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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 361 records · Page 20
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NASA NTRS1978

Effects of cloud size and cloud particles on satellite-observed reflected brightness

Satellite observations allowed obtaining data on the visible brightness of cumulus clouds over South Park, Colorado, while aircraft observations were made in cloud to obtain the drop size distributions and liquid water content of the cloud. Attention is focused on evaluating the relationship between cloud brightness, horizontal dimension, and internal microphysical structure. A Monte Carlo cloud model for finite clouds was run using different distributions of drop sizes and numbers, while varying the cloud depth and width to determine how theory would predict what the satellite would view from its given location in space. Comparison of these results to the satellite observed reflectances is presented. Theoretical results are found to be in good agreement with observations. For clouds of optical thickness between 20 and 60, monitoring cloud brightness changes in clouds of uniform depth and variable width gives adequate information about a cloud's liquid water content. A cloud having a 10:1 width to depth ratio is almost reaching its maximum brightness for a specified optical thickness.

Reynolds, D. W.↗
NASA NTRS1977

Moisture convergence from a combined mesoscale moisture analysis and wind field for 24 April 1975

Precipitable water values inferred from the Vertical Temperature Profile Radiometer data of the polar orbiting NOAA-4 satellite are used in conjunction with wind-field analyses obtained from Synchronous Meteorological Satellite visible-channel data to study the moisture convergence in the boundary layer immediately preceding a storm. This combination of data simulates the information that will be available from the Visible and Infrared Spin-Scan Radiometer on board the GOES-D satellite, which is scheduled to begin operation in the 1980s. Serviceable representations of boundary layer flow are developed through analysis of the satellite infrared cumulus velocities, although the flow representations are not exactly located in the vertical.

Negri, A. J.↗
NASA NTRS1977

Analysis of satellite derived winds for April 24, 1975

Cumulus cloud tracking based on short-interval GOES satellite imagery provided a representation of the low-level wind fields existing prior to the outbreak of severe thunderstorms. Through use of the satellite-derived winds and surface mixing ratios, moisture convergence fields were estimated. The effect of the spatial distribution of trackable clouds on the computed dynamic fields was also investigated.

Maddox, R. A.↗
NASA NTRS1977

Sulfur in lunar mare basalts as a function of bulk composition

Sulfur abundances and metallic iron abundances in 18 Apollo 12 mare basalts were determined. No correlation between sulfur abundance and metallic iron content was detected; metallic iron abundances are not primarily caused by S loss. Sulfur abundances, directly related to the bulk composition of the rocks and especially to the TiO2 content, increase with increasing degrees of fractionation and appear to result from S concentration in the melts during fractionation. Unlike the Apollo 17 melts, the Apollo 12 melts were unsaturated with respect to sulfide. Composition appears to control S content for Apollo 17 basalts, and cumulus processes may cause Fe-FeS enrichment.

Gibson, E. K., Jr.↗
NASA NTRS1975

Mare basalts - Melting experiments and petrogenetic interpretations

Equilibrium crystallization sequences are determined in melting experiments in vacuum at Fe saturation on synthetic mare basalt compositions 70215 and 15318 Red Glass (both high-Ti) as well as 15555-15016 (low-Ti). The experiments confirm that much of the chemical variation within both the high- and low-Ti suites is controlled by near-surface fractionation processes, although the two suites cannot be related by such mechanisms. The components and crystallization products of the liquidus at various temperatures and pressures are reported. Mare basalt petrogenesis is interpreted in terms of high-pressure equilibria at Fe saturation; it is suggested that low-Ti basalts represent partial melts of a differentiated olivine-pyroxenite lunar mantle at 240 km or deeper, while cumulus clinopyroxene in the source is responsible for their REE characteristics. The formation of high-Ti basalts is considered.

Kesson, S. E.↗
NASA NTRS1977

Recent improvements in the GISS model of the global atmosphere

A simulation of the July climatology by the GISS GCM produced tropospheric temperatures which were systematically 1-2 C lower than the observed temperatures in the middle latitudes of the Northern Hemisphere. Convective cloud cover was nearly double the observed level in this region. Planetary albedo was much higher than the observed July value and showed the wrong seasonal trend. These problems have been solved through modifications of the GISS scheme for the parameterization of cumulus convection.

Helfand, H. M.↗
NASA NTRS1979

Topoclimatological and snowhydrological survey of Switzerland

The author has identified the following significant results. The chosen time of overflight of HCMM seems to be ideal for the study of basic climatological events. Nocturnal temperature inversion zones are easily detectable and their dependency on the relief is clearly seen. Especially the alpine valleys show a very differentiated pattern of cold lakes, separated by warmer zones as a consequence of rock and forrest barriers or changes in the valley profile. Wet areas are usually colder than dry parts under comparable topographic conditions. Even very small topographic obstacles are able to block up the flow of cold air masses (or ground water flow). Urban areas are clearly detectable. Differences to the surface temperatures of surrounding rural land are much more significant during day-time (mainly during the summer months). Fog layers are clearly defined in the visible channel (day-time), but much more difficult to identify in the IR (mainly during the night). There is not a fundamental difference to NOAA-analysis of cloud systems. The most important advantage is the better detectability of convective cloud systems (small cumulus clouds).

Winiger, M.↗
NASA NTRS1978

Tropical sea surface temperature - An interactive one-dimensional atmosphere-ocean model

It is shown that the (cumulus) convective processes in the tropics may be described by a one-dimensional cloud model, while the near-surface ocean may similarly be described by a one-dimensional mixed-layer model. The coupling is achieved through a sea surface flux budget combined with the flux parameterizations implied by Monin-Obukhov similarity theory. The coupled one-dimensional atmosphere-ocean model is applied to the equilibrium situation in which all temperatures reach a steady state. For the ocean, the fluxes must vanish in equilibrium, but the atmosphere maintains a stable lapse rate by balancing cumulonimbus heating against net radiative cooling. All water precipitating from cumulonimbus clouds must have evaporated from the sea. It is shown that this equilibrium system is closed and determinable solely in terms of the solar constant.

Sarachik, E. S.↗
NASA NTRS1979

Petrology and origin of the shergottite meteorites

The results of petrographic studies and 1 atmosphere melting experiments of Shergotty and Zagami shergottites, the origin and evolution of the shergottites, and the relationship of the shergottite parent body to the parent bodies of the other achondrites and to the earth are examined. Shergotty and Zagami differ in the proportions of cumulus pyroxenes and crystallized intercumulus liquid, but their compositions are similar. Shergottites can be distinguished from other achondrite groups by their mineralogies, crystallization sequences, and inferred source region compositions, but their source regions can be related to other achondrite types by addition or loss of volatile components. Shergottites and terrestrial basalts show similar oxidation states and minor element concentrations which may be accounted for by accretion of similar materials to produce the terrestrial upper mantle and the shergottite parent body, or by accretion of the earth's upper mantle from planetisimals similar to the shergottite parent body.

Stolper, E.↗
NASA NTRS1978

Airborne measurements of cloud-forming nuclei and aerosol particles in stabilized ground clouds produced by solid rocket booster firings

Airborne measurements of cloud volumes, ice nuclei and cloud condensation nuclei, liquid particles, and aerosol particles were obtained from stabilized ground clouds (SGCs) produced by Titan 3 launches at Kennedy Space Center, 20 August and 5 September 1977. The SGCs were bright, white, cumulus clouds early in their life and contained up to 3.5 g/m3 of liquid in micron to millimeter size droplets. The measured cloud volumes were 40 to 60 cu km five hours after launch. The SGCs contained high concentrations of cloud condensation nuclei active at 0.2%, 0.5%, and 1.0% supersaturation for periods of three to five hours. The SGCs also contained high concentrations of submicron particles. Three modes existed in the particle population: a 0.05 to 0.1 micron mode composed of aluminum-containing particles, a 0.2 to 0.8 micron mode, and a 2.0 to 10 micron mode composed of particles that contained primarily aluminum.

Hindman, E. E., II↗
NASA NTRS1980

Occurrence and mineral chemistry of high pressure phases, Portrillo basalt, southcentral New Mexico

Inclusions of clinopyroxenite, kaersutiteclinopyroxenite, kaersutite-rich inclusions, wehrlite and olivine-clinopyroxenite together with megacrysts of feldspar, kaersutite and spinel are found loose on the flanks of cinder cones, as inclusions within lava flows and within the cores of volcanic bombs in the Quaternary alkali-olivine basalt of the West Potrillo Mountains, southcentral New Mexico. Based on petrological and geochemical evidence the megacysts are interpreted to be phenocrysts which formed at great depth rather that xenocrysts of larger crystal aggregates. These large crystals are believed to have formed as stable phases at high temperature and pressure and have partially reacted with the basalt to produce subhedral to anhedral crystal boundaries. It can be demonstrated that the mafic and ultramafic crystal aggregates were derived from an alkali-basalt source rock generated in the mantle. The inclusions are believed to represent a cumulus body or bodies injected within the lower crust or upper mantle.

Hoffer, J. M.↗
NASA NTRS1979

Shallow convection on day 261 of GATE - Mesoscale arcs

Cloudy convection in the moist layer of a cloud cluster growing in the GATE ship array is examined. Analyses suggest that the moist layer was dominated by features of horizontal dimension roughly 40 km and lifetime roughly 2 h, with arc patterns triggered by dense downdraft air accompanying rainfall, and composed of many small cumulus clouds. Aircraft recorded data on thermodynamic quantities and winds, indicating that the arcs persisted as mesoscale circulations driven by the release of latent heat in the clouds, rather than being driven by the original density current at the surface. It is also suggested that the mesoscale cloud patterns of the moist layer play a primary role in heat transfer upward within this layer, and contribute to the forcing of showering midtropospheric clouds.

Warner, C.↗
NASA NTRS1978

The characteristics of evolving mesoscale systems over mountainous terrain as revealed by radar and PAM

The paper deals with measurements made within the South Park area (which is located near Denver, Colorado, and is a natural genesis area for cumulus clouds) in July and August 1977, using powered aircraft, sailplanes, rawinsondes, boundary layer profilers, acoustic sounders, micrometeorological towers, lidar, research radar, triple-Doppler radar, and a square grid of surface meteorological stations. Extensive analysis revealed a very complex picture of thunderstorm-scale, large-mesoscale, and synoptic-scale interactions.

George, R. L.↗
NASA NTRS1978

Treatment of cloudiness in regional scale - Numerical weather prediction models

A numerical weather prediction model is considered in which cloud water and precipitation are explicitly predicted as functions of three space dimensions and time. Approximations in the thermodynamic and continuity equations are discussed in detail, as well as the cumulus parameterization and the cloud microphysics parameterization. An example of a real-data forecast indicates that very accurate quantitative precipitation and cloud cover forecasts are possible using initial observations from only the relatively sparse rawinsonde network in the U.S.

Kreitzberg, C. W.↗
NASA NTRS1978

Progress and problems in regional numerical weather prediction

The status of research and development on numerical weather prediction at a new scale, a horizontal mesh size of about 35 km over a horizontal domain of about 1700 sq km, is presented. The model forecasts weather, including clouds and stratiform and cumulus precipitation out to 24 h beyond the latest observation time. The primary problems in the development of techniques to incorporate the preceding forecast in more recent, detailed observations from surface-based and satellite observations are studied in detail.

Kreitzberg, C. W.↗
NASA NTRS1980

Properties of African squall lines inferred from time-lapse satellite imagery

Analysis of 48 h of time-lapse satellite imagery of a family of squall lines in Africa links the phenomena with a characteristic cloud cluster and with a wind field perturbation which is enhanced in passing through an African easterly wave trough. A thin 'arc line' of low-level developing cumulus, a salient feature of the squall lines on the imagery, is shown to occur at the front boundary of the mesoscale/convective scale subsidence. Analysis of the wind field indicates that a squall line is associated with a vorticity center in the mid-level easterly flow which accompanies the mesoscale subsidence which, in turn, contributes to further forced ascent of subcloud air along the front of the squall line into convective towers which merge into an extensive anvil. The squall lines evolved through a life cycle of 6 to 12 h while the larger cloud cluster and wind perturbation lasted over 48 h. The magnitude of the vertical mass exchange suggests that squall-line families contribute significantly to the tropical energy balance.

Fortune, M.↗
NASA NTRS1980

Deep convection on day 261 of GATE

The structural features of the deep convection observed on September 18, 1974, day 261 of the GARP Atlantic Tropical Experiment (GATE), as the ridge axis of a 700 mb wave passed the center of the GATE B-scale network are reported. Satellite and aircraft maps indicate the presence of clouds penetrating above 2.5 km into the middle troposphere organized in bands about 9 km apart and aligned roughly along the direction of the wind shear in the cloud layer. Radar echoes corresponding to cumulus convection of lifetime, peak height and peak rainfall rates on the orders of 30 min, 6 km and 1.3 mm/h, respectively, were observed to triple in number density as convergence at 950 hPa increased from 1.5 to 3 x 10 to the -5th/sec. The structural features of the radar echoes indicate that the day was similar to a mesoscale precipitation feature of Leary and Houe (1979), with the cluster consisting of many echoes appearing in succession. Data from aircraft penetrations of the deep convection reveal downdrafts accompanying the precipitation and updrafts immediately to their south. Shipboard and rawinsonde observations show that the convective downdrafts brought down air of low pseudo-equivalent potential temperature, with local surface convergence of up to 0.001/sec. Mean wind shears through the cloud layer to the top of a main cloud layer are found to be only 75% greater than those of Malkus (1958) for the Caribbean, with shears just above the cloud base several factors larger.

Warner, C.↗
NASA NTRS1980

Satellite-inferred morning-to-evening cloudiness changes

Outgoing infrared radiation values inferred from radiance measurements in the water vapor window taken at approximately 0900 and 2100 LT by scanning radiometers aboard the polar orbiting NOAA satellites are compared in order to determine whether a significant diurnal variation exists. Data with a resolution of 2.5 deg in latitude and longitude are mapped for latitudes between 50 deg N and 50 deg S for two seasons, June-August 1975 and December 1975-February 1976. Over land regions and coastal waters it is found that the 12-h differences in outgoing IR are dominated by middle and high clouds, likely of convective origin. Over the tropical oceans there is evidence of a morning bias in high cloudiness (possibly of convective origin) and low cloudiness (stratus, stratocumulus and trade wind cumulus), and an evening bias in middle cloudiness. Because of the compensation between these three cloud regimes the net morning to evening differences in outgoing IR are rather small except over the eastern oceans where the low cloud regime predominates and tends to produce a weak but statistically significant evening maximum.

Short, D. A.↗