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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
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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Ernest C. Kung
and
Alan J. Siegel

Abstract

The large-scale sensible and latent beat budgets in the intense winter monsoon over the Kuroshio region are studied with the AMTEX 74 and 75 observations. Energy variables involved in the sensible heat balance and latent beat balance are computed and examined from the surface to 100 mb. They are also compared with the sensible and latent heat supplies from the sea surface, which are independently estimated.

The large-scale vertical and horizontal transport processes are important in the local balance of sensible and latent heat. The adiabatic conversion term is also significant in the balance of sensible heat. The boundary layer of the atmosphere appears to be a persistent source of sensible and latent beat. The existence of the apparent sensible and latent heat sources above the boundary layer seems to be related to the prevailing synoptic pattern and existing meso-convective systems.

When the winter monsoon dominates over the warm sea, considerable heat energy is transferred from the sea surface. It appears that most of the beat energy supplied through microscale and mesoscale convection interacts directly with the system of the large-scale winter circulation.

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Ted L. Tsui
and
Ernest C. Kung

Abstract

The energy transformations ore studied with a subsynoptic-scale upper air network for three types of severe storm environments under convective, nonconvective and frontal situations.

The environment of the convective storms is most active energetically with intense generation and dissipation of kinetic energy taking place in the upper layer of the atmosphere. In the case of the non-convective environment, a strong adiabatic destruction of kinetic energy through the cross-isobaric flow takes place in the upper layer of the atmosphere. In the frontal cases the upper layer of the atmosphere becomes energetically inactive for the observed scale in terms of the gross energy budget. Examination of the kinetic energy budget during the thunderstorm passage indicates the existence of subsynoptic-scale areas of adiabatic generation and destruction of kinetic energy with the maximum destruction in the middle and upper layers in the area of the maximum storm intensity.

The eddy energy transformations in the disturbances are intensive in the active convective environment, and a significant amount of eddy kinetic energy is derived through the local baroclinic conversion process.

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