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ERNEST C. KUNG

Abstract

The design of an optimized computation scheme for kinematic vertical motion fields with an upper air network is discussed with a scheme that incorporates 14 degrees of optimization in the evaluation of divergence. The provided range of optimization enables the computation scheme to suit wide varieties of data dispostion in the observation network, and the well-known problem of bias error accumulation in the kinematic ω profiles seems to have been practically overcome. The discussions include the general construction of the scheme in terms of the sequential flow of the computation, the quality of the vertical motion field over the synoptic network through the depth of the atmosphere, and the utilization and application of the scheme under various circumstances.

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ERNEST C. KUNG

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ERNEST C. KUNG

Abstract

This is an attempt to employ a pertinent boundary layer model and proper frictional parameters in the numerical analysis of the angular momentum budget of the atmosphere. The mean zonal surface stress due to friction is examined utilizing Lettau's boundary layer model and the earth's roughness study by the writer and Lettau for the period 1945–1955. The meridional and seasonal variations of the mean zonal surface stress are described; the mountain effect is derived indirectly; the stresses over the continent and ocean are compared; and finally the sensitivity of the numerical analysis to the prescribed frictional parameters is briefly discussed.

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Ernest C. Kung

Abstract

Energy source terms in various types of mid–latitude synoptic–scale disturbances are examined with wore than 3400 computed synoptic cases during a 5–year period over North America.

It is shown that cyclones and cyclone vicinities serve as the baroclinic energy source regions, although the released energy through the eddy conversion process may be transported to other regions for generation of the kinetic energy. In the development and mature stages of cyclonic disturbances the eddy energy conversion is very active both within the cyclones and their vicinities. When cyclones are occluded the cyclone vicinities lose their importance as the baroclinic source region. In contrast to cyclonic disturbances, anticyclonic disturbances destroy kinetic energy.

In intermediate type disturbances there is a significant generation of kinetic energy. However, there is no internal energy source through the eddy conversion in these disturbances, and they depend on imported potential energy for their kinetic energy generation.

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ERNEST C. KUNG

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The diurnal variation and long-term variation of the kinetic energy generation and dissipation are investigated with the wind and geopotential data observed twice a day at 00 and 12 gmt over North America during a 5-yr. period. The generation from the work done by the horizontal pressure force and the dissipation are significantly and consistently greater at 00 gmt than at 12 gmt. The diurnal variation is especially pronounced during the summer. The annual march of the seasons and the year-to-year variation of the kinetic energy parameters are also significant.

By the use of twice-a-day observations for an extended period, the study over North America is increased in generality as an approximation to hemispherical features. However, some uncertainty remains in this respect because of the possible effects of the semidiurnal variations and unconfirmed radiation errors in the radiosonde observations. The previously reported double maxima of the generation and dissipation in the planetary boundary layer and at the jet stream level derived from limited data are confirmed in this study. The multi-annual mean of the dissipation is estimated as 4.12 watts/m.2 About half of the estimated dissipation takes place in the boundary layer, and the other half takes place in the free atmosphere.

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ERNEST C. KUNG

Abstract

Various aspects of our studies of the kinetic energy balance are discussed, using an improved scheme of computing the horizontal and vertical transports of the kinetic energy with the observed wind and geopotential data over North America. On a firmer basis than before, it has been shown that there is a considerable amount of kinetic energy dissipated outside the planetary boundary layer, particularly at the jet-stream level. This also may imply that intensity of the atmospheric general circulation is significantly higher than is being assumed in most of the numerical models of the atmosphere.

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ERNEST C. KUNG

Abstract

The latitude-height distributions of the kinetic energy generation and dissipation over North America are presented in a series of cross sections from 25° to 70° N, and from the surface to the 50-mb level. The generation was computed using the twice-daily observed wind and geopotential data for a 1-yr period. The dissipation was obtained for a 3-mo summer period as the residual term of the kinetic energy equation. Throughout all latitudes, the generation and dissipation have a maximum in the planetary boundary layer. They gradually reach a minimum in the mid-troposphere, then increase to another maximum at the jet stream level except in middle latitudes. In the upper troposphere, there seems to be a characteristic meridional distribution both for generation and dissipation. The generation is significantly large north and south of the middle latitude where the kinetic energy is adiabatically destroyed. Those latitudes of large generation in the upper troposphere are also characterized by high frictional dissipation values. Reference is also made to the results in available numerical experiments for comparison and discussion.

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ERNEST C. KUNG

Abstract

The vertical distribution and seasonal variation of the kinetic energy balance of the atmosphere are studied. From 11 months' daily wind and geopotential data during 1962 and 1963 over North America, the generation due to the work done by the horizontal pressure force, the local change, the horizontal outflow, and the vertical transport, are evaluated for 20 pressure layers from the surface to 50 mb. The dissipation is then obtained as the residual to balance the kinetic energy equation.

The generation and dissipation are at a maximum in the planetary boundary layer. They decrease gradually to a minimum in the mid-troposphere, increase again to the second maximum in the upper part of the atmosphere, then decrease again farther upward. The generation and dissipation are approximately balanced in the lower troposphere, particularly in the boundary layer, for the large-scale domain of analysis.

The generation and dissipation of the kinetic energy are significantly large both in the lower troposphere and in the upper part of the atmosphere. However, in view of the amount of the kinetic energy contained in different portions of the atmosphere, the energy generation and dissipation are most intense in the lower troposphere, especially in the boundary layer. The efficiency of the dissipation in different portions of the atmosphere is also examined in terms of the depletion time. The depletion time is orders of magnitude shorter in the boundary layer than in the mid-troposphere.

A seasonal change of the energetics is depicted for the one-year period by means of the pressure-time cross sections.

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Ernest C. Kung

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Ernest C. Kung

Abstract

The spectral energetics of the general circulation are presented for the entire FGGE year based on the GFDL analyses of FGGE observations. The global energy balance and those of the Northern and Southern hemispheres show a reasonable agreement. However, examining the energy flow in the wavenumber domain reveals a marked contrast between the two hemispheres in both energy and energy transformations. The annual variations of energy variables are large, and there are also pronounced differences of seasonal characteristics between the hemispheres.

With the one-year time series of energy variables, time spectra of transient waves are examined at 500 and 100 mb in order to evaluate their contribution to the time-averaged kinetic energy and baroclinic conversion. Characteristic distributions of power spectra for kinetic energy and available potential energy are described for the Northern and Southern hemispheres. In cyclone-scale disturbance almost the entire baroclinc conversion is supported by transient waves. There are pronounced contrasts between the Northern and Southern hemispheres in the conversion cospectra at various zonal wavenumbers.

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