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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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NASA NTRS1975

Possible new Jovian thermospheric models

Possibilities of models for the Jovian thermosphere, based upon mechanical heating, have been explored. Under certain reasonable assumptions about the magnitude of the critical Richardson number, the correction to the conventional expression for the eddy heat flux, and the height dependence of the eddy diffusion coefficient, a very hot thermosphere could result, yielding exospheric temperatures more in tune with the bounds being suggested by the recent optical and radio occultation experiments.

Prasad, S. S.↗
NASA NTRS1981

Energetics of a sudden stratospheric warming simulated with a three-dimensional, spectral, quasi-geostrophic model

The energetics of a three dimensional, quasi-geostrophic simulation of a sudden stratospheric warming which developed spontaneously during an annual cycle simulation are described. Daily values of the stratospheric temperatures, zonal winds, heating rates, energies, and energy conversions are discussed and compared with those for observed warmings. It is shown that, like observed warmings, the simulated warming was preceded by an increased vertical flux of eddy kinetic energy from the troposphere and the polar heating resulted because of the strong convergence of the horizontal, eddy heat flux which was only partially balanced by adiabatic and diabatic cooling. There is a significant similarity between the energetics of the simulated and observed warmings. In addition, the warming was spontaneous and the model did not develop a major warming in each winter of the simulation. These facts suggest that this model may be useful for studying not only the warming process but also the conditions that favor its development.

Haggard, K. V.↗
NASA NTRS1974

Interhemispheric comparison of atmospheric circulation features as evaluated from Nimbus satellite data. A comparison of the structure and flow characteristics of the upper troposphere and stratosphere of the Northern and Southern Hemispheres

The general circulations of the Northern and Southern Hemispheres are compared with regard to the upper troposphere and stratosphere, using atmospheric structure obtained from multi-channel radiance data from the satellite infrared spectrometer instrument aboard the Nimbus 3 spacecraft. The inter-hemispheric comparisons are based on two months of data (one summer month and one winter month) in each hemisphere. Topics studied include: (1) mean meridional circulation in the Southern Hemisphere stratosphere; (2) magnitude and distribution of tropospheric eddy heat flux; (3) relative importance of standing and transient eddies in the two hemispheres; (4) magnitudes of energy cycle components; and (5) the relation of vortex structure to the breakdown climatology of the Antarctic stratospheric polar vortex.

Reiter, E. R.↗
NASA NTRS1999

Quantifying the Wave Driving of the Stratosphere

The zonal mean eddy heat flux is directly proportional to the wave activity that propagates from the troposphere into the stratosphere. This quantity is a simple eddy diagnostic which is easily calculated from conventional meteorological analyses. Because this "wave driving" of the stratosphere has a strong impact on the stratospheric temperature, it is necessary to compare the impact of the flux with respect to stratospheric radiative changes caused by greenhouse gas changes. Hence, we must understand the precision and accuracy of the heat flux derived from our global meteorological analyses. Herein, we quantify the stratospheric heat flux using five different meteorological analyses, and show that there are 30% differences between these analyses during the disturbed conditions of the northern hemisphere winter. Such large differences result from the planetary differences in the stationary temperature and meridional wind fields. In contrast, planetary transient waves show excellent agreement amongst these five analyses, and this transient heat flux appears to have a long term downward trend.

Newman, Paul A.↗
NASA NTRS1985

Transient Eddies in the UCLA GCM

The simulation of transient eddies in the nine level UCLA general circulation model (GCM) was examined and compared to observations, with emphasis on the Northern Hemisphere winter. Qualitatively, the UCLA GCM reproduces many features of the observed circulation and the relationship between the time mean flow and transient eddies; however, the magnitudes of transient eddies in the UCLA GCM, particularly at frequencies lower than those associated with baroclinic instability, appear to be much less than those observed. The pattern of low level transient eddy heat fluxes were similar to observations and acted to dissipate the low level seasonal mean temperature field. The simulated transient eddy kinetic energy at 300 mb is given for eddies of all time scales shorter than a season.

White, G. H.↗
NASA NTRSDate not supplied

An Examination of Autumn Southern Polar Ozone Tendencies and the Residual Circulation in MERRA-2 Products

Changes in lower stratospheric ozone caused by dynamical transport can be difficult to characterize and thus are sometimes difficult to distinguish from chemical losses. Correlations between ozone changes and various dynamical proxies (e.g., the eddy heat flux) from year to year can be of interest, but they do little in themselves to explain the ozone transport mechanisms behind such correlations. In this study, we use products from the Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) to calculate the ozone mass flux, integrating it in space and time over the upper tropospheric/lower stratospheric Southern polar cap during periods when little chemical loss is expected. The ozone mass flux is expressed in terms of components of the residual circulation of the Transformed Eulerian Mean (TEM, i.e., 𝑣𝑣̅ ∗and 𝑤𝑤(∗) as well as eddy mixing terms. We relate these terms to the local ozone mass tendency ("#! "$ ), similarly integrated, and we find that the interannual variability of the ozone changes are strongly related to the residual meridional circulation and the meridional eddy mixing terms. These directly calculated dynamical transport terms provide clearer ozone proxies. Removing these advective terms from a long-term ozone time series can more effectively reveal ozone variations and long-term trends, specifically those caused by photochemical production and losses (e.g., human-produced ozone depletion).

Ozone↗
NASA NTRS1973

Interhemispheric comparison of atmospheric circulation features as evaluated from Nimbus satellite data

Atmospheric structure derived from satellite, multichannel radiance data is used to calculate zonally averaged vertical motions in the wintertime stratosphere of both hemispheres using a heat budget approach. The Northern Hemisphere calculations based on the satellite data are shown to compare favorably with a computation carried out with conventional data, and with results of previous studies. The mean Southern Hemisphere pattern for the month of July 1969 indicates a two-celled structure with the high latitude cell centered at 60-65S. The axis of sinking motion in this cell is at approximately 50S, while the rising motion is centered at 70S. Thus the Antarctic stratospheric jet stream is associated with an indirect cell. Two individual ten-day periods from July 1969 are examined to compare the mean meridional circulation and eddy heat flux patterns in the Southern Hemisphere during a minor midwinter warming and during a quiet period.

Reiter, E. R.↗
NASA NTRS1974

A comparison of the structure and flow characteristics of the upper troposphere and stratosphere of the Northern and Southern Hemispheres

The general circulations of the Northern and Southern Hemispheres are compared with regard to the upper troposphere and stratosphere using atmospheric structure obtained from satellite, multi-channel radiance data. Specifically, the data are from the Satellite Infrared Spectrometer (SIRS) instrument aboard the Nimbus 3 spacecraft. The inter-hemispheric comparisons are based on two months of data (one summer month and one winter month) in each hemisphere. Topics studied include: mean meridional circulation in the Southern Hemisphere stratosphere; magnitude and distribution of tropospheric eddy heat flux; magnitudes of energy cycle components; and the relation of vortex structure to the breakdown climatology of the Antarctic stratospheric polar vortex.

Adler, R. F.↗
NASA NTRS1975

Mean meridional circulation in the Southern Hemisphere stratosphere based on satellite information

Atmospheric structure derived from satellite multi-channel radiance data is used to calculate zonally-averaged vertical motions in the wintertime stratosphere of both hemispheres using a heat budget approach. The Northern Hemisphere calculations based on the satellite data are shown to compare favorably with a computation carried out with conventional data, and with results of previous studies. The mean Southern Hemisphere pattern for the month of July 1969 indicates a high-latitude cell with the axis of sinking motion at approximately 50 deg S, while the rising motion is centered at 70 deg S. Thus the Antarctic stratospheric jet stream is associated with an indirect cell. Two individual 10-day periods from July 1969 are also examined to compare the mean meridional circulation and eddy heat flux patterns in the Southern Hemisphere during a minor midwinter warming and during a quiet period.

Adler, R. F.↗
NASA NTRS1978

On the mean meridional mass motions of the stratosphere and mesosphere

Using a simplified, approximate 'Lagrangian-mean' dynamical formulation, the mean meridional mass circulation of the stratosphere and mesosphere is discussed. Under solstice conditions, it is shown that this Lagrangian-mean circulation may be inferred, as a first approximation, from the Eulerian-mean diabatic heating. Diabatic heating rates for the solstices, originally derived by Murgatroyd and Goody (1958), result in Lagrangian-mean rising motion at the tropical tropopause, subsidence across the extra-tropical tropopause, and a very strong summer-to-winter pole flow in the mesosphere. This circulation is exactly that obtained by Murgatroyd and Singleton (1961) for the solstices. Those authors, however, attempted to identify this circulation as the Eulerian-mean motion, and were later criticized for their neglect of the meridional eddy heat flux in the calculation, which proved to be extremely important in the winter hemisphere. The present study, nevertheless, indicates that Murgatroyd and Singleton's circulation may in fact be representative of actual air parcel motions in the stratosphere and mesosphere.

Dunkerton, T.↗
NASA NTRS1981

On the warming of the polar troposphere during the stratospheric warming of January 1977

In January 1977, a warming of the polar troposphere occurred following a major stratospheric warming. The temperature increase in the polar troposphere is found to be larger below 400 mb than in the upper troposphere. Analysis of the heat budget of the polar troposphere shows that the eddy heat flux convergence is the major factor responsible for the tropospheric warming.

Hansen, A. R.↗
NASA NTRS1985

Middle atmosphere modeling

Breaking gravity waves generate and maintain a background level of turbulence which is capable of producing substantial cooling and/or heating in the upper mesosphere and lower thermosphere. The net thermodynamic effect of breaking gravity waves is critically dependent on the eddy Prandt number (P sub t) applicable to mesospheric turbulence. When P sub t is approximately 1, the calculations of the heat budget for the mesopause region imply that the globally averaged eddy or turbulent diffusion coefficient cannot exceed .000001 sq cm/s. This upper limit on turbulant diffusion applies to both potential temperature transport and chemically inert tracer transport when radiative damping is neglible. For chemically active species larger diffusion coefficients are permitted, because the effective eddy diffusion coefficient is increased by an additive term L/2 gamma (sup 2), where L is the chemical loss rate and gamma is the vertical wavenumber. For P sub t is approximately 4 to 6, the turbulent diffusion of momentum (D sub M) is sufficiently greater than the turbulent diffusion of heat (D sub H) that the conversion of gravity wave energy to heat with high efficiency nearly balances the divergence of the downward eddy heat flux in the wave breaking zone. Therefore the heat budget of the mesopause region would no longer provide a powerful and useful constraint on D sub H. If P sub t exceeds 6 with high efficiency for energy conversion to heat, gravity waves would heat the mesosphere throughout the wave breaking region.

Strobel, D. F.↗
NASA NTRS1992

An investigation into the causes of stratospheric ozone loss in the southern Australasian region

Measurements of total ozone at Macquarie Island (55 deg S, 159 deg E) reveal statistically significant reductions of approximately twelve percent during July to September when comparing the mean levels for 1987-90 with those in the seventies. In order to investigate the possibility that these ozone changes may not be a result of dynamic variability of the stratosphere, a simple linear model of ozone was created from statistical analysis of tropopause height and isentropic transient eddy heat flux, which were assumed representative of the dominant dynamic influences. Comparison of measured and modeled ozone indicates that the recent downward trend in ozone at Macquarie Island is not related to stratospheric dynamic variability and therefore suggests another mechanism, possibly changes in photochemical destruction of ozone.

Lehmann, P.↗
NASA NTRS1993

GCM simulations of intraseasonal variability in the Pacific/North American region

General circulation model (GCM) simulations of low-frequency variability with time scales of 20 to 70 days are analyzed for the Pacific sector during boreal winter. The GCM's leading mode in the upper-tropospheric zonal wind is associated with fluctuations of the East Asian jet; this mode resembles, in both structure and amplitude, the Pacific/North American (PNA) pattern found in the observations on these time scales. In both the model and observations, the PNA anomaly is characterized by: (1) a linear balance in the upper-tropospheric vorticity budget with no significant Rossby wave source in the tropics, (2) a barotropic conversion of kinetic energy from the time mean Pacific jet, and (3) a north/south displacement of the Pacific storm track. In the GCM, the latter is associated with synoptic eddy heat flux and latent heat anomalies that appear to contribute to a strong lower-tropospheric source of wave activity over the North Pacific. This is in contrast to the observations, which show only a weak source of wave activity in this region.

Schubert, Siegfried↗
NASA NTRS1993

Rotational effects on convection simulated at different latitudes

We simulate numerically convection inside the solar convection zone under the influence of rotation at different latitudes. The computational domain is a small rectangular box with stress-free upper and lower boundaries, and with periodicity assumed in the lateral directions. We study the transport of angular momentum, which is important for the generation of differential rotation. The sign and the latitudinal dependence of the horizontal Reynolds stress component turn out to be in good agreement with correlation measurements of sunspot proper motions and with predictions from the theory of the Lambda effect. We also investigate the other components of the Reynolds stress as well as the eddy heat flux tensor, both of which are needed in mean field models of differential rotation.

Pulkkinen, Pentti↗
NASA NTRS1993

Thermodynamic balance of three-dimensional stratospheric winds derived from a data assimilation procedure

The NASA/Goddard three-dimensional chemistry and transport model is driven by winds from a stratospheric data assimilation system. Synoptic- and planetary-scale patterns, apparent in satellite observations of trace constituents, are successfully reproduced for seasonal integrations. As model integrations proceed, however, the quality of simulations decreases, and systematic differences between calculation and measurement appear. The differences are explained by examining the zonal-mean residual circulation. The vertical velocity w-bar (sup star) is calculated two ways: (1) from the diabatic heating rates and temperature tendency and (2) from the Eulerian vertical velocity and the horizontal eddy heat flux convergence. The results from these calculations differ substantially. Periodic insertion of observational data during the assimilation process continually shocks the general circulation model and produces these differences, which leads to an overestimate of the mean vertical heat and cconstituent transport. Such differences are expected to be general to all data assimilation products. This interpretation is corroborated by two-dimensional (2D) model calculations. When w-bar(sup star) is calculated from (2), the 2D ozone evolution is unrealistic and qualitatively similar to the 3D model simulation. The 2D ozone evolution is reasonable when w-bar (sup star) from (1).

Weaver, Clark J.↗
NASA NTRS2002

The Temperature of the Arctic and Antarctic Lower Stratosphere

The temperature of the polar lower stratosphere during spring is the key factor in changing the magnitude of ozone loss in the polar vortices. In this talk, we will review the results of Newman et al. [2000] that quantitatively demonstrate that the polar lower stratospheric temperature is primarily controlled by planetary-scale waves. In particular, the tropospheric eddy heat flux in middle to late winter (January--February) is highly correlated with the mean polar stratospheric temperature during March. Strong midwinter planetary wave forcing leads to a warmer spring Arctic lower stratosphere in early spring, while weak midwinter forcing leads to cooler spring Arctic temperatures. In addition, this planetary wave driving also has a strong impact on the strength of the polar vortex. These results from the Northern Hemisphere will be contrasted with the Southern Hemisphere.

Newman, Paul A.↗
NASA NTRS2009

Convective and Stratiform Precipitation Processes and their Relationship to Latent Heating

The global hydrological cycle is central to the Earth's climate system, with rainfall and the physics of its formation acting as the key links in the cycle. Two-thirds of global rainfall occurs in the Tropics. Associated with this rainfall is a vast amount of heat, which is known as latent heat. It arises mainly due to the phase change of water vapor condensing into liquid droplets; three-fourths of the total heat energy available to the Earth's atmosphere comes from tropical rainfall. In addition, fresh water provided by tropical rainfall and its variability exerts a large impact upon the structure and motions of the upper ocean layer. An improved convective -stratiform heating (CSH) algorithm has been developed to obtain the 3D structure of cloud heating over the Tropics based on two sources of information: 1) rainfall information, namely its amount and the fraction due to light rain intensity, observed directly from the Precipitation Radar (PR) on board the TRMM satellite and 2) synthetic cloud physics information obtained from cloud-resolving model (CRM) simulations of cloud systems. The cloud simulations provide details on cloud processes, specifically latent heating, eddy heat flux convergence and radiative heating/cooling, that. are not directly observable by satellite. The new CSH algorithm-derived heating has a noticeably different heating structure over both ocean and land regions compared to the previous CSH algorithm. One of the major differences between new and old algorithms is that the level of maximum cloud heating occurs 1 to 1.5 km lower in the atmosphere in the new algorithm. This can effect the structure of the implied air currents associated with the general circulation of the atmosphere in the Tropics. The new CSH algorithm will be used provide retrieved heating data to other heating algorithms to supplement their performance.

Tao, Wei-Kuo↗