Transient Kinetic Energy Research Articles

Improved hybrid approach to transient stability assessment

The characteristics of the minimum transient kinetic energy of post-fault trajectories are studied in order to develop a tool for dynamic security assessment during the operation mode analysis of power systems. Using available commercial software a strategy for the transient stability study is introduced to enable harmless contingencies to be screened out and the classification of high-risk and harmful contingencies to be performed. Based on these characteristics, an approach to transient stability assessment is proposed and applied to the assessment at the hybrid transient energy margin for high-risk and harmful contingencies. The significant advantage of this approach is that the identification of a critical machine group is completely unnecessary. Case studies on a small test system, the ten-generator New England test power system and a realistic system, the middle-China power network are presented to verify the effectiveness and efficiency of this method.

The QDIA and regularized QDIA closures for inhomogeneous turbulence over topography

The dynamics and spectra of the quasi-diagonal direct interaction approximation (QDIA) closure for inhomogeneous two-dimensional turbulence over mean (single realization) topography are compared with results from direct numerical simulations (DNS). A more efficient version of the closure, termed the cumulant update QDIA (CUQDIA), has also been formulated and tested. Studies are performed for a range of resolutions, for large scale Reynolds numbers between very low (R L < 1) and moderate (R L 300) and for wide ranges of topographic spectra and initial mean field and transient spectra. The QDIA-type closures are shown to be computationally tractable for general inhomogeneous flows, particularly in cumulant update form, and to perform extremely well when the turbulence is weak. At low (R L 60) to moderate (R L ≃ 300) Reynolds numbers the presence of significant amplitude small-scale mean fields and topography reduces the under-estimation of small-scale transient kinetic energy that is characteristic of the Eulerian direct interaction approximation (DIA). A regularized version of the CUQDIA closure (RCUQDIA) in which interactions are localized in wavenumber space, depending on specified cut-off ratios, has also been tested at moderate Reynolds number for cases when the small-scale mean fields and topography are weak. Excellent agreement has been found between the RCUQDIA closure and DNS results for turbulent flows with properties broadly similar to atmospheric spectra.

A New Perspective on Blocking

Abstract It is argued that the essential aspect of atmospheric blocking may be seen in the wave breaking of potential temperature (θ) on a potential vorticity (PV) surface, which may be identified with the tropopause, and the consequent reversal of the usual meridional temperature gradient of θ. A new dynamical blocking index is constructed using a meridional θ difference on a PV surface. Unlike in previous studies, the central blocking latitude about which this difference is constructed is allowed to vary with longitude. At each longitude it is determined by the latitude at which the climatological high-pass transient eddy kinetic energy is a maximum. Based on the blocking index, at each longitude local instantaneous blocking, large-scale blocking, and blocking episodes are defined. For longitudinal sectors, sector blocking and sector blocking episodes are also defined. The 5-yr annual climatologies of the three longitudinally defined blocking event frequencies and the seasonal climatologies of blocking ...

The effects of closure-based eddy diffusion on the climate and spectra of a GCM

A recently developed horizontal eddy diffusion parameterization based on closure theory has been implemented in the CSIRO atmospheric global climate model (GCM). Detailed studies of the effects of the parameterization on the simulated atmospheric circulation, transient kinetic energy and kinetic energy spectra have been carried out for different months throughout the year. These diagnostics have been compared with corresponding results from observations and from control simulations using an ad hoc diffusion parameterization also employed in earlier works with this model. The new diffusion parameterization has improved the simulated atmospheric circulation in the following ways. Zonal and total wavenumber spectra now have approximate -3 power laws for ranges of intermediate wavenumbers, as in the observations, while the control simulation spectra are considerably flatter. Peak values of transient kinetic energy near the tropospheric jet cores are considerably larger than in the control and in better agreement with observations, particularly in boreal winter. The strength and location of the tropospheric jets are also improved with the new diffusion parameterization, with monthly averaged zonal mean winds in the Northern Hemisphere and Southern Hemisphere jet cores stronger than for the control by as much as 5 m s-1 in boreal winter and spring. The GCM simulations are also stable with longer timesteps with the new eddy diffusion parameterization. It is suggested that further improvements in GCM simulations may be achievable through parameterizations of the nondiagonal elements of the covariance matrix of eddy fluxes such as the eddy-topographic force.

The effects of closure-based eddy diffusion on the climate and spectra of a GCM

A recently developed horizontal eddy diffusion parameterization based on closure theory has been implemented in the CSIRO atmospheric global climate model (GCM). Detailed studies of the effects of the parameterization on the simulated atmospheric circulation, transient kinetic energy and kinetic energy spectra have been carried out for different months throughout the year. These diagnostics have been compared with corresponding results from observations and from control simulations using an ad hoc diffusion parameterization also employed in earlier works with this model. The new diffusion parameterization has improved the simulated atmospheric circulation in the following ways. Zonal and total wavenumber spectra now have approximate −3 power laws for ranges of intermediate wavenumbers, as in the observations, while the control simulation spectra are considerably flatter. Peak values of transient kinetic energy near the tropospheric jet cores are considerably larger than in the control and in better agreement with observations, particularly in boreal winter. The strength and location of the tropospheric jets are also improved with the new diffusion parameterization, with monthly averaged zonal mean winds in the Northern Hemisphere and Southern Hemisphere jet cores stronger than for the control by as much as 5 m s−1 in boreal winter and spring. The GCM simulations are also stable with longer timesteps with the new eddy diffusion parameterization. It is suggested that further improvements in GCM simulations may be achievable through parameterizations of the nondiagonal elements of the covariance matrix of eddy fluxes such as the eddy-topographic force. DOI: 10.1034/j.1600-0870.2003.201329.x

The processes governing horizontal resolution sensitivity in a climate model

One of the questions that climate modellers should address is whether their models have sufficient spatial resolution to resolve the physical processes affecting climate. This study addresses this question using the Hadley Centre climate model, HadAM3 (Hadley Centre Atmospheric climate Model version 3, the climate version of the Met Office's Unified Model). The model is run in AMIP2 (Atmospheric Model Intercomparison Project number 2) mode at four resolutions ranging from N48 (2.5° × 3.75°) to N144 (0.833° × 1.25°). The convergence of the model on increasing resolution is evaluated, and the processes leading to resolution sensitivity are investigated in some detail. A parallel set of four dynamical core integrations give an indication of the sensitivity of the dynamics with simple physical parametrization feedback. Increments from individual parametrization schemes during short 'spin-up' integrations with full physics are used to diagnose the sensitivity of individual schemes. The dependency of the results on particular details of the model are also investigated to see how general the results are. Model biases are reduced when resolution is increased. In particular, the troposphere warms, the jets shift polewards, mean sea level pressure over the poles falls, and transient vertical velocity and eddy kinetic energy increase. Some features of the model converge while a number of significant features do not. Non-linearity in both the hydrological cycle and the dynamics play an important role in the lack of convergence.

Relaxation kinetics of excitons in cuprous oxide

Due to a simple band structure, the excitons in cuprous oxide $({\mathrm{Cu}}_{2}\mathrm{O})$ are a model system for kinetic studies. Cuprous oxide appeared to be a host for a Bose-Einstein condensate of excitons, as the excitons showed transient kinetic energy distributions which matched those expected for a Bose gas near the critical density for Bose-Einstein condensation. However, recent absolute measurements of the exciton density made it clear that two-exciton annihilation is limiting the exciton density to far below the quantum density. This paper reconciles the measured exciton density with the observed exciton energy distributions by using a Boltzmann equation approach. We include experimentally determined rates for acoustic- and optical-phonon emission, conversion between exciton spin states, and two-exciton annihiliation, and use recent diffusion-Monte-Carlo estimates of the exciton-exciton elastic scattering cross section. Many experiments intending to produce a dense exciton gas in ${\mathrm{Cu}}_{2}\mathrm{O}$ used surface photoexcitation, and we found it important to include the resulting spatial inhomogeneities in the model by following the exciton occupation numbers as functions of space as well as momentum and time. A detailed but straightforward numerical integration of the resulting Boltzmann equation does in fact match the experimental results, without the assumption of quantum statistics for the excitons.

Two-dimensional turbulence properties of the ECMWF reanalyses

A spherical harmonic analysis is made of the stationary and transient rotational motions during14 winter and 15 summer seasons from the reanalyses of the European Centre for Medium-Range Weather Forecasts (ECMWF) for the northern hemisphere. Vertically-integrated kineticenergy, enstrophy, rotational non-linear interactions and the baroclinic source term are diagnosedas a function of total wavenumber n. The contributions to the non-linear transfers fromtriads involving wavenumber and frequency bands of meterological relevance are mapped. Theinter-seasonal and intra-seasonal variability are computed. The non-linear energy and enstrophytendencies and fluxes are examined and compared to existing geophysical turbulence theories.The transient divergent kinetic energy is less than the rotational energy. The spectral energyslope seen in the range n ˜ 10—40 is roughly - 2.5 ˜ - 2.6. Based on the variability of the slopeon seasonal and 10-day time scales, this slope is significantly different than - 3. There is noindication of the – 5/3 mesoscale energy regime seen in observations. A broad enstrophy dissipationregimes is seen for n > 40. Non-linear terms transfer transient energy from a band centeredat n ˜ 15 to one at n ˜ 7, with the latter predominantly associated with non-zonal (zonal wavenumberm0) flow. Non-linear terms transfer mean energy from n=7 to the mean zonal flowm=0, n=3 and n=5. The non-linear transfer of transient energy is quite variable, with about 16% of 10-day periods yielding a tendency twice the mean, and 16% showing no upscaletendency whatever. This variability is greatly reduced when interactions involving only synopticscales (n ˜ 10—40) are retained. The latter set of interactions are associated mostly with triadsinvolving both high and low frequencies, with associated periods in the 1–9 day and 11—90range, respectively. Non-local planetary wave advective interactions play an important rôle inthe downscale transfer of enstrophy. More local interactions involving synoptic scales dominatethe non-linear energy transfers. The main seasonal effects are a weakening in summer of thetotal energy and shifting to higher wave number of the peak, and a distinct shift to smallerscales in the transition between the large-scale and synoptic-scale regimes in the energy budget.The predominant time scale for non-linear maintenance of the planetary waves (about 9 days)is roughly the same as that of the baroclinic support of larger synoptic scale waves. The timescale of baroclinic conversion which maintains the smaller synoptic waves (n ˜ 20—40) is shorter(about 4 days).

Transient stability analysis of multimachine power system using swallowtail catastrophe model

In this paper the principle of energy balance approach is applied to develop a swallowtail catastrophe model for transient stability analysis of a multimachine power system. A new swallowtail catastrophe manifold function equation is created with the help of a simple energy balance equation of the critical machine in the interconnected multimachine power system, which is the sum of its transient kinetic energy during the fault-on period and the potential energy of the post fault period. The bifurcation set of the swallowtail catastrophe gives the transient stability region of the power system, and the critical fault clearing time is computed from the swallowtail catastrophe manifold function equation. The computer simulation on a three-machine power system is presented, and the simulation results are compared with the standard step-by-step numerical method of integration. The method appears to be a promising technique for on-line transient stability assessment of multimachine power systems.

The Dynamical Simulation of the NCAR Community Climate Model Version 3 (CCM3)*

The dynamical simulation of the standard configuration of the latest version of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) is examined, including the seasonal variation of its mean state and its intraseasonal and interannual variability. A 15-yr integration in which the model is forced with observed monthly varying sea surface temperatures (SSTs) since 1979 is compared to coexisting observations. Results show that the most serious systematic errors in previous NCAR CCM versions have either been eliminated or substantially reduced. At sea level, CCM3 reproduces the basic observed patterns of the pressure field very well. Simulated surface pressures are higher than observed over the subtropics, however, an error consistent with an easterly bias in the simulated trade winds and low-latitude surface wind stress. Amplitude errors and phase shifts of the subpolar low pressure centers over both hemispheres during winter produce the largest regional errors, which are on the order of 5 mb. In the upper troposphere, both the amplitude and location of the major circulation centers are very well captured by the model, in agreement with relatively small regional biases in the simulated winds. Errors in the zonal wind component at 200 mb are most notable between 40° and 50° lat of both hemispheres, where the modeled westerlies are stronger than observed especially over the Southern Hemisphere during winter. A ∼50% reduction in the magnitude of the zonally averaged westerly bias in the equatorial upper troposphere that plagued previous CCM versions can be attributed to a significantly improved tropical hydrologic cycle and reduced Walker circulation. Over middle latitudes, the CCM3 realistically depicts the main storm tracks, although the transient kinetic energy is generally underestimated, especially over the summer hemispheres. Over lower latitudes, the model simulates tropical intraseasonal oscillations with marked seasonality in their occurrence. Typical periodicities, however, are near 20–30 days, which are shorter than observed, and the simulated amplitudes are weaker than in both observations and previous versions of the model. The simulated response to interannual variations in tropical SSTs is also realistic in CCM3. A simulated index of the Southern Oscillation agrees well with the observed, and the model captures the overall structure and magnitude of observed shifts in tropical and subtropical convergence zones and monthly rainfall anomalies associated with the tropical SST changes.

The generation of available potential energy: a comparison of results from a general circulation model with observations

The generation of available potential energy (APE) in the space-time domain in January and July in a present-day climate simulation with a general circulation model (GCM) is compared with observations. An attempt is made to explain the differences. The generation is computed from the fields of diabatic heating and temperature. The heating is computed with the residual method, using UKMO (United Kingdom Meteorological Office) Unified Model GCM circulation data and ECMWF (European Centre for Medium-Range Weather Forecasts) initialized analyses for the period 1989–1992. The global value of the generation of APE is about 35% larger in the GCM climate than the value computed from the analyses. This is mainly because the generation of transient eddy APE in the GCM is too large, due to the more than 40% too large generation of transient eddy kinetic energy by baro-clinic processes. In most of the extratropics the local contribution to the generation of transient eddy APE in the GCM climate is more than twice as large as the contribution computed from the analyses. A possible qualitative explanation for this difference is presented.

Nonlinear kinetic energy transfer in the upper troposphere during summer monsoon 1979

Upper tropospheric (300–100 hPa) nonlinear kinetic energy (KE) converts to rotational and divergent motion and the conversion is computed in the wavenumber domain for July 1979 in the latitude belt 10°S–30°N. They are further partitioned into stationary and transient components. It is shown by comparing the rotational and divergent KE spectra for stationary and transient motions that the best nondivergent level is 300 hPa, and 200 hPa is the most representative level in the upper troposphere for monsoon studies. Wavenumbers 3 and 7 are identified as the most preferred transient waves from the rotational transient kinetic energy spectrum. It is concluded that in the planetary‐scale dynamics of the monsoon region, wave‐wave interaction plays a secondary role. The net gain of rotational kinetic energy is proportional to its value, and the proportionality constant is nearly the same for all wave categories. It is found that planetary and synoptic waves in the upper troposphere during the monsoon are maintained by energy transfer from divergent kinetic energy. KE in the monsoon region is transported by nonlinear wave‐wave interaction. In particular, transient synoptic‐scale eddies are also maintained by energy transfer from transient synoptic‐scale divergent motion. It is further inferred from the energy balance that the stationary‐transient wave‐wave interaction is important for the maintenance of transient subsynoptic waves. It is noticed that kinetic energy conversion for transient subsynoptic waves is from the divergent to the rotational component at 200 hPa only and is opposite to that in the upper troposphere. The energy budget for transient waves 3 and 7 is investigated.

Transient-induced Climate Drift

The climate drift of various quantities associated with deep, planetary-scale, equilibrated, transient Rossby waves are estimated for the Southern Hemisphere extratropical summer as revealed by the DERF II (Dynamical Extended Range Forecasting) dataset. It is found that the vertical structures of these waves systematically become too baroclinic during the course of integration. There are two time scales associated with this climate drift. There is one very short time scale, estimated to be of the order of one day, when the waves become more barotropic. It is followed by a period when the wave baroclinicity monotonically increases, and after roughly 10 days the model structures appear to have reached their statistically equilibrated state. In the meantime, the kinetic energy of the transient waves decreases substantially to roughly half the observed value. After this initial drop, however, the transient kinetic energy increases again, and it is not clear if an equilibrium value has been reached after 30 days, which is the limit of the DERF II dataset. This third time scale is not found in the quantities directly associated with the vertical structures per se, but it is hypothesized to be a consequence of these errors. A theory is utilized that in a simplified way takes into account the processes that determine the vertical structure of baroclinic waves as well as their robustness as a means of understanding the processes leading to these errors. The implications from this theory are that the formulation and magnitude of the dissipative and diffusive processes in the model are the most likely problem, but there are other possibilities.

Sensitivity of Simulated Climate to Model Resolution

Dynamical measures of the climate (e.g., winds, eddy fluxes) simulated by a general circulation model are compared at different horizontal and vertical resolutions for the December, January, and February period. The simulations of the troposphere are found to improve significantly as the horizontal resolution increases in the range of spectral truncations from T21 to T63. Little sensitivity is found to changes in vertical resolution between about 2.8 km and 0.7 km vertical grid spacing. The improvements in the Southern Hemisphere troposphere are greater than in the Northern Hemisphere as the horizontal resolution increases. The eddy momentum fluxes and kinetic energies in both hemispheres increase monotonically with horizontal resolution. At T63, the Southern Hemisphere winds, eddy fluxes, and eddy kinetic energies agree favorably with observations, while serious discrepancies are present at lower resolutions. In the Northern Hemisphere, the eddy momentum flux at T63 is slightly larger than observed, while the transient eddy kinetic energy is still barely half of the observed. The gravity wave drag parameterization plays a significant role in the simulations at all resolutions. Eddy momentum fluxes increase when gravity wave drag is removed with a corresponding increase in low-level winds and surface stress.

Intraseasonal fluctuations in low-level meridional winds over the Indian Ocean and monsoonal convection over South Asia

Some aspects of 30-60 day meridional wind fluctuations over the mid-latitude Indian Ocean were investigated using lag correlation maps for the 5 summers of 1979-1983. At times, the equatorial low-frequency (30-60 day) modes exhibit a systematic eastward propagation. However, they are occasionally interrupted by irregular movements or even westward propagation. This study concentrates only on those periods with a systematic eastward propagation and a well-defined tropical-extratropical atmospheric teleconnection pattern. Low-level meridional wind fluctuations in the low-frequency domain are prominent over the western Indian Ocean off the east coast of Africa. The anomalous southerly flows, which are initiated around northern Madagascar move northward and, after crossing the equator, contribute to the intensification of the monsoonal westerlies over South Asia, thus, enhancing convection over the monsoon region. In comparison, 30-60 day southerlies (anomaly) over the eastern Indian Ocean off the west coast of Australia tend to enhance equatorial convection over the western Pacific between about 150°E and the date line. Perturbations with periods shorter than 30 days are considered transient disturbances. Spectral analysis of transient eddy kinetic energy in the extratropical regions reveals a significant peak in the low-frequency range. This is associated with an amplitude modulation of transient disturbances. Thus, it is plausible that transient disturbances, as a group, provide energy for the enhancement of 30-60 day planetary-scale perturbations over the subtropics. DOI: 10.1111/j.1600-0870.1988.tb00411.x

Northern hemisphere kinetic energy during the first GARP global experiment year

A comparison of the monthly vertically integrated northern hemisphere kinetic energy (in the isentropic domain) during the First GARP (Global Atmospheric Research Program) Global Experiment (FGGE) year with 5‐year monthly means (isobaric domain) shows only small seasonal differences, which are probably related to the different domains. Ratios of monthly total kinetic energy to available potential energy yield similar results. Daily values of the zonal and eddy kinetic energy indicate that the first part of the FGGE year differed considerably from a 5‐year mean in that the zonal kinetic energy was as large as the eddy component. Seasonal maps of the kinetic energy show anomalous winter and spring distributions, with the Atlantic and Pacific maxima equal in winter but with a near disappearance of the Atlantic maximum in spring. Similar differences are noted in cyclone activity. The transient kinetic energy plotted as a function of month and latitude appears to fit the normal pattern, but here longitudinal differences are obscured.

Seasonality in Southern Hemisphere Eddy Statistics at 500 mb

An analysis has been made of the spatial and frequency dependence of transient eddy statistics in the Southern Hemisphere at 500 mb. This study emphasizes summer versus winter differences in order to complement previous results of Trenberth (1981), which are shown to nearly correspond to the mean of the summer plus winter statistics. Variance fields of geopotential height, the north–south and east–west geostrophic velocity components, the transient kinetic energy and the poleward transient eddy momentum flux have been analyzed for nine winter and eight summer 128-day seasons from 1972–80. The fields are examined in the frequency domain using Lorenz' (1979) “poor man's spectral analysis” technique. The total fields and the contributions from two broad frequency bands covering periods of 2–8 and 8–64 days are geographically mapped and their zonal means are presented. The spatial distribution of the eddy statistics is quite similar in summer and winter, although the variances in winter are larger and of broader latitudinal extent, thereby indicating a more vigorous circulation overall than in summer. The seasonal changes in eddy statistics closely follow corresponding changes in the mean westerly wind field and are very small over the Indian Ocean, while the largest changes occur in the Pacific Ocean region. A storm track, as indicated by the high frequency fluctuations, exists in the Indian Ocean along 50°S in both summer and winter. The main low frequency variations including blocking-type phenomena occur south of New Zealand and southeast of South America in both seasons, but with small changes in location. Storms in the Pacific Ocean region have a somewhat longer time scale than over the Indian Ocean. A comparison has been made with results from previous studies and, in particular, with statistics based upon station data analyzed at GFDL. The GFDL analyses produce relatively weaker wind speeds over the data sparse oceans. The variance fields are comparable in magnitude but differ in detail, and the GFDL analyses fail to capture the characteristic patterns in the storm track and blocking regions of the hemisphere.

A Comparative Study of Observed Northern Hemisphere Circulation Statistics Based on GFDL and NMC Analyses. Part II: Transient Eddy Statistics and the Energy Cycle

Abstract The comparison between two sets of observed circulation statistics undertaken by Lau and Oort (1981) is continued in this study by examining the temporal variance and covariance statistics in these sets. The first (GFDL) set is compiled by interpolating monthly averaged station statistics. The second set is based on twice-daily operational NMC analyses. The statistics for six winter and six summer seasons within the 1966–73 period are compared. The hemispheric fields examined include transient eddy kinetic energy at 300 mb, root-mean-squares of geopotential height and temperature at 300 and 850 mb, respectively, the horizontal transport by transient eddies of westerly momentum and geopotential height at 300 mb, and of heat at 850 mb. The patterns of horizontal eddy transports are presented in a vectorial format to delineate local relationships with the time-mean flow and the centers of eddy activity. Latitude–height distributions for zonally-averaged patterns of the above statistics are also pres...

On the kinetic energy budget of the summer-mean flow at 200 mb in the tropics

The 200-mb wind data of the 1967 summer in the tropics is used to analyze the kinetic energy budget of the tropical time-mean flow. The horizontal distributions of the kinetic energy variables in the tropics are investigated and compared with the midlatitude studies of Holopainen (1978) and Lau (1979). The results reveal that the large-valued transient kinetic energy extends from the maximum core to the downstream of the tropical easterly jet. The maximum kinetic energy of the tropical time-mean flow goes hand in hand with this jet core. The relative locations of the maximum kinetic energy of the time-mean and transient flows in the tropics differ from those in the midlatitudes. The geographic distributions of horizontal fluxes of kinetic energy in the tropics shown in this study and the vertical circulations in the upstream and downstream sides of the tropical easterly jet shown by Krishnamurti (1971a, b) indicate that the kinetic energetics of the tropical easterly jet may be similar to that of the westerly jet in the midlatitudes. DOI: 10.1111/j.2153-3490.1982.tb01792.x

Observed Southern Hemisphere Eddy Statistics at 500 mb: Frequency and Spatial Dependence

Nearly eight years of daily Southern Hemisphere analyses at 500 mb have been used to define the spatial dependence of the variance fields of geopotential height and the two geostrophic wind components, the corresponding covariance fields, and the transient kinetic energy. The fields are further examined in the frequency domain by using Lorenz' (1979) “poor man's spectral analysis” technique. In view of the small variation in eddy statistics as a function of the time of the year in the SH, this study removes the first four harmonies of the annual cycle and then considers all data together, so that contributions from all time scales from 2 to 4096 days (∼11 years) can be resolved. The main results are based on analyses from May 1972–January 1978 but are verified with analyses from the relatively data-rich FGGE period. Results for the zonal mean statistics are compared with those from previous studies. The zonal means of the geopotential height and westerly wind component have spectra which roughly follow that of red noise with an autocorrelation of about 0.5, whereas the northward wind component spectra closely resembles red noise with autocorretation of 0.2, resulting in considerable anisotropy in the wind fields. The northward component of transient kinetic energy is larger than the eastward component at high frequencies in middle latitudes but the reverse is true for periods of greater than two months. The westerly momentum flux by the transient eddies has a broad spectral peak at 8–32 days and is dominated by contributions from fluctuations of less than about two weeks period. The geographical dependence of the eddy statistics is mapped for four broad frequency bands covering periods of roughly less than one week, one week to two months, two months to two years, and greater than two years, thereby separating out contributions from transient baroclinic eddies, episodes of blocking, and intermonthly and interannual variability. The spatial patterns of the statistics are interpreted in the light of synoptic behavior of systems and storm tracks as defined by synoptic studies and satellite observations in the Southern Hemisphere. For periods less than a week, variances are largest in the southern Indian Ocean and relationships between the storm tracks and eddy statistics are similar to those found in the Northern Hemisphere by Blackmon, Lau, Wallace and others. However, there also are differences associated with the differences in the mean flow in each hemisphere and these are discussed in the context of baroclinic theory. At periods longer than a week geopotential height variances are largest near southern New Zealand and, to a lesser extent, southeast of South America and appear to be related to the incidence of blocking in the Southern Hemisphere. The corresponding transient kinetic energy has a maximum further north in association with cutoff cold-centered lows. In general, the high-frequency transient eddies play a much larger role in the circulation of the Southern Hemisphere than is true for the winter circulation of the Northern Hemisphere, and the eddy statistics are more zonally symmetric.