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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
and
Paul H. Chan

Abstract

Energetics characteristics of the Asian winter monsoon are studied with twice-daily upper air data during a 20-year period over its source region. It is found that the energetics features over Siberia, North-eastern Asia, China Main and the Japan Sea, are distinctly different reflecting the different roles and characteristic flow patterns of these regions in the system of the winter monsoon.

Siberia, under the dominance of the anticyclonic flow, shows a general adiabatic destruction of kinetic energy through cross-isobaric motion. Northeastern Asia, under the influence of a major cyclonic system, is dominated by typical patterns of energy transformations as observed in most areas of transient synoptic disturbances. The strong westerlies dominate over the general area of the China Main, East China Sea and Japan Sea and the kinetic energy is intensely generated in this portion of the flow. Most of the kinetic energy generated over China Main is exported. Over the Japan Sea area where the series of cyclonic disturbances develops, a strong dissipation takes place.

During the cold air outbreaks, which are recognized with the intrusion of a strong cyclonic upper level flow into China Main, the kinetic energy generation and dissipation are drastically increased in the general area of the China Main, East China Sea and Japan Sea. However, basic energetics features of different regions in the prevailing systems of the Asian winter monsoon remain unchanged. A case study of a cold air outbreak is also presented.

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Thomas R. Heddinghaus
and
Ernest C. Kung

Abstract

Eigenvector and harmonic analyses have been performed with monthly mean values of upper air parameters of the Northern Hemispheric circulation for the period from April 1955 to December 1974. The parameters used involve the 700 and 500 mb temperatures, the 700–500 mb thickness, the 300 mb kinetic and eddy kinetic energies, and the 700, 500 and 300 mb zonal/meridional flow indicators. The zonal/meridional flow indicator is defined as the ratio | u |/| v | , where the bar indicates the monthly mean.

The first eigenvectors of the normalized parameters are associated with the annual variation of the basic patterns. For the temperature field the first eigenvector overwhelmingly dominates. It reflects the annual variation of temperature in the mid and higher latitudes with an effect of the land-ocean configuration. The second eigenvector shows a land-ocean contrast. The long-term variation of temperature in the lower latitudes also stands out. For the kinetic energy and zonal/meridional flow indicator the first eigenvectors are not as dominant as that of temperature. They reflect the subtropical jet and other hemispherical-scale circulations. The third eigenvector of kinetic energy and second eigenvector of the zonal/meridional flow indicator appear to be associated with the semiannual oscillations of the large-scale wind systems including summer and winter monsoons. It also appears that high-numbered eigenvectors of kinetic energy and zonal/meridional flow indicators are associated with long-term variations in the lower latitudes and short-term variations in the mid to high latitudes.

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Ernest C. Kung
and
Lester I. Merritt

Abstract

The maintenance of large-scale tropical disturbances has been examined with the source terms of kinetic energy generation utilizing the special 1958 upper-air observations in the Marshall Islands area. An optimized objective analysis scheme for the computation of kinematic vertical velocity as well as the method for evaluation of energy variables is presented.

The time mean budgets of kinetic energy source terms are presented in terms of vertical profiles and intensity of processes represented by each term. The eddy conversion of available potential energy has its primary maximum in the layer between 400 and 200 mb, whereas the eddy kinetic energy generation shows maxima in the lower boundary and upper troposphere between 200 and 100 mb. In terms of the time mean budget only a fraction of the released energy by eddy conversion contributes to the eddy generation of kinetic energy in the area.

Through examination of the time series of energy variables, it is revealed that horizontal eddy flux convergence of potential energy is the dominant term in determining the local generation of eddy kinetic energy. The migration pattern of the ITCZ further suggests that this horizontal eddy flux term is closely associated with the position of the ITCZ, with a significant divergence of eddy flux of potential energy when the ITCZ is located to the south of the area.

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Ernest C. Kung
and
Taher A. Sharif

Abstract

It is shown that the recorded onset dates of the summer monsoon in southwestern India can be closely related functionally to the antecedent upper air conditions. The antecedent upper air conditions are represented by April mean values of the daily upper air parameters at 100 and 700 mb from 1958 to 1978. It is further demonstrated that the multi-regression scheme on the basis of such a functional relationship may be utilized in an objective forecast of the onset date. The forecasted dates are shown to be reasonably close to the recorded onset dates. Various aspects of the approach and scheme are discussed. Because of the time variations of the patterns of the general circulation, a constant updating of the regression equation should be an integral part of the multi-regression forecasting scheme.

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Ernest C. Kung
and
Hiroshi Tanaka

Abstract

A global energetics analysis is presented for the FGGE SOP-1 and SOP-2 with ECMWF and GFDL data sets. Both global integral properties and spectral characteristics are examined.

There is a large discrepancy between the present FGGE analysis and previously available estimates concerning the level of available potential energy and kinetic energy. This discrepancy is attributable to an earlier restriction of data coverage. There is a significant seasonal difference in the energy reservoir of the Northern Hemisphere, whereas the difference is minor in the Southern Hemisphere. This leads to a seasonal contrast of the globally integrated energy budget which comes mostly from the Northern Hemisphere. Both the global energy level and the intensity of the general circulation are more pronounced during SOP-1 than during SOP-2.

One major focus of attention in this study is an energetics comparison of ECMWF and GFDL data sets. There is a twofold difference in the intensity of the general circulation as measured with these two data sets. The energetics diagnosis indicates that the operational modes of the general circulation as described by these two data sets also differ considerably. The contrasts between SOP-1 and SOP-2 and between the ECMWF and GFDL versions of the data sets are apparent in the pattern of energy flow in the wavenumber domain.

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Ernest C. Kung
and
Hiroshi Tanaka

Abstract

Global features and meridional variations of spectral energy transformations are investigated for the first and second special observation periods (SOP-1 and SOP-2) of FGGE. The latitudinal distribution of the kinetic energy balance is also examined. The diagnosis presented is based on the GFDL data set.

The spectral distributions of the global transformations, R(n) between the zonal mean and eddy components of the available potential energy, M(n) between the zonal mean and eddy components of the kinetic energy and C(n) between the available potential energy and the kinetic energy, all show specific seasonal characteristics for SOP-1 and SOP-2.

The characteristic latitudinal distribution of cell conversion C(0) and eddy conversion C(n) at various wavenumbers are presented with their vertical totals and latitude-height profiles. The equatorial maximum of C(0) is associated with the upward motion of the Hadley cells. During SOP-1 the middle latitude maximum of eddy conversion C(n) in the Northern Hemisphere is identified with the very active long waves n=1, 2 and 3. During SOP-2 the pronounced C(1) and C(2) in the Northern Hemisphere are associated with the summer monsoon system, and the Southern Hemispheric conversion is intense in the Antarctic region at n=0 and 1.

There is maximum production of the kinetic energy −V.∇ϕ at subtropical latitudes, with a secondary maximum at higher middle latitudes. Between these two regions of maximum production, there is a region of adiabatic destruction of kinetic energy above the lower troposphere. The convergence of the kinetic energy −∇.Vk is an important additional source of kinetic energy in middle latitudes. Dissipation D is at its maximum in middle latitudes. The seasonal contrast of the energy transformation is much more pronounced in the Northern Hemisphere than in the Southern Hemisphere, leading to more intense global energy processes during SOP-1 than SOP-2.

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Ernest C. Kung
and
Ted L. Tsui

Abstract

The balance of kinetic energy under severe storm conditions is investigated with a subsynoptic-scale upper-air network. The general shape of vertical profiles of the kinetic energy.generation and dissipation is very similar to that observed in well-developed major cyclones. The overall average magnitude of the observed energy transformations in the severe storm area is comparable to that of major synoptic-scale cyclones, but for a given storm the magnitude of energy transformations may vary widely depending on the existence and strength of mesoconvective systems in the area.

The balance of kinetic energy is also studied for the transient disturbances detected with the subsynoptic- scale upper-air network. Energetics features for those disturbances are depicted and discussed. The mid and lower troposphere appear to be the major source region of eddy kinetic energy.

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H. L. Tanaka
and
Ernest C. Kung

Abstract

Three-dimensional normal mode functions are applied to the analysis of the energetics of the general circulation during the FGGE year. The GFDL FGGE data are used for the computation of both the normal mode energetics and the standard spectral energetics.

The normal mode energetics of the global circulation are presented in a barotropic and baroclinic decomposition for the zonal mean and eddy energies for the stationary and transient components of the flow. The energy generated in the zonal mean baroclinic component is first transformed to the eddy baroclinic component through the process of atmospheric baroclinic instability. It is then further transformed to eddy and zonal mean barotropic components by the nonlinear up-scale cascade of kinetic energy. The zonal mean kinetic energy thus maintains its barotropic structure by the activities of baroclinic waves. The time series of energy variables during the FGGE Northern Hemisphere winter clearly indicates a sequence of energy transformations from the zonal baroclinic component via the synoptic-scale baroclinic component, to the planetary-scale barotropic component.

Comparison of the normal mode energetics with the standard spectral energetics in the zonal wavenumber domain indicates a general consistency of both schemes in the spectral energy transformations.

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Ernest C. Kung
and
Wayman E. Baker

Abstract

The spectral energetics of the Northern Hemisphere circulation during blocking episodes of the FGGE year is investigated with gridded analyses of observational data and Parallel simulation experiments. The purpose of this study is to describe the energetics distinctions of the observed and simulated blockings in the context of the general circulation and to assess the capability of the model to simulate blockings.

In the observed circulation a pronounced winter blocking is developed and maintained by the nonlinear wave-wave interaction L(1) from the kinetic energy source for n = 3–10, where L(n) is the transfer of eddy kinetic energy from all other wavenumbers to wavenumber n. In the case of the. double blocking in the winter, both L(1) and L(2) support the blocking. The kinetic energy source of n=3–10 for upscale input at n = 1 and 2 is supported by the baroclinic conversion at n3–10. The simulated winter circulation shows strong baroclinic conversion at all wavenumbers, including ultralong waves. However, the simulation fails to produce pronounced blocking for the absence of L(1), and the converted energy cascades down to shorter waves. The wave-mean transfer of kinetic energy from the large-scale disturbances to the zonal mean component further prevents the accumulation of the kinetic energy at the ultralong waves.

In contrast to the winter situation, the summer blocking seems to be directly supported by both L(4) and baroclinic conversion at other planetary-scale waves. Consequently, the summer circulation is better simulated than the winter circulation.

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