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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 235 records · Page 13
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NASA NTRS1985

Mean winds of the upper middle atmosphere (60-110 km): A global distribution from radar systems (M.F., METEOR, VHF)

Since the development of the last CIRA in 1972, the number of radars providing winds in the upper middle atmosphere has increased significantly. These systems fill the data gap between 60 km and 110 km. The radars include medium frequency (MF) radars or partial reflection systems giving data from 60/70 to 100/110 km; meteor radars, 80 to 110 km, and M.S.T. radars operating as meteor radars. Data from 12 locations are shown, which represent a good Northern Hemispheric (NH) North American chain, an Oceanian chain which is mainly in the Southern Hemisphere (SH), and some Western Europe data. Generally tidal oscillations have been removed from days or groups of days, and the remaining mean winds and longer period oscillations plotted as height-time contours. Composite cross sections from the years 1978 to 1982 were formed where possible so that only the major temporal features remain.

Manson, A. H.↗
NASA NTRS1989

Middle atmosphere measurements of small-scale electron density irregularities and ion properties during the MAC/Epsilon campaign

Rocket payloads designed to measure small scale electron density irregularities and ion properties in the middle atmosphere were flown with each of the three main salvos of the MAC/Epsilon campaign conducted at the Andoya Rocket Range, Norway, during October to November 1987. Fixed bias, hemispheric nose tip probes measured small scale electron density irregularities, indicative of neutral air turbulence, during the rocket's ascent; and subsequently, parachute-borne Gerdien condensers measured the region's polar electrical conductivity, ion mobility and density. One rocket was launched during daylight (October 15, 1052:20 UT), and the other two launches occurred at night (October 21, 2134 UT: November 12, 0021:40 UT) under moderately disturbed conditions which enhanced the detection and measurement of turbulence structures. A preliminary analysis of the real time data displays indicates the presence of small scale electron density irregularities in the altitude range of 60 to 90 km. Ongoing data reduction will determine turbulence parameters and also the region's electrical properties below 90 km.

Blood, S. P.↗
NASA NTRS1994

The response of middle atmospheric ozone to solar UV irradiance variations with a period of 27 days

A one-dimensional photochemical-dynamical-radiative time-dependent model was used to study the response of middle atmospheric temperature and ozone to solar UV irradiance variations with the period of 27 days. The model solar UV O(x), HO(x), NO(x), and CIO(x)families and modeled solar UV variations. The amplitude of the primary temperature response to the solar UV variation is plus 0.4 K at 85-90 km with a phase lag of about 6 days. A secondary maximum response of plus 0.3 K at 45-50 km appears with a phase lag of 1 day. There is a maximum positive ozone response to the 27-day solar UV oscillation of 2.5 percent at 80-90 km with a phase lag of about 10 days after the solar irradiance maximum. At 70 km the ozone response is about 1.2 percent and is out of phase with the solar variation. In the upper stratosphere (40-50 km) the relative ozone variation is small, about 0.2 percent to 0.3 percent, and there is a negative phase of about 4 days between the ozone and solar oscillations. These oscillations are in phase in the middle stratosphere (35-40 km) where there is again a maximum relative response of about 0.6 percent. The reasons for these ozone amplitude and phase variations are discussed.

Chen, LI↗
NASA NTRS1986

Observations and a model of gravity-wave variability in the middle atmosphere

A major goal was to determine what portion of the gravity-wave frequency spectrum accounted for the majority of the momentum flux and divergence, as this has important implications for the middle atmosphere response. It was found that approx. 70% of the total flux and divergence was due to wave motions with observed periods less than 1 hour, consistent with expectations based on the shape of the observed gravity-wave spectrum (FrItts, 1984). This dominance of the momentum flux and divergence by high-frequency motions implies a potential for the modulation of those quantities by large-amplitude motions at lower frequencies. A second, striking aspect of the velocity and momentum flux data is its dramatic diurnal variability, particularly at certain levels. This variability is illustrated with the momentum flux, computed in 8-hr blocks. The dominant contributions here are due to waves with periods less than 1 hr. The variability with height and size of the mean square velocity in the west beam and the momentum flux, energed over the 3-day period. A detailed analysis of the various tidal motions present during this data interval was performed, and it was determined that variations in the zontal wind profile imposed by the diurnal tidal motion are probably responsible for the modulation of the gravity-wave amplitudes and momentum fluxes.

Fritts, D. C.↗
NASA NTRS2000

Decadal Variability and Temperature Trends in the Middle Atmosphere From Historical Rocketsonde Data

Observational studies were performed using historical rocketsonde data to investigate long-term temperature trends, solar-cycle variations, and interactions between tropical and extratropical latitudes in the middle atmosphere. Evidence from tropical, subtropical, and midlatitude North American rocketsonde stations indicated a consistent downward trend over 25 years, with a solar cycle component superposed. The trend is about -1.4 to -2.0 K per decade and the amplitude of the decadal oscillation is about 1.1 K. Prior to trend derivation it was necessary for us to correct temperatures for aerodynamic heating in the early years. The empirically derived correction profile agrees well with a theoretical profile of Krumins and Lyons. A study was also performed of the correlation between equatorial winds and north polar temperatures in winter, showing that the entire stratospheric wind profile near the equator -- including the quasi-biennial oscillation (QBO) and stratopause semiannual oscillation (SAO) -- is important to the extratropical flow, not merely the QBO component as previously thought. A strong correlation was discovered between winter polar temperatures and equatorial winds in the upper stratosphere during the preceding September, suggesting a role for the second cycle of the SAO.

Dunkerton, Timothy J.↗
NASA NTRS1987

Circulation in the mesosphere and lower thermosphere during the MAP (Middle Atmosphere Program)/WINE (Winter in the Northern Europe) period

One of the scientific programs in the MAP project, Winter in the Northern Europe (WINE) 1983 to 1984 involved an analysis of circulation processes in the middle atmosphere which characterized that winter period. Rocket soundings were conducted at many stations. In order to investigate deviations of the mean winds for the MAP/WINE period from the circulation conditions of other winters and from the climatic norm, rocket sounding data of Churchill and Barrow stations was well as the Pressure Modulated Radiometer channel 3000 data enabled the compilation of geopotential fields and the calculation of winds in the geostrophic approximation for comparison with the meteor winds. The large scale processes of the winter which determined the circulation in the period of the experiment were analyzed briefly. The analysis and results are discussed.

Tarasenko, D. A.↗
NASA NTRS1985

Mean Winds of the Upper Middle Atmosphere (60-110 Km): a Global Distribution from Radar Systems (MF, Meteor, VHF)

During the last decade a large number of radars have been developed, which have produced substantial quantities of tidally corrected mean winds data in the upper middle atmosphere. The distribution of the radars is not global, but many areas are well covered. Zonal and meridional wind height-time cross sections from 60 to 80 km (MF/meteor radar) to approx. 110 km were preared for the last 5 to 6 years. They are compared with cross sections from CIRA 1972 for zonal winds, and GROVES (1969) for meridional winds. It is shown that while CIRA 1972 is still a useful model for many purposes, significant differences exist between it and the new radar data. The latter demonstrate important seasonal, latitudinal, longitudinal and hemispheric variations. The new meridional cross sections are of great value. The common features with GROVES (1969) are the equatorward cells in summer near 85 km; however, their strength (approx. 10 m/s) and size are less. Systematic and somewhat different variations emerge at (higher 52 N) and lower (35 to 44 deg) latitudes.

Manson, A. H.↗
NASA NTRS1985

On the interannual variability of the middle atmosphere during winter

Reference atmospheres such as the new CIRA (COSPAR International Reference Atmosphere), which will be based on global satellite data form a very useful basis for climatological studies. When using such climatologies it is important to be aware of the interannual variability which in the middle atmosphere is particularly large during the northern winters and southern springs. For a comparison of the two polar regions, the monthly mean temperature data for 90 deg N and 90 deg S are shown in the form of frequency distributions. The main features to be noted are: (1) in the middle stratosphere the variability during the northern midwinters is much larger than during the southern midwinters due to the major midwinter warmings which take place only during the northern winters (the largest variations over Antarctics are observed during late spring, i.e., October and November when very intense final warmings bring about the transition into summer); (2) the variability in the middle stratosphere is very small in summer when the planetary waves of the troposphere cannot propagate upwards into the stratosphere due to the prevailing easterly winds (this is true for both polar regions); and (3) the annual temperature range is larger over the South Pole, because winters are colder and summers warmer than over the North Pole. In addition, the Canadian, midwinter, and final warmings occurring during northern winters are characterized and the recent cooling trend in the arctic is discussed.

Labitzke, K.↗
NASA NTRS1983

Parametrization of Fresnel returns in middle-atmosphere radar experiments

Weak reflections from sharp discontinuities in radio refractivity are usually invoked to explain the results of radio propagation experiments. The characteristics of refractivity structures required to produce Fresnel returns are examined and experimental evidence for Fresnel returns in middle-atmosphere radar experiments is reviewed. The consequences of these returns on estimating the turbulence and wind parameters are outlined.

Rastogi, P. K.↗
NASA NTRS1985

Middle atmosphere (60-110 km) tidal oscillations at Saskatoon, Canada (52 deg N, 107 deg W) during 1983/84

Since mid-1978, the medium frequency (2.2 MHz; M.F.) radar at Saskatoon has run continuously, measuring winds by the spaced antenna method in the upper middle atmosphere. As there is so much dynamics activity during the years of MAP it seems very important to establish the features of the tidal field at Saskatoon during 1983 to 1984, and compare these with the climatology from the four years 1978 to 1979 and 1981 to 1982. Wind profiles with 60 to 110 km (80 to 110 km at night) with 3 km resolution are obtained every 5 minutes by means of a full-correlation analysis. Hourly means are formed and harmonic analysis applied to sets of data to obtain the mean winds and tidal oscillation amplitudes and phases. The zonal wind field at Saskatoon is structurally similar to CIRA-72; however, the wind eastward cell is weaker and much more structured, and the summer eastward cell above 85 km is also weaker. For the semidiurnal tide, a strong seasonal change exists, with larger amplitudes and shorter wavelengths, in winter-like months and the reverse in summer-like months. A summary of the tidal parameters at 90 km is given, where mean values from 1978 to 1982 are also shown. This seasonal variation of tides is a midlatitude climatology, as comparisons with Monpazier, France and Christchurch, New Zealand show very similar behavior, as does Durham; and requires antisymmetric tidal modes such as 2,3 and 2,5. Considering the diurnal tide, for most months centered on summer there are long wavelength modes, or superposition of several models. However, some winter months show a short wavelength mode. A summary of the 90 km characteristics is presented.

Manson, A. H.↗
NASA NTRS1989

Middle Atmosphere of the Southern Hemisphere (MASH) Global meteor observations system (GLOBMET) Solar Spectral Irradiance Measurements (SSIM) Global Observations and Studies of Stratospheric Aerosols (GOSSA): Progress with the MASH project

The aim of the MASH project is to study the dynamics of the middle atmosphere in the Southern Hemisphere, emphasizing inter-hemispheric differences. Both observational data and data from simulations with numerical models are being used. It is intended that MASH will be complemented by parallel studies on the transport and photochemistry of trace species in the Southern Hemisphere. Impetus for such studies has come from the unexpected finding of a springtime ozone hole over Antarctica. A summary of recent progress with the MASH project is given. Data from polar orbiting satellites are used to discuss the large scale circulation found in the Southern Hemisphere at extratropical latitudes. Comparisons are made with that of the Northern Hemisphere. Particular attention is paid to the springtime final warming, the most spectacular large scale phenomenon in the statosphere of the Southern Hemisphere. The circulation before and after this event has to be taken into account in theories for the formation and subsequent disappearance of the ozone hole.

Oneill, A.↗
NASA NTRS1989

Mean, tidal, and fluctuating winds in the middle atmosphere and lower thermosphere observed during MAP/WINE in Northern Scandinavia

During the MAP/WINE campaign in winter 1983 to 1984 several instrumental techniques, such as meteorological rockets, sounding rockets, MST radar and incoherent scatter radar, were applied to measure wind velocities in the middle atmosphere. Profiles of mean, tidal and fluctuating wind velocities were obtained up to 90 to 100 km altitude. These are compared with profiles from models, measurements at other locations and at other times as well as satellite derived data. The results are discussed in terms of ageostropic winds, planetary waves, tidal modes and the possibility of a saturated gravity wave spectrum in the mesosphere.

Roettger, J.↗
NASA NTRS1985

Response of the middle atmosphere to Sco X-1

On the night of Mar. 9, 1983 (UT) at Punta Lobos Launch Site, Peru (12.5 deg S, 76.8 deg W, magnetic dip -0.7 deg), a sequence of sounding rockets was flown to study the electrical structure of the equatorial middle atmosphere and to evaluate perturbations on this environment induced by the X-ray star Sco X-1. The rocket series was anchored by two Nike Orion payloads (31.032 and 31.033) which were launched at 0327 and 0857 UT, near Sco X-1 star-rise and after it had attained an elevation angle of 70 deg E. An enhanced flux of X-rays was observed on the second Nike Orion flight (31.033). This increase is directly attributed to Sco X-1, both from the spectral properties of the measured X-ray distribution and by spatial information acquired from a spinning X-ray detector during the upleg portion of the 31.033 flight. Simultaneously, a growth in ion conductivity and density was seen to occur in the lower mesosphere between 60 and 80 km on the second flight, specifically in the region of maximum energy deposition by the Sco X-1 X-rays. The results imply the presence of a significant number of ionized heavy constituents within the lower mesosphere, with masses possibly in the submacroscopoic range.

Goldberg, R. A.↗
NASA NTRS1992

Maintenance of strong rotational winds in Venus' middle atmosphere by thermal tides

The cloud-level atmosphere of Venus takes little more than four days to complete one rotation, whereas the solid planet below has a 243-day period. Computer simulations of the circulation of the Venus middle atmosphere between 40 and 85 kilometers, as driven by solar radiation absorbed in the clouds, reproduce (1) the observed cloud-level rotation rate, (2) strong vertical shears above and below the cloud tops, and (3) midlatitude jets and strong poleward flow on the day side. Simulated circulations converge to yield nearly the same zonal winds when initialized with both stronger or weaker rotation rates. These results support the hypothesis that the observed cloud-top rotation rate is maintained by statistical balance between fluxes of momentum by thermal tides and momentum advection by mean meridional circulation.

Newman, Matthew↗
NASA NTRS1980

Structure and meteorology of the middle atmosphere of Venus Infrared remote sensing from the Pioneer orbiter

The results of the Pioneer Venus orbiter radiometric temperature-sounding experiment are presented with examples of each of the primary data products. The measured temperature field is used to model the dynamics of the middle atmosphere from 60 to 140 km, and the thermal and solar fluxes are used to calculate the planetary radiation budget. The data for the diurnal variation of temperature at a given height show fairly small amplitudes up to an altitude of about 95 km, above which the day to night contrast increases rapidly with height. At the equator the dependence of temperature in the stratosphere on solar longitude is dominated by a wave number 2 solar tide with an amplitude of about 10 K. The equator to pole gradients are larger than expected, and the stratosphere is typically 15 to 20 K warmer at the pole than at the equator. The most significant discovery concerning the cloud morphology is a dipole structure consisting of two clearings in the cloud at locations straddling the pole and rotating around it every 2.7 days.

Taylor, F. W.↗
NASA NTRS1979

The middle atmosphere

A quick introduction to some of the important electrical properties, and to the factors that influence them and their variability are provided. The following topics are discussed: (1) production of ionization; (2) ion concentration; (3) ion composition; and (4) variability of the various sources of middle atmospheric ionization.

Reid, G. C.↗