Stellar occultations by turbulent planetary atmospheres - A wave-optical theory including a finite scale height
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Hubbard, W. B.↗
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Effects of turbulence on average refraction angles in occultations by planetary atmospheres
Four separable effects of atmospheric turbulence on average refraction angles in occultation experiments are derived from a simplified analysis, and related to more general formulations by B. S. Haugstad. The major contributors are shown to be due to gradients in height of the strength of the turbulence, and the sense of the resulting changes in refraction angles is explained in terms of Fermat's principle. Because the results of analyses of such gradient effects by W. B. Hubbard and J. R. Jokipii are expressed in other ways, a special effort is made to compare all of the predictions on a common basis. We conclude that there are fundamental differences, and use arguments based on energy conservation and Fermat's principle to help characterize the discrepancies.
Eshleman, V. R.↗
Ortho- and para-hydrogen in dense clouds, protoplanets, and planetary atmospheres
If ortho- and para-hydrogen achieve a thermal ratio on dynamical time scales in a molecular hydrogen cloud, then the specific heat is high enough in the temperature range 35-70 K to possibly induce hydrodynamic collapse. The ortho-para ratio in many interstellar cloud fragments is expected to meet this condition. The same may have been true for the primitive solar nebula. Detailed hydrodynamic and hydrostatic calculations are presented that show the effects of the assumed ortho-para ratio on the evolution of Jupiter during its protoplanetary phase. Some possible consequences of a thermalized ortho-para ratio in the atmospheres of the giant planets are also discussed.
Decampli, W. M.↗
Interstellar cloud material - Contribution to planetary atmospheres
A statistical analysis of the properties of dense interstellar clouds indicates that the solar system has encountered at least a dozen clouds of sufficient density to cause planets to accumulate nonnegligible amounts of some isotopes. The effect is most pronounced for neon. This mechanism could be responsible for much of the neon in Earth's atmosphere. For Mars, the predicted amount of neon added by cloud encounters greatly exceeds the present abundance.
Butler, D. M.↗
Evaporation of ice in planetary atmospheres: Ice-covered rivers on Mars
The evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. The thickness of the ice is governed principally by the solar flux which penetrates the ice layer and then is conducted back to the surface. Evaporation from the surface is governed by wind and free convection. In the absence of wind, eddy diffusion is caused by the lower density of water vapor in comparison to the density of the Martian atmosphere. For mean martian insolations, the evaporation rate above the ice is approximately 10 to the minus 8th power gm/sq cm/s. Evaporation rates are calculated for a wide range of frictional velocities, atmospheric pressures, and insolations and it seems clear that at least some subset of observed Martian channels may have formed as ice-chocked rivers. Typical equilibrium thicknesses of such ice covers are approximately 10m to 30 m; typical surface temperatures are 210 to 235 K.
Wallace, D.↗
Nephelometer evaluation for measurement of cloud parameters in earth and planetary atmospheres
Initial work was concerned with determining whether the radiation emitted from a laser source could be sufficiently collimated to provide a suitable source for a nephelometer-type instrument. It was necessary to develop a standard scatterer that could be used to evaluate the performance of a nephelometer. The possible use of a gallium arsenide diode as a radiation source also was investigated. The first of these utilized a single lens to focus the light scattered from a target onto a ring detector. The second configuration used reflecting and refracting axicons as optical-system elements. The work performed in each of these areas is described.
Ballard, G. S.↗
The origins and early histories of planetary atmospheres
Ancient dry river beds detected on Mars by the Viking spacecraft suggest that the early Martian atmosphere may have been much more massive than at present. Degassing of a late-accreting, volatile-rich veneer may account for the primitive atmosphere of both Mars and earth. The primitive earth atmosphere could have produced a greenhouse effect sufficient to maintain temperatures above 273 K without NH3 and with low solar luminosity. The Venutian veneer, according to preliminary Pioneer results, was probably richer in noble gases relative to carbon and nitrogen than were the Martian and earth veneers. The highly evolved atmosphere of Titan, the large satellite of Saturn, is also discussed.
Owen, T.↗
Evaporation of ice in planetary atmospheres - Ice-covered rivers on Mars
The existence of ice covered rivers on Mars is considered. It is noted that the evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. It is determined that even with a mean Martian insolation rate above the ice of approximately 10 to the -8th g per sq cm/sec, a flowing channel of liquid water will be covered by ice which evaporates sufficiently slowly that the water below can flow for hundreds of kilometers even with modest discharges. Evaporation rates are calculated for a range of frictional velocities, atmospheric pressures, and insolations and it is suggested that some subset of observed Martian channels may have formed as ice-choked rivers. Finally, the exobiological implications of ice covered channels or lakes on Mars are discussed.
Wallace, D.↗
Effective depth of spectral line formation in planetary atmospheres
The effective level of line formation for spectroscopic absorption lines has long been regarded as a useful parameter for determining average atmospheric values of the quantities involved in line formation. The identity of this parameter was recently disputed. The dependence of this parameter on the average depth where photons are absorbed in a semi-infinite atmosphere is established. It is shown that the mean depths derived by others are similar in nature and behavior.
Lestrade, J. P.↗
Planetary atmospheres
The present paper deals with some of the principal data on extraterrestrial atmospheres obtained during the period 1975-1978. The atmospheres of Venus, Mars, Jupiter, and the Jovian satellites are examined, showing that many first-order questions concerning composition, physical state, and kinematics of these atmospheres have been answered.
Ingersoll, A. P.↗
Formation of H2 on amorphous ice grains and their importance for planetary atmospheres
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Smoluchowski, R.↗
Two-stream approximations to radiative transfer in planetary atmospheres - A unified description of existing methods and a new improvement
Existing two-stream approximations to radiative transfer theory for particulate media are shown to be represented by identical forms of coupled differential equations if the intensity is replaced by integrals of the intensity over hemispheres. One set of solutions thus suffices for all methods and provides convenient analytical comparisons. The equations also suggest modifications of the standard techniques so as to duplicate exact solutions for thin atmospheres and thus permit accurate determinations of the effects of typical aerosol layers. Numerical results for the plane albedos of plane-parallel atmospheres are given for conventional and modified Eddington approximations, conventional and modified two-point quadrature schemes, the hemispheric-constant method and the delta-function method, all for comparison with accurate discrete-ordinate solutions. A new two-stream approximation is introduced that reduces to the modified Eddington approximation in the limit of isotropic phase functions and to the exact solution in the limit of extreme anisotropic scattering. Comparisons of plane albedos and transmittances show the new method to be generally superior over a wide range of atmospheric conditions (including cloud and aerosol layers), especially in the case of nonconservative scattering.
Meador, W. E.↗
A line parameter list for the nu2 and nu4 bands of /C-12/H4 and /C-13/H4, extended to J-prime = 25 and its application to planetary atmospheres
Line parameters (transition frequencies, line strengths, line widths, ground state energies and quantum identifications) for the nu2 and nu4 bands of (C-12)H4 and (C-13)H4 have been calculated for J-prime equal to or less than 25 using the simultaneous coupled fitting procedure of Gray and Robiette. Molecular constants for the nu2 band of (C-13)H4 were estimated from isotopic shifts from (C-12)H4 values. Agreement with laboratory spectra, where available, is always well within 1 kayser over the entire spectral range covered by the list. The most serious problem in comparison with laboratory data is the omission of lines belonging to 'hot' bands in this spectral region. This list is valuable in remote sensing problems for sorting out lines of trace species from weak methane lines and for determining the atmospheric opacity in relatively transparent spectral regions. Applications of the parameter list are demonstrated for remote sounding of the Jovian atmosphere.
Orton, G. S.↗
Application of the method of discrete ordinates to the solution of the transport equation in the case of an inhomogeneous planetary atmosphere
A version of the method of discrete ordinate (MDO) which can be used for an optically thick inhomogeneous atmosphere was developed. The MDO may be implemented as an algorithm simpler than those proposed earlier. The algorithm is the same for each azimuth dependent component of intensity. The MDO can determine the scattered radiation field over its entire length along the vertical. It is shown the MDO, when used for homogeneous atmospheres is in agreement with the results obtained by other methods.
Zasova, L. V.↗
Inelastic scattering in planetary atmospheres. I - The Ring effect, without aerosols
The contribution of inelastic molecular scattering (Rayleigh-Brillouin and rotational Raman scattering) to the filling-in of Fraunhofer lines in the light of the blue sky is studied. Aerosol fluorescence is shown to be negligible, and aerosol scattering is ignored. The angular and polarization dependences of the filling-in detail for single scattering are discussed. An approximate treatment of multiple scattering, using a backward Monte Carlo technique, makes it possible to investigate the effects of the ground albedo. As the molecular scatterings alone produce more line-filling than is observed, it seems likely that aerosols dilute the effect by contributing unaltered sunlight to the observed spectra.
Kattawar, G. W.↗
Effective depth of spectral line formation in planetary atmospheres
The effective level of line formation for spectroscopic absorption lines has long been regarded as a useful parameter for determining average atmospheric values of the quantities involved in line formation. The identity of this parameter has recently been disputed. This paper reestablishes the dependence of this parameter on the average depth at which photons are absorbed in a semi-infinite atmosphere and shows that the mean depths derived by others are similar in nature and behavior.
Lestrade, J. P.↗
The rigid shell component for superrotation in planetary atmospheres: Angular momentum budget, mechanical analog and simulation of the spin up process
An analysis of superrotation in the atmosphere of planets, with rotation axis perpendicular to the orbital plane is presented. As the atmosphere expands, Hadley cells develop producing a redistribution of mass and angular momentum. A three dimensional thermally driven zonally symmetric spectral model and Laplace transformation simulate the time evolution of a fluid leading from corotation under globally uniform heating to superrotation under globally nonuniform heating. For high viscosities the rigid shell component of atmospheric superrotation can be understood in analogy with a pirouette. During spin up angular momentum is transferred to the planet. For low iscosities, the process is reversed. A tendency toward geostrophy, combined with increase of surface pressure toward the poles (due to meridional mass transport), induces the atmosphere to subrotate temporarily at lower altitudes. Resultant viscous shear near the surface permits angular momentum to flow from the planet into the atmosphere propagating upwards to produce high altitude superrotation rates.
Mayr, H. G.↗
Planetary atmospheres program
Chemical and physical models of the Jovian subnebula are addressed. Halide cloud condensation and volatile element inventories on Venus and considered. Computation methods for isolated grain condensation behavior are examined.
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