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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
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NASA NTRS1983

Stratospheric wind errors, initial states and forecast skill in the GLAS general circulation model

Relations between stratospheric wind errors, initial states and 500 mb skill are investigated using the GLAS general circulation model initialized with FGGE data. Erroneous stratospheric winds are seen in all current general circulation models, appearing also as weak shear above the subtropical jet and as cold polar stratospheres. In this study it is shown that the more anticyclonic large-scale flows are correlated with large forecast stratospheric winds. In addition, it is found that for North America the resulting errors are correlated with initial state jet stream accelerations while for East Asia the forecast winds are correlated with initial state jet strength. Using 500 mb skill scores over Europe at day 5 to measure forecast performance, it is found that both poor forecast skill and excessive stratospheric winds are correlated with more anticyclonic large-scale flows over North America. It is hypothesized that the resulting erroneous kinetic energy contributes to the poor forecast skill, and that the problem is caused by a failure in the modeling of the stratospheric energy cycle in current general circulation models independent of vertical resolution.

Tenenbaum, J.↗
NASA NTRS1983

Energetics analysis of the global circulation during the special observation periods of FGGE

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 diference 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.

Kung, E. C.↗
NASA NTRS1984

Quasi-periodic oscillations in a symmetric general circulation model

Observational evidence has been presented for the existence of quasi-periodic fluctuations of the tropical circulation with periods around two weeks and around 40 days. It is expected that an understanding of the mechanisms of these quasi-periodic oscillations in the tropical atmosphere will improve the predictability of the short range climate fluctuations in the tropics. The present study evolved as an outgrowth of an investigation conducted by Goswami et al. (1984). In this investigation remarkable oscillations of the Hadlay circulation for an ocean covered earth were observed. In the current study evidence is presented regarding the episodic behavior of the tropical circulation in general, and the propagation characteristics of these oscillations in the lower atmosphere. Attention is given to the results of six different experiments.

Goswami, B. N.↗
NASA NTRS1984

The effect of realistic conductivities on the high-latitude neutral thermospheric circulation

The dynamics of the high latitude thermosphere are dominated by the ion circulation pattern driven by magnetospheric convection. The reaction of the neutral thermosphere is influenced by both the magnitude of the ion convection velocity and by the conductivity of the thermosphere. Using a three-dimensional, time-dependent, thermospheric, neutral model together with different ionospheric models, the effect of changes in conductivity can be assessed. The ion density is described by two models: the first is the empirical model of Chiu (1975) appropriate for very quiet geomagnetic conditions, and the second is a modified version of the theoretical model of Quegan et al. (1982). The differences in the neutral circulation resulting from the use of these two ionospheric models emphasizes the need for realistic high latitude conductivities when attempting to model average or disturbed geomagnetic conditions, and a requirement that models should couple realistically the ionosphere and the neutral thermosphere. An attempt is made to qualitatively interpret some of the features of the neutral circulation produced at high latitudes by magnetospheric processes.

Fuller-Rowell, T. J.↗
NASA NTRS1984

Differential rotation in a solar-driven quasi-axisymmetric circulation

The concept of a quasi-axisymmetric circulation is used to explore the global scale dynamics of planetary atmospheres. A numerical circulation model applicable to Jupiter is presented, and an analytical study is performed elucidating the conditions leading to differential rotation in an atmosphere which is convectively unstable. A linear system forced by solar differential heating is considered, with nonlinear effects arising from advection being represented in the form of eddy diffusion. An empirical, latitudinal spectrum of the observed zonal wind field on Jupiter is discussed. Numerical solutions are presented which reveal banded wind fields with alternating and equatorial zonal jets and a multicellular Ferrel-Thomson meridional circulation consistent with the observed cloud striations on Jupiter. The vertical derivatives are parameterized to construct a simplified one-layer model.

Mayr, H. G.↗
NASA NTRS1985

Diagnostics of severe convection and subsynoptic scale ageostrophic circulations

Diagnostics of severe convection and subsynoptic scale ageostrophic circulations are reported. Mesoscale circulations through forcing of ageostrophic motion by adiabatic, diabatic and frictional processes were studied. The development and application of a hybrid isentropic sigma coordinate numerical model was examined. The numerical model simulates mesoscale ageostrophic circulations associated with propagating jet streaks and severe convection. A complete list of publications and these completed through support of the NASA severe storms research project is included.

Source record↗
NASA NTRS1984

A diabatic circulation experiment in a two-dimensional photochemical model

A two-dimensional photochemical model based on diabatic circulation has been used to simulate the behavior of N2O, CFCl3(F-11) and CF2Cl2(F-12) The circulation is based on estimates of net heating from the ground to 60 km. Eddy diffusion has been reduced with respect to other model studies with Kzz = 2000 sq cm/s everywhere bove 100 mbar. Resulting tracer profiles show reasonable agreement with measured profiles in the tropics and fall off much more sharply with altitude than those produced by models using larger values of Kzz. The agreement obtained is at least as good as that obtained with adjustable, eddy diffusion parameters. The diabatic circulation treatment is more closely related to related to real physical processes and thus more easily interpreted. Diffusive mixing appears to be more important in determining the details of the tracer distributions than the basic morphology.

Guthrie, P. D.↗
NASA NTRS1984

The influence of ocean surface temperature gradient and continentality on the Walker circulation. I - Prescribed tropical changes

A coarse mesh global climate model has been developed to assess ocean surface temperature (OST) gradient and continentality influences on the Walker circulation, which is characterized in the zonal plane by three pairs of clockwise and counterclockwise cells in the troposphere. The model response exhibits statistically significant changes in the intensity of the various cells and branches with small shifts in the east-west extent. The overall structure in the zonal plane for experiments with the coldest and with mean temperatures, however, remained unchanged. In an experiment involving the replacement of the South American continent by an ocean with OSTs linearly interpolated from the eastern Pacific to the western Atlantic, a dramatic change took place in the structure of the Walker circulation. It is concluded that both continentality and OST gradient are important Walker circulation forcing mechanisms.

Chervin, R. M.↗
NASA NTRS1984

Stratospheric circulation in the southern summer/northern winter 1980-81 - Behavior of zonal waves 1-10

Daily global grids of high quality, satellite-borne microwave measurements have been used to study the behavior of stratospheric waves during November 1980-March 1981. The primary motivation was to investigate, by comparing with earlier analyses, the interannual variation of recently reported medium-scale wave domination of Southern Hemisphere (SH) summer circulation. Zonal means, as well as time-mean and transient zonal waves 1-10, are studied. In addition, space-time spectra are determined from the 138-day record. Prominent medium-scale features are found to occur in 1980-81, although wave 4 is strongest, in contrast to the Global Weather Experiment period (1978-79), when wave 5 dominated the SH summer circulation. The same highly continuous, regular eastward phase movement of SH medium-scale waves is found in 1980-81 as in 1978-79. A second noteworthy observation is that of strong, time-mean waves 3-4 with symmetry about the equator, with positive temperature perturbations over the western Pacific and Atlantic equatorial regions, and negative anomalies over South America, Africa, and Indonesia. Confidence in the SH spectral results is enhanced by good agreement between our Northern Hemisphere (NH) medium-scale analyses and recent geopotential height studies by other investigators. These results serve to bring into sharper focus the question of why, in contrast with the more wellknown NH, the SH circulation evidences such robust and highly continuous medium-scale eddies in summer.

Yu, W.-B.↗
NASA NTRS1984

Effects of diabatic heating on the ageostrophic circulation of an upper tropospheric jet streak

Higher temporal resolution data from NASA's fourth Atmospheric Variability Experiment (April 24-25, 1975) are used to study the role of diabatic heating within the convective region in altering the ageostrophic mass circulation in the entrance region of the jet streak. The modifying effect this diabatic heating in the mesoscale storm exerts on the synoptic-scale environmental flow through dynamical mechanisms which link the mass circulation of these two scales is examined. The effect of diabatic heating on the ageostrophic motion within the thermally direct circulation of the jet streak and the mesoscale convective complexes is investigated. Diabatic modes of ageostrophic motion that intensify the upper tropospheric jet streak downstream are identified.

Keyser, D. A.↗
NASA NTRS1984

Modeling the middle atmosphere circulation

Some of the motivations for constructing models of the middle atmosphere circulation are given. These are as follows: (1) to provide a better understanding of middle atmosphere dynamics; (2) to study the coupling of middle atmosphere dynamics with radiation and chemistry; (3) to study the sensitivity of tropospheric climate modeling and/or weather forecasting to changes in the middle atmosphere; (4) to better understand the limitations of more simplified models; (5) to supply a proxy for atmospheric data for diagnostic analysis; and finally, (6) for forecast-analysis of data. Different types of models are discussed in relation to their anticipated use. Various model simplifications, such as using the quasi-geostrophic set of equations and simplified radiative transfer, are discussed as are some of the consequences of these simplifications. Some of the accomplishments of middle atmosphere circulation modeling are presented as are some of the difficulties in existing models. Finally, some of the problems in constructing and verifying middle atmosphere circulation models are discussed.

Geller, M. A.↗
NASA NTRS1984

Axisymmetric circulations forced by heat and momentum sources - A simple model applicable to the Venus atmosphere

A simple mechanistic model of a zonally averaged circulation forced by heat and momentum sources is developed and applied to the Venus atmosphere in the light of recent data. Basic equations for a steady-state axisymmetric circulation are discussed, and the parametric dependence of a nearly inviscid Hadley circulation in the absence of eddy forcing is examined and extended to a wide range of thermal Rossby numbers. The effect of diffusion is considered and found to be small for the Venus cloud region. The zonally averaged eddy sources and sinks required to support the zonal superrotation on Venus are determined.

Hou, A. Y.↗
NASA NTRS1985

Circulation of energetic ions of terrestrial origin in the magnetosphere

Shelley et al. (1972) have first reported that ions of terrestrial origin might represent a nonnegligible component of the hot magnetospheric plasmas. The present paper is concerned with those observational results which provide keys to the circulation of energetic magnetospheric ions of terrestrial origin, taking into account ions having energies greater than approximately 10-100 eV. It is pointed out that these are the ions which might be expected to circulate through the plasma sheet. On the basis of the observed ion composition of plasma storage regions (the plasma sheet and ring current) and the source and transport regions (auroral zone acceleration region, polar cap, boundary layers and magnetotail lobes), it is concluded that during magnetically active periods the primary circulation of energetic terrestrial ions is directly from the auroral acceleraton region into the plasma sheet boundary layer and central plasma sheet.

Shelley, E. G.↗
NASA NTRS1985

The Southern Hemisphere circulation during the FGGE and its representativeness

An analysis of the global redistribution of mass during the FGGE year indicates that the global circulation was highly anomalous in several respects, especially from April to July 1979. For the 56 to year period 1924-1980, sea-level pressures over the northern hemisphere during the FGGE year were second highest in spring and highest in summer. In April and June, the anomalies were 1-in-100-year events. At the same time, sea-level pressure deficits and an exceptionally deep circumpolar trough were recorded over the Southern Hemisphere. Such compensation between the hemispheres, through the constraint of conservation of mass, provides support for the highly typical nature of the circulation analyzed to exist over the Southern Hemisphere throughout the FGGE year. The Southern Hemisphere circulation was characterized by an exceptionally deep circumpolar trough, an increase in westerlies from 40 deg to 70 deg S, and a decrease in westerlies to the north. In winter, the subtropical jet was weaker and the polar jet stronger than normal, so that a pronounced double jet structure prevailed. In summer, the jet was shifted south by 3 deg latitude. A southward shift in storm tracks accompanied these changes year round in a manner consistent with theory.

Trenberth, K. E.↗
NASA NTRS1985

Wave-mean flow interaction in the NCAR stratospheric general circulation model

A version of the NCAR General Circulation Model has been developed which extends from the surface into the mesosphere. The model was forced by climatological January sea surface temperatures and insolation and gives a fairly reasonable simulation of the troposphere and stratosphere. The transformed Eulerian formation is used to examine the interaction of the eddies with the mean flow in the winter hemisphere. The essence of the transformed Eulerian formation is an attempt to distinguish between the mean meridional circulation driven by diabatic heating and that driven by eddies. The net effect of eddies can then be determined, and is given by the Eliassen-Palm (EP) flux divergence. In practice, this method works reasonably well but is far from perfect. For instance, in the absence of eddy forcing, the winter stratosphere would go to radiative equilibrium and there would be no diabatic heating to drive a mean meridional circulation.

Boville, B. A.↗
NASA NTRS1986

Circulation regime-dependent nonlinear interactions during northern hemisphere winter

Data of 500 mb geopotential heights, obtained in Januaries from 1963-1977 are used to study the relationship between the interaction of different scales of motion and the circulation regime characterizing the large-scale pattern. Geostrophic and 500 mb height streamfunctions and energy and enstrophy spectra are computed. Differences in the height variance, kinetic energy, and enstrophy spectra of the large positive anomaly events are compared to normal circulation. Systematic differences in the nonlinear cascading are examined. The data reveal that transient eddies perform a regime-dependent function in the interactions with atmospheric circulation modes on the scale of the persistent anomalies.

Brown, P. S.↗
NASA NTRS1986

The 14 month wind stressed residual circulation (pole tide) in the North Sea

From published research it is known that a quasi-periodic 14 month atmospheric pressure oscillation of a few tenths of a millibar exists in the region of the North and Baltic Seas. At some time in the cycle the associated wind stress has a westerly component that drives a circulation in the North Sea. The results of a dynamical model and comparisons with several North Sea residual circulation studies show that a large sea level gradient results along the Dutch coast. It is this feature that has been referred to as the enhanced pole tide. The dynamical similarity of this pole tide in the North and Baltic Seas to the annual and seasonal wind forced circulations is considered. It is inferred that the large deviations of the pole tide from equilibrium at coastal stations are the result of this sea level set up forces by the 14 month wind stress cycle.

Oconnor, W. P.↗
NASA NTRS1987

Large-scale static investigation of circulation-control-wing concepts applied to upper surface-blowing aircraft

The use of a circulation control to deflect turbofan engine thrust beyond 90 deg. has been proven in full-scale static ground tests of the circulation-control-wing/upper-surface-blowing (CCW/USB) concept. This powered high-lift system employs a circular, blown trailing edge to replace the USB mechanical flaps to entrain engine-exhaust flow, and to obtain both a vertical-thrust component and an augmented circulation lift for short takeoff and landing (STOL) applications. Previous tests (Phase 1), done in 1982, of a basic configuration installed on the Quiet Short Haul Research Aircraft confirmed these CCW/USB systems capabilities. A second phase (Phase 2) of full-scale, static, thrust-deflection investigations has reconfirmed the ability to deflect engine thrust from 40 to 102 deg., depending on thrust level. Five new configurations were evaluated and performance improvements noted for those configurations with larger blown span, fences or favorable engine interactions, smaller slot height, and larger radii with less than 180 deg. of CCW surface arc. In general, a 90 deg. circular arc with a smaller slot height provided the best performance, demonstrating that adequate thrust turning can be produced by a trailing-edge shape which may have minimal cruise-performance penalty. Thrust deflections were achieved at considerably lower blowing momentum than was required for the baseline case of Phase 1. Improved performance and versatility were thus confirmed for the CCW/USB system applied to STOL aircraft, where the potential for developing a non-moving-parts pneumatic thrust deflector to rapidly vary horizontal force from thrust to drag, while maintaining constant vertical force, appears quite promising. The conversion from high-lift to lower-drag cruise mode by merely terminating the blowing provides an effective STOL aircraft system.

Shovlin, M. D.↗