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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

The behavior of wave 2 in the Southern Hemisphere stratosphere during late winter and early spring

The behavior of wave 2 in the Southern Hemisphere (SH) winter and early spring stratosphere has been examined in detail using 10 years of NMC data. Wave 2 is characterized by a broad meridional structure peaking between 55 and 65 S, and regular eastward propagation, with periods ranging from 5 to 40 days. The range of maximum geopotential height amplitudes is from 600 to 1000 m for a year. Consideration is also given to the relationship of wave 2 to other features of stratospheric circulation, Eliassen-Palm fluxes, and synoptic maps. The results obtained show that the zonal mean state of the SH stratosphere frequently satisfies conditions for instability. It is concluded that both instability of zonally symmetric and asymmetric states, and nonlinear interactions between wave 1 and wave 2 are of importance for determining the behavior of wave 2 in the SH winter and spring stratosphere.

Manney, G. L.↗
NASA NTRS1983

The influence of the tropics upon the prediction of the Southern Hemisphere circulation within the GLAS GCM

An examination is undertaken of the sensitivity of short term Southern Hemisphere circulation prediction to tropical wind data and tropical latent heat release. The data assimilation experiments employ the Goddard Laboratory for Atmospheric Sciences' fourth-order general circulation model. Two of the experiments are identical, but for the fact that one uses tropical wind data while the other does not. A third experiment contains the identical initial conditions of forecasts with tropical winds, while suppressing tropical latent heat release.

Baker, W. E.↗
NASA NTRS1985

A sudden warming in the middle atmosphere of the southern hemisphere

The present analysis of a wave-mean flow interaction, or minor warming, near the southern hemisphere stratopause on July 15-30, 1974, is primarily based on data from the selective chopper radiometer aboard Nimbus 5. Eliassen-Palm (E-P) cross sections are given for the event, and a good correlation is found between the E-P flux convergence and the deceleration. The channeling of the E-P fluxes from the tropopause to the convergent region is in broad agreement with the refractive index distribution, but a region of E-P flux divergence is noted at high levels in polar latitudes which suggests a source of wave activity. The event is shown to be associated with an incursion of low latitude air into middle latitudes, with a corresponding, irreversible mixing of potential vorticity which resembles the McIntyre and Palmer (1983) northern hemisphere 'wave breaking'.

Al-Ajmi, D. N.↗
NASA NTRS1979

Search for H2 emission at 2.1 microns in ten southern hemisphere sources

The 2.12-micron line of molecular hydrogen was searched for in emission from a variety of southern hemisphere objects, including infrared sources associated with molecular clouds and H II regions, the galactic center, and three external galaxies. Negative results are reported for all sources.

Scoville, N. Z.↗
NASA NTRS1983

Persistent anomalies of the Southern Hemisphere circulation

The persistent features of large anomalies have been examined and the locations of blocking in the Southern Hemisphere were determined. The data set used here contains daily maps of 500 mb geopotential heights for 100 months (June 1, 1972 to Nov. 30, 1980) covering from 10S to 90S. The seasonal cycle was defined as a 8 year mean and the 8th (annual) and 16th (semiannual) Fourier components of the time series at each grid point. Anomalies were defined as the difference between the total field and the seasonal cycle for each grid point.

Mo, K. C.↗
NASA NTRS1991

Intraseasonal oscillation of convective activity in the tropical Southern Hemisphere - May 1984-April 1986

This paper studies the intraseasonal oscillation of convection and related variables in the Southern Hemisphere tropics utilizing European Centre for Medium-range Weather Forecasts analyses of 1984 to 1986. One aspect of the research was that the original, unfiltered, time series of various variables was first analyzed to determine if a statistically significant signal occurred on the intraseasonal time scale. The analysis showed that two variables, outgoing longwave radiation and velocity potential at 200 hPa, provided the best evidence of an intraseasonal oscillation. The oscillation propagated eastward, and the convective activity for both years was more intense over the Indian Ocean-Indonesia-western Pacific region than elsewhere.

Vincent, Dayton G.↗
NASA NTRS1993

Intraseasonal interactions between the tropics and extratropics in the Southern Hemisphere

Observational evidence is presented of connections between tropical heating and circulation changes in subtropical and extratropical latitudes of the Southern Hemisphere (SH) in summer and winter, and the processes responsible for these interactions are described. The observational evidence suggests that, during SH summer (but not SH winter), both the acceleration of westerly winds south of the heating region through meridional overturnings and excitation of Rossby waves are possible. During winter, the enhanced tropical convective activity results again in local meridional overturning with zonal wind acceleration of Rossby waves farther south.

Berbery, Ernesto H.↗
NASA NTRS1986

Northern vs. Southern Hemisphere energy conversions in January 1979

The methodology applied by Huang and Vincent (1985) for the diagnosis of the zonal and eddy energy conversions in the Southern Hemisphere was used to diagnose the energetics of the Northern Hemisphere for the same period (i.e., January 10-27, 1979). It was found that, in both hemispheres, the larger synoptic-scale waves are important in the AZ-AE-KE conversion. However, in the Northern Hemisphere, the long waves make the most significant contribution to this conversion cycle, whereas in the Southern Hemispere, the intermediate waves dominate.

Hurrell, James W.↗
NASA NTRS1991

Venus southern hemisphere - Geologic character and age of terrains in the Themis-Alpha-Lada region

Arecibo high-resolution radar images of the southern hemisphere of Venus extending to 78 deg S show that the surface of the Themis-Alpha-Lada region is characterized by linear deformation zones with volcanoes and corona-like features and by regional volcanic deposits (primarily plains, small shields, and large edifices). Large-scale areal deformation is limited to the tessera of Alpha Regio. Lada Terra, in the southern high latitudes, contains several large coronae, in contrast to Ishtar Terra in the northern high latitudes. The density of craters of possible impact origin is somewhat lower than that observed in the Venera 15 and 16 coverage; these data extend to 43 percent of the areas of the surface of Venus with ages of less than about 1 billion years.

Campbell, D. B.↗
NASA NTRSDate not supplied

Martian B Storm Evolution: Modeling Dust Activity over the Receding South Polar CO 2 Ice Cap at Southern Hemisphere Summer Solstice

Observations of annually recurring, elevated (25 km) atmospheric warming and associated dust concentrations over the south polar cap near Southern Hemisphere (SH) summer solstice are the defining features of the regional dust storm known as the B storm [1]. Our observational analysis of MCS and TES temperature and dust retrievals include all Mars Years (MY) lacking a global dust storm (GDS) between MY 26 and MY 33 (Figure 1). The data indicate the B storm is initiated around perihelion (L s =252°) in the southern midlatitudes and reaches maximum height and intensity over the south pole near SH summer solstice at L s ~267°. At peak intensity, mid-level atmospheric temperatures are elevated by as much as 30 K and mid-level atmospheric dust mixing ratios are more than triple pre-B storm levels (1.5-2 ppm to 7-8 ppm). Cap edge lifting may contribute significantly to initial dust mobilization in the B storm since surface wind stress along the receding cap edge is likely strengthened by the combined effects of the sea breeze circulation and katabatic winds at this time of year [2, 3, 4]. We are investigating dust lifting and lofting near the south pole of Mars during SH summer using the NASA Ames Mars Global Climate Model (MGCM). The NASA Ames MGCM is a finite-volume numerical model with a cubed sphere grid ideal for modeling processes at high latitudes. Initial simulations at low resolution (4x4 degrees) capture some elevated dust and associated warming at the south pole around L s =265°, but the model fails to capture the intensity of the B storm. We will examine and present the model-predicted surface stress and vertical velocities near the receding seasonal CO 2 cap edge and at the south pole during solstice. Finally, we will present higher resolution simulations to better capture small-scale dynamics and features at the pole.

Courtney M. L. Batterson↗
NASA NTRS1987

A GCM study on the maintenance of the June 1982 blocking in the Southern Hemisphere

GCM experiments are used to study several possible mechanisms associated with the maintenance of the June 1982 blocking in the Southern Hemisphere. The mechanisms considered include changed orography, sea surface temperature anomalies, tropical heating, regional heating in the Pacific area, land-sea contrast, and sensible heating in the Antarctic area. It is concluded that asymmetric heating due to land-sea contrast was the most important boundary forcing associated with maintenance of the block. A 'no Australia' experiment confirms this result and suggests that local land-sea contrast kept the block stationary. High-latitude sensible heating associated with cold air outbreaks from Antarctica was also important in maintaining the block.

Mo, Kingtse C.↗
NASA NTRS1991

Dynamics of the 4-day wave in the Southern Hemisphere polar stratosphere

Horizontal wind and temperature data are employed to investigate the dynamics of the 4-day wave in the Southern Hemisphere polar stratosphere. They were derived from synoptic maps of satellite-measured brightness temperatures, which were generated using the fast Fourier synoptic mapping technique of Salby (1982). Circulation statistics from these data are compared to those from the NMC operational stratospheric analyses, demonstrating improvements afforded by detailed treatment of asynoptic sampling effects. The 40-day wave is isolated using temporally filtered data. Several events of wave growth and decay are observed in the upper stratosphere during August 1980. Derived zonal-mean and eddy statistics suggest that the 4-day wave results from an instability of the zonal-mean flow near 55-60S, at and above 1 mb. It is inferred from climatological data that the source of the instability is the 'double-jet' structure in the upper stratosphere and mesosphere.

Randel, William J.↗
NASA NTRS1994

Evolution of the Southern Hemisphere subpolar middle atmosphere during summer and autumn

The evolution of zonal wind and zonal wavenumber one (wave 1) in the Southern Hemisphere subpolar middle atmosphere is described for the period December 1978 - May 1979 using temperature and ozone measurements from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment. In late December maximum zonal easterlies of approx. -70 m/s are observed at 0.1 mb, 60 deg S. A zonal flow reversal occurs during late February and westerlies subsequently increase to 60-70 m/s in the upper stratosphere by April - May. LIMS zonal winds are compared with rocketsonde measurements and nadir sounder (derived) winds for summer and autumn. Although quantitative agreement is found at stratospheric levels, substantial discrepancies are evident in the mesosphere, most likely a reflection of sampling and resolution differences in the respective datasets. Stationary and traveling wave 1 temperature disturbances (amplitudes approx. 1 - 2 K at 60 deg S) are observed by LIMS during summer. The stationary wave is confined to the lower stratosphere near the level of zero zonal- mean wind flow, whereas the traveling wave is prominent in the middle stratosphere moves west at a rate similar to the zonal-mean wind, and exhibits a vertical - meridional structure similar to a P(sub 4)(sup 1) normal mode Rossby wave. A substantial intensification of wave 1 activity occurs during autumn (amplitudes approx. 5 - 10 K), which is found to be associated with an upward-directed Eliasse - Palm flux near the subpolar tropopause level. Evidence relating wave 1 activity in the lower - middle stratosphere to the occurrence of zonal ozone perturbations of 10% - 20% amplitude is presented for summer and autumn.

Miles, T.↗
NASA NTRS2004

The Southern Hemisphere Additional Ozonesondes (SHADOZ) 1998-2002 Tropical Ozone Climatology: Instrumentation and Station-to-Station Variability - 3

Abstract: Since 1998 the Southern Hemisphere ADditional OZonesondes (SHADOZ) project has collected more than 2000 ozone profiles from a dozen tropical and subtropical sites using balloon-borne electrochemical concentration cell (ECC) ozonesondes. The data (with accompanying pressure-temperature-humidity soundings) are archived. Analysis of ozonesonde imprecision within the SHADOZ dataset revealed that variations in ozonesonde technique could lead to station-to-station biases in the measurements. In this paper imprecisions and accuracy in the SHADOZ dataset are examined in light of new data. When SHADOZ total ozone column amounts are compared to version 8 TOMS (2004 release), discrepancies between sonde and satellite datasets decline 1-2 percentage points on average, compared to version 7 TOMS. Variability among stations is evaluated using total ozone normalized to TOMS and results of laboratory tests on ozonesondes (JOSE-2O00, Julich Ozonesonde Intercomparison Experiment). Ozone deviations from a standard instrument in the JOSE flight simulation chamber resemble those of SHADOZ station data relative to a SHADOZ-defined climatological reference. Certain systematic variations in SHADOZ ozone profiles are accounted for by differences in solution composition, data processing and instrument (manufacturer). Instrument bias leads to a greater ozone measurement above 25 km over Nairobi and to lower total column ozone at three Pacific sites compared to other SHADOZ stations at 0-20 deg.S.

Thompson, Anne M.↗
NASA NTRS2003

A Comparison of Northern and Southern Hemisphere Cross-tropopause Ozone Flux

A novel method of calculating the downward ozone flux across the midlatitude (30 deg-60 deg) tropopause shows the Northern Hemisphere (NH) ozone flux to be significantly larger (approximately 24%) than that calculated in the Southern Hemisphere (SH) during the year 2000. This diagnostic method makes it possible to separate dynamical aspects of transport from the seasonal cycle of ozone in the lowermost stratosphere and explain the hemispheric difference in the ozone flux. The SH total horizontal area of exchange is equal to or slightly greater than the area of exchange in the NH throughout an annual cycle. The mean changes in potential vorticity of parcels near the tropopause are also similar or slightly greater in the SH, suggesting that NH and SH downward total mass transport to the troposphere are comparable. These results imply that the greater NH ozone flux is mostly due to the amount of ozone available for exchange rather than net hemispheric dynamical differences near the tropopause level.

Olsen, M. A.↗
NASA NTRS1980

Photometry of Southern Hemisphere red dwarf stars

Results are presented for a photometric investigation of a spectroscopically selected sample of red dwarf stars in the Southern Hemisphere. Absolute magnitudes and distances for the stars are estimated from broadband red colors. Three stars which may be subluminous are identified, as are several stars which may be within 25 pc. The tangential velocity and velocity dispersion of the sample are similar to values found in other studies of nearby late-type stars.

Weistrop, D.↗