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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Soil texture and granulometry at the surface of Mars

The microtexture of the near-surface Martian soil was sensed with three diagnostic parameters: (1) the albedo A at normal incidence and phase angle 5 degrees, which relates to the composition of the top surface exposed layer; (2) the polarization parameter b characterizes the texture of the top surface layer in terms of grain size; and (3) the thermal inertia parameter I which refers to the soil compaction through the first few decimeters below the top surface sensed by polarimetry, in terms of size for the pieces making a granular regolith. Parameter b was derived from instrument VPM on board the Soviet spacecraft MARS-5, inertial I is from IRTM on the American Viking, and albedo A from both. The polarimetric scans racked strips covering two contrasted regions, the dark hued Mare Erythraeum, and the adjacent bright orange Thaumasia. Erythraem is characterized everywhere by a same type of terrain, despite the large geomorphological diversity of the surface. There is an ubiquitous coating or mantling with small dark grains, of both albedo 12.7 percent and particle size 10 to 20 microns, above a subsurface dislocation in pieces around 300 to 600 microns. A simple model is with sand-size particles completely coated with 15 micron dark grains.

Dollfus, A.↗
DOE OSTI2021

Modeling potential air temperature reductions yielded by cool roofs and urban irrigation in the Kansas City Metropolitan Area

In this work, we evaluate two mitigation strategies for urban heat island (UHI) in the Kansas City Metropolitan Area (KCMA). Using the Weather Research and Forecasting (WRF) model, we assess the potential benefits of reflective “cool” roofs and urban irrigation on air temperature in typical summer conditions between 2011 and 2015, and during six of the strongest historical heat waves from 2005 to 2016. Under the typical summer conditions, we simulate 2-m air temperature for 10 summer weeks, finding average daytime (07:00–19:00 local time) temperature reductions of 0.08 and 0.28 °C for cool roofs and urban irrigation, respectively. During the six heat-wave episodes, we find daytime temperature reductions of 0.02 and 0.26 °C for the two scenarios, similar to those under typical summer conditions. Our results suggest that urban irrigation can be more efficient than cool roofs in mitigating UHI in metropolitan regions where the majority of the land cover is comprised of areas with low urban (i.e., non-vegetated) fractions. Finally, we find the alteration of surface conditions due to enhanced roof albedos influences precipitation within the WRF simulation, in particular during the heat waves. Further research would be necessary to determine the robustness of this last finding.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1973

New techniques for determining sizes of satellites and asteroids.

It is pointed out that until very recently not even a crude idea of the sizes was available for any but the five brightest satellites and, more marginally, the three brightest asteroids. Attention is given to three new techniques which are yielding radii for dozens of small objects and which, by virtue of their independence of angular size, are capable of extension to even smaller and fainter objects. The first new technique, and by far the most precise, is to derive the radius, and in many cases the shape as well, from timings of an occultation of a star by the small body. Both of the other new techniques are based on methods of determining surface reflectivities, since once the geometric albedo is known, the radius can be determined from the brightness.

Morrison, D.↗
NASA NTRS1973

Jovian satellite - Satellite eclipses and occultations.

Toward the end of 1973 and in the first part of 1974, when the planes of the orbits of the four large Galilean satellites cross the sun and the earth, satellite-satellite eclipses and occultations will occur. Calculations indicate that during this period 350 such events will occur, most of them potentially observable. From observation of a few of these events the ephemerides of the satellites can be improved, radii and limb darkening curves determined, and crude information about the degree and extent of albedo fluctuations deduced. If a concerted effort were made and a large fraction of these events carefully observed, it would be possible to invert the light curves to obtain albedo maps of most of the surface area at a typical resolution of about 100 km for JI and JII and somewhat poorer for JIII and JIV.

Brinkmann, R. T.↗
NASA NTRS1973

Meteorological interpretation of clouds or cloud systems appearing on pictures of the Alpine region received from the Earth Resources Technology Satellite (ERTS-1)

The author has identified the following significant results. Three examples of cloud-interpretation from ERTS-1 pictures are presented. When the wind speed is large enough, the cumuli are found arranged in lines that are in average two kilometers apart from each other. These lines are grouped in lines made of small cumuli and in lines made up of well developed ones. These last lines are fused on the APT picture and appear as single lines. Fog-mapping for a given region is possible if the topography of the region is known. The stratified clouds lying over mountains or in valleys begin to dissolve above the middle of the valleys and not against the slopes. As water shows a weak albedo in the near infrared, wet surfaces will appear darker than their neighborhoods. This feature seems to be confirmed by the dark spot in the north of Bozen (Southern Tyrol) that can be seen on the ERTS-1 picture taken on 31 August 1972.

Piaget, A.↗
NASA NTRS1979

Sulphur flows on Io

Flows of liquid sulfur are discussed as the sources of the variegated color patterns observed on Io. The variation of the viscosity of liquid sulfur as it cools from black to red to orange to yellow are shown to explain the black and red-black colors of the calderas, where molten sulfur reaches the surface, the red sinuous deposits presumably formed by high-viscosity laminar flows, and the yellow and orange-yellow plains, a product of rapid, turbulent flows. The sulfur allotropes responsible for these colors are preserved in the rapid quenching of molten sulfur, with a characteristic decay time under Ionian conditions estimated to be greater than the lifetime of Io. Observations of an atmospheric pressure of 10 to the -6th bar indicate that only a small fraction of Io is molten at any one time, however the entire surface is renewed in color and albedo by sulfur flows every thousand years.

Sagan, C.↗
NASA NTRS1981

Long-wave stratospheric transmission of Mount St. Helens ejecta

The NASA/Ames Research C-141 aircraft underflew the Mount St. Helens ejecta plume in Utah three days after the eruption. Upward-looking 20-40-microns on-board radiometry provided data resulting in a calculated long-wave transmission of 0.93. From this value, an optical depth of 0.073 is inferred. This value is compared with an accepted background, stratospheric infrared optical depth of 0.06. Assumptions on particle size, shortwave albedo, and thermal warming imply little surface temperature change caused by the ejecta on the third day immediately following the eruption.

Kuhn, P. M.↗
NASA NTRS1981

Global and local fluctuations of winter and summer simulations with the GLAS climate model

Winter and summer simulations were carried out with an improved version of the GLAS general circulation model. An improved method of computing the boundary layer fluxes, and a more realistic specification of the albedo of snow and ice covered surfaces were used. Each particular diagnostic quantity was computed from the model data and each of the 15 years of observations in precisely the same way, wherever possible. The reported observational results are averaged over the 15 winters or summers, as appropriate.

Straus, D. M.↗
NASA NTRS1980

Fractures on Europa - Possible response of an ice crust to tidal deformation

The surface of Europa contains a planetwide system of low albedo lineaments which have been interpreted as fractures in an icy crust. The pattern of fractures on the surface consists of radial and concentric fractures having the general appearance of tension cracks within a region near the antipode of the sub-Jupiter point. Outside this region, linear fractures intersect at angles near 60 deg, suggesting that they are conjugate shear fractures. The orientation of this pattern on the surface suggests that a principal axis of the deformation that produced the fractures was approximately radial to Jupiter. Fracturing may thus be consistent with an origin due to cyclical tidal deformation resulting from orbital eccentricity. Orbital eccentricity related to a relatively recent establishment of orbital resonance among the Galilean satellites may explain the presence of fractures in a relatively young, lightly cratered planetary surface.

Helfenstein, P.↗
NASA NTRS1984

Mobility of water ice on Callisto - Evidence and implications

Voyager images of Callisto reveal evidence for the accumulation of a bright volatile, presumably water ice, on north-facing slopes in the north polar region. The geometry of these accumulations suggests that ice migration in Callistoan high latitudes is dominated by thermal sublimation, controlled by insolation-dependent surface temperature contrasts. Such sublimation-dominated migration may result in the cold-trapping of most of the surface ice in discrete high-albedo regions.

Spencer, J. R.↗
NASA NTRS1986

Infrared observations of the Uranian system

Initial results are presented from analyses of IR interferometer spectrometer data collected by Voyager 2 during passes of Uranus and the moons Miranda and Ariel. The data covered reflected solar radiation in the visible and near-IR and thermal emissions between 25 and 50 microns. An equatorial atmospheric He mole fraction of 0.10-0.20 and a mass fraction of 0.16-0.34 was observed for Uranus. Para-hydrogen was also a significant fraction Uranus CH4 atmosphere. Average polar and equatorial spectra were employed to generate vertical temperature profiles between 60-900 mbar, with the finding that the temperatures at the equator and the poles are markedly similar between 400-900 mbar. The effective temperature of Uranus had a calculated upper limit of about 59.4 K, while the subsolar temperatures of Miranda and Arial were around 86 and 84 K, respectively. The albedos of the two satellites indicated surface microstructures composed of isotopically scattering grains.

Hanel, R.↗
NASA NTRS1987

Research relative to angular distribution of snow reflectance/snow cover characterization and microwave emission

Remote sensing has been applied in recent years to monitoring snow cover properties for applications in hydrologic and energy balance modeling. In addition, snow cover has been recently shown to exert a considerable local influence on weather variables. Of particular importance is the potential of sensors to provide data on the physical properties of snow with high spatial and temporal resolution. Visible and near-infrared measurements of upwelling radiance can be used to infer near-surface properties through the calculation of albedo. Microwave signals usually come from deeper within the snow pack and thus provide depth-integrated information, which can be measured through clouds and does not relay on solar illumination.Fundamental studies examining the influence of snow properties on signals from various parts of the electromagnetic spectrum continue in part because of the promise of new remote sensors with higher spectral and spatial accuracy. Information in the visible and near-infrared parts of the spectrum comprise nearly all available data with high spatial resolution. Current passive microwave sensors have poor spatial resolution and the data are problematic where the scenes consist of mixed landscape features, but they offer timely observations that are independent of cloud cover and solar illumination.

Dozier, Jeff↗
NASA NTRS1992

Mars: Compositional variability of ferric/ferrous minerals and polar volatiles from groundbased imaging spectroscopy

In an attempt to further constrain the ferric and ferrous mineralogy of Mars, Bell et al. (1989; 1990) obtained high resolution imaging spectroscopic data of much of the Martian surface in the visible and near-infrared (0.4-1.1 micron) during the 1988 opposition. Preliminary analysis of these data showed further evidence of crystalline hematite absorption features at 0.8-0.9 microns and 0.6-0.7 microns. Additionally, the 0.6-0.7 micron Fe(III) band was shown to vary across the surface, with a substantial correlation with albedo in the region studied. Calibration of this 1988 data set (along with a similar data set obtained during the 1990 opposition) has been ongoing, and some of the most recent results of the analysis of these data using linear spectral mixture modeling are reported.

Bell, James F., III↗
NASA NTRS1992

Late quaternary time series of Arabian Sea productivity: Global and regional signals

Modern annual floral and faunal production in the northwest Arabian Sea derives primarily from upwelling induced by strong southwest winds during June, July, and August. Indian Ocean summer monsoon winds are, in turn, driven by differential heating between the Asian continent and the Indian ocean to the south. This differential heating produces a strong pressure gradient resulting in southwest monsoon winds and both coastal and divergent upwelling off the Arabian Peninsula. Over geologic time scales (10(exp 4) to 10(exp 6) years), monsoon wind strength is sensitive to changes in boundary conditions which influence this pressure gradient. Important boundary conditions include the seasonal distribution of solar radiation, global ice volume, Indian Ocean sea surface temperature, and the elevation and albedo of the Asian continent. To the extent that these factors influence monsoon wind strength, they also influence upwelling and productivity. In addition, however, productivity associated with upwelling can be decoupled from the strength of the summer monsoon winds via ocean mechanisms which serve to inhibit or enhance the nutrient supply in the intermediate waters of the Indian Ocean, the source for upwelled waters in the Arabian Sea. To differentiate productivity associated with wind-induced upwelling from that associated with other components of the system such as nutrient sequestering in glacial-age deep waters, we employ a strategy which monitors independent components of the oceanic and atmospheric subsystems. Using sediment records from the Owen Ridge, northwest Arabian Sea, we monitor the strength of upwelling and productivity using two independent indicators, percent G. bulloides and opal accumulation. We monitor the strength of southwest monsoon winds by measuring the grain-size of lithogenic dust particles blown into the Arabian Sea from the surrounding deserts of the Somali and Arabian Peninsulas. Our current hypothesis is that the variability associated with the 41 kyr power in the G. bulloides and opal accumulation records derive from nutrient availability in the intermediate waters which are upwelled via monsoon winds. This hypothesis is testable by comparison with Cd records of intermediate and deep waters of the Atlantic and Indian Ocean.

Clemens, Steven C.↗
NASA NTRS1994

Handbook of the Radiation Regime of the Arctic Basin: Results from the Drift Stations

This Handbook summarizes the radiation data from the Soviet 'North Pole' drifting research stations operated in the Arctic from 1950 to 1991. The Handbook contains reduced mean monthly values of the fluxes of solar radiation for solar elevations up to 35 deg at 5 deg intervals, monthly totals of the net radiation and its constituents, and mean monthly values of the albedo of the sea-ice surfaces. The Handbook presents information of interest to specialists studying the physics of the atmosphere, climatology, geography, and related disciplines.

Mishin, A. A.↗
NASA NTRS1990

The Galileo dust detector

The Galileo Dust Detector is intended to provide direct observations of dust grains with masses between 10(sup -19) kg and 10(sup -9) kg in interplanetary space and in the Jovian system, to investigate their physical and dynamical properties as functions of the distances to the Sun, to Jupiter and to its satellites, to study its interaction with the Galilean satellites and the Jovian magnetosphere. Surface phenomena of the satellites (like albedo variations), which might be effects of meteoroid impacts will be compared with the dust environment. Electric charges of particulate matter in the magnetosphere and its consequences will be studied; e.g. the effects of the magnetic field on the trajectories of dust particles and fragmentation of particles due to electrostatic disruption. The investigation is performed with an instrument that measures the mass, speed, flight direction and electric charge of individual dust particles. It is a multi-coincidence detector with a mass sensitivity 10(sup 6) times higher than that of previous in-situ experiments which measured dust in the outer solar system. The instrument weighs 4.2 kg, consumes 2.4 W, and has a normal data transmission rate of 24 bits/s in nominal spacecraft tracking mode. On December 29, 1989 the instrument was switched-on. After the instrument had been configured to flight conditions cruise science data collection started immediately. In the period to May 18, 1990 at least 168 dust impacts have been recorded. For 81 of these dust grains, masses and impact speeds have been determined. First flux values are also given.

Gruen, E.↗
NASA NTRS2001

Shortwave Radiative Fluxes, Solar-Beam Transmissions, and Aerosol Properties: TARFOX and ACE-2 Find More Absorption from Flux Radiometry than from Other Measurements

The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2) made simultaneous measurements of shortwave radiative fluxes, solar-beam transmissions, and the aerosols affecting those fluxes and transmissions. Besides the measured fluxes and transmissions, other obtained properties include aerosol scattering and absorption measured in situ at the surface and aloft; aerosol single scattering albedo retrieved from skylight radiances; and aerosol complex refractive index derived by combining profiles of backscatter, extinction, and size distribution. These measurements of North Atlantic boundary layer aerosols impacted by anthropogenic pollution revealed the following characteristic results: (1) Better agreement among different types of remote measurements of aerosols (e.g., optical depth, extinction, and backscattering from sunphotometers, satellites, and lidars) than between remote and in situ measurements; 2) More extinction derived from transmission measurements than from in situ measurements; (3) Larger aerosol absorption inferred from flux radiometry than from other measurements. When the measured relationships between downwelling flux and optical depth (or beam transmission) are used to derive best-fit single scattering albedos for the polluted boundary layer aerosol, both TARFOX and ACE-2 yield midvisible values of 0.90 +/- 0.04. The other techniques give larger single scattering albedos (i.e. less absorption) for the polluted boundary layer, with a typical result of 0.95 +/- 0.04. Although the flux-based results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., unknown gas absorption). Current uncertainties in aerosol single scattering albedo are large in terms of climate effects. They also have an important influence on aerosol optical depths retrieved from satellite radiances. More tests are needed of the consistency among different methods and of the effects of changing humidity on aerosol.

Russell, Philip B.↗