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Capone, L. A.

Publications and source records attributed to Capone, L. A..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

A two-dimensional model simulation of the EL Chichon volcanic eruption cloud

Using a two-dimensional model of sulfate photochemistry, transport, and aerosol microphysics, a 2-year period following the eruptions of El Chichon have been simulated. Present calculations suggest that the residence time of the cloud in the stratosphere exceeds 2 years. The model reproduces the observed optical depth, lidar backscatter, and infrared extinction coefficients, if about 10 megatonnes of SO2 are injected. The major deficiency of the model is a somewhat too rapid transport.

Capone, L. A.↗
NASA NTRS1983

Galactic cosmic rays and N2 dissociation on Titan

The electromagnetic and particle cascade resulting from the absorption of galactic cosmic rays in the atmosphere of Titan is shown to be an important mechanism for driving the photochemistry at pressures of 1 to 50 mbar in the atmosphere. In particular, the cosmic ray cascade dissociates N2, a process necessary for the synthesis of nitrogen organics such as HCN. The important interactions of the cosmic ray cascade with the atmosphere are discussed. The N2 excitation and dissociation rates and the ionization rates of the principal atmospheric consituents are computed for a Titan model atmosphere that is consistent with Voyager 1 observations. It is suggested that HCN may be formed efficiently in the lower atmosphere through the photodissociation of methylamine. It is also argued that models of nitrogen and hydrocarbon photochemistry in the lower atmosphere of Titan should include the absorption of galactic cosmic rays as an important energy source.

Capone, L. A.↗
NASA NTRS1982

Predicted electrical conductivity between 0 and 80 km in the Venusian atmosphere

Calculations of the space charge, ion density, and conductivity in the Venus atmosphere were made. The presence of the cloud particles on Venus causes a profund reduction in the calculated values of the ion density and conductivity compared to the values that are obtained without consideration of the cloud particles. When the cloud particles are included in the calculations, the results for the ion density and conductivity are approximately the same as those of the terrestrial atmosphere at the same pressure-altitude. Because the particles span such a large range of sizes and are abundant over a substantial range of pressure, the space charge varies strongly with altitude and particle size. Differential settling of the particles is expected to produce weak electric fields in the clouds.

Borucki, W. J.↗
NASA NTRS1982

The satellite power system - Assessment of the environmental impact on middle atmosphere composition and on climate

Numerical models were developed to calculate the total deposition of watervapor, hydrogen, CO2, CO, SO2, and NO in the middle atmosphere from operation of heavy lift launch vehicles (HLLV) used to build a satellite solar power system (SPS). The effects of the contaminants were examined for their effects on the upper atmosphere. One- and two-dimensional models were formulated for the photochemistry of the upper atmosphere and for rocket plumes and reentry. An SPS scenario of 400 launches per year for 10 yr was considered. The build-up of the contaminants in the atmosphere was projected to have no significant effects, even at the launch latitude. Neither would there by any dangerous ozone depletion. It was found that H, OH, and HO2 species would double in the thermosphere. No measurable changes in climate were foreseen.

Whitten, R. C.↗
NASA NTRS1982

Prediction of corridor effect from the launching of the satellite power system

A diagnostic model is developed to define the parameters which control the corridor effect of contaminants deposited in a narrow latitudinal band of the earth's atmosphere by numerous launches of the STS and heavy lift launch vehicles for construction of satellite solar power systems. Identified factors included the pollution injection rate, the ambient background levels of the pollutant species, and the transport properties related to the dilution rate of the chemicals. If the chemical life of the pollutant was shorter or the same length of time as the transport time, alterations in the chemical production and loss rates were found to be parameters necessarily added to the model. A comparison with NASA Ames Research Center two-dimensional model results indicate that the corridor effect was possile with operations above 60 km in the case of H2O, H2, and NO production.

Borucki, W. J.↗
NASA NTRS1981

Formation of organic molecules on Titan

A mechanism is proposed for the formation of complex organic nitrogen compounds in the dense lower atmosphere of Titan. The mechanism is based on three-body association reactions with HCNH(+) ions formed by the reaction of N(+) with CH4, which lead to the production of ethyl cyanide, vinyl cyanide and cyanoacetylene. Calculations for a model atmosphere consistent with the preliminary interpretation of Voyager 1 data for the region of maximum cosmic ray activated chemistry, corresponding to a temperature between 150 and 160 K and a pressure of 20 mbar, are presented which show substantial organic nitrile and hydrogen cyanide production rates. Based on these production rates, it is expected that significant equilibrium concentrations of these compounds will be found on Titan.

Capone, L. A.↗
NASA NTRS1981

Long wavelength carbonyl sulfide photodissociation

The aeronomic implications of a preliminary observation of weak OCS photoabsorption above 270 nm are investigated. It is argued that the measured cross section is consistent with a forbidden transition in this wavelength region. Model calculations are made for the OCS photodissociation rates in daylight, the OCS and SO2 distributions in the upper atmosphere, and the budgets of sulfur in the stratosphere and OCS in the troposphere, assuming various extrapolations of the measured OCS absorption cross sections and quantum yields to longer wavelengths. It is shown that weak OCS absorption above 300 nm can have important consequences for all of these quantities. Laboratory and field experiments are identified which might lead to a better understanding of the atmospheric OCS cycle.

Turco, R. P.↗
NASA NTRS1981

Two-dimensional model studies of the effect of supersonic aircraft operations on the stratospheric ozone content

For a fleet of 250 aircraft, the change in the ozone column is predicted to be very close to zero; in fact, the ozone overburden may actually increase as a result of show that above 25 to 30 km the ozone abundance decreases via catalytic destruction, but at lower heights it increases, mainly as a result of coupling with odd hydrogen species. Water vapor released in the engine exhaust is predicted to cause ozone decreases; for the hypothetical engines used in the study, the total column ozone changes due to water vapor emission largely offset the predicted ozone increases due to NOx emission. The actual effect of water vapor may be less than calculated because present models do not include thermal feedback. Feedback refers to the cooling effect of additional water vapor that would tend to slow the NOx reactions which destroy ozone.

Whitten, R. C.↗
NASA NTRS1981

Implications of smaller concentrations of stratospheric OH - A two-dimensional model study of ozone perturbations

There is growing observational evidence that stratospheric OH concentrations are smaller than models have been predicting. Using very recent HOx reaction rate coefficient measurements in a two-dimensional photochemical model, results which support these observations are obtained. As a consequence of smaller OH concentrations, we show that perturbations of stratospheric ozone by NOx (SST emissions and nitrogen fertilizers) may be larger than expected, while perturbations due to added water vapor and chlorine (SSTs and chlorofluoromethanes, respectively) may be smaller.

Whitten, R. C.↗
NASA NTRS1981

Ozone photochemistry and OH - A two-dimensional model study

Recent measurements of key HO(x) reaction rates are presented which imply that OH concentrations at altitudes below 30 km are lower than those predicted by current photochemical models. The consequences of the lower OH abundances are examined with respect to calculated perturbations of ozone by added nitrogen oxides, chlorine, and water vapor. Consideration is also given to the perturbation of stratospheric ozone by continuing release of chlorofluoromethanes in light of the new HO(x) reaction rates. The ozone loss is found to be reduced by about 25% compared with earlier estimates, mainly because the reduced OH abundance below 30 km slows the reaction between OH and HCl.

Whitten, R. C.↗
NASA NTRS1981

Sensitivity tests of two-dimensional model predictions of corridor effects

Future aerospace-vehicle systems, such as supersonic transport fleets, the Space Shuttle (SS), and the Heavy-Lift Launch Vehicle (HLLV) system will inject substantial amounts of pollutants into the stratosphere. It is, therefore, pertinent to ask whether the operation of these systems will lead to deleterious effects in the atmosphere. The current investigation is concerned with the development of criteria to assess the likelihood of a detectable corridor effect being caused by the long-term deposition of pollutants at a single latitude. The sources are assumed to operate continuously and at a uniform rate for periods of many years. It is found that transport by meridional winds and by eddy processes acts to diminish the corridor effect by advecting the pollutants out of the region of injection and by mixing them with the ambient air. Attention is given to the altitude for which a detectable corridor effect can be expected for the hypothetical launching of 400 HLLV's per year for 10 years.

Borucki, W. J.↗
NASA NTRS1980

Cosmic ray synthesis of organic molecules in Titan's atmosphere

The possible synthesis of organic molecules by the absorption of galactic cosmic rays in an N2-CH4-H2 Titan model atmosphere has been studied. The cosmic-ray-induced ionization results in peak electron densities of 2000/cu cm, with NH(+), C3H9(+), and C4H9(+) being among the important positive ions. Details of the ion and neutral chemistry relevant to the production of organic molecules are discussed. The potential importance of N(2D) reactions with CH4 and H2 is also demonstrated. Although the integrated production rate of organic matter due to the absorption of the cosmic ray cascade is much less than that by solar ultraviolet radiation, the production of nitrogen-bearing organic molecules by cosmic rays may be greater.

Capone, L. A.↗
NASA NTRS1980

Environmental effects of SPS: The middle atmosphere

The heavy lift launch vehicle associated with the solar power satellite (SPS) would deposit in the upper atmosphere exhaust and reentry products which could modify the composition of the stratosphere, mesosphere, and lower ionosphere. In order to assess such effects, atmospheric model simulations were performed, especially considering a geographic zone centered at the launch and reentry latitudes.

Whitten, R. C.↗
NASA NTRS1980

Stratospheric ozone decrease due to chlorofluoromethane photolysis - Predictions of latitude dependence

A two-dimensional model is used to predict the 1990 reduction in ozone due to the chlorine compounds formed by chlorofluoromethane (CFM) photolysis when the CFM release rate is held constant at the 1975 value. The predicted globally averaged ozone reduction of 3.5% is similar to that predicted by one-dimensional models that did not include chlorine nitrate chemistry, and used lower values for the reactions rates of NO + HO2 yielding NO2 + OH and O3 + HO2 yielding OH + 2O2. When the 5.7 ppbv increase in chlorine compounds predicted by one-dimensional models to occur under steady-state conditions is simulated by the two-dimensional model, a 26% decrease in atmospheric ozone is predicted. The latitude dependence of the ozone reduction is discussed in terms of the relevant photochemical reaction and transport. The chemical reactions that most strongly influence the meridional dependence of the ozone depletion are identified as those associated with the reactions of chlorine monoxide and atomic oxygen, the recombination of ozone and atomic oxygen, and the photodissociation of molecular oxygen.

Borucki, W. J.↗
NASA NTRS1980

Nitrogen fertiliser and stratospheric ozone - Latitudinal effects

Substantial increases in atmospheric N2O resulting from the increased use of nitrogen fertilizers might cause large (to 10%) decreases in the stratospheric ozone content. Such ozone decreases would be caused by catalytic reaction cycles involving odd-nitrogen that is formed by N2O decomposition in the upper stratosphere. Turco et al. (1978), using a background chlorine level of 2 ppbv, have shown that if the measured values of specified reactions are used a 50% increase in N2O would lead to a 2.7% increase in the stratospheric column density, although the ozone content above 30 km would be reduced by more than 5%; they also estimated (unpublished data) that the change in the ozone column density caused by doubling the N2O abundance would be very close to zero (within about 0.1%). The present paper extends these calculations of N2O/ozone effects to two dimensions, thereby identifying the latitude dependence expected for such ozone perturbations. The effects of changes in stratospheric chlorine levels on predicted ozone changes are also discussed.

Whitten, R. C.↗
NASA NTRS1979

Cosmic ray ionization of the Jovian atmosphere

An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic-ray-induced cascade may be especially important in ionizing the atmosphere at levels where the total number density exceeds 10 to the 19th per cu cm (well below the ionospheric layers produced by solar EUV). A model containing both positive and negative ion reactions has been employed to compute electron and ion number densities. Peak electron number densities of the order of 1000 per cu cm may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH4(+) and CnHm(+) cluster ions, with n at least 2; it is suggested that the absorption of galactic cosmic-ray energy at such relatively high pressures in the Jovian atmosphere (M about 10 to the 18th to 10 to the 20th per cu cm) and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.

Capone, L. A.↗
NASA NTRS1978

SSTs, nitrogen fertiliser and stratospheric ozone

A recently revised model of the stratosphere is used to show that a substantial enhancement in the ozone layer could accompany worldwide SST fleet operations and that water vapor may be an important factor in SST assessments. Revised rate coefficients for various ozone-destroying reactions are employed in calculations which indicate a slight increase in the total content of stratospheric ozone for modest-sized fleets of SSTs flying below about 25 km. It is found that water-vapor chemical reactions can negate in large part the NOx-induced ozone gains computed below 25 km and that increased use of nitrogen fertilizer might also enhance the ozone layer.

Turco, R. P.↗