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  • Other Sources  (1,244)
  • LUNAR AND PLANETARY EXPLORATION  (880)
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  • 1990-1994  (1,244)
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  • 1991  (1,244)
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  • 1990-1994  (1,244)
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  • 1
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    Estimation of raindrop size distribution parameters from a dual-parameter spaceborne radar measurement (1991)
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    Publication Date: 2011-08-24
    Description: A method to estimate raindrop size distribution (DSD) parameters from a combined Zm profile and path-integrated attenuation is shown, and a test result of the method using the data from an aircraft experiment is presented. The 'semi' dual-parameter (SDP) measurement is employed to estimate DSD parameters using the data obtained from an aircraft experiment conducted by Communications Research Laboratory, Tokyo, in conjunction with NASA. The validity of estimated DSD parameters is examined using measured Ka-band radar reflectivities. The estimated path-averaged N(0) is consistent with the Ka/X Ze ratio, and the use of estimated DSD shows excellent agreement between the rain rates estimated from the X-band and K-band Zes. The feasibility of estimating DSD parameters from space is confirmed.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: In: International Conference on Radar Meteorology, 25th, Paris, France, June 24-28, 1991, Preprints (A93-37626 15-47); p. 384-387.
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  • 2
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    A potential method for the estimation of drop size distribution from a dual-wavelength airborne radar (1991)
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    Publication Date: 2011-08-24
    Description: In order to investigate the role of the drop size distribution (DSD) from a dual-wavelength airborne radar and to recover profiled rain rates, a procedure is described for the purpose of estimating the DSD. The method differs from previous approaches in that it provides 2n + 1 parameters of the profiled DSD (where n is the number of range gates) and it uses a recursive procedure beginning at the range gate near the surface progressing backwards toward the storm top. The method is argued to be useful both as a diagnostic tool and as a means by which more detailed information on the vertical structure of the precipitation can be obtained.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: In: International Conference on Radar Meteorology, 25th, Paris, France, June 24-28, 1991, Preprints (A93-37626 15-47); p. 380-383.
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  • 3
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    Meteorological radar methods for validating space observations of precipitation (1991)
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    Publication Date: 2011-08-24
    Description: Meteorological approaches to verification of space measurements of rainfall are examined; validation of Tropical Rainfall Measuring Mission (TRMM) observations is expected to depend significantly on ground-based radars. Two methods of comparison are initially contemplated. TRMM rainfall data over time periods of a month for large areas (500 x 500 km) are averaged and compared with similarly averaged ground truth measurements. Both the rainfall and height distribution data from TRMM are compared with the instantaneous values observed at one or more 'ground truth' stations and from airborne radar and radiometers as available.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: In: International Conference on Radar Meteorology, 25th, Paris, France, June 24-28, 1991, Preprints (A93-37626 15-47); p. 374-379.
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  • 4
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    Comparison of numerically-simulated microphysical characteristics of convective storms with multiparameter radar observations during COHMEX (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The microphysical/dynamical nature and evolution of numerically simulated convective storms observed on July 11, 1986 during the Cooperative Huntsville Meteorological Experiments are investigated with the Goddard Cumulus Ensemble model. The model-simulated hydrometeor and radar reflectivity structure is verified with results derived from the multiparameter radar observations, which includes a description of the reflectivity, differential reflectivity, linear depolarization ratio, and hail signal for two thunderstorm cases analyzed by Fulton and Heymsfield (1990). Radar analysis shows the storm to split with the newer more vigorous cell in the SE quadrant. Echo tops are near 15 km while peak reflectivities exceed 50 dBZ. Preliminary model simulations likewise show a splitting storm with regeneration occurring on the SSE flank. Echo tops are around 14 km with peak reflectivities over 45 dBZ.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: In: International Conference on Radar Meteorology, 25th, Paris, France, June 24-28, 1991, Preprints (A93-37626 15-47); p. 706, 707.
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  • 5
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    Radar and microphysical characteristics of convective storms simulated from a numerical model using a new microphysical parameterization (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The basic features of a new and improved bulk-microphysical parameterization capable of simulating the hydrometeor structure of convective systems in all types of large-scale environments (with minimal adjustment of coefficients) are studied. Reflectivities simulated from the model are compared with radar observations of an intense midlatitude convective system. Simulated reflectivities using the novel four-class ice scheme with a microphysical parameterization rain distribution at 105 min are illustrated. Preliminary results indicate that this new ice scheme works efficiently in simulating midlatitude continental storms.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: In: International Conference on Radar Meteorology, 25th, Paris, France, June 24-28, 1991, Preprints (A93-37626 15-47); p. 782-785.
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  • 6
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    Atmospheric weather regimes over tropical South America (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Infrared radiance measurements by the GOES-6 satellite during April 1986 through April 1987 were used to characterize and identify distinct regimes of persistent large-scale cloudiness patterns over the Amazon Basin. It is suggested that the energetics of the tropical troposphere over the Amazon Basin can be directly related to the GOES large-scale cloudiness patterns. The geometry and persistence of the cloud patterns are influenced by shifts in general circulation features and are likely modulated by 4- to 5-day and 40- to 60-day waves. Diurnal forcing effects are more pronounced during weather regimes characterized by prominently clear skies over land areas.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: ; : Strong shock waves
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  • 7
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    Multi-parameter airborne rain radar experiment in the western Pacific (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The study presents preliminary results from an airborne radar/radiometer experiment (Typhoon Experiment) which was conducted in the western Pacific Ocean during September 1990, with emphasis on the multiparameter radar results. One of the objectives of this experiment is to make radar/radiometer measurements over rain to support the algorithm development and science studies for the Tropical Rainfall Measuring Mission (TRMM) and the spaceborne weather sensors. The extremely high linear depolarization ratio value observed at the melting height is considered to be procured by the melting particle with large eccentricity. It is shown that the multiparameter airborne radar provides valuable information by distinguishing the hydrometeor particles of the rainfall.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: In: International Conference on Radar Meteorology, 25th, Paris, France, June 24-28, 1991, Preprints (A93-37626 15-47); p. 400-403.
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  • 8
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    Imaging spectroscopy of Mars during 1990 (1991)
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    Publication Date: 2011-08-24
    Description: Preliminary results are presented of observations of Mars using three telescopes and a CCD camera, grating-array spectrometers, and a near-IR array camera. Martian albedo features are shown to be similar in the visible and 1.3-3.5-micron range, and reflectances of nearly zero are noted in the image at 3.02 microns. The results demonstrate that these techniques provide effective maps of spatial variations in spectral absorption features caused by Martian atmospheric volatiles and by surface minerals.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: EOS (ISSN 0096-3941); 72; 47, N; 521
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  • 9
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    Global climate change (1991)
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    Publication Date: 2011-08-24
    Description: Present processes of global climate change are reviewed. The processes determining global temperature are briefly described and the concept of effective temperature is elucidated. The greenhouse effect is examined, including the sources and sinks of greenhouse gases.
    Keywords: METEOROLOGY AND CLIMATOLOGY
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  • 10
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    GLOBE backscatter - Climatologies and mission results (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Global Backscatter Experiment (GLOBE) goals require intensive study of the global climatology of atmospheric aerosol backscatter at IR wavelengths. Airborne and ground-based lidars have been developed to measure atmospheric backscatter profiles at CO2 laser wavelengths. Descriptions of the calibration techniques and selected measurement results are presented.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: In: Laser radar VI; Proceedings of the Meeting, Los Angeles, CA, Jan. 23-25, 1991 (A93-17851 05-36); p. 139-146.
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  • 11
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    Effect of a finite outer scale on the Zernike decomposition of atmospheric optical turbulence (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Phase distortions in optical systems induced by atmospheric turbulence are investigated with the use of Zernike polynominal decompositions. An analytic solution for the variances of the Zernike coefficients is found for the case of Kolmogorov turbulence with a finite outer-scale length. It is shown that the effect of finite outer scale is to attenuate low-order Zernike components, even when the outer-scale length is much larger than the optical aperture. Effects are investigated for constant outer-scale size and for height-dependent outer scales. It is found that seeing effects on large telescopes are dependent more on the magnitude of the outer scale than on the shape of the outer-scale vertical profile.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Optical Society of America, Journal, A: Optics and Image Science (ISSN 0740-3232); 8; 1568-157
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  • 12
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    Space-based surface wind vectors to aid understanding of air-sea interactions (1991)
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    Publication Date: 2011-08-24
    Description: A novel and unique ocean-surface wind data-set has been derived by combining the Defense Meteorological Satellite Program Special Sensor Microwave Imager data with additional conventional data. The variational analysis used generates a gridded surface wind analysis that minimizes an objective function measuring the misfit of the analysis to the background, the data, and certain a priori constraints. In the present case, the European Center for Medium-Range Weather Forecasts surface-wind analysis is used as the background.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: EOS (ISSN 0096-3941); 72; 201
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  • 13
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    On the wave forcing of the semi-annual zonal wind oscillation (1991)
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    Publication Date: 2011-08-24
    Description: Observational evidence of rather large period waves (23-60 d) in the troposphere/stratosphere, particularly during the winter months, is presented. Wind data collected on a regular basis employing high-altitude balloons and meteorological rockets over the past few years are used. Maximum entropy methods applied to the time series of zonal wind data indicate the presence of 23-60-waves more prominently than shorter-period waves. The waves have substantial amplitudes in the stratosphere and lower mesosphere, often larger than those noted in the troposphere. The mean zonal wind in the troposphere (5-15 km altitude) during December, January, and February exhibits the presence of strong westerlies at latitudes between 8 and 21 deg N.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 53; 1181-119
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  • 14
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    A nested grid, nonhydrostatic, elastic model using a terrain-following coordinate transformation - The radiative-nesting boundary conditions (1991)
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    Publication Date: 2011-08-24
    Description: This study presents a nested-grid nonhydrostatic and elastic model using a terrain-following coordinate transformation as well as a unique application of grid-nesting techniques to the time-splitting elastic model. A simulation of the 10-m-high Witch of Agnesi Mountain provides the control to test this new model. The results show that the model produces the same solution as that derived from a simple linear analytic model. It is demonstrated that the new nested-grid model improves model resolution without resorting to the costly method of placing a fine-resolution grid over the entire domain. Since the wave reflection from the boundaries of the fine-grid model is well controlled, the boundary of the nested fine-grid model can be located even at the wave-active region. The model can be used to simulate various weather systems in which scale interactions are important.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 2852-286
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  • 15
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    A Great Salt Lake waterspout (1991)
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    Publication Date: 2011-08-24
    Description: Results are presented of observations of a waterspout funnel and spray ring performed under a cumulus line over the Great Salt Lake for about 5 min shortly after sunrise on June 26, 1985. These observations were used as the basis for a study of the initiation and evolution of waterspouts through a series of numerical experiments at two scales, that of a cloud and a waterspout. The cloud scale was simulated using an improved Goddard-Schlesinger model with nearby Salt Lake City soundings. Results showed that for each mode of cloud initiation, the vortex that started at the anticyclonic center grew faster than those started at other centers. This result strongly suggests that the cloud vorticity was important in its initiation. The greatest azimuthal speed for the bubble-initiated cloud was 11 m/s, when the vortex model was started at 28-min cloud time with time-varying boundary conditions, whereas it was 21 m/s when started at 12 min in the line-initiated cloud. The results support the hypothesis that, at least in some circumstances, cloud processes alone can produce waterspouts in the absence of external vorticity sources such as surface convergence lines or other shear features.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 2741-277
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  • 16
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    Uranus as a radio source (1991)
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    Publication Date: 2011-08-24
    Description: The complex nature of the Uranus radio emissions, both magnetospheric and atmospheric, is reviewed, with emphasis on the identification of distinct components and the determination of their source locations. Seven radii components were discovered in addition to the RF signature of lightning in the planet's atmosphere. Six of the seven magnetospheric components are freely propagating emissions; one component, the nonthermal continuum, is trapped in the density cavity between the magnetopause and the dense inner magnetosphere. The radio components are divided into two types according to their emission signature: bursty emission and smooth emission. The inferred source location for the dominant nightside emission is above the nightside magnetic pole, largely overlapping the UV auroral region and the magnetic polar cap. The N-burst component appears to be associated with solar-wind enhancements at Uranus, consistent with the idea that the solar wind was triggering magnetospheric substormlike activity during the encounter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 17
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    Energetic particles at Uranus (1991)
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    Publication Date: 2011-08-24
    Description: The energetic particle measurements by the low-energy charged-particle and cosmic-ray instruments on the Voyager 2 spacecraft in the magnetosphere of Uranus are reviewed. Upstream events were observed outside the Uranian bow shock, probably produced by ion escape from the magnetosphere. Evidence of earthlike substorm activity was discovered within the Uranian magnetosphere. A proton injection event was observed within the orbit of Umbriel and proton events were observed in the magnetotail plasma-sheet boundary layer that are diagnostic of earthlike substorms. The magnetospheric composition is totally dominated by protons, with only a trace abundance of H(2+) and no evidence for He or heavy ions; the Uranian atmophere is argued to be the principal plasma source. Phase-space densities of medium energy protons show inward radial diffusion and are quantitatively similar to those observed at the earth, Jupiter, and Saturn. These findings and plasma wave data suggest the existence of structures analogous to the earth's plasmasphere and plasmapause.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 18
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    The plasma environment of Uranus (1991)
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    Publication Date: 2011-08-24
    Description: An overview of the observational results on the plasma environment at Uranus is given, and the implications of these observations for magnetospheric physics at Uranus are discussed. During the Voyager 2 encounter with Uranus, an extended magnetosphere filled with a tenuous plasma was detected. This low-energy plasma was found to consist of protons and electrons, with no significant heavy ion contribution, and with a density in the regions sampled by the spacecraft of at most three electrons per cubic centimeter. The plasma electrons and ions exhibit both a thermal component (with temperatures of tens of eV) and a hot component (with temperatures of a few keV). The thermal ion component is observed both inside and outside an L-shell value near 5, whereas the hot ion and electron component is excluded from the region inside of that L-shell. The source of the thermal component of the plasma is either the planetary ionosphere or the neutral hydrogen corona surrounding Uranus, whereas the hot component is convected in from the magnetotail, with probably an ionospheric source.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 19
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    Diagnostic evaluation of numerical model simulations using the tendency equation (1991)
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    Publication Date: 2011-08-24
    Description: A procedure is proposed to expand the diagnostic capabilities of the pressure tendency equation of a primitive equation NWP model by computing the pressure tendency in physical coordinates. The advantages of isolating the density advection as a diagnostic tool to understand pressure changes is shown. By simple thermodynamic arguments it is demonstrated that in areas of synoptic-scale cyclonic development, the vertically integrated density advection is more than sufficient to explain the depletion of mass over a growing depression. Consequently, the joint contribution of the net divergence and vertical motion opposes the pressure fall. This is illustrated for a case of rapid cyclogenesis in southern South America.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 2936-295
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  • 20
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    Solid C triple bond N bearing material on outer solar system bodies (1991)
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    Publication Date: 2011-08-24
    Description: Recent telescopic observations have led to the identification of cyanogroup-containing molecules in the dark surface solids of several D-class asteroids, cometary dusts, and the rings of Uranus, as well as the low-albedo atmosphere of Iapetus. The occurrence of the 2.2-micron overtone of C triple-bond N's stretching fundamental mode in all four classes of small solar system bodies is presently suggested to serve as a diagnostic of both exposure duration and degree of modification of surface materials.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 94; 345-353
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  • 21
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    Automated cloud screening of AVHRR imagery using split-and-merge clustering (1991)
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    Publication Date: 2011-08-24
    Description: Previous methods to segment clouds from ocean in AVHRR imagery have shown varying degrees of success, with nighttime approaches being the most limited. An improved method of automatic image segmentation, the principal component transformation split-and-merge clustering (PCTSMC) algorithm, is presented and applied to cloud screening of both nighttime and daytime AVHRR data. The method combines spectral differencing, the principal component transformation, and split-and-merge clustering to sample objectively the natural classes in the data. This segmentation method is then augmented by supervised classification techniques to screen clouds from the imagery. Comparisons with other nighttime methods demonstrate its improved capability in this application. The sensitivity of the method to clustering parameters is presented; the results show that the method is insensitive to the split-and-merge thresholds.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Remote Sensing of Environment (ISSN 0034-4257); 38; 77-121
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  • 22
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    Sources of error in planetary photoclinometry (1991)
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    Publication Date: 2011-08-24
    Description: A quantitative analysis of error sources in 1D planetary photoclinometry is presented. The technique is affected by error sources arising from the spacecraft image, the planetary body, and the scan line orientation. Slope errors are calculated for each of these sources, using examples of Voyager imaging of Ganymede and Viking orbiting imaging of Mars. Slope errors are investigated for a variety of viewing and lighting geometries, slope angles, and slope orientations. The results are broken down into nonsystematic and systematic errors. Derivations that allow the calculation of photoclinometric slope errors for any photometric function are presented, and the implications of these results for 2D photoclinometric techniques are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 20
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  • 23
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    Graben and extension in northern Tharsis, Mars (1991)
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    Publication Date: 2011-08-24
    Description: A morphometric analysis of north-south trending graben at 35 deg N in northern Tharsis is used to provide the first quantitative measurements of crustal extension in and strain for areas of the Martian crust that have undergone both extreme and mild deformation. These estimates also demonstrate the viability of the Viking data for making such quantitative assessment. Graben in the region accommodate about 8 km of post Early Amazonian east-west extension. This extension corresponds to a net regional strain of 0.45-0.61 percent; local strains vary from less than 1 percent to 5 percent. Extension is nonuniform and localized near 110 deg (south of Alba Patera and north of Ceraunius Fossae) because of reactivation of preexisting fractures in underlying basement and possibly due to superposition of stress fields from Tharsis and Alba Patera. A major mechanical discontinuity in the shallow crust, probably representing the base of or a strength contrast within the megaregolith, is observed. It occurs at a depth of 2 km on the profile flanks and is depressed to about 7.5 km near 110 deg due to loading of the crust by the volcano.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 18
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  • 24
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    Infrared radiation parameterizations in numerical climate models (1991)
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    Publication Date: 2011-08-19
    Description: This study presents various approaches to parameterizing the broadband transmission functions for utilization in numerical climate models. One-parameter scaling is applied to approximate a nonhomogeneous path with an equivalent homogeneous path, and the diffuse transmittances are either interpolated from precomputed tables or fit by analytical functions. Two-parameter scaling is applied to parameterizing the carbon dioxide and ozone transmission functions in both the lower and middle atmosphere. Parameterizations are given for the nitrous oxide and methane diffuse transmission functions.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Climate (ISSN 0894-8755); 4; 424-437
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  • 25
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    Meridional Martian water abundance profiles during the 1988-1989 season (1991)
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    Publication Date: 2011-08-19
    Description: The Martian southern hemisphere atmospheric water vapor column abundance measurements reported agree with Viking Orbiter atmospheric water detectors during early southern spring and southern autumnal equinox; profiles obtained in southern mid- and late summer, however, indicate the presence of twice as much water both in the southern hemisphere and planetwide. This discrepancy is accounted for by the high optical depths created by two global dust storms during the Viking year, while the present observations were obtained in the case of the relatively dust-free atmosphere of the 1988-1989 opposition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 205-213
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  • 26
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    Automatic analysis of stereoscopic satellite image pairs for determination of cloud-top height and structure (1991)
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    Publication Date: 2011-08-19
    Description: Results are presented on an automatic stereo analysis of cloud-top heights from nearly simultaneous satellite image pairs from the GOES and NOAA satellites, using a massively parallel processor computer. Comparisons of computer-derived height fields and manually analyzed fields show that the automatic analysis technique shows promise for performing routine stereo analysis in a real-time environment, providing a useful forecasting tool by augmenting observational data sets of severe thunderstorms and hurricanes. Simulations using synthetic stereo data show that it is possible to automatically resolve small-scale features such as 4000-m-diam clouds to about 1500 m in the vertical.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology (ISSN 0894-8763); 30; 257-281
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  • 27
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    Spectroscopic observations of bright and dark emission features on the night side of Venus (1991)
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    Publication Date: 2011-08-19
    Description: Near-infrared spectra of a bright and a dark thermal emission feature on the night side of Venus have been obtained from 2.2 to 2.5 microns at a spectral resolution of 1200 to 1500. Both bright and dark features show numerous weak absorption bands produced by CO2, CO, water vapor, and other gases. The bright feature emits more radiation than the dark feature throughout this spectral region, but the largest contrasts occur between 2.21 s 2.32 microns, where H2SO4 clouds and a weak CO2 band provide the only known sources of extinction. The contrast decreases by 55 to 65 percent at wavelengths longer than 2.34 microns, where CO, clouds, and water vapor also absorb and scatter upwelling radiation. This contrast reduction may provide direct spectroscopic evidence for horizontal variations in the water vapor concentrations in the Venus atmosphere at levels below the cloud tops.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 252; 1293-129
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  • 28
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    Venus volcanism - Initial analysis from Magellan data (1991)
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    Publication Date: 2011-08-19
    Description: Magellan images confirm that volcanism is widespread and has been fundamentally important in the formation and evolution of the crust of Venus. High-resolution imaging data reveal evidence for intrusion (dike formation and cryptodomes) and extrusion (a wide range of lava flows). Also observed are thousands of small shield volcanoes, larger edifices up to several hundred kilometers in diameter, massive outpourings of lavas, and local pyroclastic deposits. Although most features are consistent with basaltic compositions, a number of large pancake-like domes are morphologically similar to rhyolite-dacite domes on earth. Flows and sinuous channels with lengths of many hundreds of kilometers suggest that extremely high effusion rates or very fluid magmas (perhaps komantiites) may be present. Volcanism is evident in various tectonic settings (coronae, linear extensional and compressional zones, mountain belts, upland rises, highland plateaus, and tesserae). Volcanic resurfacing rates appear to be low (less than 2 cu km/yr) but the significance of dike formation and intrusions, and the mode of crustal formation and loss remain to be established.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 252; 276-288
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    Martian regolith as space radiation shielding (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Mars exploration crews will be exposed to such high radiation dosages in route from earth that as to sharply reduce the allowable dose they should receive while on the Martian surface. An account is presently given of the possibility of using Martian regolith as crew shielding to maintain very low short-term dose limits. NASA-Langley's nucleon and heavy-ion transport computer codes are used to predict the propagation and interaction of the free-space nucleons and heavy ions through the Martian atmosphere and then through various thicknesses of regolith. The largest reduction in dose occurs in the first 15-20 cm of regolith material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 7
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    Global precipitation estimates from satellite - Using difference fields of outgoing long-wave radiation (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Global precipitation estimates using satellite data are derived using difference fields of outgoing long-wave radiation (OLR). The difference fields consist of clear OLR minus cloudy OLR, which is a measure of long-wave cloud radiative forcing at the top of the earth-atmosphere system; and clear daytime OLR minus clear night-time OLR, which is a measure of the diurnal variation of surface heating. All geophysical parameters used to compute OLR are derived from an analysis of the HIRS2/MSU sounding data. The derived global precipitation estimates show good agreement with collocated raingage data over land.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Atmosphere - Ocean (ISSN 0705-5900); 29; 150-174
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    Determination of the half-life of Ca-41 from measurements of Antarctic meteorites (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Accelerator mass spectrometry is utilized to determine the half-life of Ca-41 from the decrease of its concentration with terrestrial age in five Antarctic meteorites and a recent fall. The meteorites were selected on the basis of their Cl-36 concentrations, which showed a span of terrestrial ages of about 600 ka, and on the basis of other cosmogenic nuclide concentrations which indicated that the meteorites had small preatmospheric sizes, and sufficiently long irradiation times in space that the concentrations of Ca-41 and Cl-36 were in secular equilibrium prior to the meteorites' fall to earth. The half-life of Ca-41 is determined at 103 + or - 7 ka. Topics discussed include the effects of undersaturation (short exposure time in space), shielding (the samples are from the interior of a large meteorite), and weathering on the cosmogenic nuclide concentrations in meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 103; 1-4,; 79-83
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    An analytic model for the Phobos surface (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Analytic expressions are derived to model the surface topography and the normal to the surface of Phobos. The analytic expressions are comprised of a spherical harmonic expansion for the global figure of Phobos, augmented by addition terms for the large crater Stickney and other craters. Over 300 craters were measured in more than 100 Viking Orbiter images to produce the model. In general, the largest craters were measured since they have a significant effect on topography. The topographic model derived has a global spatial and topographic accuracy ranging from about 100 m in areas having the highest resolution and convergent, stereo coverage, up to 500 m in the poorest areas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science (ISSN 0032-0633); 39; 355-376
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    Results of TV imaging of Phobos - Experiment VSK-Fregat (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: From February to March 1989 the Phobos 2 spacecraft took 37 TV images of Phobos at a distance of 190-1100 km. These images complement Mariner-9 and Viking data by providing higher-resolution coverage of a laarge region west of the crater Stickney (40-160 deg W) and by providing disk-resolved measurements of surface brightness at a greater range of wavelengths and additional phase angles. These images have supported updated mapping and characterization of large craters and grooves, and have provided additional observations of craters' and grooves' bright rims. Variations in surface visible/near-infrared color ratio of almost a factor of 2 have been recognized; these variations appear to be associated with the ejecta of specific large impact craters. Updated determinations of satellite mass and volume allow calculation of a more accurate value of bulk density, 1.90 + or - 0.1 g/cu cm. This is sigificantly lower than the density of meteoritic analogs to Phobos' surface, suggesting a porous interior perhaps containing interstitial ice.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science (ISSN 0032-0633); 39; 281-295
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    Comparisons between satellite-derived gradient winds and radar-derived winds from the CIRA-86 (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The zonal and meridional wind contours in the 60-120 km region obtained from satellite radiance data were compared with radar-derived contours of winds obtained from the CIRA-1986 reference atmosphere. It was found that the agreement between the directly observed zonal winds and the zonal mean gradient winds from the reference atmosphere wind model was good, especially below 80 km. However, differences were found in both the Southern and the Northern Hemispheres.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 48; 411-428
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    The structure of the Venus ionosphere (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The morphology and temporal variability of the Venus ionosphere are characterized, reviewing the results of recent theoretical investigations, observations, and in situ measurements, especially by the Pioneer Venus Orbiter (PVO). Consideration is given to the Pioneer mission and orbit evolution, early radio occultation profiles of ionospheric N(e), the mean structure and thermal balance of the ionosphere, the ion composition and its dawn-dusk asymmetry, the small-scale spatial structure on the nightside, latitudinal and seasonal variations, solar-cycle effects, suprathermal electrons and superthermal ions, and the global configuration and stability of the ionopause. Data from a single PVO passage through the ionotail are discussed in detail, examining the implications for ion escape and the solar-cycle and short-term variability. The differences among the terrestrial, Martian, and Venusian ionospheres are outlined; the PVO data base is described; and the sources of measurement error are indicated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews (ISSN 0038-6308); 55; 81-163
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    Triton's global heat budget (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Internal heat flow from radioactive decay in Triton's interior along with absorbed thermal energy from Neptune total 5 to 20 percent of the isolation absorbed by Triton, thus comprising a significant fraction of Triton's surface energy balance. These additional energy inputs can raise Triton's surface temperature between about 0.5 and 1.5 K above that possible with absorbed sunlight alone, resulting in an increase of about a factor of about 1.5 to 2.5 in Triton's basal atmospheric pressure. If Triton's internal heat flow is concentrated in some areas, as is likely, local effects such as enhanced sublimation with subsequent modification of albedo could be quite large. Furthermore, indications of recent global albedo change on Triton suggest that Triton's surface temperature and pressure may not now be in steady state, further suggesting that atmospheric pressure on Triton was as much as ten times higher in the recent past.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 251; 1465-146
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    Air-sea fluxes and surface layer turbulence around a sea surface temperature front (1991)
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    Publication Date: 2011-08-19
    Description: The observed effects of sharp changes in sea surface temperature (SST) on the air-sea fluxes, surface roughness, and the turbulence structure in the surface layer and the marine atmospheric boundary layer are discussed. In situ flux and turbulence observations were carried out from three aircraft and two ships within the FASINEX framework. Three other aircraft used remote sensors to measure waves, microwave backscatter, and lidar signatures of cloud tops. Descriptions of the techniques, intercomparison of aircraft and ship flux data, and use of different methods for analyzing the fluxes from the aircraft data are described. Changing synoptic weather on three successive days yielded cases of wind direction both approximately parallel and perpendicular to a surface temperature front. For the wind perpendicular to the front, wind over both cold-to-warm and warm-to-cold surface temperatures occurred. Model results consistent with the observations suggest that an internal boundary layer forms at the SST.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 8593-860
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    Differences in global data sets of atmospheric and surface parameters and their impact on outgoing longwave radiation and surface downward flux calculations (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 9227-926
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    A simple parameterization of ozone infrared absorption for atmospheric heating rate calculations (1991)
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    Publication Date: 2011-08-19
    Description: A simple parameterization of ozone absorption in the 9.6-micron region which is suitable for two- and three-dimensional stratospheric and tropospheric models is presented. The band is divided into two parts, a brand center region and a band wing region, grouping together regions for which the temperature dependence of absorption is similar. Each of the two regions is modeled with a function having the form of the Goody random model, with pressure and temperature dependent band parameters chosen by empirically fitting line-by-line equivalent widths for pressures between 0.25 and 1000 mbar and ozone absorber amounts between 1.0 x 10 to the -7th and 1.0 cm atm. The model has been applied to calculations of atmospheric heating rates using an absorber amount weighted mean pressure and temperature along the inhomogeneous paths necessary for flux computations. In the stratosphere, maximum errors in the heating rates relative to line-by-line calculations are 0.1 K/d, or 5 percent of the peak cooling at the stratopause. In the troposphere the errors are at most 0.005 K/d.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 9065-907
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    A description of the correlated k distributed method for modeling nongray gaseous absorption, thermal emission, and multiple scattering in vertically inhomogeneous atmospheres (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A radiative transfer method for treating nongray gaseous absorption and thermal emission in vertically inhomogeneous multiple scattering atmospheres is described. Probability density distributions of absorption coefficient strength are derived from line-by-line calculations to construct line-by-line and band model based k distributions. The monotonic ordering of absorption coefficient strengths in these k distributions implicitly preserves the monochromatic structure of the atmosphere at different pressure levels, thus simulating monochromatic spectral integration at a fraction of the line-by-line computing cost. The k distribution approach also permits accurate modeling of overlapping absorption by different atmospheric gases and accurate treatment of nongray absorption in multiple scattering media. It is shown that the correlated k distribution method is capable of achieving numerical accuracy to within 1 percent of cooling rates obtained with line-by-line calculations throughout the troposphere and most of the stratosphere.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 9027-906
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    Calculations of transmission functions in the infrared CO2 and O3 bands (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An efficient method for computing the transmission function in the 15-micron CO2 and the 9.6-micron O3 bands is presented. An inhomogeneous atmospheric path is treated as homogeneous by applying simple pressure and temperature scaling approximations. The transmission functions are then derived from small precomputed tables. Because the atmospheric cooling rate is primarily contributed from adjacent layers, the simple scaling approximations can be used to accurately compute transmission functions in both the middle and lower atmosphere. Applying the parameterization to vastly different atmospheric conditions, the difference with line-by-line calculations is small. In the region between 0.01 mbar and the earth's surface, the cooling rate difference is less than 0.3 C/d in the 15-micron CO2 band and less than 0.1 C/d in the 9.6-micron O3 band.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 9003-901
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    The 2-micron polar haze of Jupiter (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Model spectra have been constructed for the CH4 lines of the polar regions of Jupiter in such as way as to encompass the hydrogen pressure-induced opacity and haze layers revealed by high-resolution spectroscopy. Comparisons between observation and model spectra indicate that, for optically thin haze models, the polar haze is primarily located between the 70 and 5 mbar pressure levels; for opaque haze models, the top of the haze layers lies in the vicinity of the 15-mbar level. It is concluded that the polar haze is widely distributed over both polar regions and exhibits no strong correlation with auroral activities.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 91; 145-153
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    Phase equilibrium of methane and nitrogen at low temperatures - Application to Titan (1991)
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    Publication Date: 2011-08-19
    Description: Since the vapor phase composition of Titan's methane-nitrogen lower atmosphere is uniquely determined as a function of the Gibbs phase rule, these data are presently computed via integration of the Gibbs-Duhem equation. The thermodynamic consistency of published measurements and calculations of the vapor phase composition is then examined, and the saturated mole fraction of gaseous methane is computed as a function of altitude up to the 700-mbar level. The mole fraction is found to lie approximately halfway between that computed from Raoult's law, for a gas in equilibrium with an ideal solution of liquid nitrogen and methane, and that for a gas in equilibrium with pure liquid methane.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 91; 112-124
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    Boundary-layer moisture regimes (1991)
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    Publication Date: 2011-08-19
    Description: Boundary-layer moisture fluctuations are estimated by analyzing HAPEX and FIFE data collected on 52 aircraft flight legs. Moisture fluctuations were given considerable attention in the HAPEX flights, which were 120 km long, and flew 150 m over one area of homogeneous terrain. The repetitions permit statistical consideration of motion characteristics on horizontal scales. Two prototypical boundary layer regimes are discovered: the entrainment-drying boundary layer, and the moistening boundary layer. The latter demonstrates positive moisture skewness close to the surface related to high surface evaporation. The former is characterized by boundary-layer instability, weak surface evaporation, and drier air aloft, leading to unexpected negative moisture skewness. It is noted that 10 km moisture variations with horizontal gradients are often found in narrow zones of horizontal convergence, called mesoscale moisture fronts. A negative moisture to temperature correlation, due to surface energy budget inhomogeneity, is shown to incur large mesoscale variations of relative humidity.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Royal Meteorological Society, Quarterly Journal (ISSN 0035-9009); 117; 151-176
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    On the response of exospheric temperature on Venus to solar wind conditions (1991)
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    Publication Date: 2011-08-19
    Description: Exospheric temperatures, T(ex), inferred from in situ measurements of neutral densities by the Pioneer Venus Orbiter have been analyzed to examine any possible dependence on solar wind dynamic pressure, P(sw). No linear relationship was found between P(sw) and T(ex). However, on one occasion when P(sw) was unusually high for a prolonged period, an unmistakable temperature enhancement was observed. Minor enhancement of T(ex) were also observed in few other cases, with sustained but moderately high P(sw).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 7901-790
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    Phobos - Spectrophotometry between 0.3 and 0.6 micron and IR-radiometry (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A 0.3 - 0.6 micron UV-visible spectrophotometer and a 5 - 50 micron radiometer in the KRFM experiment on Phobos 2 measured two groundtracks in the equatorial region of Phobos. Preliminary results indicate that three surface units can be recognized on the basis of differing UV-visible spectral reflectance properties. One of the units is most comparable spectrally to optically darkened mafic material, and a second is comparable either to anhydrous carbonaceous chondrite or to blackened mafic material. Spectral properties of the third unit do not resemble those of known meteorite types. Brightness temperatures measured by the radiometer are consistent with a typical surface thermal inertia of 1 - 3 x 10 to the -3 cal/(sq cm deg s exp 1/2), as suggested by previous investigations, implying a lunar-like regolith texture. At least one area of possibly higher thermal inertia has been tentatively identified, where a large degraded crater is crossed by several grooves. These results indicate significant lateral heterogeneity in the optical and textural properties of Phobos' surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science (ISSN 0032-0633); 39; 311-326
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    Observations of cloud cluster hierarchies over the tropical western Pacific (1991)
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    Publication Date: 2011-08-19
    Description: The structure and propagation of tropical-cloud clusters are investigated during two contrasting periods over the tropical western Pacific in order to determine possible similarities or differences and to compare with previous studies. Three fundamental periodicities are found in tropical convection in the region: 1 day, 2-3 days, and 10-15 days. It is noted that the 10-15-day time scale is closely related to the intraseasonal oscillations propagating from the Indian Ocean to the western Pacific. Large convective complexes, supercloud clusters (SSC) are found to organize in this time scale. The SCC is made up from several cloud clusters generated at 2-3-day intervals. The diurnal variation is found to be most pronounced over the maritime continent, and the amplitude of the diurnal cycle is shown to be modulated by the 2-3-day and 10-15-day oscillations.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 3197-320
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    Dynamics of planetary rings (1991)
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    Publication Date: 2011-08-19
    Description: The modeling of the dynamics of particle collisions within planetary rings is discussed. Particles in the rings collide with one another because they have small random motions in addition to their orbital velocity. The orbital speed is roughly 10 km/s, while the random motions have an average speed of about a tenth of a millimeter per second. As a result, the particle collisions are very gentle. Numerical analysis and simulation of the ring dynamics, performed with the aid of a supercomputer, is outlined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: American Scientist (ISSN 0003-0996); 79; 44-59
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    The dynamics of particle disks. III - Dense and spinning particle disks (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The kinetic theory of planetary rings developed by Araki and Tremaine (1986) and Araki (1988) is extended and refined, with a focus on the implications of finite particle size: (1) nonlocal collisions and (2) finite filling factors. Consideration is given to the derivation of the equations for the local steady state, the low-optical-depth limit, and the steady state at finite filling factors (including the effects of collision inelasticity, spin degrees of freedom, and self-gravity). Numerical results are presented in extensive graphs and characterized in detail. The importance of distinguishing effects (1) and (2) at low optical depths is stressed, and the existence of vertical density profiles with layered structures at high filling factors is demonstrated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 139-171
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    Europa's phase curve - Implications for surface structure (1991)
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    Publication Date: 2011-08-19
    Description: The surface of the Jovian satellite Europa is characterized on the basis of an analysis of ground photoelectric photometry at 470 and 550 nm and Voyager images. The data are presented in extensive tables and graphs and discussed in detail. At 550 nm, Europa has single-scattering albedo 0.964, opposition-effect amplitude 0.5, opposition-effect width 0.0016, double-lobed Henyey-Greenstein factors b = -0.429 and c = 0.113, and mean roughness angle 10 deg (much lower than on other solar-system objects). From the small roughness and the 96-percent porosity implied by the narrow opposition peak, it is concluded that the surface was formed mainly by endogenic processes. It is also noted that only one of three observational criteria for preferential ion bombardment of the trailing hemisphere are met in Europa.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 30-42
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    Comparative global albedo and color maps of the Uranian satellites (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The surfaces of the Uranian satellites Ariel, Miranda, Oberon, Titania, and Umbriel are characterized on the basis of Voyager observations. Tables of spectrophotometric data and maps of normal reflectances, green/violet ratios, and possible geological formations are presented and discussed in detail. Variations in albedo are found to be associated with impact features, and it is inferred from color differences that the upper surface of Ariel contains a higher proportion of redder material (tentatively identified as accreted low-albedo meteoritic dust) than those of the other moons.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 1-13
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    Surface wind convergence as a short-term predictor of cloud-to-ground lightning at Kennedy Space Center (1991)
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    Publication Date: 2011-08-19
    Description: Cloud-to-ground lightning is a significant forecast problem at the Kennedy Space Center (KSC) in Florida. In this study, cloud-to-ground lightning is related in time and space to surface convergence for 244 days during the convective seasons of 1985 and 1986 over a 790 sq-km network at KSC. The method uses surface convergence, particularly the average over the area, to identify the potential for new, local thunderstorm growth, and it can be used to specify the likely time and location of lightning during the life cycle of the convection. A threshold of 75 x 10 to the -6th/s change in divergence is the main criterion used to define a convergence event, and a set of flashes less than 30 min apart defines a lightning event. Time intervals are found from the study to be approximately 1 h from beginning convergence to first flash, and another hour to the end of lightning. The influences of low-level winds and midlevel moisture in determining the location and intensity of convection are discussed. This is the first known dynamically-based forecast method for lightning prediction. The technique, currently in use at KSC, has been shown to be a systematic, quantitative tool for predicting lightning onset in situations where conventional analysis tools such as radar and satellite are limited.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Weather and Forecasting (ISSN 0882-8156); 6; 49-64
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    Low-frequency intraseasonal tropical-extratropical interactions (1991)
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    Publication Date: 2011-08-19
    Description: Using seven years (1981-1987) of ECMWF initialized analyses, the low-frequency (20-70 day) intraseasonal variability during Northern Hemisphere winter is examined, with emphasis on the zonal wind variability in the Pacific sector and on its relationship to the tropical convection and the middle-altitude wave propagation. Particular consideration is given to changes in the propagation characteristics associated with variations in the subtropical jet and the implications for low-frequency variability in middle latitudes. Also investigated is the relationship between the Pacific sector u-wind fluctuations and tropical convection anomalies.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 48; 629-650
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    Determination of precipitation profiles from airborne passive microwave radiometric measurements (1991)
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    Publication Date: 2011-08-19
    Description: This study presents the first quantitative retrievals of vertical profiles of precipitation derived from multispectral passive microwave radiometry. Measurements of microwave brightness temperature (Tb) obtained by a NASA high-altitude research aircraft are related to profiles of rainfall rate through a multichannel piecewise-linear statistical regression procedure. Statistics for Tb are obtained from a set of cloud radiative models representing a wide variety of convective, stratiform, and anvil structures. The retrieval scheme itself determines which cloud model best fits the observed meteorological conditions. Retrieved rainfall rate profiles are converted to equivalent radar reflectivity for comparison with observed reflectivities from a ground-based research radar. Results for two case studies, a stratiform rain situation and an intense convective thunderstorm, show that the radiometrically derived profiles capture the major features of the observed vertical structure of hydrometer density.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 8; 148-158
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    Retrieval of monthly rainfall indices from microwave radiometric measurements using probability distribution functions (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An algorithm for the estimation of monthly rain totals for 5 deg cells over the ocean from histograms of SSM/I brightness temperatures has been developed. There are three novel features to this algorithm. First, it uses knowledge of the form of the rainfall intensity probability density function to augment the measurements. Second, a linear combination of the 19.35 and 22.235 GHz channels has been employed to reduce the impact of variability of water vapor. Third, an objective technique has been developed to estimate the rain layer thickness from the 19.35- and 22.235-GHz brightness temperature histograms. Comparison with climatologies and the GATE radar observations suggest that the estimates are reasonable in spite of not having a beam-filling correction. By-products of the retrievals indicate that the SSM/I instrument noise level and calibration stability are quite good.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 8; 118-136
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    Aircraft overflight measurements of midwest severe storms - Implications on geosynchronous satellite interpretations (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The instrumented NASA ER-2 aircraft overflew severe convection with IR V features for the first time in the midwest United States during May 1984. Measurements taken by the ER-2 were: visible and IR imagery, high-frequency passive microwave (92, 183 GHz) imagery, nadir lidar backscattered return, and flight altitude information. The May 7 and May 13, 1984 cases are analyzed in detail and the various data sources are combined and compared with GOES imagery. The high resolution aircraft IR imagery shows that thermal couplets are considerably more pronounced than in GOES imagery. In one of the cases (May 7, 1984) the minimum cloud-top IR temperature was located upshear of the overshooting cloud top in the lidar height field. The IR temperatures in the downshear anvils were as much as 5 C warmer than the ambient air temperatures, implying that the upwelling IR radiance comes from about 0.5-1.0 km below the cloud top. The in situ ER-2 measurements of temperature and air velocity 3-4 km above the overshooting tops showed very intense temperature and vertical velocity, perturbations. These perturbations are suggestive of lee waves generated by the overshooting tops or a cold dome above the squall line possibly due to tropopause lifting by the storms.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 436-456
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    Human exploration of Mars (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Novel approaches to the human exploration of Mars are considered with emphasis on a space suit design, extraterrestrial surface mobility, and water supply. A possible way of transporting personnel on the surface of Mars uses a suborbital rocket that will hop from one site to the next, refuelling each time it lands and giving the Martian explorers effective global mobility. Telepresence could be used to avoid limiting the people on Mars to a small exploration area as a result of a lack of transportation infrastructure. Drawings and photographs are included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Spaceflight (ISSN 0038-6340); 33; 208-212
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    Clouds and the Earth's Radiant Energy System (CERES) - An Earth Observing System experiment (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An overview is presented of the CERES experiment that is designed not only to monitor changes in the earth's radiant energy system and cloud systems but to provide these data with enough accuracy and simultaneity to examine the critical climate/cloud feedback mechanisms which may play a major role in determining future changes in the climate system. CERES will estimate not only the flow of radiation at the top of the atmosphere, but also more complete cloud properties that will permit determination of radiative fluxes within the atmosphere and at the surface. The CERES radiation budget data is also planned for utilization in a wide range of other Earth Observing System interdisciplinary science investigations, including studies of land, biological, ocean and atmospheric processes.
    Keywords: METEOROLOGY AND CLIMATOLOGY
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    A collection of diverse micrometeorites recovered from 100 tonnes of Antarctic blue ice (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new type of meteoritic material, intermediate in size between meteorites and interplanetary dust particles (IDPs), is described. Melting and filtering of about 100 tons of blue ice near Cap Prudhomme, Antarctica, yielded 7500 or more irregular, friable particles and about 1500 melted spherules, about 100 microns in size, both showing a 'chondritic' composition suggestive of an extraterrestrial origin. Analyzed irregular particles appear to be unmelted and have similarities with the fine-grained matrix of primitive carbonaceous chondrites, but are extremely diverse in composition. Isotopic analysis of trapped neon confirms an extraterrestrial origin for 16 of 47 irregular particles and 2 of 19 spherules studied and strongly suggests that they were exposed in space as micrometeoroids. These large Antarctic micrometeorites constitute a new family, or at least a new population, of solar system objects, in a mass range corresponding to the bulk of extraterrestrial material accreted by the earth today.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 351; 44-47
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    Mexican site for K/T impact crater? (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Research throughout the Caribbean suggests that the geophysical anomalies in the Yucatan first noted by Penfield and Camargo (1981) and called the Chicxulub crater could be the site of the impact purported to have caused the K/T extinctions. A semicircular ring of sink holes, known locally as cenotes, which correlates with the geophysical anomalies has been identified, and it is argued that the origin of the cenote ring is related to postimpact subsidence of the Chicxulub crater rim. If there is indeed a crater, the region within the cenote ring corresponds to its floor and the crater rim diameter is probably larger than 200 km. If confirmed as a site of impact, the Chicxulub crater would be the largest terrestrial impact crater known, which is consistent with the uniqueness of the K/T global catastrophe.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 351; 105
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    Aircraft multifrequency passive microwave observations of light precipitation over the ocean (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Aircraft passive microwave observations at 18, 37, 92, and 183 GHz of light oceanic precipitation are studied in conjunction with visible and infrared observations and ground-based radar data. Microwave signatures for clear, cloudy, and precipitating conditions are defined, with results in general agreement with previous theoretical results. Emission signatures are evident at 18, 37, and 92 GHz with clouds and precipitation producing an increase in brightness temperature over that observed over the low-emissivity ocean background. Polarization differences at 18 and 37 GHz also decrease in precipitation areas to minima of 30 K at 18 GHz and 15 K at 37 GHz. The 92-GHz brightness temperature shows a double-valued relationship, with an increase in cloudy and very lightly raining areas and a subsequent decrease for higher rain rates and deeper clouds where the ice scattering process becomes important. The 183-GHz observations display a distinct sensitivity to small amounts of ice. Simple channel differences are shown to compare favorably to the rain field, including polarization differences at 18 and 37 GHz and frequency differences between 92 and 37 GHz and between 183 and 92 GHz.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 8; 201-220
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    Cold-air outbreak during GALE - Lidar observations and modeling of boundary layer dynamics (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Two cold-air outbreaks were studied during the Genesis of Atlantic Lows Experiment. A lidar system was operated to observe the boundary layer evolution and the development of clouds. On the first day (January 30, 1986) boundary layer rise was less than 50 percent of the value for the second day (March 2, 1986). On the first day only a thin broken cloud cover formed, while on the second day a thick solid cloud deck formed - although the average moisture content was 60 percent of that on the first day. A trajectory slab model was employed to simulate the evolution of the layer over the ocean near the east Atlantic shore. The model allows for vertical gradients in conservative variables under neutrally buoyant conditions. The primary effect of these assumptions, which are based on observed thermodynamic profiles, is to reduce cloudiness to be more in line with observations. Boundary-layer depth was reasonably well predicted as was sensible and latent heat flux.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 1132-115
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    Shortwave shape factor inversion of earth radiation budget observations (1991)
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    Publication Date: 2011-08-19
    Description: Results are presented on an investigation of the effects of various assumptions (including assumptions of a constant flux field, a constant albedo field, and a variable albedo field) used for deriving the shortwave shape factor on the estimates, from radiometric measurements, of the albedo at the top of the atmosphere. The accuracies and the resolutions of the shape-factor-flux estimates obtained using these assumptions are determined by simulating the shape factor inversion technique with scanner data from the Earth Radiation Budget Experiment (ERBE). The resulting biases and variances are given for both the ERBE medium-field-of-view and wide-field-of-view radiometers.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 48; 390-402
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    Fluctuations of high clouds and 500-mb geopotential heights in baroclinic waveguides (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The spatial phase relationship between the atmospheric circulation and the bandpass fluctuations in cloudiness are investigated using satellite retrievals of high cloud areas reported by Stowe et al. (1988, 1989) NMC 500-mb geopotential heights in northern extratropics. Results of the analysis suggest that the high-cloud structures of baroclinic waves are less spatially coherent than the internal geopotential-height structures. It is shown that over the North Pacific, small-scale (latitudinal wavenumber 13-18) fluctuations in geopotential play a greater role in forcing high cloudiness than do medium-scale (latitudinal wavenumber 7-12) fluctuations in geopotential.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 73-83
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    Analysis of a general circulation model simulation of the atmospheric response to the observed sea surface temperature anomalies of January and February 1983 (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new version of the Goddard Laboratory for Atmospheres GCM is utilized to simulate the influence of an observed sea surface temperature anomaly on rainfall and atmospheric circulation. The model can reproduce many essential features of the observed tropical rainfall and circulation anomalies during January-February 1983. Particularly, the model simulates realistic patterns of tropical anomalies of sea level pressure, 200 mb geopotential heights, and horizontal winds at the 200 and 850 mb levels. The model-simulated tropical precipitation anomaly patterns appear realistic, although the precipitation is rather excessive and the atmosphere is too energetic.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Climate (ISSN 0894-8755); 4; 107-115
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    What maintains the zonal circulation in planetary atmospheres? (1991)
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    Publication Date: 2011-08-19
    Description: The latest Voyager observations have shown large zonal velocities in Neptune's atmosphere, with some indication of alternating jets. Similar wind velocities have also been observed on Venus and are characteristic of planetary atmospheres in general, which is remarkable considering that the available solar or internal heating varies by more than a factor of 1000. A simplified model of the planetary circulation which provides some qualitative understanding is discussed. The basic assumption is that the source driving the circulation is also generating the dissipating eddies which are simulated by diffusion. Thus, the magnitude and structure of the zonal circulation are independent both of the source and the dissipation rate. The zonal velocities are related to the speed of sound and are of comparable magnitude in different atmospheres; although the available heating varies by a large factor, and the planetary parameters vary over a wide range. The alternating jets are described by a convective eigenmode which develops when energy transport out of the planetary interior is important, as is the case on Jupiter, Neptune, and Saturn.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 367; 361-366
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    Phosphates in pallasite meteorites as probes of mantle processes in small planetary bodies (1991)
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    Publication Date: 2011-08-19
    Description: Trace element analyses of the phosphates minerals in stony-iron pallasite meteorites are used here to investigate the magmatic history of the silicate portions of pallasites. In Eagle Station and seven other pallasites, the phosphates have relatively low concentrations of REEs and are strongly enriched in heavy relative to light REE. These patterns are consistent with formation of phosphate by subsolidus reactions between metal and silicate, in which phosphate inherits the REE pattern of olivine. In Springwater and Santa Rosalia, calcium-rich phosphates have higher concentrations of REE, are enriched in light relative to heavy REE, and have negative europium anomalies. These patterns are consistent with crystallization of phosphate from a europium-depleted chondritic liquid. This is unlikely to have happened near the base of the differentiating parent-body mantle; it suggests that some pallasites may come from regions of their parent bodies much nearer the surface than the core-mantle boundary.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 353; 637-640
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    Dual-parameter radar rainfall measurement from space - A test result from an aircraft experiment (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An aircraft experiment has been conducted with a dual-frequency (X/Ka-bands) radar to test various rainfall retrieval methods from space. The authors test a method to derive raindrop size distribution (DSD) parameters from the combination of a radar reflectivity profile and a path-integrated attenuation derived from surface return, which may be available from most spaceborne radars. The estimated DSD parameters are reasonable in that the values generally fall within the range of commonly measured ones and that shifts in DSD parameters appear to be correlated with changes in storm type. The validity of the estimation result is also demonstrated by a consistency check using the Ka-band reflectivity profile which is independent of the DSD estimation process. Although errors may occur in the cases of nonuniform beam filling, these test results indicate the feasibility of the dual-parameter radar measurement from space in achieving a better accuracy in quantitative rainfall remote measurements.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 690-703
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    Herman-Wallis factors in the C2H2nu5 infrared fundamental near 14 microns (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The presence of acetylene has been confirmed for some time in the atmospheres of the outer planets Jupiter, Saturn, Neptune, and Saturn's satellite Titan. For these atmospheres, the determination of C2H2 abundances using its strong nu5 fundamental requires laboratory line position and intensity measurements. The 1-m Fourier transform spectrometer at McMath solar telescope of Kitt Peak National Observatory was used to measure C2H2 at an unapodized spectral resolution of 0.0025/cm. Synthetic spectra are generated by convolving a Voigt line shape with an instrument function and varying intensity parameters by means of a nonlinear least squares technique. Intensities of 37 nu5 lines spanning P18 through R20 were measured using 0.123 torr of gas in a 1-cm cell. A Herman-Wallis intensity correction parameter of 1.3(4) x 10 to the -3rd has been derived using a least squares linear fit.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 17
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    Horizontal wind fluctuations in the stratosphere during large-scale cyclogenesis (1991)
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    Publication Date: 2011-08-19
    Description: The meteorological measurement system (MMS) on the U-2 aircraft measured pressure, temperature, and the horizontal wind during a cyclogenesis event over western United States on April 20, 1984. The mean horizontal wind in the stratosphere decreases monotonically with altitude. Superimposed on the mean stratospheric wind is a perturbation wind vector, which is an elliptically polarized wave with an amplitude of 4 to 10 m/s and a vertical wavelength of 2 to 3 km. The perturbation wind vector rotates anticyclonically (clockwise) with altitude and produces alternating advection in the plane of the aircraft flight path. This differential advection folds surfaces of constant tracer mixing ratio and contributes to the observed tracer laminar structures and inferred cross-jet transport.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 17
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    Estimation of the diurnal cycle of oceanic precipitation from SSM/I data (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A study of differences between the morning and evening monthly rainfall for 5 x 5 deg cells over the oceans from the SSM/I data has been conducted. The monthly rainfalls are estimated from the technique given by Wilheit et al. The difference between the morning and evening monthly rainfall arises due to the various random errors involved in the retrieval process, the sampling error in the observations, and the diurnal component of oceanic rainfall. The diurnal component is weak but clearly visible when averaged over large areas and for long time periods. The analysis shows that morning rainfall is consistently greater than evening rainfall. The Northern Hemisphere seem to have a larger diurnal variation than does the Southern Hemisphere. The maximum ratio between the morning and evening monthly rainfall is 1.7 while 1.2 is the more typical value.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 2168-217
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    Simulation of the spectral content of the 7.8-micron emission from Jupiter at high resolution (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The present simulation of 1100-1400/cm region emissions ascribable to (C-12)H4, (C-13)H4, and CH3D, as seen by earth observers from a 4-km altitude, conclusively show that the polar hot-spots and other midlatitude features of broadband observations are stratospheric effects. Although signal enhancement in the broadband observations is obtained at increased Doppler shifts and zenith angles approaching zero, the magnitude in the former case is a function of stratospheric temperature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 93; 174-178
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    Ganymede and Callisto - Surface textural dichotomies and photometric analysis (1991)
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    Publication Date: 2011-08-19
    Description: Complete solar phase curves of the Ganymede and Callisto leading and trailing hemispheres, which have been obtained by reducing Voyager imaging observations and combining them with ground-based telescopic data, are presently fit to scattering models in order to derive hemispherical values of the single scattering albedo, the single particle phase function (SPPF), the compaction state (CS) of the optically active portion of the regolith, and the mean slope angle of macroscopic features. While Callisto's leading side is composed of particles that are more strongly backscattering than the trailing side, no hemispheric differences are found in the CS, surface roughness, or SPPF.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 92; 312-323
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    Midinfrared (2.5-13.5 microns) reflectance spectra of powdered stony meteorites (1991)
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    Publication Date: 2011-08-19
    Description: Asteroid spectral measurements are presently approached via comparisons with reflectance spectra from 60 powdered meteorite samples representing 50 different meteorites. While the powdered meteorites have undergone alteration by exposure to water vapor and by hydrocarbon contamination characterized by absorption bands near 3.45 microns, they retain various other spectral features which render them useful for identification. While these features can be used independently to ascertain mineralogy and meteorite type, the use of the entire spectrum in a digital search library is preferred for successful identification.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 92; 280-297
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    The 27-28 October 1986 FIRE Cirrus case study - Retrieval of cloud particle sizes and optical depths from comparative analyses of aircraft and satellite-based infrared measurements (1991)
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    Publication Date: 2011-08-19
    Description: Infrared radiance measurements were acquired from a narrow-field nadir-viewing radiometer based on the NASA ER-2 aircraft during a coincident Landsat 5 overpass on October 28, 1986 as part of the FIRE Cirrus IFO in the vicinity of Lake Michigan. The spectral bandpasses are 9.90-10.87 microns for the ER-2-based radiometer and 10.40-12.50 microns for the Landsat thematic mapper band. After adjusting for spatial and temporal differences, a comparative study using data from these two instruments is undertaken in order to retrieve cirrus cloud ice-crystal sizes and optical depths. Retrieval is achieved by analysis of measurement correlations between the two spectral bands and comparison to multistream radiative transfer model calculations. The results indicate that the equivalent sphere radii of the cirrus ice crystals were typically less than 30 microns. Such particles were too small to be measured by the available in situ instrumentation. Cloud optical depths at a reference wavelength of 11.4 microns ranged from 0.3 to 2.0 for this case study. Supplemental results in support of this study are described using radiation measurements from the King Air aircraft, which was also in near coincidence with the Landsat overpass.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Monthly Weather Review (ISSN 0027-0644); 119; 1673-169
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    Waves in Venus's middle and upper atmosphere - Implications of Pioneer Venus probe data above the clouds (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper reevaluates Pioneer Venus probe data which show the presence of waves in Venus's middle and upper atmosphere. The data are extended to 138 km. Uncertainties in the temperature are typically about 0.1 times amplitude, supporting the reliability of large-amplitude oscillations approaching 40 K at 120 km. Growth rates above 100 km follow approximately the inverse square root of density and 'saturation' occurs. The waves then break at the 120 km level, providing a source for the 'friction' required in models to match the observed day-night temperature contrast in the lower thermosphere. The data correlated to an unexpected degree with temperatures from the Pioneer Venus orbiter atmospheric drag experiment. The observations lead to the suggestion that the thermospheric waves are solar-fixed, induced either by the major subsidence across the termination or as continuation upward of waves in the middle atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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    Comparison of ice-phase microphysical parameterization schemes using numerical simulations of tropical convection (1991)
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    Publication Date: 2011-08-19
    Description: The performance of several ice parameterizations has been evaluated through a numerical cloud model. Ice effects using different schemes are contrasted with each other and with an ice-free control by incorporating them into the cloud model and by applying them to simulations of tropical squall systems. The latter are simulated in 2D so that a large domain can be used to incorporate a complete anvil. Nonsquall-type convective lines are simulated in 3D owing to their smaller horizontal scale. It is concluded that inclusion of ice microphysics in the cloud model enhanced the agreement of the simulated convection with some features of observed convection, including the proportion of surface rainfall in the anvil region and the intensity and structure of the radar brightband near the melting level in the anvil. In the experiments with bulk microphysics, three ice categories produced much better results than two ice categories, which in turn was better than no ice. For the tropical squall-type and nonsquall-type systems the optimal mix was ice, snow, and graupel.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology (ISSN 0894-8763); 30; 985-1004
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    Coherent backscatter model for the unusual radar reflectivity of icy satellites (1991)
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    Publication Date: 2011-08-19
    Description: The coherent backscatter model is investigated experimentally by means of an analog to examine the nature of the radar reflectivity of icy satellites. The laboratory analog involves the examination of He-Ne laser light with a wavelength of 0.633 microns reflected from 0.497-micron polystyrene beads suspended in water. A photomultiplier and a polarizing filter are employed to observe the radar at phase angles greater than zero which are extrapolated to infer observation at zero phase angle. The polarization angles measured at optical frequencies are found to be equivalent to those observed in the radar data. The results suggest that the regoliths of the icy satellites consist of matrices of small complex refractive indices which contain scatterers separated by distances of the order of a wavelength. The experiment explains the high reflectivity of Jupiter's icy satellites which results in the observation of narrow opposition-effects peaks at optical frequencies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 352; 46
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    Visual detection of 1981S13, Saturn's eighteenth satellite, and its role in the Encke gap (1991)
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    Publication Date: 2011-08-19
    Description: Careful inspection of many images taken by the Voyager spacecraft reveals the presence within the Encke gap of Saturn's eighteenth satellite. Its existence had been inferred from gravitational disturbances seen in Voyager data, and it falls close to the predicted orbit, its shepherding effect is responsible for keeping the Encke gap open, and it may also be the progenitor of a narrow ringlet within the gap.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 351; 709-713
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    On the dependence of travelling wave stability on basic state wave phase speed (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The dependence of stability on basic state wave phase speed is examined in a nondivergent barotropic model on a sphere for planetary scale waves with phase speeds typical of waves observed in the atmosphere. Triad interactions are examined analytically and compared to numerical results from a full spectral model. A number of triads may result in growth of the perturbation components for each basic state wave; for each triad there is a basic state wave phase speed where it is resonant, identified as the point where the critical amplitude for instability to that perturbation becomes zero. Critical amplitudes for instability obtained using the full spectral model generally agree well with triad results. Since the basic state wave phase speed determines which triad will grow, spatial structure and critical amplitudes for instability for the growing disturbances depend strongly on basic state wave phase speed. The results of this idealized study suggest that phase speed may be an important factor in determining the stability of planetary scale waves in the atmosphere.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Royal Meteorological Society, Quarterly Journal (ISSN 0035-9009); 117; 319-331
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  • 81
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    Electron impact excitation and dissociation of N2 via the b 1Pi(u) state (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Electron impact excitation of the b 1Pi(u) state in N2 plays a prominent role in the dissociation of the molecule and thus in the production of atomic nitrogen in planetary atmospheres. Electron impact excitation cross sections combined with electron-impact-induced fluorescence measurements can yield the corresponding dissociation cross sections. Serious discrepancies exist among excitation cross sections reported in the literature. To clarify the situation, these cross sections were measured at two impact energies using electron energy loss spectroscopy. The new results are in agreement with recent values deduced from optical measurements and fall midway between previous results which are too high or low by factors of 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 17
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  • 82
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    The Galileo Venus encounter (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Galileo's instruments obtained a broad range of planetary measurements during the spacecraft's Venus encounter on February 10, 1990. The instrumentation brought to bear encompassed UV spectra, limb haze studies, and particles-and-fields experiments. These data, in conjunction with ground-based observations conducted during the encounter, have yielded accurate information on the Venus plasma environment, cloud patterns, and the possibility of interpreting certain impulsive events as lightning.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 253; 1516-151
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  • 83
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    Studies on the dynamics of Venus ionosphere - Effects of varying the ionopause height and the onset of turbulence (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The conservation equations of plasma dynamics in the upper ionosphere of Venus have been solved by using a spectral method in the horizontal and finite differencing in the vertical direction. The effect of varying the ionopause height on the computed nightside ion densities is investigated. These ion densities show a sharp decrease as the ionopause altitude is reduced to 300 km. The effect of viscous forces on the horizontal plasma flow is investigated for a wide range of values of the coefficient of viscosity. The Reynolds numbers characteristics of the flow are calculated and the conditions for the onset of turbulence discussed. It is found that the Reynolds number can be large (greater than 1000) in the subsolar region for a coefficient of viscosity of up to 1.6 x 10 to the -10th g/cm s. The influence of magnetic fields on viscosity is also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Indian Journal of Radio and Space Physics (ISSN 0367-8393); 20; 150-156
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  • 84
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    Physical properties of the regolith of Phobos (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results of two experiments performed onboard the Phobos spacecraft are presented: spectrophotometry in the 300-600 nm range and thermal radiometry, i.e., intrinsic thermal emission in the 6-50 micron range. The thermophysical characteristics of the Phobos regolith are indicated by a thermal inertia coefficient which is similar to that of the moon. The reflectivity of the regolith is inhomogeneous in the region investigated and depends mostly on the relief features, primarily craters and their age. The expected similarity of the reflection spectra with those of carbonacenous chondrites was not confirmed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Kosmicheskie Issledovaniia (ISSN 0023-4206); 29; 621-640
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  • 85
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    Partitioning of siderophile elements in the Fe-Ni-S system - 1 bar to 80 kbar (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Partition coefficients for Au, Ni, P, and Ge between solid Fe-Ni metal and sulfur-bearing metallic liquids have been measured at 7, 27 and 80 kbar. These are the only such data for Au, P, and Ge at high pressure. Comparison of the present partitioning results to those obtained at 1 bar indicate that only the 80-kbar Ge data differ significantly from the 1-bar experiments. Thus, many low-pressure partitioning experiments in the Fe-Ni-S-P system may have applicability to the greater portion of the earth's upper mantle or, alternatively, the entire mantle of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 105; 1-3,; 127-133
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  • 86
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    Thermal stress tectonics on the satellites of Saturn and Uranus (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Thermal stress histories of the Saturnian and Uranian satellites are investigated. To this end, the thermal evolution of an icy satellite subjected to accretional and radiogenic heating, thermal conduction, and solid-state convection is modeled, and changes in the internal stress that occur during satellite evolution are examined. Results show that internal temperature changes that occur during normal evolution of many of the satellites of Saturn and Uranus can be expected to generate large extensional stresses in the satellites' outer regions. These stresses arise from three sources: (1) radiogenic warming, causing thermal expansion of materials in the satellite's deep interior; (2) radiogenic warming in larger satellites that can induce a phase transition from ice II to ice I and to produce a volume increase in the deep interior; and (3) accretional heating depositing heat in the satellite'e outer regions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 87
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    Ganymede and Callisto - Complex crater formation and planetary crusts (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are presented on measurements of crater depths and other morphological parameters (such as central peak and terrace frequency) of fresh craters on Ganymede and Callisto, two geophysically very similar but geologically divergent large icy satellites of Jupiter. These data were used to investigate the crater mechanics on icy satellites and the intersatellite crater scaling and crustal properties. The morphological transition diameters of and complex crater depths on Ganymede and Callisto were found to be similar, indicating that the crusts of both satellites are dominated by water ice with only a minor rocky component.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 88
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    Reconciliation of stress and structural histories of the Tharsis region of Mars (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: New information is presented on the structural and stratigraphic evolution of the Tharsis region of Mars, along with a lithospheric deformation model that can account for the observations. According to this model, the lithosphere beneath Tharsis consists of a thin elastic crustal cap on the rise, which is mechanically detached from the strong upper mantle by a volcanically thickened, hot, weak lower crust; these layers merge into a single cooler strong lithospheric layer around the edges of the rise. It is suggested that the nonuniform distribution of tectonic features and strain around Tharsis is due to the concentration of regional stresses near weaker volcanotectonic centers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 89
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    Detectability of Martian carbonates from orbit using thermal neutrons (1991)
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    Publication Date: 2011-08-19
    Description: Numerical simulations of Martian neutron leakage flux spectra are made in order to explore the detectability of magnesium and calcium carbonate deposits using neutron spectroscopic techniques from orbit. The primary signature of such deposits is found to be an enhanced thermal amplitude. Although this enhancement is weakened by: (1) partial burial beneath an aeolian regolith blanket; (2) admixture with regolith on a microscopic (centimeter) or macroscopic (tens of centimeters) scale; and (3) reduction in the areal size of the deposit, near-surface stratigraphies of carbonates hypothesized by some authors as possible on Mars are still detectable by simple neutron sensors from orbit. However, the large variations in the magnitude of the thermal neutron enhancements caused by different carbonate deposit configurations found in this study require a combined gamma ray and neutron analysis for their unique specification.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 90
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    Satellite observations of variations in tropical cyclone convection caused by upper-tropospheric troughs (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Satellite observations and numerical model results have been used to study the relationship between upper-tropospheric forcing and the oscillation of convection of tropical cyclones Florence (1988) and Irene (1981) during their mature stage over open warm oceans (SST greater than or equal to 26 C). It is suggested that the initiation and maintenance of intense convective outbreaks in tropical cyclones are related to the channeling and strengthening of their outflow by upper-tropospheric troughs. It is possible to enhance the convection in response to the outflow jet-induced import of eddy relative angular momentum and ascending motion associated with the thermally direct circulation. Both Florence and Irene are found to intensify after the onset of these convective episodes. It is also suggested that the cessation in the convection of the two tropical cyclones occurs when the upper-tropospheric troughs move near or over the tropical cyclones, resulting in the weakening of their outflow and the entrainment of dry upper-tropospheric air into their inner core.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Applied Meteorology (ISSN 0894-8763); 30; 1163-118
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  • 91
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    Early outgassing of Mars supported by differential water solubility of iodine and xenon (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Martian atmosphere has a high X-129/Xe-132 ratio compared to the Martian mantle. As Xe-129 is the daughter product of the extinct nuclide I-129, a means of fractionating iodine from xenon early in Martian history appears necessary to account for the X-129/Xe-132 ratios of its known reservoirs. A model is presented here to account for the Marian xenon data which relies on the very different solubilities of xenon and iodine in water to fractionate them after outgassing. Atmospheric xenon is lost by impact erosion during heavy bombardment, followed by release of Xe-129 produced from I-129 decay in the crust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 352; 697-699
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  • 92
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    The derivation of cloud parameters from satellite-measured radiances for use in surface radiation calculations (1991)
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    Publication Date: 2011-08-19
    Description: A simple scheme is developed for calculating the cloud amount, optical thickness, and height from satellite-measured radiances and is applied to the International Satellite Cloud Climatology Project B3 radiance data to compute the surface radiative fluxes over the tropical and subtropical western Pacific regions for July 1983, using a radiative transfer model. Results are presented on the sensitivity of surface radiation to the cloud scheme. In addition, the validity of an empirical relationship between the solar fluxes at the surface and at the top of the atmosphere is examined.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 48; 1549-155
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  • 93
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    Contributions to the implementation of the Arakawa-Schubert cumulus parameterization in the GLA GCM (1991)
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    Publication Date: 2011-08-19
    Description: The roles of the Critical Cloud Work Function (CCWF) data set and the upper and lower bounds on entrainment by cumulus plumes in the Arakawa-Schubert cumulus parameterization (ASCP) in the GLA GCM (Geller et al., 1988) were investigated in two sets of experiments. It was found that the horizontal and vertical distribution of cumulus heating can be altered in ASCP by adjusting these parameters. These changes can have a strong influence on the vertical structure of condensation heating, water vapor distribution, temperature, and rainfall. The CCWF is an important limiting parameter that controls the onset of different cloud types; increasing the threshold values of CCWF for all clouds tends to concentrate the rainfall into a narrower ITCZ and affects the rainfall during the initial adjustment period.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 48; 1573-158
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  • 94
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    First detection of HDO in the atmosphere of Venus at radio wavelengths - An estimate of the H2O vertical distribution (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The 225.9 GHz line of HDO has been detected in absorption in the atmosphere of Venus, with the 30-m IRAM antenna. This measurement gives information regarding the vertical distributions of HDO, and thus H2O, in this planet. The observations are consistent with an H2O vertical distribution strongly depleted by saturation at an altitude of 95 km, and, assuming a D/H enrichment of 120 with respect to the terrestrial value, with a mixing ratio of 3.5 (+ or - 2.0) ppm in the range 65-95 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 246; 1, Ju
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  • 95
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    The effect of snow cover on the climate (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Large-scale snow cover anomalies are thought to cause significant changes in the diabatic heating of the earth's surface in such a way as to produce substantial local cooling in the surface temperatures. This theory was tested using the GISS 3D GCM (General Circulation Model). The results of the GCM experiment showed that snow cover caused only a short term local decrease in the surface temperature. In the surface energy budget, reduction in absorbed shortwave radiation and the increased latent heat sink of melting snow contributed to lower temperatures. However, all the remaining heating terms contribute to increasing the net heating over a snow covered surface. The results emphasize the negative feedback which limits the impact of snow cover anomalies over longer time scales.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Climate (ISSN 0894-8755); 4; 689-706
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  • 96
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    The effect of the solar cycle on the maintenance of the nightside ionosphere of Venus (1991)
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    Publication Date: 2011-08-19
    Description: The behavior of the Venus nightside ionosphere at solar maximum and solar minimum is discussed based on Pioneer Venus radio occultation measurements. Although some solar maximum measurements are similar to those observed at minimum, which have an average peak density of about 7000/cu cm, others show much higher peak densities, reaching values of about 40,000/cu cm. These elevated peak densities also occur at higher altitudes. The integrated electron column densities for these measurements indicate the presence of substantial ionization above the main peak. The magnitudes of both the peak density and the integrated content above the peak are anticorrelated with the solar wind dynamic pressure, indicating that these enhancements during solar maximum are due to transterminator transport of O(+) ions from the dayside. The resulting ionization peak can be many times the concentration produced by energetic electron fluxes impacting the neutral atmosphere on the nightside.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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  • 97
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    Pioneer Venus Orbiter search for Venusian lightning (1991)
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    Publication Date: 2011-08-19
    Description: The results are reported of a search during 1988 and 1990 for optical pulses from lightning on the Venus nightside using the star sensor aboard the Pioneer Venus Orbiter. No optical evidence for lightning activity is found. These searches covered a much larger latitude range than any previous search. The results show that the Beta and Phoebe Regio areas previously identified by Russell et al. (1988) as areas with high rates of lightning activity were not active during the two seasons of the present observations. The results imply that the global flash rate and energy dissipation rate derived by Krasnopol'sky (1983) from observations of a single storm are too high. Experimental measurements performed to determine the amount of scattering occurring in the star scanner optics indicate that a previously determined upper bound to lightning activity is too low.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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  • 98
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    Plasma motion in the Venus ionosphere - Transition to supersonic flow (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A remarkable feature of the ionosphere of Venus is the presence of nightward supersonic flows at high altitude near the terminator. In this paper it is shown that the relatively high pressure dayside plasma wells up slowly, and at high altitude it is accelerated horizontally through a relatively constricted region near the terminator toward the low-density nightside. In effect, the plasma flows through a 'nozzle' that is first converging, then diverging, permitting the transition to supersonic flow. The model plasma accelerates to supersonic speeds, reaching sonic speed just behind the terminator. The ion transport rates are sufficient to produce and maintain the nightside ionosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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  • 99
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    Heat fluxes and roll circulations over the western Gulf Stream during an intense cold-air outbreak (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Turbulence and heat fluxes in the marine atmospheric boundary layer (MABL) for three aircraft stacks near the western Gulf Stream front, observed during the Genesis of Atlantic Lows Experiment (GALE) January 28, 1986 cold-air outbreak, has been studied using mixed-layer scaling. The GOES image and stability parameter indicates that these three stacks were in the roll vortex regime. The turbulence structure in the MABL is studied for this case, as well as the significance of roll vortices to heat fluxes. The roll circulations are shown to contribute significantly to the sensible (temperature) and latent heat (moisture) fluxes with importance increasing upward. The results suggest that the entrainment at the MABL top might affect the the budgets of temperature and humidity fluxes in the lower MABL, but not in the unstable surface layer.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Boundary-Layer Meteorology (ISSN 0006-8314); 55; 3, Ma
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    The radiative effects of clouds and their impact on climate (1991)
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    Publication Date: 2011-08-19
    Description: The radiative effects of clouds on the climate system are reviewed on the basis of data published over the last 15-20 years and some relevant unpublished model studies. Emphasis is placed on the impact of clouds on the incoming and outgoing radiation at the top of the atmosphere and the two-way interaction of clouds with other variables of the climate system, i.e., the cloud/climate feedback problem, as revealed by climate model simulations. Investigations aimed at determining the overall effects of clouds on the climate system (climate forcing) show that clouds have a net cooling effect. Two estimates of the global annual average effect of clouds on the net flux at the top of the atmosphere, based on recent satellite observations, show wide discrepancies. The sign of cloud feedback is found to be positive when the spatial distribution of clouds is allowed to vary in response to climate change. It is concluded that clouds may have a strong influence on climate change, but the magnitude of this influence is unknown.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: American Meteorological Society, Bulletin (ISSN 0003-0007); 72; 795-813
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