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S. K. Kao

Abstract

A statistical model for three-dimensional turbulent diffusion from instantaneous and continuous sources is constructed. It is shown that this diffusion model satisfies the continuity condition and the boundary condition of three-dimensional terrains.

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S-K. Kao

Abstract

An analysis of the kinetics and dynamics of the relative dispersion of particles in a stratified rotating fluid is made. The expressions for the relative displacement tensor, and the power- and cross-spectra of the relative velocity are derived. Their characteristics for large and small diffusion times are examined. The governing equations for the motion of marked fluid particles are separated into two sets of equations, one governing the motion of the center of mass and the other governing the motion of individual particles relative to the center of mass. Discussions of the concentration distribution in clusters of marked fluid particles are made. A turbulent diffusion model is constructed for the estimate of the effects of thermal stratification and rotation on the dispersion of particles in the atmosphere.

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S-K. Kao

Abstract

The properties of the volume integral of momentum vorticity are examined. These results are applied to the study of the maintenance of zonal circulation of a polar cap. It is shown that the rate of change of the vertical component of relative momentum vorticity is mainly due to (1) the effect of the convergence of meridional flux of angular momentum and its lateral boundary surface, (2) the frictional force at the earth's surface, and (3) the action of the mountains on the atmosphere. A model for the mean state of the atmosphere in the northern hemisphere, based on the distribution of the mean surface zonal wind, is studied; and the maintenance of the zonal circulation is discussed on the basis of the meridional transports of both angular momentum and momentum vorticity. It is shown that in the middle latitudes the meridional transfer of momentum vorticity is directed toward the north pole, whereas in the lower latitudes, as well as in the polar region, the transport is directed toward the equator. These results agree with the mean meridional transport of momentum vorticity in the month of January 1949, computed from the geostrophic winds.

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S-K. Kao

Abstract

A theoretical model is constructed and tested for the analysis and prediction of radioactive concentration in the troposphere. It is found that turbulent motion near the jet core plays the major role in the transport of radioactive debris from the stratosphere into the troposphere, whereas the mean motion of the jet core contributes to the spring maximum and autumn minimum of the concentration. A semiannual period in the variation of concentration exists, resulting from the interaction between the meridional gradient of the mean concentration and the mean motion of the jet core. It is also found that the average value of the vertical component of the eddy diffusivity in the troposphere is about 107 cm2 sec−1, and that the time required for diffusing radioactive particles from the tropopause level to the surface of the earth is about 11 hours.

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S. K. Kao

Abstract

No Abstract Available.

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S-K. Kao

Abstract

No abstract available.

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S. K. Kao

Abstract

An analytical solution to the Navier-Stokes equations for three-dimensional stationary flows of small Reynolds number in the atmospheric boundary layer over terrain is presented.

Analyses of the effects of topography, horizontal pressure gradient and Coriolis forces on the velocity distribution in the atmospheric boundary layer indicate that 1) the horizontal component of the velocity in the boundary layer turns right (left) with increasing height in the Northern (Southern) Hemisphere, 2) upward (downward) motion occurs on the windward (lee) side of the mountain, and 3) upward (downward) motion also occurs on the slope to the right (left) of the geostrophic wind in the Northern Hemisphere, whereas in the Southern Hemisphere downward (upward) motion occurs on the slope to the right (left) of the geostrophic wind.

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S-K. Kao

Abstract

The governing equations, power and cross spectra for the atmospheric motion, and transports in the frequency, wave-number space are derived. Discussions are made of the contributions of the nonlinear interactions of atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies, and to the meridional transports of angular momentum and sensible heat in the atmosphere.

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S-K. Kao

Abstract

An analysis of the wavenumber-frequency spectra of temperature in the free atmosphere is made. It is found that a striking similarity exists between the spectrum of temperature and that of the large-scale wind velocity in the free atmosphere. The wavenumber-frequency spectrum of temperature shows a preferred spectral domain of wave activities, oriented primarily from a region of low wavenumbers and low frequencies to a region of high wavenumbers and negative frequencies assigned to waves moving from west to east. In the high-wavenumber range, the wavenumber spectrum of temperature is approximately proportional to the –3 power of the wavenumber. In the high-frequency range, the frequency spectrum of temperature is approximately proportional to the –1 power of the frequency. These indicate that the structure of the temperature field in the free atmosphere is essentially affected by the large-scale two-dimensional turbulent motion. It is also found that most of the sensible heat is associated with the stationary zonal mean motion, and that there is more sensible heat associated with nonstationary waves than with stationary waves in the atmosphere.

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S-K. Kao and B. L. Niemann

Abstract

Analyses of the isotropic and anisotropic diffusion of clusters of fluid particles in the atmosphere are made. Lin's theory of diffusion is subjected to an observational test. The autocorrelation coefficients of the vector acceleration are computed and the value of B 0 in Lin's one particle theory is found to be 3 and 5 cm2 sec−3 for two series of experiments. The mean autocorrelation coefficients of the vector relative acceleration are computed and the value of B in Lin's isotropic diffusion theory is found to be 68 and 28 cm2 sec−3 for two series of experiments. The horizontal eddy diffusivities for the isotropic diffusion process are found to range from 0.4×103 to 6.4×103 cm2 sec−1. The mean cross-covariance coefficient of the relative acceleration is computed and the value of Bij in Lin's anisotropic diffusion theory is found to be 30 cm2 sec−3. The values of the diffusion tensor for the anisotropic diffusion process are found to range from 0.3×103 to 1.8×103 cm2 sec−1.

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