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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

A Cascade Model of Wave Turbulence with Applications to Surface Gravity and Capillary Waves

A heuristic approach to the derivation of power spectra of wave motion is described and applied to capillary waves. The case of gravity waves studied earlier is briefly reviewed. In contract to the previous studies, the nonlinearity of the wave motion is not required to be small, and the mean number of resonantly interacting wave harmonics is not limited to a smallest possible number (which is 4 for gravity waves on a deep fluid and 3 for capillary waves). The main external parameter of the problem is the input flux Q of the wave energy related to the mean wind velocity. Depending on its value, wave spectra take various forms---from that corresponding to the weak-turbulence limit to that corresponding to the saturated (Phillips') wave spectra...

Glazman, Roman E.↗
DOE OSTI2025

The Energy Exascale Earth System Model Version 3: 1. Overview of the Atmospheric Component

This paper describes the atmospheric component of the US Department of Energy's Energy Exascale Earth System Model (E3SM) version 3. Significant updates have been made to the atmospheric physics compared to earlier versions. Specifically, interactive gas chemistry has been implemented, along with improved representations of aerosols and dust emissions. A new stratiform cloud microphysics scheme more physically treats ice processes and aerosol‐cloud interactions. The deep convection parameterization has been largely improved with sophisticated microphysics for convective clouds, making model convection sensitive to large‐scale dynamics, and incorporating the dynamical and physical effects of organized mesoscale convection. Improvements in aerosol wet removal processes and parameter re‐tuning of key aerosol and cloud processes have improved model aerosol radiative forcing. The model's vertical resolution has increased from 72 to 80 layers with the extra eight layers added in the lower stratosphere to better simulate the Quasi‐Biennial Oscillation. These improvements have enhanced E3SM's capability to couple aerosol, chemistry, and biogeochemistry and reduced some long‐standing biases in simulating tropical variability. Compared to its predecessors, the model shows a much stronger signal for the Madden‐Julian Oscillation, Kelvin waves, mixed Rossby‐gravity waves, and eastward inertia‐gravity waves. Aerosol radiative forcing has been considerably reduced and is now better aligned with community best estimates, leading to significantly improved skill in simulating historical temperature records. Its simulated mean‐state climate is largely comparable to E3SMv2, but with some notable degradation in shortwave cloud radiative effect, precipitable water, and surface wind stress, which will be addressed in future updates.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1998

A Theoretical and Observational Study of Large and Small-Scale Dynamics in the Mesosphere and Lower Thermosphere in Support of TIMED

The long-term objectives of this IDS component of the TIMED mission are to define, through a combination of modeling and data analysis efforts, the influences of large- and small-scale waves (tidal, planetary, and gravity waves) on the circulation, structure, composition, and variability of the mesosphere and lower thermosphere. Particular emphasis is aimed at the TIMED core science objectives of defining the structure and energetics of the TIMED core region, approx. 60 to 180 km. To do so, however, it is also essential to understand the dynamical influences and contributions because of their considerable direct and indirect influences on structure and energetics. To accomplish these goals, we anticipate two parallel modeling efforts and a significant data analysis effort following TIMED launch. The modeling efforts will address both: the residual circulation response to mean and variable wave forcing of the MLT through development of a spherical model addressing balanced flow dynamics and transience and a more comprehensive effort addressing gravity wave propagation, interactions, nonlinearity, and spectral evolution and transports in canonical and realistic environments. The data analysis effort is envisioned to involve application of ground-based measurements and TIMED data analyses to a quantification of gravity wave forcing and effects at one or more sites with comprehensive measurement suites and extension of the inferred forcing globally, based on distributed ground-based measurements. Research results and publications resulting from the research are included.

Fritts, David C.↗
NASA NTRS1986

Middle Atmosphere Program. Handbook for MAP, volume 20

Various topics related to investigations of the middle atmosphere are discussed. Numerical weather prediction, performance characteristics of weather profiling radars, determination of gravity wave and turbulence parameters, case studies of gravity-wave propagation, turbulence and diffusion due to gravity waves, the climatology of gravity waves, mesosphere-stratosphere-troposphere radar, antenna arrays, and data management techniques are among the topics discussed.

Bowhill, S. A.↗
NASA NTRS1976

Midlatitude sporadic-E layers

The partially transparent echo from midlatitude sporadic E layers was recorded by ionosondes between the blanketing frequency and the maximum frequency. The theory that the midlatitude sporadic E layers are not uniform in the horizontal plane but contain localized regions of high electron density was evaluated using data obtained by incoherent scatter radar and found to provide a satisfactory explanation. The main features of midlatitude sporadic E layers are consistent with the convergence of metallic ions as described by the wind shear theory applied to gravity waves and tides. The interference of gravity waves with other gravity waves and tides can be recognized in the altitudes of occurrence and the structure of the layers. Small scale horizontal irregularities are attributed in some cases to critical level effects and in others to fluid instabilities. The convergence of a meteor trail can, under some circumstances, account for localized enhancement of the electron density in the layer.

Miller, K. L.↗
NASA NTRS2000

Modeling Planetary Waves in the Middle Atmosphere

In our 3D Numerical Spectral Model (NSM) that incorporates the Doppler Spread Parameterization of Hines, planetary waves are generated with zonal wavenumbers 1-4 that have amplitudes as large as 25 m/s and periods between 50 and 2 days. The waves are generated spontaneously, i.e., without external source, and presumably represent normal modes. Numerical experiments are discussed to shed light on the generation mechanisms. For the wavenumbers 1 and 2 with periods primarily between 4 and 15 days, both eastward and westward propagating waves are generated and their amplitudes are affected significantly by the gravity wave source. For the wavenumbers, 3 and 4 in the upper mesosphere, the waves are virtually monochromatic, with periods around 2.5 days and they propagate westward. These waves behave like Rossby gravity waves; their amplitudes are largest during solstice where the baroclinic instability is playing an important role, but the waves decay when the gravity wave momentum source is turned off. The planetary waves generated in the model produce large amplitude modulations of the diurnal tides at altitudes above 80 km, but contrary to expectations they are not playing an important role for the seasonal variations of the tides. Preliminary results show that such Rossby gravity waves are also generated near the tropopause and are influencing significantly the QBO that is generated in the model.

Mengel, J. G.↗
NASA NTRS1972

Internal gravity wave-atmospheric wind interaction - A cause of clear air turbulence.

The interaction between an internal gravity wave (IGW) and a vertical wind shear is discussed as a possible cause in the production of clear air turbulence in the free atmosphere. It is shown that under certain typical condition the interaction of an IGW with a background wind shear near a critical level provides a mechanism for depositing sufficient momentum in certain regions of the atmosphere to significantly increase the local mean wind shear and to lead to the production of turbulence.

Bekofske, K.↗
NASA NTRS1991

Evidence of gravity wave-tidal interaction observed near the summer mesopause at Poker Flat, Alaska

An analysis of gravity wave-tidal interaction observed near the mesopause by the MST radar at Poker Flat in July of 1986 is presented. The observations revealed daily mean wind maxima of about 60 m/sec westward and 20 m/sec southward with daily mean momentum fluxes, contributed by gravity waves with periods less than 1 hour of 4-5 sq m/sec sq eastward and 1-2 sq m/sec sq northward. Considerable hourly height variability was found to exist for both winds and momentum fluxes. A significant modulation of the fluxes by tidal winds was observed, characterized by out-of-phase correlations over a number of heights.

Wang, Ding-Yi↗
NASA NTRS1992

Seasonal and latitudinal variations of gravity wave-driven fluctuations in OH nightglow

A model which incorporates extended OH-layer emission and gravity-wave dynamics with eddy diffusivities is set forth to analyze seasonal and latitudinal variations in the OH nightglow. The 2D analysis is aimed at determining the nature of the relationship between the oscillation in intensity about a mean intensity and the oscillation in temperature of the emission region about a mean temperature. Competing eddy diffusivities modify the local values and altitudes of maximum wave amplitude, so long-period characterization of the relationship is imprecise. Seasonal trends in the relationship are noted for periods of several hrs or less that are primarily related to seasonal changes in the mesopause undisturbed temperature. Latitudinal trends are shown to be less pronounced, and trends that exist at intermediate periods are difficult to isolate due to interference effects.

Hickey, M. P.↗
NASA NTRS1994

'Downward control' of the mean meridional circulation and temperature distribution of the polar winter stratosphere

According to the 'downward control' principle, the extratropical mean vertical velocity on a given pressure level is approximately proportional to the meridional gradient of the vertically integrated zonal force per unit mass exerted by waves above that level. In this paper, a simple numerical model that includes parameterizations of both planetary and gravity wave breaking is used to explore the influence of gravity wave breaking in the mesosphere on the mean meridional circulation and temperature distribution at lower levels in the polar winter stratosphere. The results of these calculations suggest that gravity wave drag in the mesosphere can affect the state of the polar winter stratosphere down to altitudes below 30 km. The effect is most important when planetary wave driving is relatively weak: that is, during southern winter and in early northern winter. In southern winter, downwelling weakens by a factor of 2 near the stratospause and by 20% at 30 km when gravity wave drag is not included in the calculations. As a consequence, temperatures decrease considerably throughout the polar winter stratosphere (over 20 K above 40 km and as much as 8 K at 30 km, where the effect is enhanced by the long radiative relaxation timescale). The polar winter states obtained when gravity wave drag is omitted in this simple model resemble the results of simulations with some general circulation models and suggest that some of the shortcomings of the latter may be due to a deficit in mesospheric momentum deposition by small-scale gravity waves.

Garcia, Rolando R.↗
NASA NTRS1985

Equatorial waves in the NCAR stratospheric general circulation model

Equatorially trapped wave modes are very important in the tropical stratospheric momentum balance. Kelvin waves and mixed Rossby-gravity waves are believed to be responsible for the quasi-biennial oscillation of the zonal winds in the equatorial lower stratosphere. Both Kelvin and mixed Rossby-gravity waves have been identified in observations and in numerical models. Kelvin and mixed Rossby-gravity waves are identified in a general circulation model extending from the surface into the mesosphere and looks at the effect on the waves of lowering the top of the model.

Boville, B. A.↗
NASA NTRS1994

Meso-beta scale numerical simulation studies of terrain-induced jet streak mass and momentum perturbations

An in-depth analysis of observed gravity waves and their relationship to precipitation bands over the Montana mesonetwork during the 11-12 July 1981 CCOPE case study indicated two episodes of coherent waves. While geostrophic adjustment, shearing instability, and terrain were all implicated separately or in combination as possible wave generation mechanisms, the lack of upper-air data within the wave genesis region made it difficult to define the genesis processes from observations alone. The first part of this paper, 3D Numerical Modeling Studies of Terrain-Induced Mass/Momentum Perturbations, employs a mesoscale numerical model to help diagnose the intricate early wave generation mechanisms during the first observed gravity wave episode. The meso-beta scale numerical model is used to study various simulations of the role of multiple geostrophic adjustment processes in focusing a region for gravity wave genesis. The second part of this paper, Linear Theory and Theoretical Modeling, investigates the response of non-resting rotating homogeneous and continuously stratified Boussinesq models of the terrestrial atmosphere to temporally impulsive and uniformly propagating three-dimensional localized zonal momentum sources representative of midlatitude jet streaks. The methods of linear perturbation theory applied to the potential vorticity (PV) and wave field equations are used to study the geostrophic adjustment dynamics. The total zonal and meridional wind perturbations are separated into geostrophic and ageostrophic components in order to define and follow the evolution of both the primary and secondary mesocirculations accompanying midlatitude jetogenesis forced by geostrophic adjustment processes. This problem is addressed to help fill the gap in understanding the dynamics and structure of mesoscale inertia-gravity waves forced by geostrophic adjustment processes in simple two-dimensional quiescent current systems and those produced by mesoscale numerical models simulating the orographic and diabatic perturbation of three-dimensional quasi-geostrophically balanced synoptic scale jet streaks associated with complex baroclinic severe storm producing environments.

Lin, Yuh-Lang↗
NASA NTRS1973

Short and long periodic atmospheric variations between 25 and 200 km

Previously collected data on atmospheric pressure, density, temperature and winds between 25 and 200 km from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others were analyzed by a daily difference method and results on the distribution statistics, magnitude, and spatial structure of gravity wave and planetary wave atmospheric variations are presented. Time structure of the gravity wave variations were determined by the analysis of residuals from harmonic analysis of time series data. Planetary wave contributions in the 25-85 km range were discovered and found to have significant height and latitudinal variation. Long period planetary waves, and seasonal variations were also computed by harmonic analysis. Revised height variations of the gravity wave contributions in the 25 to 85 km height range were computed. An engineering method and design values for gravity wave magnitudes and wave lengths are given to be used for such tasks as evaluating the effects on the dynamical heating, stability and control of spacecraft such as the space shuttle vehicle in launch or reentry trajectories.

Justus, C. G.↗
DOE OSTI2026

Gravitational Waves as a Source of Large-Scale White Noise: New Constraints

A stochastic gravitational wave (GW) background sources a shear in the flow of cosmic fluid which, through non-linear mode coupling, generates large-scale white noise (LSWN) in the kurvature density field. Building on the LSWN framework of our previous work, we derive the amplitude of this GW-induced LSWN and translate the observational non-detection of LSWN into bounds on the production redshift and density of gravity waves. In particular, a minimal constraint on gravity waves with $z=0$ density parameter $Ω_\mathrm{GW0}^*$ in frequency band $f_*$ generated at redshift $z_*$ must satisfy ${z_*}^2\,Ω_\mathrm{GW0}^*<5\times10^7\,(f_*/\mathrm{nHz})^{3/2}$. This, for example, precludes the gravity waves recently detected by pulsar timing arrays \cite{NANOGrav:2023hvm} from being present before $z_*\sim10^8$, long after the quark hadron phase transition. While orders of magnitude stronger than other constraints on gravity waves, this is a minimal LSWN constraint as realistic modeling of early universe gravity wave production, including the granularity of the gravity-wave sources and the LSWN produced by the associated acoustic waves would probably tighten this constraint by orders of magnitude.

Barenboim, Gabriela [Valencia U., IFIC; Valencia U↗
NASA NTRS1979

Ionospheric and satellite remote sensing of tornadic storms

Gravity waves associated with tornadoes were studied by using a ground-based ionospheric sounding system and satellite visible and infrared photographs of clouds associated with storms. Examples were chosen from gravity waves associated with a group of tornadoes and with isolated tornadic storms. Ray tracing computation was carried out to identify the location of the wave source. It is found that the wave sources of gravity waves associated with tornadoes were located on the squall line and/or isolated clouds where the tornado touched down one hour after the gravity waves were excited.

Hung, R. J.↗
NASA NTRS1993

Gravity wave-driven fluctuations in the O2 atmospheric (0-1) nightglow from an extended, dissipative emission region

The wave-driven fluctuations in the O2(0-1) atmospheric nightglow is modeled and the parameter (eta) is calculated using a model that accounts for either three-body recombination of atomic oxygen atoms alone to form the O2(b exp 1 Sigma(g)(+)) state directly, or by the further inclusion of the process that allows the formation of the O2(c exp 1 Sigma(u)(-)) intermediate state. The calculations are performed for a latitude of 18 deg N and for the months of March and June. The general results, which display how (eta) varies with wave period, horizontal wavelength, season, and chemical scheme, show that for given values of wave period and horizontal wavelength it is not possible to discriminate between seasonal effects and between the effects of different chemical schemes at evanescent and short gravity wave periods. It is shown that, when quenching by atomic oxygen is ignored, the resulting values of (eta) calculated with the complete chemistry are similar to those obtained from the three-body recombination scheme alone.

Hickey, Michael P.↗
DOE OSTI2023

High-resolution lithospheric structure of continental China from joint inversion of surface wave and gravity data

The lithospheric structure of continental China has been previously determined by seismic travel time tomography, surface wave tomography, and joint inversion of body wave and surface wave data. However, due to the inherent limitations of seismic data, the lithospheric structure of continental China is still not well resolved in the shallow part and in some regions where the station coverage is relatively sparse. In this study, we aim at improving the lithospheric structure by joint inversion of seismic surface wave data and satellite gravity data to take advantage of the uniform distribution and complementary strength of the gravity data. Here, the empirical relationship between velocity and density is used as a bridge for joint inversion of surface wave and gravity data. The joint inversion shear-wave velocity Vs (density) model, named as USTClitho1.0g, can fit both surface wave and gravity data well. This high-resolution Vs model can better fit the active airgun source seismic arrival times and better delineate some features in continental China, such as the velocity contrast across the north–south gravity lineament (NSGL), the lithosphere thinning in eastern China, the crustal footprint of the Hainan mantle plume, the likely magma chamber beneath volcanos in northeast China, the middle-lower crust low velocity layer beneath the Tibetan plateau, and the tearing of subducted Indian mantle lithosphere. Our joint inversion Vs model can provide a reference model for geosciences in continental China and surrounding areas.

58 GEOSCIENCES↗