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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

W-Band ARM Scanning Cloud Radar (WSACR) 2nd Generation CF-Radial Spectral Data, Vertically-Pointing Scan, Cross-Polarization Model (a1)

ARM's scanning cloud radars are fully coherent dual-frequency, dual-polarization Doppler radars mounted on a common scanning pedestal. Each pedestal includes a Ka-band radar (2kW peak power) and the deployment location determines whether the second radar is a W-band (WSACR; 1.7 kW peak power) or X-band (XSACR; 20 kW peak power). Beamwidths at Ka and W bands are roughly matched at 0.3 degrees. Due to the narrow antenna beamwidth, ARM’s scanning cloud radars use scanning strategies that are unlike typical weather radars. Rather than focusing on plan position indicator, or PPI, scans, the Ka-SACR uses range height indicator, or RHI, scans at numerous azimuths to obtain cloud volume data. Measurements collected with the W-SACR are copolar and cross-polar radar reflectivity, Doppler velocity, spectra width and spectra when not scanning, and linear depolarization ration.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1980

Calculation of Water Drop Trajectories to and About Arbitrary Three-Dimensional Bodies in Potential Airflow

Calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Any subsonic, external, non-lifting flow can be accommodated; flow into, but not through, inlets also can be simulated. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Code descriptions include operating instructions, card inputs and printouts for example problems, and listing of the FORTRAN codes. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

Norment, H. G.↗
NASA NTRS1982

Light scattering calculations for the nephelometer experiment on the 1981/1982 Jupiter Orbiter-Probe mission

A variety of studies were carried out to help establish the accuracy of quantities describing physical characteristics of cloud particles (such as size, shape, and composition) that are to be inferred from light scattering data obtained with the nephelameter experiment on the Galileo spacecraft. The objectives were to provide data for validating and testing procedures for analyzing the Galileo nephelameter data with light scattering observations in a variety of on-going laboratory and field measurement programs for which simultaneous observations of the physical characteristics of the scattering particles were available.

Grams, G. W.↗
NASA NTRS1984

Remote sensing of atmospheric particulates: Technological innovation and physical limitations in applications to short-range weather prediction

Techniques for remote sensing of particles, from cloud droplet to hailstone size, using optical and microwave frequencies are reviewed. The inherent variability of atmospheric particulates is examined to delineate conditions when the signal can give information to be effectively utilized in a forecasting context. The physical limitations resulting from the phase, size, orientation and concentration variability of the particulates are assessed.

Curran, R. J.↗
NASA NTRS1984

Aircraft lattitude survey measurements of the El Chichon eruption cloud

Solar spectral extinction measurements made with a solar photometer aboard a NASA research aircraft, whose flights were conducted during May, July, and December 1982 over a range of latitudes, are presently used to derive aerosol optical thicknesses. The large thickness increases over background levels found at all latitudes studied for the stratosphere are attributed to the El Chichon eruption cloud. The spectral dependence of the aerosol optical thickness, which is different on one side of 30 deg N latitude from the other side, suggests that the two portions of the cloud have different aerosol size distributions.

Shah, G. M.↗
NASA NTRS1985

The Pioneer Venus Orbiter event of February 11, 1982 - Of cometary of solar origin?

On February 11, 1982, an unusual cusp-shaped temporal variation in the interplanetary magnetic field was detected by the Pioneer Venus orbiter. While variations of the helium content of the solar wind were detected on the preceding day, these changes had no obvious relationship to the occurrence of the cusp-shaped temporal variation in the IMF on February 11. In fact the solar wind the content was quite nominal on February 11. The magnetic variations were also quite unlike those previously reported to be magnetic clouds. Moreover, the scale size of the disturbance had to be smaller than 4 x 10 to the 6th km and thus of cometary dimensions rather than of dimensions usually found in solar initiated events. Thus, there seems to be no need to alter the original interpretation that the observations of Pioneer Venus on February 11, 1982 were consistent with the passage of a comet close to Venus.

Russell, C. T.↗
NASA NTRS1985

Is the Kolmogoroff model applicable to large-scale turbulence?

In view of the present discussion, the Heisenberg-Kolmogoroff (HK) model of turbulence that is often used for turbulent phenomena on all scales is actually valid for a turbulent spectrum wavelength band typically much smaller than the size of the system, and cannot describe phenomena at large scales in astrophysical systems. The results of mixing length theory cannot be accommodated within the HK model's framework without the adoption of an unreasonable coupling constant. It is also noted that the use of the observed velocity-size relationship in molecular clouds with turbulent velocity values of about l to the 1/2-power, within the HK model, gives rise to a growth rate that does not correspond to any known physical processes suspected of operating in molecular clouds.

Canuto, V. M.↗
NASA NTRS1985

Calculation of water drop trajectories to and about arbitrary three-dimensional lifting and nonlifting bodies in potential airflow

Subsonic, external flow about nonlifting bodies, lifting bodies or combinations of lifting and nonlifting bodies is calculated by a modified version of the Hess lifting code. Trajectory calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Inlet flow can be accommodated, and high Mach number compressibility effects are corrected for approximately. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

Norment, H. G.↗
NASA NTRS1986

The Arecibo S-band radar program

Reduction to images of the 1983 monostatic Venus mapping data was completed. Analysis of the images, including detailed comparisons with Pioneer Venus data and Soviet Venera 15/16 images, continued. Feature locations in Arecibo Venus radar images produced between 1975 and 1983 were used to make a new determination of the rotation vector. This result is of general interest but was also required for planning and cartographic purposes for the Magellan mission. A new set of observations of Venus were made in March/April 1985, aimed at imaging low northern and high southern latitudes, including the south polar region, at 1 to 2km resolution. A limited number of ranging observations were made to Mercury and Venus. Ten asteroids were detected increasing the number studied with the Arecibo system to almost 40. A system to allow high time resolution, as well as high Doppler frequency resolution, studies of small asteroids or comets which make close approaches to the Earth was implemented. A radar detection of Halley's Comet was obtained when it approached to within 0.62 AU of the Earth in November/December of last year. It is still uncertain whether the echo is a reflection from the nucleus or from a cloud of cm-sized particles in the vicinity of the nucleus.

Campbell, D. B.↗
NASA NTRS1989

NASA's program on icing research and technology

NASA's program in aircraft icing research and technology is reviewed. The program relies heavily on computer codes and modern applied physics technology in seeking icing solutions on a finer scale than those offered in earlier programs. Three major goals of this program are to offer new approaches to ice protection, to improve our ability to model the response of an aircraft to an icing encounter, and to provide improved techniques and facilities for ground and flight testing. This paper reviews the following program elements: (1) new approaches to ice protection; (2) numerical codes for deicer analysis; (3) measurement and prediction of ice accretion and its effect on aircraft and aircraft components; (4) special wind tunnel test techniques for rotorcraft icing; (5) improvements of icing wind tunnels and research aircraft; (6) ground de-icing fluids used in winter operation; (7) fundamental studies in icing; and (8) droplet sizing instruments for icing clouds.

Reinmann, John J.↗
NASA NTRS1989

Denitrification in the Antarctic stratosphere

Rapid loss of ozone over Antarctica in spring requires that the abundance of gaseous nitric acid be very low. Precipitation of particulate nitric acid has been assumed to occur in association with large ice crystals, requiring significant removal of H2O and temperatures well below the frost point. However, stratospheric clouds exhibit a bimodal size distribution in the Antarctic atmosphere, with most of the nitrate concentrated in particles with radii of 1 micron or greater. It is argued here that the bimodal size distribution sets the stage for efficient denitrification, with nitrate particles either falling on their own or serving as nuclei for the condensation of ice. Denitrification can therefore occur without significant dehydration, and it is unnecessary for temperatures to drop significantly below the frost point.

Salawitch, R. J.↗
NASA NTRS1989

NASA's program on icing research and technology

NASA's program in aircraft icing research and technology is reviewed. The program relies heavily on computer codes and modern applied physics technology in seeking icing solutions on a finer scale than those offered in earlier programs. Three major goals of this program are to offer new approaches to ice protection, to improve the ability to model the response of an aircraft to an icing encounter, and to provide improved techniques and facilities for ground and flight testing. The following program elements are reviewed: (1) new approaches to ice protection; (2) numerical codes for deicer analysis; (3) measurement and prediction of ice accretion and its effect on aircraft and aircraft components; (4) special wind tunnel test techniques for rotorcraft icing; (5) improvements of icing wind tunnels and research aircraft; (6) ground de-icing fluids used in winter operation; (7) fundamental studies in icing; and (8) droplet sizing instruments for icing clouds.

Reinmann, John J.↗
NASA NTRS1996

Planetary Atmosphere Dynamics and Radiative Transfer

This research program has dealt with two projects in the field of planetary atmosphere dynamics and radiative energy transfer, one theoretical and one experimental. The first project, in radiative energy transfer, incorporated the capability to isolate and quantify the contribution of individual atmospheric components to the Venus radiative balance and thermal structure to greatly improve the current understanding of the radiative processes occurring within the Venus atmosphere. This is possible by varying the mixing ratios of each gas species, and the location, number density and aerosol size distributions of the clouds. This project was a continuation of the work initiated under a 1992 University Consortium Agreement. Under the just completed grant, work has continued on the use of a convolution-based algorithm that provided the capability to calculate the k coefficients of a gas mixture at different temperatures, pressures and spectral intervals from the separate k-distributions of the individual gas species. The second primary goal of this research dealt with the Doppler wind retrieval for the Successful Galileo Jupiter probe mission in December, 1995. In anticipation of the arrival of Galileo at Jupiter, software development continued to read the radioscience and probe/orbiter trajectory data provided by the Galileo project and required for Jupiter zonal wind measurements. Sample experiment radioscience data records and probe/orbiter trajectory data files provided by the Galileo Radioscience and Navigation teams at the Jet Propulsion Laboratory, respectively, were used for the first phase of the software development. The software to read the necessary data records was completed in 1995. The procedure by which the wind retrieval takes place begins with initial consistency checks of the raw data, preliminary data reductions, wind recoveries, iterative reconstruction of the probe descent profile, and refined wind recoveries. At each stage of the wind recovery consistency is checked and maintained between the orbiter navigational data, the radioscience data, and the probe descent profile derived by the Atmospheric Instrument Team. Preliminary results show that the zonal winds at Jupiter increase with depth to approximately 150 m/s.

Atkinson, David H.↗
NASA NTRS1998

Analysis of Ice Nucleating Aerosol Measurements during SUCCESS: April, May 1996

This section describes our research activities during year three of this effort. In the second year, preliminary archive data sets were submitted to the SUCCESS archive. After additional analyses, final versions were prepared and submitted. These are included on the SUCCESS CD-ROM data editions that were recently released by NASA Ames. Over the range of temperature and supersaturation conditions of our measurements (15 to -40 C, and from ice saturation to approximately 15% water supersaturation), IN concentrations ranged from less than 0.1 to approximately 500 per liter, being generally greater at colder temperatures and higher supersaturations. To estimate the potential of aircraft exhaust as a source of IN, we examined data from six days of the field project when the DC-8 was following closely behind other humidity conditions of our measurements. In April 1997, a microphysical workshop was convened at NCAR to select cases for in depth analyses and to address questions about the consistency of cloud ice crystal measurements (size distributions and mass concentrations) and aerosol size distributions. We attended this meeting and contributed to the discussions. A particular concern was identified in the CN measurements. On the DC-8, CN measurements were obtained by four different investigator groups, using commercially available instrumentation. The DC-8 SUCCESS CN data showed long periods where the measurements were in substantial agreement, but there were also periods with large discrepancies. Several possible factors were identified that could help explain these discrepancies, including minimum detectable particle size, response at reduced pressures, and location of sample inlet on the aircraft.

Rogers, D. C.↗