Radiative transfer in spherical shell atmospheres: II. Asymmetric phase functions     

George W. Kattawar  Charles N. Adams 《Icarus》1978,35(3):436-449

In this paper we investigate the effects of sphericity on the radiation reflected from a planet with a homogeneous, conservative scattering atmosphere of optical thicknesses of 0.25 and 1.0. We considered a Henyey-Greenstein phase function with asymmetry factors of 0.5 and 0.7. Significant differences were found when these results were compared with the plane-parallel calculations. Also, large violations of the reciprocity theorem, which is only true for plane-parallel calculations, were noted. Results are presented for the radiance versus height distributions as a function of planetary phase angle. These results will be useful to researchers in the field of remote sensing and planetary spectroscopy.  相似文献   

A pollution history of Chesapeake Bay     

Edward D. Goldberg  Vern Hodge  Minoru Koide  John Griffin  Eric Gamble  Owen P. Bricker  Gerry Matisoff  George R. Holdren  Ruth Braun 《Geochimica et cosmochimica acta》1978,42(9):1413-1425

Present day anthropogenic fluxes of some heavy metals to central Chesapeake Bay appear to be intermediate to those of the southern California coastal region and those of Narragansett Bay. The natural fluxes, however, are in general higher. On the bases of Pb-210 and Pu-239 + 240 geochronologies and of the time changes in interstitial water compositions, there is a mixing of the upper 30 or so centimeters of the sediments in the mid-Chesapeake Bay area through bioturbation by burrowing mollusks and polychaetes. Coal, coke and charcoal levels reach one percent or more by dry weight in the deposits, primarily as a consequence of coal mining operations.  相似文献   

Electrodynamic and gravitational effects of proca stresses in astrophysics     

George L. Murphy  Ronald R. Burman 《Astrophysics and Space Science》1978,56(2):363-370

If the photon were to have a rest mass near the best present upper limit,m3×10^–53 g, Maxwell's equations would be inapplicable over distances exceeding about 10¹⁵ cm, with profound implications for cosmic electrodynamics. This paper deals with electrodynamic and gravitational effects of the non-Maxwellian stresses which would be associated with large-scale magnetic fields in quasi-static plasmas in these circumstances. The existence of moderately dense interstellar gas clouds with relatively strong magnetization shows thatm10^–58 g. General relativity must be used to calculate even the Newtonian gravitational effects of electromagnetic fields, and it is shown here that the Newtonian potential caused by the non-Maxwellian stresses just cancels that caused by the non-Maxwellian energy density. Previous arguments based on the latter alone are therefore invalid.  相似文献   

Near-infrared polarization studies of Saturn and Jupiter     

James C. Kemp  Richard J. Rudy  Marcia J. Lebofsky  George H. Rieke 《Icarus》1978,35(2):263-271

Polarization measurements of Jupiter, Saturn, and Saturn's rings from 1 to 3.5 μm are presented. At 1.6 μm on the discs of the two planets, the radially directed limb polarizations observed in the visible undergo, in some cases, a surprising 90° rotation to a tangential direction, particularly on the poles. The only immediate explanation for this effect is double Mie scattering, due to aerosols which must be of the order of a micrometer in size. On Jupiter the patterns are not uniform and are not stable, reflecting variable aerosol concentrations on the two poles. The ring polarization is uniformly negative (E vector parallel to the ecliptic plane) from the visible through 3.5 μm, and is inversely proportional to the albedo. This is as expected from Wolff's model for scattering from rough solid surfaces; but the degree of polarization seems uncommonly high, exceeding 2% at 3.5 μm.  相似文献   

Scattering in the atmosphere of Venus: II. Effect of varying the scale height of the scattering particles     

George W. Kattawar  L.D.G. Young 《Icarus》1977,30(1):179-185

We have made calculations for the variation of equivalent width with phase angle (for a Venus-like atmosphere except that the cloud particles scatter isotropically). The effect of temperature variations, within our model atmosphere, is shown to be small. The effect of changing the scale height of the cloud relative to the scale height of the gas is much larger.  相似文献   

Far-infrared spectral observations of Venus,Mars, and Jupiter     

Dennis B. Ward  George E. Gull  Martin Harwit 《Icarus》1977,30(2):295-300

Spectra of Venus, Mars, and Jupiter between 45 and 115 μm have been obtained at a resolving power of ～10, observing from the NASA Lear Jet at an altitude of 13.7 km. The results are calibrated with lunar observations, and show Mars and Venus to have relatively constant brightness temperatures over this wavelength region, with Venus appearing somewhat warmer at longer wavelengths. The brightness temperature of Jupiter decreases slightly toward longer wavelengths.  相似文献   

Planetary isophotes as a clue to aerosol characteristics     

George W. Kattawar  Andrew T. Young 《Icarus》1977,30(2):367-376

A study was made to see how much information could be extracted from the Mariner 9 Mars isophotes taken at a phase angle of ～60°. We found that the Minneart functions and both isotropic and Rayleigh scattering could easily be ruled out, and that it was essential to use forward-peaked phase functions, which were computed from Mie theory. We could achieve isophotes similar to those observed assuming a semi-infinite dust cloud with a considerable variation in particle properties and size distribution, so long as the ratio of the multiply to singly scattered light was held within certain limits. These conditions are met by micron-sized, moderately absorbing mineral grains whose mean size should not be much larger than a micron. It was also found that a dust cloud of finite optical thickness bounded from below by a Lambert ground would fit the isophote data.  相似文献   

Tharsis province of Mars: Geologic sequence,geometry, and a deformation mechanism     

Donald U. Wise  Matthew P. Golombek  George E. McGill 《Icarus》1979,38(3):456-472

The early history of Mars included two large-scale events of great significance: (1) the lowering and resurfacing of one-third of the crust, followed closely by (2) evolution of the Tharsis bulge. Tharsis development apparently involved two stages: (1) an initial rapid topographic rise accompanied by the development of a vast radial fault system, and (2) an extremely long-lived volcanic stage apparently continuing to the geologic present. A deformational model is proposed whereby a first-order mantle convection cell caused early subcrustal erosion and foundering of the low third of the planet. Underplating and deep intrusion by the eroded materials beneath Tharsis caused isostatic doming. Minor radial gravity motions of surficial layers off the dome produced the radial fault system. The hot underplate eventually affected the surface to cause the very long-lived volcanic second stage. Deep crustal anisotropy associated with the locally NE-trending boundary between the highland two-thirds and the lowland one-third caused the NE elongation of many features of Tharsis.  相似文献   

Radiative transfer in spherical shell atmospheres. III. Application to Venus     

George W. Kattawar 《Icarus》1979,40(1):60-66

We have introduced a method of partitioning the radiance emerging from a planetary atmosphere in proportion to the average number of scatterings in each atmospheric layer in order to gain a more fundamental understanding of the so-called level of line formation. A realistic model of the Venus atmosphere was used to compute the radiance for a range of phase angles and two planetary colatitudes, namely, 20 and 90°. We computed the core and continuum radiances for the P(16) line of 8689-Å CO₂ band and introduced two ways of computing an effective temperature. Both definitions yielded similar results. We found that these effective temperatures varied little with phase angles up to 120°, but fell rather rapidly beyond this point. Also colder effective temperatures were found as we went from equator to pole. The results obtained are all consistent with the spectroscopic temperature determination from CO₂ band studies. We have also defined an effective optical depth, τ_eff, which we feel gives a better understanding of the level of line formation than other definitions used to date.  相似文献   

An objective Bayesian analysis of the change point problem     

Elías Moreno  George Casella  Antonio Garcia-Ferrer 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(3):191-204

The Bayesian literature on the change point problem deals with the inference of a change in the distribution of a set of time-ordered data based on a sample of fixed size. This is the so-called retrospective or off-line analysis of the change point problem. A related but different problem is that of the sequential change point detection, mainly analyzed from a frequentist viewpoint. While the former typically focuses on the estimation of the position in which the change point occurs, the latter is a testing problem which has a natural formulation as a Bayesian model selection problem. In this paper we provide such a Bayesian formulation, which generalizes previous formulations such as the well-known CUSUM stopping rule. We show that the conventional improper priors (also called non-informative, objective or default), cannot be used either for sequential detection of the change or for retrospective estimation. Then, we propose objective intrinsic prior distributions for the unknown model parameters. The normal and Poisson cases are studied in detail and examples with simulated and real data are provided.  相似文献