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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 433 records · Page 24
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NASA NTRS1985

Laboratory studies on the reactions between chlorine, sulfur dioxide, and oxygen - Implications for the Venus stratosphere

Fourier transform IR spectrophotometry is used to monitor the reactants and products in a Venus stratosphere simulation study involving the photolysis of mixtures of Cl2 and SO2, with and without O2 present in an atmosphere of N2. When several speculative reactions inferred from these experiments are incorporated by the Yung and DeMore (1982) model of Venus stratospheric chemistry, it emerges that SO2Cl2 is a key reservoir species for chlorine, and that the reaction between Cl and SO2 furnishes an important cycle for the destruction of O2 and the conversion of SO2 to H2SO4, thereby providing a possible solution to the photochemistry of the Venus stratosphere.

Demore, W. B.↗
NASA NTRS1985

Concentration of methane in the troposphere deduced from 1951 infrared solar spectra

The 1-2 percent increase in tropospheric methane determined from gas chromatographic measurements since 1977 has important implications for atmospheric photochemistry and climate. To extend the measurement baseline, solar absorption spectra have been analyzed and mean troposphere CH4 mixing ratios for the years 1951 and 1981, and an average rate of CH4 increase of 1.1 + or - 0.2 percent per year is found for this period.

Rinsland, C. P.↗
NASA NTRS1985

Implications of the comparison of ozone abundances measured by the Solar Mesosphere Explorer to model calculations

Two years of ozone measurements from the Solar Mesosphere Explorer satellite are compared to the results of a model of lower mesospheric photochemistry. The measured ozone mixing ratios are larger than those predicted by the model by as much as a factor of two at pressures near 0.1 mbar and 1.3 at 1.0 mbar using currently accepted reaction rate coefficients. The model is brought into good agreement with the measurements over a wide range of latitudes and solar zenith angles only if the efficiency of the odd hydrogen catalytic cycle which destroys odd oxygen is decreased by 30-50 percent.

Rusch, D. W.↗
NASA NTRS1985

A critical analysis of CLO and O3 in the mid-latitude stratosphere

The Caltech one-dimensional photochemical model is used to analyze important questions concerning the upper stratospheric O3 and the key HO(x), NO(x), and ClO(x) free radicals. The model is described and first order effects of the inclusion of diffuse radiation in a spherical rather than plane parallel atmosphere at solar zenith angles close to 90 deg are assessed. A comparison is made between photochemical theory and observations for upper stratospheric O3, where local photochemistry rather than dynamics should control the O3 abundance. The photochemical equilibrium relation for odd oxygen is studied, including the important radicals involves. It is concluded that a significant model ozone deficit exists in the upper stratosphere. Possible causes for such a discrepancy are investigated in light of current model and experimental uncertainties. In particular, the observational ratio of atomic oxygen to zone appears to disagree with the model results.

Froidevaux, L.↗
NASA NTRS1986

A global three-dimensional model of the circulation and chemistry of CFCl3, CF2Cl2, CH3CCl3, CCl4, and N2O

The use of a three-dimensional spectral model to study the tropospheric and stratospheric circulation, chemistry, and photochemistry of the CFCl3, CF2Cl2, CH3CCl3, CCl4, and N2O atmospheric species is examined. The components of the model are described. Lifetime, regional, and global trends and budgets for the species are evaluated. Calculated horizontal, vertical, and temporal distributions of the atmospheric species are compared with observations; good correlation is detected. The differences observed between calculated and observed surface distributions of CH3CCl3 and the vertical distribution of CCl4 are analyzed. The calculated global atmospheric lifetimes of CFCl3, CF2Cl2, CCl4, and N2O are 73, 210, 48, and 182 years, respectively.

Golombek, A.↗
NASA NTRS1985

A model investigation of the impact of increases in anthropogenic NOx emissions between 1967 and 1980 on tropospheric ozone

The impact of anthropogenic NOx emission on tropospheric ozone has been investigated. Two statistical models were used for estimating annual global emissions of NOx and for driving the trend in the emission for the years 1966-1980. Both models show a steady increase in the NOx emission, except for two brief periods of leveling off: after 1973 and after 1978. The impact was estimated by calculating the rates of emissions as functions of latitude, longitude, and year, with a one-dimensional (latitudinal) model, which included coupled tropospheric photochemistry and diffusive meridional transport. Steady-state photochemical calculations with prescribed NOx emissions appropriate for 1966 and 1980 indicate an ozone increase of 8-11 percent in the Northern Hemisphere, a result compatible with the rise in ozone suggested by the observations.

Dignon, J.↗
NASA NTRS1986

SAGE observations of stratospheric nitrogen dioxide

The global distribution of nitrogen dioxide in the middle to upper stratosphere (25-45 km altitude) for the period February 1979 to November 1981 has been determined from observations of attenuated solar radiation in the visible region 0.385-0.45 micron by the Stratospheric Aerosol and Gas Experiment (SAGE) satellite instrument. The SAGE-derived NO2 vertical profiles compare well with observations by balloon- and aircraft-borne sensors. The global SAGE NO2 distributions generally show a maximum in mixing ratio of 8 parts per billion by volume at about 35 km altitude near the equatorial latitudes at local sunset. The location of the mixing ratio peak moves synchronously with the overhead sun for the four different seasons. High-latitude NO2 column content shows strong seasonal variation, with a maximum in local summer and a minimum in local winter. Selected data at high-latitude winter seasons are presented, suggesting that the large variation shown could be explained by the coupling of both dynamics and photochemistry of the NO(x) species. Finally, profiles of the ratio of sunset to sunrise NO2 mixing ratios, peaking at about a factor of two at 30 km, are shown.

Chu, W. P.↗
NASA NTRS1986

Global distribution of peroxyacetyl nitrate

Peroxyacetyl nitrate (PAN) atmospheric concentration samples were collected hourly from an ocean vessel 50 mi off the continental coast traveling from Seattle to Chile in 1984. Air concentration data for PAN and light hydrocarbons (LHC) were also taken by aircraft in the same period over Wyoming and Colorado and over the eastern Pacific. The PAN concentrations were higher and more variable in the Northern Hemisphere than in the Southern Hemisphere, increased with altitude, and were higher in the winter than in summer. The summer PAN concentrations were higher in the continental troposphere than in the marine troposphere. The results show that photochemical models of the atmosphere which do not account for the reaction between nonmethane hydrocarbons and PAN will probably overestimate the abundances of NO(x) and HNO3. The collection of further PAN concentration data is recommended as a means to characterizing the moderating role of PAN in the photochemistry of the troposphere.

Singh, H. B.↗
NASA NTRS1985

SAGE studies of the waves and eddy fluxes of ozone and temperature near 55 deg during the late February 1979 stratospheric warming

Ozone data from the Stratospheric Aerosol and Gas Experiment have been used in conjunction with meteorological information to study the waves and eddy fluxes of ozone and temperature near 55 deg N during the late February 1979 stratospheric warming. The results indicate an intense poleward eddy ozone transport in the altitude range between approximately 24 and 38 km, and an equatorward transport above an altitude of about 38 km. It is found that this equatorward eddy ozone transport in the upper stratosphere was accompanied by a poleward eddy heat transport, as expected on the basis of the ozone photochemistry. The results also indicate that the phase relationship between ozone and temperature waves agrees qualitatively with existing model analyses.

Wang, P.-H.↗
NASA NTRS1985

Tropospheric chemistry

The chemistry of the background troposphere, the source region, and the transition regions are discussed. The troposphere is governed by heterogeneous chemistry far more so than the stratosphere. Heterogeneous processes of interest involve scavenging of trace gases by aerosols, cloud and precipitation elements leading to aqueous phase chemical reactions and to temporary and permanent removal of material from the gas phase. Dry deposition is a major removal process for ozone, as well as for other gases of importance in tropospheric photochemistry. These processes are also discussed.

Mohnen, V. A.↗
NASA NTRS1986

Planetary Fabry-Perot spectroscopy

Uranus and Jupiter HD/H2 spectra determine bulk D/H ratios which are significantly different from theoretical expectations, with the Uranus D/H about half the Jovian value. Feasibility of Mars photochemistry study with a PEPSIOS spectrometer was demonstrated with visible band O2, H2O, and CO2 spectra; and near infrared (1.57 micron) spectra of CO and CO2; and NASA/IRTF observations have been proposed in support of the Mars Observer mission objectives. Analysis of monochromatic images clearly resolve the azimuthal and radial structure in the Jovian nebula (ion partitioning, temperature structure, ion/neutral interactions), adding a unique and important post-Voyager perspective and providing a baseline for forthcoming Galileo experiments. Simultaneous ground based and IUE observations of Jovian nebula are under analysis. Doppler resolved image sequences (data cubes) of Io sodium neutrals clearly isolate the high velocity charge exchange jet, a sensitive ground-based probe of the tenuous neutral atmosphere of Io.

Trauger, J. T.↗
NASA NTRS1986

What can meteorites tell us about comets?

Cometary silicates, carbon, and volatiles are reviewed using data from the Halley probes, interplanetary dust particles, and cometary spectra. The origins of anhydrous Fe(2+)-bearing silicates; whether hydrated silicates, if present, were made by gaseous or liquid H2O3; sources of organic compounds: ion-molecule reactions, photochemistry, grain catalysis; sources of CO2 and of organic polymers; and interstellar molecules and grains in comets are discussed.

Anders, Edward↗
NASA NTRS1986

The geometric albedos of Uranus and Neptune between 2100 and 3350 A

Results are reported from large aperture IUE observations of the stratospheres of Uranus and Neptune. The data were collected using 16 Cyg A and B as solar analog stars. The spectra observed were similar to geometric albedos of the predicted in terms of Rayleigh-Raman scattering in the 2200-2800 A region. A falloff was observed near visible wavelengths, a factor which might be attributable to low-altitude haze absorbing in the 3000-4000 A interval. The data also indicated that the Uranus stratosphere does not strongly absorb UV radiation, and is not a good heating source. The stratospheric haze constituents over Uranus could therefore be condensates of CH4 and H2 photochemistry.

Wagener, R.↗
NASA NTRS1986

Vertical distributions of molecular hydrogen off the eastern and Gulf coasts of the United States

The vertical distributions of molecular hydrogen (H2) and carbon monoxide (CO) were determined during spiraling maneuvers from aircraft off the eastern coast of the United States and over the Gulf of Mexico. H2 was always at its lowest levels in the boundary layer, averaging about 500 parts per billion by volume (ppbv). H2 mixing ratios determined in the free troposphere were typically higher (600-700 ppbv), and often suggested a small progressive increase with altitude. Several large free-tropospheric H2 plumes (mixing ratios as high as 1-2 parts per million by volume) were implied by the data. These H2 plumes were not always accompanied by corresponding increases in CO mixing ratios. This result is most difficult to explain when it is noted that the primary atmospheric sources for molecular H2 are considered to be combustion and photochemistry, both of which should be strong CO sources also.

Cofer, Wesley R., III↗
NASA NTRS1986

Photochemical damping of inertio-gravity waves

A simple model is developed for the coupling effect of radiative heating and ozone photochemistry on inertio-gravity waves in the region 16-70 km. It is found that the photochemical damping rate is the weighted sum of the rates caused by two individual processes. One, suggested by Craig and Ohring, involves the temperature dependence of ozone reaction rate coefficients; the other, suggested by Leovy, involves the vertical gradient of the ozone mixing ratio. The relative importance of these two processes depends on the ratio of dynamical and chemical relaxation times. Calculations show that the most important region for coupling is near 48 km where the total relaxation time is 8 days for equinox and 6 days for summer midlatitude.

Zhu, Xun↗
NASA NTRS1986

The quasi-biennial oscillation of ozone in the tropical middle stratosphere - A one-dimensional model

A one-dimensional model of the quasi-biennial oscillation (QBO) of ozone in the tropical middle stratosphere is derived based on assumed (observed) zonal wind QBO in a coupled dynamic, radiative/photochemical system. It is found that the derived vertical variation of the ozone QBO amplitude has two maxima, one at 32 km and the other at 22 km, and a minimum at 28 km. These are in qualitative agreement with observations. In the height interval 30-35 km, the ozone QBO is closely related to temperature dependent photochemistry, and the ozone and temperature variations are out of phase. Below 28 km, where vertical ozone and thermal transports are important, ozone and temperature oscillations are in phase, but both are approximately 270 deg out of phase with the vertical wind variation.

Ling, Xiu-De↗
NASA NTRS1987

The use of atmospheric measurements to constrain model predictions of ozone change from chlorine perturbations

Atmospheric photochemistry models have been used to predict the sensitivity of the ozone layer to various perturbations. These same models also predict concentrations of chemical species in the present day atmosphere which can be compared to observations. Model results for both present day values and sensitivity to perturbation depend upon input data for reaction rates, photodissociation rates, and boundary conditions. A method of combining the results of a Monte Carlo uncertainty analysis with the existing set of present atmospheric species measurements is developed. The method is used to examine the range of values for the sensitivity of ozone to chlorine perturbations that is possible within the currently accepted ranges for input data. It is found that model runs which predict ozone column losses much greater than 10 percent as a result of present fluorocarbon fluxes produce concentrations and column amounts in the present atmosphere which are inconsistent with the measurements for ClO, HCl, NO, NO2, and HNO3.

Douglass, Anne R.↗
NASA NTRS1986

Atmospheres and ionospheres of the outer planets and their satellites

Essential aspects of physical and chemical processes in the atmospheres and ionospheres of the outer planets are examined in an introductory overview of current knowledge, intended both for graduate students of planetary science and for practicing scientists. Chapters are devoted to bulk atmospheric compositions, thermal structures, cloud structures, vertical mixing, photochemistry, the ionospheres, and the satellites. Measurement data are compiled in tables, and extensive graphs and diagrams are provided.

Atreya, Sushil K.↗