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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

The diurnal wind variation in the lowest 1500 ft in central Oklahoma - June 1966-May 1967.

A one-year accumulation of wind data from a television tower in northern Oklahoma City has been analyzed on a diurnal basis. The annual mean speeds below the third level at 296 ft are lowest at night and highest during the day, and conversely the speeds up to the seventh level at 1458 ft are lowest during the day and highest at night. Generally, speed changes occur in short time periods shortly after sunrise and near sunset. Resultant wind directions veer most with height from 1700 to 1000 CST and least during midday. At all levels winds veer with time between 2100 and approximately 1100 CST and then back with time during the remaining hours.

Crawford, K. C.↗
NASA NTRS1981

A model of temporal variations in ozone density in the Martian atmosphere

Temporal variations of the ozone density profile in the Martian atmosphere at high latitudes are calculated for the course of a Martian year, taking into account seasonal and diurnal variations in temperature, water vapor and solar radiation. Calculations are based on a model including 35 neutral photochemical reactions, and vertical eddy diffusion using a time step of 12 min for the region from the surface to 240 km altitude. Results are found to be in better agreement with Mariner 9 observations of the time and magnitude of the seasonal maximum than previous model calculations. The diurnal variation is predicted to be small near the solstices, with the nighttime ozone density greater than the daytime and the magnitude of the difference dependent on season. Opposite temporal variations are predicted for ozone densities above and below about 25 km, and an ozone density maximum at 35-40 km is obtained. It is suggested that the effects of an aerosol layer may not be important in enhancing predicted ozone concentration, and may even decrease it.

Shimazaki, T.↗
NASA NTRS1973

Ionospheric effects on one-way timing signals

A proposed navigation concept requires that a user measure the time-delay that satellite-emitted signals experience in traversing the distance between satellite and user. Simultaneous measurement of the propagation time from four different satellites permits the user to determine his position and clock bias if satellite ephemerides and signal propagation velocity are known. A pulse propagating through the ionosphere is slowed down somewhat, giving an apparent range that is larger than the equivalent free space range. The difference between the apparent range and the true range, or the free space velocity and the true velocity, is the quantity of interest. This quantity is directly proportional to the total electron content along the path of the propagating signal. Thus, if the total electron content is known, or is measured, a perfect correction to ranging could be performed. Faraday polarization measurements are continuously being taken at Fort Monmouth, N. J., using beacon emissions of the ATS-3 (137.35 MHz) satellite. Day-to-day variability of the diurnal variation of total electron content values is present with differences of up to 50% or more not being uncommon. In addition, superposed on the overall diurnal variation are smaller scale variations of approximately 5 to 10% of the total content which are attributed to ionospheric density irregularities.

Soicher, H.↗
NASA NTRS1993

A direct evaluation of the Geosat altimeter wet atmospheric range delay using very long baseline interferometry observations

The overall accuracy of the U.S. Navy Geosat altimeter wet atmospheric range delay caused by refraction through the atmosphere is directly assessed by comparing the estimates made from the DMSP Special Sensor Microwave/Imager and the U.S. Navy Fleet Numerical Ocean Center forecast model for Geosat with measurements of total zenith columnar water vapor content from four VLBI sites. The assessment is made by comparing time series of range delay from various methods at each location. To determine the importance of diurnal variation in water vapor content in noncoincident estimates, the VLBI measurements were made at 15-min intervals over a few days. The VLBI measurements showed strong diurnal variations in columnar water vapor at several sites, causing errors of the order 3 cm rms in any noncoincident measurement of the wet troposphere range delay. These errors have an effect on studies of annual and interannual changes in sea level with Geosat data.

Koblinsky, C. J.↗
NASA NTRS1984

Indirect Phase Height Measurements in Central and Eastern Europe for Monitoring D Region Plasma

Low-frequency propagation experiments for the investigation of the lower part of the ionospheric D region were at first used by BRACEWELL et al. (1951) in the early fifties. Among these was the method of indirect phase height measurements for continuous monitoring of the lower ionosphere. It is based upon field strength measurements of commercial radio transmitters in the frequency range between 50 and 200 kHz at distances from 500 to 1500 km. The field strength records show characteristic diurnal variations with maxima and minima, produced by interference between the ground wave and the ionospherically reflected sky wave, the phase difference between varies in correspondence to the diurnal variation of the reflection height. In order to check the validity of interpretations of indirect phase height data, comparisons were made with simultaneous rocket soundings. Results are summarized.

Cossart, G. V.↗
NASA NTRS1986

Chlorine chemistry in the Antarctic stratosphere - Impact of OClO and Cl2O2 and implications for observations

Theories have been proposed to relate the reduction of O3 during Antarctic spring to catalytic cycles involving chlorine and bromine species. A necessary condition for any chlorine-catalyzed scheme is that a large fraction of the chlorine must be in the form of ClO in the lower stratosphere. It has been suggested that these high levels of ClO could be maintained by fast heterogeneous reactions, whose rates are not known at present. Model calculations based on the above mechanisms predict considerable amounts of OClO and Cl2O2, particularly during the night. Results of calculations of the diurnal variations of ClO, OClO, and Cl2O2 during Antarctic spring are presented for different cases. Results from the calculations suggest that coincident measurements of the total column abundance and diurnal variation of ClO and OClO may help constrain key aspects of the proposed chemical mechanisms. Removal of O3 by the catalytic cycle involving Cl2O2 could be as important as that involving BrO for present levels of chlorine, provided that Cl2O2 photolyzes rapidly to yield Cl and ClO2. It is shown that there is no synergy between these two cycles, since they both compete for the available ClO.

Rodriguez, Jose M.↗
NASA NTRS1988

ClO and O3 stratospheric profiles - Balloon microwave measurements

Stratospheric ClO and O3 vertical profiles were measured at 32-deg N in May 1985 and October 1986. The ClO profiles and diurnal variation are in general agreement with theory, but have somewhat less midday ClO near 34 km. Measured 35-45 km O3 is larger than theoretical, and no stratospheric O3 diurnal variation was observed, as expected. HNO3 was detected, and an H2O2 upper limit was obtained.

Waters, J. W.↗
NASA NTRS1987

Average spatial distributions of energetic O(+), O(2+), O(6+), and C(6+) ions in the magnetosphere observed by AMPTE CCE

Measurements with the charge energy mass spectrometer of the AMPTE CCE spacecraft are used to determine the relative fluxes of these ions near the equatorial plane as a function of the drift shell parameter L, the magnetic activity index Kp, and the local time LT. The O(+) and O(2+) ions have radial profiles with maxima at about L = 5 and diurnal variations with a broad maximum on the dayside. The O(6+) and C(6+) ion fluxes increase with L between L = 5 and L = 7 and level off farther out. The diurnal variations of the relative O(6+) and C(6+) fluxes exhibit a pronounced minimum on the dayside. The observations can be interpreted in terms of ion convection from the tail onto quasi-trapped drift orbits and further radial diffusion onto closed drift shells. The maximum of the O(+) and O(2+) fluxes as well as the minimum of the O(6+) and C(6+) fluxes on the dayside can be explained by drift shell splitting. The inward transport is associated with ion losses, mainly by charge exchange. O(6+) and C(6+) ions are removed already at larger distances than O(+) and O(2+). As a result, the ionosphere contributes most of the oxygen ions in the magnetosphere. Important contributions from the solar wind are encountered in the outer magnetosphere.

Kremser, G.↗
NASA NTRS1987

Hydrogen Balmer alpha intensity distributions and line profiles from multiple scattering theory using realistic geocoronal models

The H Balmer alpha nightglow is investigated by using Monte Carlo models of asymmetric geocoronal atomic hydrogen distributions as input to a radiative transfer model of solar Lyman-beta radiation in the thermosphere and atmosphere. It is shown that it is essential to include multiple scattering of Lyman-beta radiation in the interpretation of Balmer alpha airglow data. Observations of diurnal variation in the Balmer alpha airglow showing slightly greater intensities in the morning relative to evening are consistent with theory. No evidence is found for anything other than a single sinusoidal diurnal variation of exobase density. Dramatic changes in effective temperature derived from the observed Balmer alpha line profiles are expected on the basis of changing illumination conditions in the thermosphere and exosphere as different regions of the sky are scanned.

Anderson, D. E., Jr.↗
NASA NTRS1983

Diurnal cloud variations over South America and the southeastern Pacific

The changing distributions of cloud cover are of particular importance in understanding the general circulation patterns of the Southern Hemisphere, whose prediction is hampered by the sparse sampling of physical qualities. In near-tropical areas, the diurnal solar heating cycle is noted to be directly responsible for many of the observed weather patterns. Among the atmosphere's familiar responses to this heating cycle are afternoon thunderstorms over tropical land areas and the 'burnoff' of morning fog or low stratus near coastal margins. Attention is given to these aspects of the atmospheric adjustment to the daily solar cycle in terms of regional scale mean cloudiness over part of the Southern Hemisphere.

Minnis, P.↗
NASA NTRS1977

The optimization of self-phased arrays for diurnal motion tracking of synchronous satellites

The diurnal motion of a synchronous satellite necessitates mechanical tracking when a large aperture, high gain antenna is employed at the earth terminal. An alternative solution to this tracking problem is to use a self phased array consisting of a number of fixed pointed elements, each with moderate directivity. Non-mechanical tracking and adequate directive gain are achieved electronically by phase coherent summing of the element outputs. The element beamwidths provide overlapping area coverage of the satellite motion but introduce a diurnal variation into the array gain. The optimum element beamwidth and pointing direction of these elements can be obtained under the condition that the array gain is maximized simultaneously with the minimization of the diurnal variation.

Theobold, D. M.↗
NASA NTRS1991

The plasma environment, charge state, and currents of Saturn's C and D rings

The charge state and associated currents of Saturn's C an D rings are studied by modeling the flow of ionospheric plasma from the mid- to low-latitude ionosphere to the vicinity of the rings. It is found that the plasma density near the C and D rings, at a given radial location, will experience a one to two order of magnitude diurnal variation. The surface charge density (SCD) of these rings can show significant radial and azimuthal variations due mainly to variation in the plasma density. The SCD also depends on structural features of the rings such as thickness and the nature of the particle size distribution. The associated azimuthal currents carried by these rings also show large diurnal variations resulting in field-aligned currents which close in the ionosphere. The resulting ionospheric electric field will probably not produce a significant amount of plasma convection in the topside ionosphere and inner plasmasphere.

Wilson, G. R.↗
NASA NTRS1962

Time-Dependent Structure of the Upper Atmosphere

The physical properties of the upper atmosphere are determined mainly by heat conduction, the heat sources and the barometric law. An analysis of the integro-differential equation which describes these physical processes has been carried out. It is found that heating of the thermosphere due to absorption of the solar extreme ultraviolet (EUV) radiation alone cannot explain the observed diurnal variation of density and temperature, since it would yield a maximum of these properties at about 17h local time, instead of 14h where it is observed. Secondly, if the EUV flux is adjusted to give the observed average temperature, then the diurnal variation in density would be much too large compared with the observed amplitude. Thirdly, it would require an extremely high efficiency for the conversion of EUV radiation into heat, if we compare the required flux with Hinteregger's measurements of the EUV flux. Thus, it is necessary to have another heat source in addition to the heating due to absorption of EUV radiation. If an additional beat source is used, which has a maximum at about 9h local time and a flux of 1 erg cm−1 sec−1, a time-dependent model of the upper atmosphere is obtained that is in good agreement with the observed densities. There is evidence that this additional heat source derives its energy ultimately from the solar corpuscular radiation. In this paper we present the results of calculations for a model in the equatorial and temperature zones of the earth, for those times when the average solar activity corresponds to a solar radiation flux of 200×110−22 Wm−2 (cps)−1 at 10.7-cm wavelength. The physical properties (temperature, density, pressure, scale height, mean molecular weight and the number densities of N2, O2, O, He and H) are given as a function of local time and for the altitudes between 120 km and 2050 km.

ATMOSPHERE↗
NASA NTRS1992

Stratocumulus cloud properties derived from simultaneous satellite and island-based instrumentation during FIRE

Cloud parameters derived from visible and infrared window data from the Geostationary Operational Environmental Satellite (GOES) are compared to corresponding properties determined from instrumentation on San Nicolas Island off the coast of California during the First ISCCP Regional Experiment marine stratocumulus intensive field observations period in July 1987. Examination of the satellite imagery revealed that the apparent bias can be explained by the persistence of the clouds over the northwest part of the island during periods of clearing around the island. Diurnal variations in the cloud cover were very significant; minimum cloudiness occurred during the late afternoon and maximum cloudiness early in the morning. Relationships were established between the satellite-derived cloud optical depth and two surface-observed quantities: cloud liquid water path and cloud thickness. Simultaneous observations of liquid water path and satellite-derived cloud optical depth were used to infer effective cloud-droplet radius, resulting in good agreement with correlative data. The diurnal variations in cloud amount are accompanied by changes in cloud thickness, cloud-top height, cloud liquid water path, and effective droplet size. These observations provide the most complete picture, to date, of the diurnal cycle of marine stratocumulus clouds, confirming previous satellite-based inferences of the diurnal behavior of marine stratocumulus at larger scales.

Minnis, Patrick↗
NASA NTRS1992

Longwave radiation budget parameters computed from ISCCP and HIRS2/MSU products

The International Satellite Cloud Climatology Project (ISCCP) retrieved cloud fields and the high-resolution radiation sounder 2 (HIRS2) retrieved cloud fields yield similar outgoing longwave radiation (OLR) due to the cancelation effect of cloud-top altitudes and cloud amount on OLR. For the large regional discrepancies of the order of 30 W/sq m found over northern Africa are largely due to surface temperature differences, and extensive discrepancies over the ocean are due to humidity differences. Harmonic analysis is applied to OLR, clear-sky OLR, and cloud-radiative forcing at the top of the atmosphere using the ISCCP products. The diurnal variations of these parameters from 60 deg S to 60 deg N are larger over land than over the ocean. The clear-sky OLR peaks around 1500 LST, usually over land areas, and is associated with the surface/air temperature maximum. The OLR over cloudy regions shows a similar diurnal phase as the cloud top pressure. The cloud radiative forcing at the top of the atmosphere has maximum value near 2100 LST mountain areas and near 0000 and 0300 LST over equatorial regions. The ISCCP-computed longwave cloud radiative forcing has smaller diurnal variations over the ocean than the HIRS2-computed longwave cloud radiative forcing. The global mean bias of OLR is around 0.74 W/sq m, and locally, the bias can be as large as 5 to 10 W/sq m. This appears to indicate that the twice-a-day measurements of the HIRS2/MSU (around 0315 and 1515 LST, which are the equatorial cross times at nadir track) can be used to derive monthly mean OLR without significant bias.

Wu, Man L. C.↗
NASA NTRSDate not supplied

Development of a Consistent Cross-Platform GEO-Satellite Cloud Mask to Support CERES

Geostationary satellites provide continuous cloud and meteorological observations over a fixed portion of the Earth’s surface, allowing them to monitor the movement of storm systems and their diurnal variation. For climate studies, geostationary observations provide valuable insight of cloud formation and evolution and how they influence the Earth’s radiation budget. The Geo-Satellite Edition 4 cloud mask (GEO Ed4) is used operationally in NASA’s Cloud and Earth’s Radiant Energy System (CERES) project to help account for diurnal variations in cloudiness on Earth’s radiation budget. The Ed4 cloud mask was applied to imager data on MSG (MeteoSat Second Generation), Himawari, GOES-West, and GOES-East satellites using as much spectral information as possible. That approach led to some discontinuities when a more modern satellite replaced an older satellite with less spectral information. A different strategy is being investigated for the CERES GEO Ed5 cloud mask that only uses spectral channels common on every satellite. Thus, a 3-channel (0.6, 3.9, 11 µm) algorithm for daytime cloud detection, and a 2-channels (3.9 and 11 µm) algorithm for nighttime cloud detection have been implemented and tested for Ed5. The goal of Ed5 cloud mask is to achieve global cloud amount consistency across five geo-satellites, and a smooth transition from an old satellite to a new satellite over each geo-location. This paper compares cloud mask results between Ed4 and a preliminary Ed5 version over the GOES-East region, using GOES-8, GOES-13, and GOES-16 satellites, each with a different spectral channel complement. Instantaneous and monthly regional mean inter-comparisons are performed and evaluated with CALIPSO cloud products to assess the accuracy and consistency of the Ed5 approach relative to that taken in Ed4. Results will be presented and discussed at the conference.

clouds↗
NASA NTRS1985

The modulation features of the long-period cosmic ray variations in connection with the sign change of the general magnetic field of the Sun

On the basis of the model and experimental investigations, the spatial distribution of cosmic ray anisotropy for the different epochs of solar activity is studied. A solution is offered to the anisotropic diffusion equation with regard to the electromagnetic conditions for the periods of minimum and maximum solar activity and cosmic ray particle drift in a regular interplanetary magnetic field. It is shown that the long period changes amplitude and phase of the diurnal variations of cosmic rays is limited not only by convection and diffusion of particles but also by the drift effect before and after the sing change of the general magnetic field of the Sun. The calculated model is compared with the results obtained on the basis of an analysis of the experimental data from the neutron super monitor station, and it is shown that for the periods when the lines of magnetic force of the Sun come from the Northern Hemisphere the phase of the first harmonic diurnal variation is shifted forwards to an earlier time.

Iskra, K.↗
NASA NTRS1985

Thermospheric hydrogen - The long-term solar influence

Atmospheric Explorer C and E satellite data are employed for a long-term analysis of the behavior of thermospheric hydrogen with respect to the 11 yr solar cycle. The data covered the period 1974-79 (increasing solar activity) and comprised in situ ionospheric (F region) and neutral atmospheric data. The data were analyzed statistically to characterize low latitude hydrogen behavior, e.g., the diurnal variation and mean concentration over the 5 yr data sampling period. Both the mean and daily maximum/minimum ratio (DMMR) varied with the solar F index. The escaping flux of H ions became a contant around 1000 K. Increasing thermospheric temperatures lowered the DMMR value. However, the DMMR values calculated were consistently large enough to require inclusion of neutral winds and/or diurnal variations in charge exchange fluxes moving in and out of the plasmasphere in any model for thermospheric hydrogen behavior.

Breig, E. L.↗