Theoretical investigation - The scattering of light by a planetary atmosphere Interim report, 22 Sep. - 22 Dec. 1965

Light scattering and polarization in planetary atmospher

Radiative effects of the El Chichon volcanic eruption. Preliminary results concerning remote sensing

The aerosols and gases resulting from the El Chichon volcanic eruption had, and may still have, significant effects on satellite measurements of the properties of the Earth's atmosphere. The sea surface temperature measured by the AVHRR was biased up to -2.5 C for many months. The total amount of ozone derived from TOMS with a standard algorithm was greatly in excess of the possible value. This apparent excess can now be explained in terms of additional absorption by SO2. Infrared temperature sounders have observed both positive and negative anomalies. These effects and others on many satellite measurements are addressed following a discussion of the history and composition of the ejecta remaining in the stratosphere. Finally, recommendations are made for further study to account for the effects of volcanic eruptions on satellite observations and for use of such observations to measure the characteristics of the ejecta

The effect of surface reflection and clouds on the estimation of total ozone from satellite measurements

The total amount of ozone in a vertical column is being measured by Nimbus 4 and 7 observations of the intensity of ultraviolet sunlight scattered from the earth. The algorithm for deriving the amount of ozone from the observations uses the assumption that the surface reflects the light isotropically and the albedo is independent of wavelength. The effects of anisotropic surfaces and clouds on the estimate of total ozone are computed for models of the earth-atmosphere system

Earth-atmosphere system and surface reflectivities in arid regions from LANDSAT multispectral scanner measurements

Programs for computing atmospheric transmission and scattering solar radiation were used to compute the ratios of the Earth-atmosphere system (space) directional reflectivities in the vertical direction to the surface reflectivity, for the four bands of the LANDSAT multispectral scanner (MSS). These ratios are presented as graphs for two water vapor levels, as a function of the surface reflectivity, for various sun elevation angles. Space directional reflectivities in the vertical direction are reported for selected arid regions in Asia, Africa and Central America from the spectral radiance levels measured by the LANDSAT MSS. From these space reflectivities, surface vertical reflectivities were computed applying the pertinent graphs. These surface reflectivities were used to estimate the surface albedo for the entire solar spectrum. The estimated albedos are in the range 0.34-0.52, higher than the values reported by most previous researchers from space measurements, but are consistent with laboratory measurements

The effect of finite field size on classification and atmospheric correction

The atmospheric effect on the upward radiance of sunlight scattered from the Earth-atmosphere system is strongly influenced by the contrasts between fields and their sizes. For a given atmospheric turbidity, the atmospheric effect on classification of surface features is much stronger for nonuniform surfaces than for uniform surfaces. Therefore, the classification accuracy of agricultural fields and urban areas is dependent not only on the optical characteristics of the atmosphere, but also on the size of the surface do not account for the nonuniformity of the surface have only a slight effect on the classification accuracy; in other cases the classification accuracy descreases. The radiances above finite fields were computed to simulate radiances measured by a satellite. A simulation case including 11 agricultural fields and four natural fields (water, soil, savanah, and forest) was used to test the effect of the size of the background reflectance and the optical thickness of the atmosphere on classification accuracy. It is concluded that new atmospheric correction methods, which take into account the finite size of the fields, have to be developed to improve significantly the classification accuracy

Effect of molecular anisotropy on the intensity and degree of polarization of light scattered from model atmospheres

Computations of the intensity, flux, degree of polarization, and the positions of neutral points are presented for models of the terrestrial gaseous and hazy atmospheres by incorporating the molecular anisotropy due to air in the Rayleigh scattering optical thickness and phase matrix. Molecular anisotropy causes significant changes in the intensity, flux and the degree of polarization of the scattered light. The positions of neutral points do not change significantly. When the Rayleigh scattering optical thickness is kept constant and the molecular anisotropy factor is included only in the Rayleigh phase matrix, the flux does not change and the intensity and positions of neutron points change by a small amount. The changes in the degree of polarization are still significant

Evolving collective behavior in an artificial ecology

Collective behavior refers to coordinated group motion, common to many animals. The dynamics of a group can be seen as a distributed model, each “animal” applying the same rule set. This study investigates the use of evolved sensory controllers to produce schooling behavior. A set of artificial creatures “live” in an artificial world with hazards and food. Each creature has a simple artificial neural network brain that controls movement in different situations. A chromosome encodes the network structure and weights, which may be combined using artificial evolution with another chromosome, if a creature should choose to mate. Prey and predators coevolve without an explicit fitness function for schooling to produce sophisticated, nondeterministic, behavior. The work highlights the role of species’ physiology in understanding behavior and the role of the environment in encouraging the development of sensory systems

Aerosol scattering of ultraviolet sunlight in the tropical maritime atmosphere

The effects of atmospheric aerosol scattering on the vertical profile of solar ultraviolet radiation are investigated. Measurements of diffuse and total ultraviolet radiation were made using a rocketborne optical sonde in the marine atmosphere of Antigua. During observations, the sun was at zenith. Vertical profiles of directly transmitted solar radiation were calculated by subtraction of the diffuse component from the total radiance. Using these values of direct downward solar UV-flux, the optical thickness of the atmosphere was derived as a function of altitude. Absorption by ozone was also considered. In the troposphere the values of observed optical thickness were in general equal to or lower than those expected theoretically from Rayleigh scattering alone. The measured radiation profiles were compared with those computed for a multiple scattering model atmosphere. Some computations regarding the interaction of UV-sunlight with maritime aerosols are presented

Nucleic acid and protein metabolism in yeasts, higher plants and plant virus infections

Research on nucleic acid and protein metabolism in yeasts, higherplants and in viral infections of higher plants is described.The antibiotic lomofungin, and 8-hydroxyquinoline were studied asinhibitors of ENA synthesis in yeast, and their mode of action wasshown to be by chelation of bivalent cations required for ENA.polymerase activity. The turnover of messenger RNA in yeast wasstudied using 8-hydroxyquinoline, and a mechanism of translationalcontrol over yeast protein synthesis proposed.Research on rates of ribosomal and messenger RNA synthesis in fission yeast (Schizosaccharomyces pombe) and budding yeast(Saccharomyces cerevisiae) suggested that for both species, synthetic rates of both types of macromolecule doubled after the period of DNA synthesis in each cell cycle. A simple model relating DNA content(gene dosage), rate of transcription and observed patterns of enzyme accumulation during the cell cycle was proposed for S_. pombe. The model was tested and elaborated by study of mutant cells differing in their genetic control over cell size; by examining haploid and diploid cells, and by a mathematical simulation. The results suggested that a cell-size related control operated over the rate of transcription, and could be important in control of cell growth rate and balanced exponential growth.Experiments with the higher plant cell cycle used the synchronous cell divisions induced in explants of Jerusalem artichoke tuber byexcision and culture. Freshly cut explants contained polyadenylated messenger RNA and ribosomal RNA. Messenger RNA synthesis predominated in the first few hours of culture; later, ribosomal ENA was accumulated in a stepwise manner, but the periodicity was shown not to be cell-cycle related. Ribosomal RNA synthesis was not required for induction of cell division or for the net accumulation of protein that occurred during the first two divisions. Two periods of putative messenger ENA synthesis were identified which were required for the occurrence of the succeeding divisions.Tobacco mosaic virus ENA was shown not to be polyadenylated, and not to have detectable méthylation. A previous report of nucleoside residues with cytokinin activity in this ENA could not be confirmed.Tobacco mosaic virus infection of tobacco plants inhibited synthesis and decreased stability of chloroplast ribosomal ENAs. Synthesis of cytoplasmic ribosomal RNA was initially stimulated, but was inhibited during active virus multiplication. Cytoplasmic ribosomal RNA stability was increased by infection. Virus infection reduced the rate of host protein synthesis by 75%» hut did not alter the host polyadenylated messenger RNA content, suggesting a control at the translational level. Changes in concentration of abscisic acid were measured after infection, and shown to be important in control of growth and ENA metabolism in infected plants.Constitutive resistance to tobacco mosaic virus controlled by the Tm-1 gene in tomato, and induced resistance to the virus in tobacco were studied, and information gained on the mechanism involved in each resistance. Methyl benzimidazol-2yl carbamate was found to inhibit tobacco mosaic virus multiplication in tobacco.NA metabolism was studied in germinating S_. pombe ascospores,and in germinating tobacco and carrot seeds.Methods were developed for detection of polyadenylated messenger 3ENAs, and for radioassay of ahscisic acid in plant extracts.A review article discussed the involvement of plant growth regulators in control of plant-virus interactions