Comments on 'A three-dimensional model of dynamical processes in the Venus atmosphere'
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Rossow, W. B.↗
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Results for “atmospheric processing”
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Processing and display of atmospheric phenomenaa data
A series of technical efforts dealing with various atmospheric phenomena is described. Refinements to the Potential in an Electrostatic Cloud (PEC) model are discussed. The development of an Apple III graphics program, the NSSL Lightning Data Program and a description of data reduction procedures are examined. Several utility programs are also discussed.
Tatom, F. B.↗
Transport Processes in the Upper Atmosphere
A proposed study to measure aerodynamic and heat transfer coefficients within the thermo-fluid-dynamic range experienced by a tethered satellite and to compare the coefficients with previous correlations is discussed. Tests are proposed on a satellite of existing design, on a satellite design consisting of models carried aboard, and on a newly designed satellite devoted to energy, mass, and momentum transfer studies on particular geometries.
Carlomagno, G. M.↗
Ionic processes in the upper atmosphere
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Huntress, W. T.↗
Chemical processes in Triton's atmosphere and surface
The Neptune moon Triton may have an appreciable atmosphere; the preliminary calculations of Delitsky (1983) have suggested that there should be a significant resultant chemistry in a possible N2 ocean with dissolved CH4, given charged-particle radiolysis of gaseous mixtures and gamma radiolysis of N2-CH4 solutions. The latter will yield substantial quantities of organic products which will be partially soluble in any N2-CH4 liquid present. Attention is presently given to the energy sources available for Triton, in order to estimate rates of synthesis and ascertain the possible history of such simple and complex organic products on Triton's surface.
Delitsky, M. L.↗
Small scale MHD wave processes in the solar atmosphere and solar wind
Solar wind observations suggesting wave-particle interactions via ion-cyclotron resonances are reviewed. The required power at high frequencies is presumably supplied via a turbulent cascade. Tu's (1987) model, which considers a turbulent cascade explicitly, is outlined. In the solar atmosphere, resonance absorption is considered. The meanings of the cusp and Alfven resonances are discussed, and it is shown how energy gets pumped into small scales. It is shown that resonance absorption can heat the corona and spicules in a manner consistent with observations, if turbulence provides an eddy viscosity.
Hollweg, Joseph V.↗
Photochemical reactions of cyanoacetylene and dicyanoacetylene: Possible processes in Titan's atmosphere
Titan has an atmosphere which is subject to dramatic chemical evolution due mainly to the dramatic effect of the UV flux from the Sun. The energetic solar photons and other particles are converting the methane-nitrogen atmosphere into the unsaturated carbon compounds observed by the Voyager probes. These same solar photons are also converting some of these unsaturated reaction products into the aerosols observed in the atmosphere which obscure the view of the surface of Titan. In particular, the photochemical reactions of cyanoacetylene, dicyanoacetylene, acetylene and ethylene may result in the formation of the higher hydrocarbons and polymers which result in the aerosols observed in Titan's atmosphere. Polymers are the principal reaction products formed by irradiation of cyanoacetylene and dicyanoacetylene. Irradiation of cyanoacetylene with 185 nm of light also yields 1,3,5-tricyanobenzene while irradiation at 254 nm yields 1,2,4-tricyanobenzene and tetracyano cyclooctatetraenes. Photolyses of mixtures of cyanoacetylene and acetylene yields mono- and di- cyanobenzenes. The 1-Cyanocyclobutene is formed from the photochemical addition of cyanoacetylene with ethylene. The photolysis of dicyanoacetylene with acetylene yields 2,3-dicyano-1,3-butadiene and 1,2-dicyanobenzene. Tetracyano cyclooctatetraene products were also observed in the photolysis of mixtures of dicyanoacetylene and acetylene with 254 nm light. The 1,2-Dicyano cyclobutene is obtained from the photolysis dicyanoacetylene and ethylene. Reaction mechanisms will be proposed to explain the observed photoproducts.
Ferris, J. P.↗
Volatile processes in Triton's atmosphere and surface
A basic model for latitudinal transport of nitrogen is reviewed focusing on its limitations and some complications associated with surface and atmospheric physics. Data obtained by 1989 Voyager encounter with the Neptune system revealed the complexity in the pure nitrogen transport which is caused by the nonuniform albedo of the frosts. It is concluded that Triton is similar to Mars in terms of the complexity of volatile transport and to understand Triton's surface-atmosphere system, Mars may be a very good analog.
Lunine, J. I.↗
Evidence for processed material in the atmospheres of Large Magellanic Cloud B supergiants
We present a high-dispersion study of the optical spectra of 11 LMC B-type supergiants. These stars had been shown previously to have a wide range in nitrogen absorption line strengths, despite having very similar temperatures and luminosities. The current study shows that the relatively rare nitrogen-weak stars also have weaker photospheric helium lines and stronger photospheric oxygen lines than the more spectroscopically typical supergiants. This pattern suggests that the vast majority of LMC B-type supergiants have had their surfaces contaminated by material from their original hydrogen-burning cores - with a resultant enhancement of surface nitrogen and helium and a depletion in oxygen - while the spectroscopically nitrogen-weak stars are more likely to have retained their main-sequence surface abundances.
Fitzpatrick, Edward L.↗
Dynamic processes in Be star atmospheres. 3: Rapid multiwavelength variability in gamma Cassiopeiae
A review of the characteristics of X-ray emission from gamma Cas suggests various weaknesses with conventional scenarios that invoke Be wind interactions with a putative binary companion. To explore whether this emission might arise instead from sporadic high-energy events on the Be star itself, we have examined the temporal behavior of Voyager 1 FUV spectra and He I lambda 6678 line profiles. The FUV continuum light curves show a continuous rapid variability with a range of greater than or = 0.2 mag over a timescale of approximately 1 hr. All indications are that this variability is real. The difference spectrum of the inferred fluctuating component is identical to the photospheric spectrum, ruling out an origin much hotter than the star's effective temperature. A histogram of flux differences formed from consecutive observations shows a flat-topped distribution out to 0.2 mag. This result bears a striking resemblance to histograms constructed from EXOSAT and Ginga data, suggesting that the X-ray and FUV variabilities could have a common origin. Evidence is also presented of rapid variability in optical spectral lines associated with the stars photosphere. Time series of difference profiles of the lambda 6678 line confirm the existence of migrating subfeatures reported by earlier studies. The comoving average of these profiles shows that these features have a shape resembling a symmetrical 'wave-packet'. Wave packets appear to be preceeded and rejuvenated by a sharp central absorption feature. We also report a transient emission feature in lambda 6678 that is similar to brief emissions once reported by Slettebak & Snow in UV resonance line profiles of Si IV and Mg II. We argue that the FUV and optical variability may find an explanation in terms of magnetic flares. Solar white-light flares offer a possible paradigm. However, problems remain with such explanations, in particular their high mean energy, frequency, and temperature.
Smith, Myron A.↗
Dynamic Processes in Be Star Atmospheres.: Simultaneous X-Ray, Ultraviolet, and Optical Variations in lambda Eridani - 6
This report describes a joint X ray/ultraviolet/ground based study of the abnormal Be star lambda Eri which has previously shown evidence of X ray flaring from Rosat observations in 1991. The 1991 flare event caught the astronomical hot star community by surprise because x ray flares have not been observed from other single B-type stars, before or since. Both optical (H-alpha) and UV/Voyager observations provide evidence for transient heating events near the surface of lambda Eri.
Smith, Myron A.↗
Modeling Chemical Growth Processes in Titan's Atmosphere: 1. Theoretical Rates for Reactions between Benzene and the Ethynyl (C2H) and Cyano (CN) Radicals at Low Temperature and Pressure
Density functional theory calculations at the B3LYP/6-31+G** level were employed to characterize the critical points for adducts, isomers, products, and intervening transition states for the reactions between benzene and the ethynyl (C2H) or cyano (CN) radicals. Both addition reactions were found to have no barriers in their entrance channels, making them efficient at the low temperature and pressure conditions that prevail in the haze-forming region of Titan's atmosphere as well as in the dense interstellar medium (ISM). The dominant products are ethynylbenzene (C6H5C2H) and cyanobenzene (C6H5CN). Hydrogen abstraction reactions were also characterized but found to be non-competitive. Trajectory calculations based on potentials fit to about 600 points calculated at the ROMP2/6-31+G** level for each interaction surface were used to determine reaction rates. The rates incorporated any necessary corrections for back reactions as ascertained from a multiwell treatment used to determine outcome distributions over the range of temperatures and pressures pertinent to Titan and the ISM and are in good agreement with the limited available experimental data.
Woon, David E.↗
Classification of Aerosol Retrievals from Spaceborne Polarimetry Using a Multiparameter Algorithm
In this presentation, we demonstrate application of a new aerosol classification algorithm to retrievals from the POLDER-3 polarimter on the PARASOL spacecraft. Motivation and method: Since the development of global aerosol measurements by satellites and AERONET, classification of observed aerosols into several types (e.g., urban-industrial, biomass burning, mineral dust, maritime, and various subtypes or mixtures of these) has proven useful to: understanding aerosol sources, transformations, effects, and feedback mechanisms; improving accuracy of satellite retrievals and quantifying assessments of aerosol radiative impacts on climate.
Atmospheric Processes Clouds & Aerosols↗
Characterization of Intermediates in Atmospherically Relevant Hydrocarbon Oxidation Processes.
Abstract not provided.
Taatjes, Craig A.↗
The role of impacting processes in the chemical evolution of the atmosphere of primordial Earth
The role of impacting processes in the chemical evolution of the atmosphere of primordial Earth is discussed. The following subject areas are covered: (1) Earth's initial atmosphere; (2) continuous degassing; (3) impact processes and the Earth's protoatmosphere; and (4) the evolution of an impact-generated atmosphere.
Mukhin, Lev M.↗
Chemical Imaging of Atmospheric Organic Particles in the Southern Great Plains Field Campaign Report
The main goal of this field project was to characterize the chemical and physical properties of atmospheric particles representative of the Southern Great Plains (SGP) environment to establish a relationship between the composition of aerosol particles and their atmospheric impacts. The specific research efforts were focused on in-depth microscopy studies of chemical and physical properties of atmospheric organic particles collected at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) SGP observatory. An array of novel molecular-level characterization and chemical imaging approaches were used to characterize chemical composition of particles and elucidate fundamental processes governing their atmospheric aging, evolution of chemical composition, optical properties, cloud formation ability, and implications for particle-cloud interactions – the most challenging problems relevant to predictive understanding of aerosol effects on climate.(1, 2) Atmospheric particles consist of a complex mixture of organic compounds with a wide range of molecular structures, morphologies, physical properties, and chemical reactivity. The chemical composition, morphology, and phase state of atmospheric particles are of crucial importance for understanding the formation and reaction mechanisms of particles, their atmospheric evolution, and their impact on climate. It is of great interest to understand how the chemical and morphological particle microstructure affects their physicochemical properties such as chemical reactivity, thermodynamics of gas-particle partitioning, phase separations inside individual particles, hygroscopicity, optical properties, and ability to form liquid droplets (cloud condensation nuclei) and ice crystals (ice nuclei) in clouds. The phase state of organic particles, which yet remains poorly understood, plays a key role in their physicochemical properties and has important implications in various atmospheric processes. Fundamental understanding of these physicochemical properties and their possible evolution in time requires advanced analytical approaches for chemical imaging of particles with a resolution on the scale of 10-100 nm.(3) Comprehensive characterization of the size-dependent chemical composition of individual particles collected at the site was carried out using advanced molecular-level characterization and imaging approaches to identify their possible sources and to correlate to their climatic properties.
Southern Great Plains, aerosols, HI-SCALE field ca↗
Simulation of nonstationary phenomena in atmospheric-pressure glow discharge
Nonstationary processes in atmospheric-pressure glow discharge manifest themselves in spontaneous transitions from the normal glow discharge into a spark. In the experiments, both so-called completed transitions in which a highly conductive constricted channel arises and incomplete transitions accompanied by the formation of a diffuse channel are observed. A model of the positive column of a discharge in air is elaborated that allows one to interpret specific features of the discharge both in the stationary stage and during its transition into a spark and makes it possible to calculate the characteristic oscillatory current waveforms for completed transitions into a spark and aperiodic ones for incomplete transitions. The calculated parameters of the positive column in the glow discharge mode agree well with experiment. Data on the densities of the most abundant species generated in the discharge (such as atomic oxygen, metastable nitrogen molecules, ozone, nitrogen oxides, and negative oxygen ions) are presented.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Modulation of the Seasonal Cycle of the Antarctic Sea Ice Extent By Sea Ice Processes and Feedbacks With the Ocean and the Atmosphere
The seasonal cycle of the Antarctic sea ice extent is strongly asymmetric, with a relatively slow increase after the summer minimum followed by a more rapid decrease after the winter maximum. This cycle is intimately linked to the seasonal cycle of the insolation received at the top of the atmosphere, but sea ice processes as well as the exchanges with the atmosphere and ocean may also play a role. To quantify these contributions, a series of idealized sensitivity experiments have been performed with an eddy-permitting (∘) NEMO-LIM3 (Nucleus for European Modelling of the Ocean–Louvain-la-Neuve sea ice model version 3) Southern Ocean configuration, including a representation of ice shelf cavities, in which the model was either driven by an atmospheric reanalysis or coupled to the COSMO-CLM2 regional atmospheric model. In those experiments, sea ice thermodynamics and dynamics as well as the exchanges with the ocean and atmosphere are strongly perturbed. This perturbation is achieved by modifying snow and ice thermal conductivities, the vertical mixing in the ocean top layers, the effect of freshwater uptake and release upon sea ice growth and melt, ice dynamics, and surface albedo. We find that the evolution of sea ice extent during the ice advance season is largely independent of the direct effect of the perturbation and appears thus mainly controlled by initial state in summer and subsequent insolation changes. In contrast, the melting rate varies strongly between the experiments during the retreat, in particular if the surface albedo or sea ice transport are modified, demonstrating a strong contribution of those elements to the evolution of ice coverage through spring and summer. As with the advance phase, the retreat is also influenced by conditions at the beginning of the melt season in September. Atmospheric feedbacks enhance the model winter ice extent response to any of the perturbed processes, and the enhancement is strongest when the albedo is modified. The response of sea ice volume and extent to changes in entrainment of subsurface warm waters to the ocean surface is also greatly amplified by the coupling with the atmosphere.
regional atmosphere ocean sea ice model↗