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At least 433 records · Page 24

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NASA NTRS1982

Morphology and movements of polarization features on Venus

Ground and spacecraft based polarization observations of Venus detected the signature of the so called 1-micron radius cloud particles that constitute the main cloud deck on Venus, as well as that of sub-micron sized particles that form a haze above this main cloud layer. Whether such observations showed any local clustering or organization in the polarimetry data remained uncertain until the relatively high resolution observations from the Pioneer Venus Orbiter Cloud Photopolarimeter (OCPP) became available. The available polarization data from this instrument was studied to see whether local organization was present, to study the morphology of such features or polarization clouds, and finally, to see if they can be followed in a sequence of observations to study their motions.

Limaye, S. S.↗

NASA NTRS1983

A laser system to remotely sense bird movements

The design and operation of a laser detection system for migrating birds are presented. A battery-powered class-III laser (operating at 904 nm, pulse-repetition rate 5 kHz, pulse duration 100 nsec, and peak power 25 W) and a photodiode receiver are mounted on poles at height 10 m and distance 850 m and equipped with 135-mm f/2.8 collimating lenses; beam diameter at the receiver is 1.7 m. The microprocessor-controlled system is found to detect the passing of an object as small as 30 sq cm in cross section at a distance of 425 m.

Korschgen, C. E.↗

NASA NTRS1984

Coseismic and postseismic vertical movements associated with the 1940 M7.1 Imperial Valley, California, earthquake

Leveling surveys conducted along two routes that cross the Imperial fault in southern California indicate spatially coherent elevation changes attributable to coseismic and postseismic effects of the 1940, M7.1 Imperial Valley earthquake. The 1931-1941 elevation changes are consistent with theoretical models of vertical deformation of an elastic half space for a finite length strike-slip fault, using fault parameters that are consistent with the observed surface offsets following the 1940 earthquake. The elevation changes suggest an earthquake scenario consisting of a large coeismic slip in the southern half of the fault which transferred stress to the northern part as well as to the Brawley fault to the northeast.

Reilinger, R.↗

NASA NTRS1984

On the flow processes in sharply inclined and stalled airfoils in parallel movement and rotation

The purpose of this study is to obtain a deeper insight into the complicated flow processes on airfoils in the region of the buoyancy maxima. To this end calculated and experimental investigations are carried out on a straight stationary, a twisted stationary and a straight rotating rectangular wing. According to the available results the method gives results which can be applied sufficiently for flow applied firmly on all sides for all rotation values. The reliability of the method may be questioned for a flow undergoing transition from the attached to the separated state or for totally separated flow and higher rotation values.

Kohler, M.↗

NASA NTRS1985

Contributions on the Subject of Longitudinal Movements of Aircraft in Wind Shears

The effect of downburst-type wind shears on the longitudinal dynamic behavior of an unguided aircraft is simulated numerically on the basis of published meteorological data and the flight characteristics of an A300-B passenger jet. The nonlinear differential equations of the aircraft motion are linearized by conventional methods, and the wind effects are introduced via the linear derivatives of the wind components referred to the wind gradients to obtain simplified technical models of the longitudinal response to all possible types of constant-gradient wind shears during the first 20-60 sec. Graphs, maps, and diagrams are provided, and a number of accidents presumed to have involved wind shears are analyzed in detail.

Krauspe, P.↗

NASA NTRS1986

A preliminary report on a possible stromatolite find from the Elephant Moraine, Antarctica: A potential directional indicator for ice movement

During the 1983 to 1984 Antarctic Search for Meteorites field season, numerous specimens of a shiny black rock were collected from among the glacial debris at the Elephant Moraine. From a distance these black rocks gave the appearance of meteorites, but upon closer inspection, distinct layering and radial crystal growth patterns became clearly visible. Laboratory investigations showed that these unusual specimens are primarily composed of carbonate minerals. Petrographically, microscopic examination of twelve randomly collected specimens revealed a variety in the habits of the carbonates, but the overall trend tends to be one of radiating acicular crystals that have the appearance of a pseudo-cellular structure reminiscent of stromatolites. It is not possible at this time to specifically identify this possible stromatolite material or its source locality.

Sipiera, P. P.↗

NASA NTRS1986

Monitoring and predicting tropical cyclone movement using geosynchronous satellite remote sensing techniques

Data collected on special hurricane days by the VISSR Atmospheric Sounder (VAS) instrument flown on a satellite in 1981 and 1982 were studied for their usefulness in forecasting motion of hurricanes. The retrieved constant pressure heights for the 500-mb surface provided the basis for reasonable forecasts of 24 hour hurricane motion. The conclusions are illustrated with examples from Hurricane Harvey (1981) and Hurricane Irene (1981). Recommendations are made for future use of the VAS type instruments for tropical cyclone forecasting.

Dubach, L.↗

NASA NTRS1987

Programming a hillslope water movement model on the MPP

A physically based numerical model was developed of heat and moisture flow within a hillslope on a parallel architecture computer, as a precursor to a model of a complete catchment. Moisture flow within a catchment includes evaporation, overland flow, flow in unsaturated soil, and flow in saturated soil. Because of the empirical evidence that moisture flow in unsaturated soil is mainly in the vertical direction, flow in the unsaturated zone can be modeled as a series of one dimensional columns. This initial version of the hillslope model includes evaporation and a single column of one dimensional unsaturated zone flow. This case has already been solved on an IBM 3081 computer and is now being applied to the massively parallel processor architecture so as to make the extension to the one dimensional case easier and to check the problems and benefits of using a parallel architecture machine.

Devaney, J. E.↗

NASA NTRS1987

The formation and movement in the stratosphere of very dry air

The possible sources of very dry stratospheric air are investigated, extending the analysis of Atticks and Robinson (1983), on the basis of data from about 16,000 radiosonde ascents obtained during the FGGE from December 1978 through November 1979, from high-resolution Tiros and GMS IR-radiance observations on January 28, 1979, and from LIMS zonal-mean H2O-mass-mixing-ratio (HMMR) observations in December 1978 and May 1979. The data are compiled in tables and graphs and analyzed statistically, and the occurrence of low radiance temperatures (below -86 C) in the IR data (0.00025) is shown to be much lower than that (about 0.25) in the radiosonde data. It is inferred that air with HMMR less than 1.5 x 10 to the -6th could be produced in Cb cloud turrets, but not by the mechanism proposed by Danielsen (1982).

Robinson, G. D.↗

NASA NTRS1988

The experimental verification of wall movement influence coefficients for an adaptive walled test section

Flexible walled wind tunnels have for some time been used to reduce wall interference effects at the model. A necessary part of the 3-D wall adjustment strategy being developed for the Transonic Self-Streamlining Wind Tunnel (TSWT) of Southampton University is the use of influence coefficients. The influence of a wall bump on the centerline flow in TSWT has been calculated theoretically using a streamline curvature program. This report details the experimental verification of these influence coefficients and concludes that it is valid to use the theoretically determined values in 3-D model testing.

Neal, G.↗

NASA NTRS1989

Fiber-Optic Sensor Would Detect Movements Of Shaft

Fiber-optic sensor senses both rotational speed and axial displacement of shaft in motor, pump, or other rotating machine. Does not require magnetic materials, notches, or grooves in shaft. Required modification of shaft is etching or plating surface to make ring black around half circumference and reflective around other half along short length at one end or some other convenient location. Triangular bundle of sending and receiving optical fibers aimed at black/reflective ring on shaft. Frequency and amplitude of output pulses of fiber-optic probe indicates rotational frequency and axial position of shaft.

Roschak, Edmund J.↗

NASA NTRS1988

Relationships of earthquakes (and earthquake-associated mass movements) and polar motion as determined by Kalman filtered, Very-Long-Baseline-Interferometry

A Kalman filter was designed to yield optimal estimates of geophysical parameters from Very Long Baseline Interferometry (VLBI) group delay data. The geophysical parameters are the polar motion components, adjustments to nutation in obliquity and longitude, and a change in the length of day parameter. The VLBI clock (and clock rate) parameters and atmospheric zenith delay parameters are estimated simultaneously. Filter background is explained. The IRIS (International Radio Interferometric Surveying) VLBI data are Kalman filtered. The resulting polar motion estimates are examined. There are polar motion signatures at the times of three large earthquakes occurring in 1984 to 1986: Mexico, 19 September, 1985 (Magnitude M sub s = 8.1); Chile, 3 March, 1985 (M sub s = 7.8); and Taiwan, 14 November, 1986 (M sub s = 7.8). Breaks in polar motion occurring about 20 days after the earthquakes appear to correlate well with the onset of increased regional seismic activity and a return to more normal seismicity (respectively). While the contribution of these three earthquakes to polar motion excitations is small, the cumulative excitation due to earthquakes, or seismic phenomena over a Chandler wobble damping period may be significant. Mechanisms for polar motion excitation due to solid earth phenomena are examined. Excitation functions are computed, but the data spans are too short to draw conclusions based on these data.

Preisig, Joseph Richard Mark↗

NASA NTRS1988

On the movement and low-level structure of cold fronts

Factors that are pertinent to the cold-front motion were examined using the results from previous studies of the low-level structure of cold fronts. Observational studies indicate the existence of two different types of behavior for a cold front. These types of behavior were related to the results of recent theoretical studies, and the mechanism responsible for front propagation was elucidated. It is shown that a necessary requirement for propagation is the existence of an alongfront temperature gradient.

Smith, Roger K.↗

NASA NTRS1988

Improved ground hydrology calculations for global climate models (GCMs) - Soil water movement and evapotranspiration

A physically based ground hydrology model is presented that includes the processes of transpiration, evaporation from intercepted precipitation and dew, evaporation from bare soil, infiltration, soil water flow, and runoff. Data from the Goddard Institute for Space Studies GCM were used as inputs for off-line tests of the model in four 8 x 10 deg regions, including Brazil, Sahel, Sahara, and India. Soil and vegetation input parameters were caculated as area-weighted means over the 8 x 10 deg gridbox; the resulting hydrological quantities were compared to ground hydrology model calculations performed on the 1 x 1 deg cells which comprise the 8 x 10 deg gridbox. Results show that the compositing procedure worked well except in the Sahel, where low soil water levels and a heterogeneous land surface produce high variability in hydrological quantities; for that region, a resolution better than 8 x 10 deg is needed.

Abramopoulos, F.↗

NASA NTRS1983