoon, the central surface pressure, the maximum surface wind and the temperature anomaly. The scheme has been tested with the 3- and 4-step MNG's. The predicted trajectories of the typhoon with these MNG's show the trend of improvement compared with those obtained by the JMA operational numerical weather prediction models. In addition, the three-dimensional structure simulated by the proposed 4-step MNG scheme is also discussed.
Five years of northern hemispheric data of specific humidity and winds have been analyzed on an annual basis to study the year to year changes in the field of the atmospheric water vapor. The major findings are; (1) the yearly mean total hemispheric precipitable water content of the atmosphere does not vary more than 4%; (2) the zonally averaged E-W flux is comparatively stable, while the zonally averaged N-S flux has interannual variations up to a factor of 2 in the magnitude of its maximum southward flow, and up to about 18% in the maximum northward transport; (3) withh few exceptions, the locations of the large positive and negative centers in the maps of annual mean E-W and N-S flux components do not shift more than three degrees, but the magnitude of the center value does change substantially within the five-year period; and (4) the deviations of the water vapor content and its flux are affected by Tibetan Plateau, Rocky Mountains, monsoon activity and the year-to-year shift of the North Pacific high.
The author considers a fringe effect upon the electric field in the Gerdien condenser. The potential field in the neighborhood of the edge of the electrodes is numerically calculated by the relaxation method to solve the difference equations deduced from a Laplace equation. Solving the equation of motion of an atmospheric ion under the effect of the field, he investigates what portion of ions with arbitrary initial conditions should be removed by the stray flux of the electric lines of force at the entrance of the Gerdien condenser. The correction for this fringe effect is evaluated for various measurements with actual instruments. It is shown that this effect should be small when using an electric conductivity meter or an ion mobility spectrometer but very large on a total small ion number density meter.
The smallest particle radius (γL) detectable in Pollak counter was estimated experimentally using a heated platinum wire aerosol generator of variable size, a Pollak counter with standard volume expansion ratio and an ion mobility analyzer. The values of γL obtained in this study were from 1.3 to 1.4•10-7cm in aerodynamical radius and were nearly close to the theoretical ones predicted by the dry-adiabatic expansion.