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At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Horizontal energy propagation in a baroclinic atmosphere with meridional and zonal structure

A baroclinic model was developed. The model is linear, steady state, baroclinic (2 level) and based on the primitive equations. The unique features of the model are: (1) The basic state u and T fields are functions of wavelength, theta, and rho, (2) A mean meridional circulation v, w, which may be a function of wavelength, theta, and rho, and p may be included, (3) Dissipation may be a function of theta, wavelength, rho, p (e.g., differ over land and sea). Because the basic state is a function of longitude, the equations are not separable in wavelength and the usual semi-spectral solution procedure is not applicable. The model solutions can be found in a straight forward (brute force) way by discretizing the model equations directly on a wavelength, theta, rho, p grid. There are six dependent (perturbation) variables: u, v, and geopotential at levels 1 and 2. The thermal forcing is prescribed at the intermediate vertical level. The linearized equations may be written.

Youngblut, C.↗
NASA NTRS1984

Fluvial drainage systems: Margaritifer Sinus and Agyre (NC, NE) quadrangles, Mars

Fluvial drainage systems, delineated by mapping on stereo pairs of Viking Orbiter images, have developed in various-sized basins in the Margaritifer Sinus (MC-19) and Agyre (MC-26) Quadrangles, Mars. The Ladon Valles system is the largest, draining into and through two multi-ringed impact basins. Smaller fluvial basins to the southeast of the Ladon structural basin appear to have internal drainage. An intermediate-scale fluvial basin containing Himera Vallis extends along a north-south axis at 22 W and opens northward toward outflow channels south of Margaritifer Chaos. Stereo-pair mapping was extended furhter to the east, in MC-19 Ne, Se, and MC-26 NE, to investigate sources of outflow to the Ares Vallis system. The direction of flow in the channel at the northeast quadrant of the Ladon Basin is unresolved at present because of the poor quality of images available to form stereo pairs. However, an easterly drainage basin boundary running north-south along longitude 9 W, and extending westward at latitude 32-35 S, encloses a series of longitudinal drainage systems. Both the Parana Valles-Loire Vallis system and the Samara Valles system appear to drain in a northwesterly direction. The Samara flows to the Himera drainage basin, and the Parana-Loire to the northeast Ladon channel area.

Boothroyd, J. C.↗
NASA NTRS1984

The study of the physics of cometary nuclei

The observations of comet P/Holmes 1892III, exhibiting two 8 to 10 magnitude bursts, were carefully analyzed. The phenomena are consistent with the grazing encounter of a small satellite with the nucleus. The grazing encounter produced, besides the first great burst, an active area on the nucleus, which was rotating retrograde with a period of 16.3 hr and inclination nearly 180 deg. After the final encounter, the spin period was essentially unchanged, but two areas became active, separated some 164 deg in longitude on the nucleus. After the first burst the total magnitude fell less than two magnitudes, while the nuclear region remained diffuse or complex, rarely if ever showing a stellar appearance. The fading was much more rapid after the second burst (barely naked eye at maximum) while the nucleus frequently stellar after the first day. It seems reasonable to conclude that the grazing encounter distributed a volume of large chunks in the neighborhood of the nucleus, maintaining activity for weeks.

Whipple, F. L.↗
NASA NTRS1984

Vegetation, land-use and seasonal albedo data sets: Documentation of archived data tape

Global data bases of vegetation, land use, and land cover were compiled at a 1 deg latitude x 1 deg longitude resolution, drawing on approximately 100 published sources complemented by a large collection of satellite imagery. Six datasets prepared and archived at NCAR are described: a vegetation data set (VEGTYPE) representing natural (pre-agricultural) vegetation based on the UNESCO classification system; a cultivation intensity data set (CULTINT) defining the areal extent (expressed as %) of presently cultivated land in the 1 x 1 cells; and four integrated surface-albedo data sets (January, April, July, October) for snow-free conditions except for permanently snow-covered continental ice, incorporating natural vegetation and cultivation characteristics from the vegetation and cultivation-intensity data sets. Non-zero data are included for permanent land only, including continental ice. Documentation of the data-tape format as well as descriptions and regional maps of the individual data sets are presented.

Matthews, E.↗
NASA NTRS1982

The geology of Mare Acidalium quadrangle Mars

The Mare Acidalium quadrangle is described. Mare Acidalium quadrangle lies between 30 - 60 N latitude and 0 - 60 W longitude. Materials that were used in mapping the quadrangle include Mariner and Viking single-frame images and photomosaics. Preliminary geologic mapping was done on five 1:2,000,000-scale photomosaics and selected higher resolution photomosaics. The data were then compiled on one sheet at a scale of 1:5,000,000. The Mariner 9 mission revealed a striking planetary dichotomy; high-standing, heavily-cratered terrain in the south that contrasts with low-lying, lightly-cratered terrain in the north. Both of these terrain types occur in Mare Acidalium quadrangle. The boundary separating the elevated cratered plateau from the lower plains is, in many places, an escarpment 1-2 km-high, however, in a few places where there is no escarpment, plains materials embay and overlap the heavily-cratered plateau material.

Witbeck, N. E.↗
NASA NTRS1984

Helium 10830 Angstrom Irradiance: 1975-1983

A fairly complete time series from late 1974 to mid-1983 is available of values of the equivalent width of the He I 10830A chromospheric spectrum line averaged over the visible solar disk. Variation from about 25 mA in 1975 to about 80 mA in late 1981 is the major component of the signal. The 10830 variation reaches minimum about a year before the sunspot minimum and reaches maximum about a year after sunspot maximum. Superposed on the solar cycle variation is a modulation of up to + or - 13 mAdu to the passage of active regions across the disk. Power spectral analysis of the time series shows a major peak at a synodic rotation period of 27.42 days and smaller peaks at 1/2, 1/4 and 1/6 of this period. The spectrum is well modeled by a basic fluctuating component with an exponentially decaying autocovariance function of scale time of 43 days. Analysis of the data indicates that the rotational modulation occurs in episodes that last from 4 to 10 rotations. These episodes arise when active regions tend to occur in a limited longitude range. The analysis also shows that the apparent rotation period increased from 1977 to 1981. The apparent rotation period since 1981 is markedly shorter.

Harvey, J. W.↗
NASA NTRS1981

Moments of inclination error distribution computer program

A FORTRAN coded computer program is described which calculates orbital inclination error statistics using a closed-form solution. This solution uses a data base of trajectory errors from actual flights to predict the orbital inclination error statistics. The Scott flight history data base consists of orbit insertion errors in the trajectory parameters - altitude, velocity, flight path angle, flight azimuth, latitude and longitude. The methods used to generate the error statistics are of general interest since they have other applications. Program theory, user instructions, output definitions, subroutine descriptions and detailed FORTRAN coding information are included.

Myler, T. R.↗
NASA NTRS1983

Conservation laws of wave action and potential enstrophy for Rossby waves in a stratified atmosphere

The evolution of wave energy, enstrophy, and wave motion for atmospheric Rossby waves in a variable mean flow are discussed from a theoretical and pedagogic standpoint. In the absence of mean flow gradients, the wave energy density satisfies a local conservation law, with the appropriate flow velocity being the group velocity. In the presence of mean flow variations, wave energy is not conserved, but wave action is, provided the mean flow is independent of longitude. Wave enstrophy is conserved for arbitrary variations of the mean flow. Connections with Eliassen-Palm flux are also discussed.

Straus, D. M.↗
NASA NTRS1983

The control networks of Tethys and Dione

Control networks of the Saturnian satellites Tethys and Dione have been established photogrammetrically from pictures taken by the two Voyager spacecraft during their flybys. Coordinates of 110 points on Tethys and 126 points on Dione are listed; selected points are identified on U.S. Geological Survey maps of the satellites, and many are identified by name. Measurements of these points were made on six pictures from Voyager 1 and 21 from Voyager 2 for Tethys, and on 27 pictures from Voyager 1 and one from Voyager 2 for Dione. The longitude systems on the satellites have been defined by craters on their surfaces. The mean radii have been determined as 524 + or - 5 km for Tethys and 559 + or - 5 km for Dione.

Davies, M. E.↗
NASA NTRS1983

Mapping electrostatic potentials from the ionosphere to the magnetosphere

Techniques for mapping observed ionospheric-potential distributions into the magnetosphere are discussed and illustrated using published Millstone Hill and Chatanika incoherent-scatter-radar data. It is shown that the mapping of a given field line to the equator is subject to strong diurnal and seasonal variations (attributed to the combination of internal and tail-current magnetic-field sources at auroral latitudes and the diurnal variation of solar declination in dipole coordinates) and longitude-dependent differences in ionospheric geometry. A mapping based on the tilt-dependent model of Olson and Pfitzer (1977) and using an empirical ionospheric-potential distribution derived from Chatanika plasma-drift measurements produces a relativity uniform magnetospheric electric field in the tail region. The field at 12 earth radii (Re) is found to be between 1 and 2 kV/Re; at the dawn-dusk meridian beyond the plasmasphere it is as high as 5 kV/Re. The plasmasphere is shown to have a dusk bulge in its equipotential structure and to be almost symmetric about the dawn-dusk meridian.

Sojka, J. J.↗
NASA NTRS1983

Differences in the temporal variations of solar UV flux, 10.7-cm solar radio flux, sunspot number, and Ca-K plage data caused by solar rotation and active region evolution

Attention is given to two types of temporal variations in the solar UV spectral irradiance caused by solar rotation and active region evolution. It is noted that the first type of dissimilar temporal behavior occurs when concentrations of solar active regions evolve at solar longitudes nearly 180 deg apart. Both the UV observations and modeled UV fluxes based on Ca-K plage data then exhibit pronounced 13-day periodicity, whereas the 10.7-cm solar radio flux and sunspot number exhibit quite dissimilar temporal variations. This type of dissimilarity is related to the modeled UV flux and has a dependence on the solar central meridian distance that is narrower than that for the 10.7-cm radio flux or for sunspot numbers. A second case of marked dissimilarity is seen when major new solar active regions arise and dominate the full-disk fluxes for several rotations. It is found that the strongest peaks in 10.7 cm and sunspot numbers tend to occur on their first rotation, for example, during major dips in the total solar irradiance, whereas the Ca-K plages and UV enhancements peak on the next rotation and then decay more slowly on subsequent rotations.

Donnelly, R. F.↗
NASA NTRS1983

Some observational constraints on the global-scale wind systems of Mars

The present investigation is concerned with the results of a study of wind direction indicators contained in the Viking and Mariner 9 data sets. It is found that wind direction measurements from a variety of indicators, taken over several Mars years at many longitudes, exhibit a high degree of consistency and seasonal reproducibility. It is, therefore, possible to interpret most of the observations in terms of the zonally symmetric circulation of Mars. When combined with models of the atmospheric circulation, observed wind directions can be used to set loose constraints on the polar cap mass fluxes and thermal fields which drive the flows. It is pointed out that polar cap formation seems to control the wind directions at mid and high latitudes in both hemispheres during autumn and early winter.

Kahn, R.↗
NASA NTRS1983

Seventh Foray - Whitlockite-rich lithologies, a diopside-bearing troctolitic anorthosite, ferroan anorthosites, and KREEP

Seventeen nonmare samples, most of them pristine, are characterized, and implications of the new data are discussed. Five pristine samples are from Apollo 14, near the center of the KREEP-rich zone in the moon's western hemisphere. Three of them are alkali anorthosites rich in Ca-phosphate (whitlockite), which apparently crystallized from magmas with REE contents roughly 6 x those of high-K KREEP. The alkali anorthosites probably formed from Mg-rich magmas that assimilated large amounts of urKREEP, but some might have formed by metasomatism of ferroan anorthosite by urKREEP. The gabbronorite/norite classification scheme is not well suited to western hemisphere lithologies, probably due mainly to the overriding effects of longitude-petrochemistry correlations. A diopside-bearing Mg-rich lithology indicates that a low degree of melting was not a prerequisite for producing gabbroic (high-Ca pyroxene-rich) Mg-rich magmas, and suggests that some source regions of Mg-rich magmas were relatively Ca-rich. Several pristine KREEP fragments from Apollo 15 station 2 are texturally and compositionally much like other pristine KREEP, and thus reinforce the evidence that KREEP is highly uniform. The pristine anorthosites, on the other hand, demonstrate further that lunar anorthosites are diverse.

Warren, P. H.↗
NASA NTRS1983

Mars - Subsurface properties from observed longitudinal variation of the 3.5-mm brightness temperature

Extensive 3.5-mm measurements are reported which show a variation in the brightness temperature of Mars, with the Central Meridian Longitude that is generally in phase with the variation at 2.8 cm and is opposite in sign from the variations at 20 microns. It is pointed out that the phase result is not unexpected, since 3.5 mm is longer than the wavelength at which the phase behavior is expected to change. The result that the 3.5-mm rotation curve amplitude is larger than the amplitudes at both 20 microns and 2.8 cm, however, is unexpected. This result, it is noted, can be explained as a consequence of subsurface scattering from rocks smaller than 1.5 cm in radius. A correlation of subsurface scatterers with the location of the high-thermal inertial regions would be consistent with the hypothesis that rock abundance predominates in determining the thermal inertia.

Epstein, E. E.↗
NASA NTRS1983

Venus gravity field - Pioneer Venus Orbiter navigation results

The gravity field of Venus has been modeled by a spherical harmonic expansion of the potential to degree and order seven. The estimates of these coeficients were obtained by combining information from 43 short arcs (4 hr) of line-of-sight Doppler data centered at periapsis. The data arcs were distributed in longitude and time over more than two circulations of Venus by the Pioneer Venus Orbiter subperiapsis point which was confined to the band of latitudes from 14 deg N to 17 deg N. Convergence of the solution has been assured by iterating upon the initial estimate. All estimates were performed with zero a priori information on the gravity coefficients. Since the altitude of periapsis for most of the orbits was within the sensible Venusian atmosphere, drag effects on the estimated harmonics have been removed using an exponential atmosphere density model. Estimates of the mass parameter (GM) of Venus using this dataset are also evaluated.

Williams, B. G.↗
NASA NTRS1983

The control network of Rhea

A control network of the Saturnian satellite Rhea has been established photogrammetrically from pictures taken by the two Voyager spacecraft. Coordinates of 288 control points on Rhea have been computed and listed; some of these are identified on the preliminary U.S. Geological Survey map of Rhea and many of the control point features have been named. Pixel measurements of these points were made on 81 Voyager 1 and 3 Voyager 2 pictures. The longitude system on Rhea is defined by the crater Tore; the 340 deg meridian passes through the center of this crater. The mean radius of Rhea has been determined at 764 + or - 4 km.

Davies, M. E.↗
NASA NTRS1984

Is stellar differential rotation observable?

Daily measures of the disk integral 2.8 GHz solar flux from the years 1947 through 1982 are analyzed to determine the detectability of stellar differential rotation using the tracer method. Autocorrelation and power spectral analyses of 1 yr data sets yield rotation periods whose scatter about the mean period is too large to permit detection of the expected differential rotation signal. The principal noise source is the random appearance of tracer regions on the solar surface, in time and longitude. Criteria are given for optimizing stellar observations and analyses to detect differential rotation.

Labonte, B. J.↗
NASA NTRS1983

Measurements of stratospheric SO2 after the EL Chichon eruptions

Samples of stratospheric trace gases were obtained on eight flights of NASA high-altitude aircraft from April 16 through December 13, 1982. The sampling occurred at altitudes from 15 to 22 km, latitudes from 23 to 52 deg N, and longitudes from 108 to 130 deg W. The cryogenically concentrated samples were analyzed by gas chromatography for SO2, a primary precursor of the gas-to-particle conversion process. The measured mixing ratio of SO2 varied between 8 and 132 pptv. Evidence from aerosol measurements indicates that a few of our early samples may have been collected in the fringes of the volcanic cloud from El Chichon. Samples obtained on some later flights may have been from the eruption cloud but were taken at times when most of the volcanically injected SO2 should have been converted to H2SO4.

Vedder, J. F.↗