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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 55 records · Page 3
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NASA NTRS1983

Predictability of planetary waves - Interhemispheric differences and the effects of stationary forcing

An attempt is made to determine the way in which errors appear in the ultralong waves of numerical weather prediction models, as well as the means by which such errors may be alleviated. Such efforts to improve the numerical forecasting of planetary waves derive their importance from the fact that energetic large scale phenomena are the basis for prospective improvements in extended range forecasting. A simple, linear, quasi-geostrophic and barotropic model is presently used in real data forecast simulations to explore, in an idealized context, several effects that may clarify discrepancies betweeen predictability theory and the performance of current numerical weather prediction models. Attention is given to the degree to which discrepancies may be accounted for by linear theory.

Roads, J. O.↗
NASA NTRS1984

Atmospheric methane in the recent and ancient atmospheres Concentrations, trends, and interhemispheric gradient

Rasmussen and Khalil (1981) have shown that the concentration of methane is increasing in the earth's atmosphere. A continuing increase of methane may perturb the global environment in the future by warming the earth and leading to more ozone and carbon monoxide in the atmosphere. It appears that the present concentration of methane may be more than twice as high as the natural levels of 150 years ago. An analysis of air bubbles buried long ago in polar ice makes it possible to deduce the concentrations of methane in the old and ancient atmospheres. The present investigation is concerned with the results of an analysis of more than 80 ice core samples, taking into account both polar regions of the earth. The samples range in age from about 100 to nearly 3000 years old. It is found that the concentration of methane started changing significantly about 150 years ago. These findings suggest that the increase of methane is probably indirectly caused by the rapid increase of human population.

Rasmussen, R. A.↗
NASA NTRS1985

Interhemispheric interactions

Diagnoses of global data sets are presented that indicate strong coupling between the regions of enhanced tropical convection of the summer hemisphere and subtropical jet stream maxima of the winter hemisphere. One curious aspect of this coupling is that it tends to occur through zones of easterly winds at upper tropospheric levels. This characterizes the El Nino event of 1983, an upper connection of the Asian monsoon to the Australian jet in FGGE and DST data and shorter term transitions during the First Special Observing Period of FGGE. The reasons for the apparent propagation through easterly wind zones remain to be clarified.

Paegle, J.↗
NASA NTRS1988

Late Pleistocene variations in Antarctica sea ice. I - Effect of orbital isolation changes. II - Effect of interhemispheric deep-ocean heat exchange

A dynamic-thermodynamic sea-ice model is presently used to ascertain the effects of orbitally-induced insolation changes on Antarctic sea-ice cover; the results thus obtained are compared with modified CLIMAP reconstructions of sea-ice 18,000 years ago. The minor influence exerted by insolation on Pleistocene sea-ice distributions is attributable to a number of factors. In the second part of this investigation, variations in the production of warm North Atlantic Deep Water are proposed as a mechanism constituting the linkage between climate fluctuations in the Northern and Southern hemispheres during the Pleistocene; this hypothesis is tested by examining the sensitivity of the dynamic-thermodynamic model for Antarctic sea-ice changes in vertical ocean heat flux, and comparing the simulations with modified CLIMAP sea-ice maps for 18,000 years ago.

Crowley, Thomas J.↗
NASA NTRS1994

Interhemispheric asymmetry of the high-latitude ionospheric convection pattern

The assimilative mapping of ionospheric electrodynamics technique has been used to derive the large-scale high-latitude ionospheric convection patterns simultaneously in both northern and southern hemispheres during the period of January 27 to 29, 1992. When the interplanetary magnetic field (IMF) B(sub z) component is negative, the convection patterns in the southern hemisphere are basically the mirror images of those in the northern hemisphere. The total cross-polar cap potential drops in the two hemispheres are similar. When B(sub z) is positive and absolute value of B(sub y) greater than B(sub z), the convection configurations are mainly determined by B(sub y) and they may appear as normal 'two-cell' patterns in both hemispheres much as one would expect under southward IMF conditions. However, there is a significant difference in the cross-polar-cap potential drop between the two hemispheres, with the potential drop in the southern (summer) hemisphere over 50% larger than that in the northern (winter) hemisphere. As the ratio of absolute value of B(sub y)/B(sub z) decreases (less than one), the convection configuration in the two hemispheres may be significantly different, with reverse convection in the southern hemisphere and weak but disturbed convection in the northern hemisphere. By comparing the convection patterns with the corresponding spectrograms of precipitating particles, we interpret the convection patterns in terms of the concept of merging cells, lobe cells, and viscous cells. Estimates of the ' merging cell' potential drops, that is, the potential ascribed to the opening of the dayside field lines, are usually comparable between the two hemispheres, as they should be. The 'lobe cell' provides a potential between 8.5 and 26 kV and can differ greatly between hemispheres, as predicted. Lobe cells can be significant even for southward IMF, if absolute value of B(sub y) greater than the absolute value of B(sub z). To estimate the potential drop of the 'viscous cells,' we assume that the low-latitude boundary layer is on closed field lines. We find that this potential drop varies from case to case, with a typical value of 10 kV. If the source of these cells is truly a viscous interaction at the flank of the magnetopause, the process is likely spatially and temporally varying rather than steady state.

Lu, G.↗
NASA NTRS1995

Interhemispheric differences in polar stratospheric HNO3, H2O, ClO, and O3

Simultaneous global measurements of nitric acid (HNO3), water (H2O), chlorine monoxide (ClO), and ozone (O3) in the stratosphere have been obtained over complete annual cycles in both hemispheres by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite. A sizeable decrease in gas-phase HNO3 was evident in the lower stratospheric vortex over Antarctica by early June 1992, followed by a significant reduction in gas-phase H2O after mid-July. By mid-August, near the time of peak ClO, abundances of gas-phase HNO3 and H2O were extremely low. The concentrations of HNO3 and H2O over Antarctica remained depressed into November, well after temperatures in the lower stratosphere had risen above the evaporation threshold for polar stratospheric clouds, implying that denitrification and dehydration had occurred. No large decreases in either gas-phase HNO3 or H2O were observed in the 1992-1993 Arctic winter vortex. Although ClO was enhanced over the Arctic as it was over the Antarctic, Arctic O3 depletion was substantially smaller than that over Antarctica. A major factor currently limiting the formation of an Arctic ozone 'hole' is the lack of denitrification in the northern polar vortex, but future cooling of the lower stratosphere could lead to more intense denitrification and consequently larger losses of Arctic ozone.

Santee, M. L.↗
NASA NTRS1999

Evolution of Plasmaspheric Refilling: A Comparison of Measurements with an Interhemispheric Plasmasphere Model

The evolution of plasmasphere is closely coupled to processes governing flux tube refilling and transport. In this study we follow this evolution through a series of sequential ion observations made by RIMS on the DE 1 satellite and with the intervening time intervals filled by simulations made with the FLIP model. The FLIP model solves the continuity and momentum equations for the major ion species as well as the energy equations for ions and electrons along entire flux tubes rom 100 k altitude in both hemispheres. Convection has recently been included, driven a dawn-dusk electric field model. Since the observations are necessarily restricted to two local time passes through the plasmasphere per orbit, the FLIP code will follow the observed flux tubes as they corotate and convect through the other local times. The period of DE 1 is such that nearly the same flux tubes are observed every second day or every sixth orbit. The composite of observations and simulations allows assessment of the degree to which the degree to which the FLIP simulations accurately describe the processes which govern flux tube refilling over the two-day period between observations of the same flux tubes.

Comfort, Richard H.↗
NASA NTRS2000

Elevated Tropospheric Ozone Over the South Tropical Atlantic in January-February 1999: An Ozone Paradox Due to Interhemispheric Transport, Lightning, or Stratospheric Exchange?

On this first North American to southern African oceanographic cruise with ozonesonde launches (January and February 1999 on board the NOAA Research Vessel Ronald H Brown between Norfolk, VA, and Cape Town, South Africa) we found: (1) high ozone, CO, and aerosols off northern equatorial Africa from biomass burning, but even higher ozone concentrations off southern Africa which was not burning - an "ozone paradox"; (2) TOMS satellite evidence that south Atlantic elevated ozone in January-February 1999 was a regional feature similar in extent to the well-known September-October ozone maximum. Several mechanisms are considered to explain the "ozone paradox." Convection transporting air from the lower troposphere rich in ozone and/or ozone precursors to the upper troposphere through the ITCZ (intertropical Convergence Zone) may lead to cross-hemisphere transport of pollution. This is supported by trajectory linkage of lower-tropospheric ozone maxima with smoke seen by the TOMS satellite. Lightning-generated NO (nitric oxide) leading to ozone peaks of > 100 ppbv observed at 7-10 km altitude is another explanation. The TRMM (Tropical Rainfall Measuring Mission) Lightning Imaging Sounder shows many lightning flashes over southern Africa, which trajectories link to the high-ozone layers south of the ITCZ. The highest ozone peaks in the middle troposphere correspond to very low water vapor, which may point to photochemical destruction of ozone or subsidence from the upper troposphere which had interacted with stratospheric ozone.

Thompson, Anne M.↗
NASA NTRS1994

Interhemispheric Differences in Dentifrication and Related Processes Affecting Polar Ozone

The severe depletion of stratospheric ozone over Antarctica in late winter and early spring is caused by enhanced CLO abundances arising from heterogeneous reactions on polar stratospheric clouds (PSCs). CLO abundances comparable to those over Antarctica have also been observed throughout the Arctic Vortex, but the accompanying loss of Arctic ozone has been much less severe.

ozone depletion↗
NASA NTRS2009

Evidence for Interhemispheric Coupling during the Unusual Northern Polar Summer Mesosphere of 2002

Data from the MaCWAVE MIDAS Rocket Program launched during July, 2002, from Andoya Rocket Range (ARR) in Norway have demonstrated that the temperature structure of the summer polar mesosphere during this period was atypical, at least above ARR. The summer polar mesopause region was warmer than normal and of shorter duration than for other years analyzed. Theoretical studies have since been published that imply that the abnormal characteristics of this polar summer were generated by unusual dynamical processes occurring in the southern polar winter hemisphere. We have used data from the SABER instrument aboard the NASA TIMED Satellite to study these characteristics on a global scale and compare them with the features observed in the ensuing seven years. For background, The TIMED Satellite was launched on December 7, 2001 to study the dynamics and energy of the mesosphere and lower thermosphere (MLT). The SABER instrument on TIMED is a limb scanning infrared radiometer designed to measure a large number of minor constituents as well as temperature of the MLT. In this study, we have investigated the temperature characteristics of the polar mesosphere as a function of spatial and temporal considerations. We have used the most recent SABER dataset (1.07) that includes the improved temperature retrievals in Earth polar regions, Weekly averages were used 10 make the comparisons between the winter and summer hemispheres. The unusually short polar summer in the northern hemisphere during 2002 is clearly defined by this analysis and is shown to be unique for the 7 years analyzed. Furthermore, the data analysis agrees with recent theoretical studies showing that this behavior is a result of anomalous heating events in the southern polar stratosphere. The time sequence of the coupling process, as predicted by recent theoretical models, is well defined in a sequence of weekly temperature contour maps measured by SABER.

Goldberg, Richard A.↗
NASA NTRS2023

Theoretical Study of Interhemispheric Electron Bouncing Within Pulsating Aurora

Wave-particle interaction processes in the equatorial magnetosphere initiate time-dependent electron precipitation in the pulsating aurora. These electrons enter loss-cone and bounce between the two magnetically conjugate hemispheres, collide with the atmospheric constituents, and introduce additional time scales in electron precipitation dynamics. In this letter we present preliminary results of pulsating aurora formation using the time-dependent SuperThermal Electron Transport code, which considers the magnetosphere-ionosphere-atmosphere energy coupling between the two magnetically conjugate regions and discuss their contribution to the peculiarities of electron distribution function formation within the pulsating aurora.

Pulsating Aurora↗
NASA NTRS1997

Callosally projecting neurons in the macaque monkey V1/V2 border are enriched in nonphosphorylated neurofilament protein

Previous immunohistochemical studies combined with retrograde tracing in macaque monkeys have demonstrated that corticocortical projections can be differentiated by their content of neurofilament protein. The present study analyzed the distribution of nonphosphorylated neurofilament protein in callosally projecting neurons located at the V1/V2 border. All of the retrogradely labeled neurons were located in layer III at the V1/V2 border and at an immediately adjacent zone of area V2. A quantitative analysis showed that the vast majority (almost 95%) of these interhemispheric projection neurons contain neurofilament protein immunoreactivity. This observation differs from data obtained in other sets of callosal connections, including homotypical interhemispheric projections in the prefrontal, temporal, and parietal association cortices, that were found to contain uniformly low proportions of neurofilament protein-immunoreactive neurons. Comparably, highly variable proportions of neurofilament protein-containing neurons have been reported in intrahemispheric corticocortical pathways, including feedforward and feedback visual connections. These results indicate that neurofilament protein is a prominent neurochemical feature that identifies a particular population of interhemispheric projection neurons at the V1/V2 border and suggest that this biochemical attribute may be critical for the function of this subset of callosal neurons.

Non-NASA Center↗
NASA NTRS1976

Characteristics of Southern Hemisphere 200 mb flow as determined from satellite data

Characteristics of Southern Hemisphere 200 mb flow are examined using geopotential height fields constructed with the aid of satellite based thermal structure. Similar Northern Hemisphere, satellite based fields are developed in order to make interhemispheric comparisons. Results indicate that both the zonal and meridional components of the S.H. eddy kinetic energy are as large as their N.H. counterparts. In winter the principal interhemispheric difference with respect to eddy kinetic energy is that the S.H. standing eddies are much less important only to the meridional component. Zonal component standing energy is about equal in the two hemispheres. In summer the S.H. has larger zonal eddy kinetic energy than the N.H. and smaller standing eddy contributions in both components. The meridional spectra show a preference for intermediate size transient waves.

Adler, R. F.↗
NASA NTRS1984

The influence of neutral winds on He(+) distributions in the equatorial ionospshere

The effects of F-region neutral winds on the distribution of He(+) in the equatorial ionosphere have been examined using a theoretical model and an observational data set. It is shown by the model that components of neutral wind in the magnetic meridian up to only 50 m/s can produce He(+) gradients in the northern and southern sectors of a flux tube that differ by more than 80 percent. This is associated with interhemisphere transport velocities of He(+) as large as 15 m/s at 800 km. A substantial latitude gradient in the He(+) distribution across the dip equator also results from the redistribution of He(+). The changes in the He(+) concentration at the dip equator and the latitude distribution of H(+) in response to different neutral wind components is determined from the model and used to construct longitude distributions of He(+) to compare with observations made at equinox. Good agreement between the calculations and observations is obtained both at the geographic and geomagnetic equators using the relationship between neutral winds, interhemispheric transport velocity and He(+) concentration derived from the model. If these relationships can be extrapolated to accommodate the different conditions expected during solstice, the He(+) distributions expected during this season can also be discussed.

Murphy, J. A.↗