Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “heat tracer”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Constraints on gravity wave induced diffusion in the middle atmosphere

A review of the important constraints on gravity wave induced diffusion of chemical tracers, heat and momentum is given. Ground-based microwave spectroscopy measurements of H2O and CO and rocket-based mass spectrometer measurements of Ar constrain the eddy diffusion coefficient for constituent transport (K sub zz) to be (1-3) x 10 to the 5th sq cm/sec in the upper mesosphere. Atomic oxygen data also limits K sub zz to a comparable value in the mesopause. From the energy balance of the upper mesosphere the eddy diffusion coefficient for heat transport (D sub H) is, at most, 6 x 10 to the 5th sq cm/sec at the mesopause and decreasing substantially with decreasing altitude. The available evidence for mean wind deceleration and the corresponding eddy diffusion coefficient for momentum stresses (D sub M) suggests that it is at least 1 x 10 to the 6th sq cm/sec in the upper mesosphere. Consequently the eddy Prandtl number for macroscopic scale lengths is greater than 3.

Strobel, Darrell F.↗
NASA NTRS1989

Constraints on gravity wave induced diffusion in the middle atmosphere

A review of the important constraints on gravity wave induced diffusion of chemical tracers, heat and momentum is given. Ground-based microwave spectroscopy measurements of H20 and CO and rocket-based mass spectrometer measurements of Ar constrain the eddy diffusion coefficient for constituent transport (K sub zz) to be (1-3) x 10 to the 5th sq cm/sec in the upper mesosphere. Atomic oxygen data also limits K sub zz to a comparable value in the mesopause. From the energy balance of the upper mesosphere the eddy diffusion coefficient for heat transport (D sub H) is at most, 6 x 10 to the 5th sq cm/sec at the mesopause and decreasing substantially with decreasing altitude. The available evidence for mean wind deceleration and the corresponding eddy diffusion coefficient for momentum stresses (D sub M) suggests that it is at least 1 x 10 to the 6th sq cm/sec in the upper mesosphere. Consequently the eddy Prandtl number for macroscopic scale lengths is greater than 3.

Strobel, Darrell F.↗
NASA NTRS1997

The Effect of Enhanced Diabatic Heating on Stratospheric Circulation

The objective of this research focuses on the stratospheric dynamical response to the increase in aerosol loading and subsequent enhanced diabatic heating resulting from the eruption of Mt. Pinatubo. The Langley research Center three dimensional general circulation model and modifications made to that model for this study are described (addition of hydrogen fluoride tracer and diabatic heating enhancement). Unperturbed hydrogen fluoride distribution is compared to the hydrogen fluoride distribution measured by HALOE. A comparison of control and perturbed model runs is presented.

Kleb, Mary M.↗
NASA NTRS1989

Introduction and data summary, chapter 5

A subset of data representing most of the participating model groups was discussed and reviewed. The results are presented for intercomparisons of that subset of data. Subsequent to the workshop, the various modeling groups had the opportunity to either update or add to the data sets discussed at the workshop. The overall revised data sets as of December 1988 are presented. Data from all the models (where available) are grouped according to: (1) photochemistry and radiation (photodissociation coefficients, and ultraviolet heating and infrared cooling); (2) transport (net radiative heating, tropospheric source tracer experiment, time-dependent source conserved tracer experiment, stratospheric source tracer experiment, and O3 column); (3) current atmosphere (integrated columns of trace gases, Cl(y) and NO(y), nitrogen gases, chlorine gases, O(x) and HO(x) gases, and source gases); and (4) perturbed circulations and temperatures. The data presented provide a detailed summary of the two-dimensional picture of the atmosphere as seen by current atmospheric models.

Source record↗
NASA NTRS1992

Self-diffusion of magnesium in spinel and in equilibrium melts - Constraints on flash heating of silicates

An isotopic tracer is used to measure Mg self-diffusion in spinel and coexisting melt at bulk chemical equilibrium. The diffusion coefficients were calculated from the measured isotope profiles using a model that includes the complementary diffusion of Mg-24, Mg-25, and Mg-26 in both phases with the constraint that the Mg content of each phase is constant. The activation energy and preexponential factor for Mg self-diffusion in spinel are, respectively, 384 +/- 7 kJ and 74.6 +/- 1.1 sq cm/s. These data indicate Mg diffusion in spinel is much slower than previous estimates. The activation energy for Mg self-diffusion in coexisting melt is 343 +/- 25 kJ and the preexponential factor is 7791.9 +/- 1.3 sq cm/s. These results are used to evaluate cooling rates of plagioclase-olivine inclusions (POIs) in the Allende meteorite. Given a maximum melting temperature for POIs of about 1500 C, these results show that a 1-micron radius spinel would equilibrate isotopically with a melt within about 60 min.

Sheng, Y. J.↗
NASA NTRS1993

Improved Large-Field Focusing Schlieren System

System used to examine complicated two- and three-dimensional flows. High-brightness large-field focusing schlieren system incorporates Fresnel lens instead of glass diffuser. In system with large field of view, image may also be very large. Relay optical subsystem minifies large image while retaining all of light. Facilities candidates for use of focusing schlieren include low-speed wind and water tunnels. Heated or cooled flow tracers or injected low- or high-density tracers used to make flows visible for photographic recording.

Weinstein, Leonard M.↗
NASA NTRS2016

The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) Contribution to CMIP6: Investigation of Sea-Level and Ocean Climate Change in Response to CO2 Forcing

The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) aims to investigate the spread in simulations of sea-level and ocean climate change in response to CO2 forcing by atmosphere-ocean general circulation models (AOGCMs). It is particularly motivated by the uncertainties in projections of ocean heat uptake, global-mean sealevel rise due to thermal expansion and the geographical patterns of sea-level change due to ocean density and circulation change. FAFMIP has three tier-1 experiments, in which prescribed surface flux perturbations of momentum, heat and freshwater respectively are applied to the ocean in separate AOGCM simulations. All other conditions are as in the pre-industrial control. The prescribed fields are typical of pattern and magnitude of changes in these fluxes projected by AOGCMs for doubled CO2 concentration. Five groups have tested the experimental design with existing AOGCMs. Their results show diversity in the pattern and magnitude of changes, with some common qualitative features. Heat and water flux perturbation cause the dipole in sea-level change in the North Atlantic, while momentum and heat flux perturbation cause the gradient across the Antarctic Circumpolar Current. The Atlantic meridional overturning circulation (AMOC) declines in response to the heat flux perturbation, and there is a strong positive feedback on this effect due to the consequent cooling of sea-surface temperature in the North Atlantic, which enhances the local heat input to the ocean. The momentum and water flux perturbations do not substantially affect the AMOC. Heat is taken up largely as a passive tracer in the Southern Ocean, which is the region of greatest heat input, while the weakening of the AMOC causes redistribution of heat towards lower latitudes. Future analysis of these and other phenomena with the wider range of CMIP6 FAFMIP AOGCMs will benefit from new diagnostics of temperature and salinity tendencies, which will enable investigation of the model spread in behaviour in terms of physical processes as formulated in the models.

thermosteric sea-level change↗
NASA NTRS2019

Extratropical Large-Scale Traveling Weather Systems in the Southern Hemisphere on Mars

From late-autumn through early-spring, the middle- and high-latitudes of both hemispheres of Mars and its predominantly carbon-dioxide atmosphere support mean equator-to-pole thermal contrasts, and then, support a strong mean westerly polar vortex. Observations from orbiting spacecraft indicate that this intense mean baroclinicity-barotropicity supports large-scale eastward traveling weather systems (i.e., transient, traveling synoptic-period waves, on the order of the Rossby deformation scale). On Earth, extratropical weather disturbances arise from wind-shear instabilities, and these are critical components of the terrestrial global circulation. So it is the case for Mars. Large-scale traveling weather systems on Mars serve as agents in the transport of heat, momentum and scalar and tracer quantities (e.g., atmospheric dust, watervapor, ice clouds, chemical species, etc). Such weather systems interact with other large-scale atmospheric circulation components, namely, quasi-stationary (i.e., forced Rossby) modes; global thermal tidal modes; and then, upon large-/continental- geographical scales, upslope/ down-slope flows amongst high relief, low relief, impact basins, and volcanic rises, and more. The character of Mars' traveling extratropical weather disturbances in its southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (i.e., Mars GCM), and one from the Agency's Mars Climate Modeling Center (MCMC) based at the NASA Ames Research Center. The climate model includes several complex atmospheric physical packages. With such physics modules, our global climate simulations present comparatively well with observations of the planet's current water cycle (Haberle et al.,2019). The climate model is "forced" with an annual dust cycle (i.e., nudged based on MGS/TES observations). Compared to the northern-hemisphere counterparts, the southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are less intense. Influences of the zonally asymmetric (i.e., east-west varying) topography on southern large-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern storm zone in late winter and early spring presents in the western hemisphere via orographic influences from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate dynamical differences amongst the simulations and these are presented.

Hollingsworth, Jeffery L.↗
NASA NTRS2005

Warm Molecular Gas Traced with CO J = 7 --> 6 in the Galaxy's Central 2 Parsecs: Dynamical Heating of the Circumnuclear Disks

We present an 11" resolution map of the central 2 pc of the Galaxy in the CO J = 7 --> 6 rotational transition. The CO emission shows rotation about Sgr A* but also evidence for noncircular turbulent motion and a clumpy morphology. We combine our data set with available CO measurements to model the physical conditions in the disk. We find that the molecular gas in the region is both warm and dense, with T approx. 200-300 K and n(sub H2) approx. (5-7) x 10(exp 4) cm(exp -3). The mass of warm molecular gas we measure in the central 2 pc is at least 2000 M(solar), about 20 times the UV-excited atomic gas mass, ruling out a UV heating scenario for the molecular material. We compare the available spectral tracers with theoretical models and conclude that molecular gas is heated with magnetohydrodynamic shocks with v approx. 10-20 km s(exp -1) and B approx. 0.3- 0.5 mG. Using the conditions derived with the CO analysis, we include the other important coolants, neutral oxygen and molecular hydrogen, to estimate the total cooling budget of the molecular material. We derive a mass-to-luminosity ratio of approx. 2-3 M(solar)(L(solar)exp -1), which is consistent with the total power dissipated via turbulent decay in 0.1 pc cells with v(sub rms) approx. 15 kilometers per second. These size and velocity scales are comparable to the observed clumping scale and the velocity dispersion. At this rate, the material near Sgr A* is dissipating its orbital energy on an orbital timescale and cannot last for more than a few orbits. Our conclusions support a scenario in which the features near Sgr A* such as the circumnuclear disk and northern arm are generated by infalling clouds with low specific angular momentum.

galatic nuclei↗
NASA NTRS1988

A 3-dimensional numerical simulation of the atmospheric injection of aerosols by a hypothetical basaltic fissure eruption

Researchers simulated the atmospheric response to a hypothetical basaltic fissure eruption using heating rates based on the Roza flow eruption. The simulation employs the Colorado State University Regional Atmospheric Model (RAMS) with scavenging effects. The numerical model is a three-dimensional non-hydrostatic time-split compressible cloud/mesoscale model. Explicit microphysics include prediction of cloud, rain, crystal, and hail precipitation types. Nucleation and phoretic scavenging are predicted assuming that the pollutant makes an effective cloud droplet nucleus. Smoke is carried as a passive tracer. Long and short wave radiation heating tendencies, including the effects of the smoke, are parameterized. The longwave emission by the lava surface is neglected in the parameterization and included as an explicit heating term instead. A regional scale domain of 100 x 100 km in the horizontal and 22 km high is used. The horizontal grid spacing is taken to be 2 km and the vertical spacing is taken to be 0.75 km. The initial atmospheric state is taken to be horizontally homogenous and based on the standard atmospheric sounding. The fissure is assumed to be 90 km long and oriented in a zig/zag pattern.

Tripoli, Gregory J.↗
NASA NTRS2016

Traveling Weather Disturbances in Mars Southern Extratropics: Sway of the Great Impact Basins

As on Earth, between late autumn and early spring on Mars middle and high latitudes within its atmosphere support strong mean thermal contrasts between the equator and poles (i.e. "baroclinicity"). Data collected during the Viking era and observations from both the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) indicate that this strong baroclinicity supports vigorous, large-scale eastward traveling weather systems (i.e. transient synoptic-period waves). Within a rapidly rotating, differentially heated, shallow atmosphere such as on Earth and Mars, such large-scale, extratropical weather disturbances are critical components of the global circulation. These wave-like disturbances act as agents in the transport of heat and momentum, and moreover generalized tracer quantities (e.g., atmospheric dust, water vapor and water-ice clouds) between low and high latitudes of the planet. The character of large-scale, traveling extratropical synoptic-period disturbances in Mars' southern hemisphere during late winter through early spring is investigated using a high-resolution Mars global climate model (Mars GCM). This global circulation model imposes interactively lifted (and radiatively active) dust based on a threshold value of the instantaneous surface stress. Compared to observations, the model exhibits a reasonable "dust cycle" (i.e. globally averaged, a more dusty atmosphere during southern spring and summer occurs). In contrast to their northern-hemisphere counterparts, southern synoptic-period weather disturbances and accompanying frontal waves have smaller meridional and zonal scales, and are far less intense synoptically. Influences of the zonally asymmetric (i.e. east-west varying) topography on southern large-scale weather disturbances are examined. Simulations that adapt Mars' full topography compared to simulations that utilize synthetic topographies emulating essential large-scale features of the southern middle latitudes indicate that Mars' transient barotropic/baroclinic eddies are significantly influenced by the great impact basins of this hemisphere (e.g., Argyre and Hellas). In addition, the occurrence of a southern storm zone in late winter and early spring is keyed particularly to the western hemisphere via orographic influences arising from the Tharsis highlands, and the Argyre and Hellas impact basins. Geographically localized transient-wave activity diagnostics are constructed that illuminate fundamental differences amongst such simulations and these are described.

Weather disturbances↗
NASA NTRS1992

A reexamination of the radiative balance of the stratosphere

The radiative balance of the stratosphere is examined in the light of the possible sensitivity of tracers to small changes in the diabatic heating. A comprehensive radiative transfer algorithm is developed on the basis of accurate and efficient methods for use in coupled stratospheric models of chemistry, dynamics, and radiative transfer, and the individual components of the code are validated against available line-by-line calculations. Finally, the results of different approximations commonly employed in radiative transfer algorithms are compared, and their effects on tracer transport are evaluated using a 2D ozone model.

Olaguer, Eduardo P.↗
NASA NTRS1996

ATMOS/ATLAS-3 Observations of Long-Lived Tracers and Descent in the Antarctic Vortex in November 1994

Observations of the long-lived tracers N2O, CH4 and HF obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument in early November 1994 are used to estimate average descent rates during winter in the Antarctic polar vortex of 0.5 to 1.5 km/month in the lower stratosphere, and 2.5 to 3.5 km/month in the middle and upper stratosphere. Descent rates inferred from ATMOS tracer observations agree well with theoretical estimates obtained using radiative heating calculations. Air of mesospheric origin (N2O less than 5 ppbV) was observed at altitudes above about 25 km within the vortex. Strong horizontal gradients of tracer mixing ratios, the presence of mesospheric air in the vortex in early spring, and the variation with altitude of inferred descent rates indicate that the Antarctic vortex is highly isolated from midlatitudes throughout the winter from approximately 20 km to the stratopause. The 1994 Antarctic vortex remained well isolated between 20 and 30 km through at least mid-November.

Abrams, M. C.↗
NASA NTRS1987

The stratosphere - Climatologies of the radiative heating and cooling rates and the diabatically diagnosed net circulation fields

Stratospheric solar, IR, and net radiative heating are calculated on a monthly basis using solar and IR radiative codes and satellite derived distributions of ozone, water vapor, and temperature. Divergence-free, zonally averaged, advective fields are diagnosed using the calculated diabatic heating; associated stream functions are derived. The stratospheric transport of inert tracers is studied. Analysis of the diagnosed advective fields reveal that: (1) entry into the mid- to upper stratosphere of tropospheric air is mainly from altitude regions of + or - 10 deg at the equatorial tropopause; (2) at latitudes poleward of + or - 15 deg, tracers transported from the troposphere into the stratosphere are transported toward the pole and then downward and out of the stratosphere; and (3) the presence of net cooling cells in the lower stratospheric polar regions is important. The interannual variability of the diabatic circulation is estimated using heating and advection fields derived from LIMS data.

Callis, Linwood B.↗
NASA NTRS1989

Ageostrophic effects on the stratospheric residual circulation and tracer distributions

The behaviors of idealized geostrophic and ageostrophic circulations forced by differential heating and parameterized eddy mixing in the absence of boundary drag are examined for a range of mixing values and boundary conditions, using a nonlinear version of Holton's (1986) channel model. It was found that geostrophic and ageostrophic flows can have fundamentally different behaviors. This may have important implications for the circulation and trace gas distributions in the stratosphere. It is shown that, as eddy forcing vanishes, an ageostrophic system is not constrained to approach radiative equilibrium and may tend to the limit of an inviscid diabatic circulation under a range of boundary conditions.

Hou, Arthur Y.↗
NASA NTRS1991

Transport of N2O in the stratosphere related to the equatorial semiannual oscillation

The double-peak structure observed in the distribution of N2O during the spring equinoctial condition is studied by means of a 2D time-dependent tracer model. The meridional transport circulation is determined from computed diabatic heating rates, and the horizontal eddy diffusion coefficients are computed as residuals by potential vorticity conservation, using observed mean winds to compute the budget of zonal mean potential vorticity. This model is used to predict the 30-d evolution of the observed N2O field. The integrated results are generally in good agreement with observed tracer fields up to the midstratosphere. It is proposed that standard climatologies underestimate the strength of the equatorial semiannual oscillation in the zonal mean wind and temperature fields.

Choi, Woo Kap↗
NASA NTRS1986

A dynamically based transport parameterization for one-dimensional photochemical models of the stratosphere

The net vertical tracer flux in the stratosphere is due primarily to advection by the global-scale mean meridional circulation, not to diffusion by turbulent eddies. Using a simple model of this circulation, it is shown that the net flux can be approximated by a flux-gradient relationship in which the vertical 'eddy transport' coefficient is proportional to the square of the diabatic heating rate and inversely proportional to the rate at which meridional tracer gradients are destroyed by horizontal eddy mixing and chemical damping. Thus the transport coefficient will differ for tracers with differing chemical lifetimes. Profiles computed for various source gases (CH4 N2O, CF2Cl2, and CFCl3) show that this parameterization provides an improvement over conventional formulations that utilize a single transport coefficient for all species.

Holton, J. R.↗