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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Teleconnections in the Southern Hemisphere

Monthly anomalies from climatology of sea level pressure and 500 mb geopotential height are used to study teleconnection patterns in the Southern Hemisphere. The data and method used are described, and correlations between zonally averaged anomalies are given. The zonal wavenumber three patterns and teleconnection patterns are given, and the results of eigenvector analysis with teleconnection patterns at 500 mb are reported. The zonally averaged anomalies display two patterns of variability; an out-of-phase relation between high and low latitudes and a pattern in which anomalies in midlatitudes vary out of phase with anomalies in low and high latitudes. In winter, midlatitudes are dominated by three centers of positive correlations over the oceans while the negative correlations are found at high and low latitudes. The teleconnection pattern in summer at 500 mb shows an out-of-phase relation between heights over the subtropical continents and heights in the midlatitude oceans.

Mo, K. C.↗
NASA NTRS1991

On the maintenance of short-term subtropical wind maxima in the Southern Hemisphere during SOP-1, FGGE

The extent to which divergent circulations, induced by tropical heating, help to maintain westerly maxima in the Southern Hemisphere subtropics during the SOP-1 of FGGE is explored using Level III-b analyses from the Goddard Laboratory for Atmospheres. The contribution of the divergent wind component to the total ageostrophic flow in the subtropics is examined, as are the roles of other forcing terms in the localized Eliassen-Palm (1961) flux zonal momentum equation. Throughout the summertime subtropics, it is generally found that the dominant term in the zonal momentum budget is the Coriolis force applied to the diabatically driven meridional circulation. The largest positive tendencies due to this term are found in the entrance regions of the subtropical westerly maxima, and divergent circulations account for nearly all of the total ageostrophic flow. In the SPCZ region, however, it is found that transient eddies play an important role by partially offsetting the strong Coriolis acceleration in the entrance region of the local jet, and they help accelerate the westerly flow in the exit region through both barotropic and baroclinic processes. Energetically, the dominant term in the rotational kinetic energy budget throughout the subtropical belt is the conversion of divergent to rotational kinetic energy. The evidence supports the view that tropical heating in transient events drives or enhances local meridional overturning in the atmosphere, which, in turn, strengthens the summer subtropical westerly jet stream.

Hurrell, James W.↗
NASA NTRS2010

Southern Hemisphere Carbon Monoxide Inferannual Variability Observed by Terra/Measurement of Pollution in the Troposphere (MOPITT)

Biomass burning is an annual occurrence in the tropical southern hemisphere (SH) and represents a major source of regional pollution. Vegetation fires emit carbon monoxide (CO), which due to its medium lifetime is an excellent tracer of tropospheric transport. CO is also one of the few tropospheric trace gases currently observed from satellite and this provides long-term global measurements. In this paper, we use the 5 year CO data record from the Measurement Of Pollution In The Troposphere (MOPITT) instrument to examine the inter-annual variability of the SH CO loading and show how this relates to climate conditions which determine the intensity of fire sources. The MOPITT observations show an annual austral springtime peak in the SH zonal CO loading each year with dry-season biomass burning emissions in S. America, southern Africa, the Maritime Continent, and northwestern Australia. Although fires in southern Africa and S. America typically produce the greatest amount of CO, the most significant inter-annual variation is due to varying fire activity and emissions from the Maritime Continent and northern Australia. We find that this variation in turn correlates well with the El Nino Southern Oscillation precipitation index. Between 2000 and 2005, emissions were greatest in late 2002 and an inverse modeling of the MOPITT data using the MOZART chemical transport model estimates the southeast Asia regional fire source for the year August 2002 to September 2003 to be 52 Tg CO. Comparison of the MOPITT retrievals and NOAA surface network measurements indicate that the latter do not fully capture the inter-annual variability or the seasonal range of the CO zonal average concentration due to biases associated with atmospheric and geographic sampling.

Edwards, D. P.↗
NASA NTRS1999

Southern Hemisphere Storm Zones on Mars: Implications of MOLA Topography

Using the NASA Ames Mars general circulation model and recent Mars orbiter laser altimeter (MOLA) global topography, annual-cycle simulations have been performed corresponding to a lowglobally-averaged atmospheric dust loading (tau= 0 - 3). Comparisons of key global circulation fields as simulated utilizing previous topography datasets and those using the new Mars global topography have been carried out. Values of globally and/or hemispheric averaged kinetic energy associated with the longitudinally averaged (i.e., zonal) circulation and longitudinal departures (i.e., eddy components) as a function of season for simulations using the different topography datasets are provided contributions arising frommeteorological variability associated with thermal tides, stationary circulation components and recurrent weather systems (transient baroclinc and/or barotropic eddies). It can be noted that eddy activity in the northern hemisphere (NH) is substantially diminished using the new topographic data, and that at some seasons, the southern hemisphere (SH) activity is moderately increased. Additional information is contained in the original extended abstract.

Hollingsworth, J. L.↗
NASA NTRS1986

Large-amplitude, short-scale stationary Rossby waves in the Southern Hemisphere - Observations and mechanistic experiments to determine their origin

Further observational evidence of the existence of large-amplitude stationary waves in the Southern Hemisphere during January 1979 is presented. Possible forcing mechanisms for the stationary waves are discussed, and two control experimental forecasts are presented: 15-day integrations with the GLAS Fourth Order GCM, starting from January 5 and Febuary 4, 1979. These forecasts are compared with the GLAS analyses for the same periods, discussing the extent to which the observed January waves are reproduced in the forecast. Several mechanistic experiments are reported in which the Andean orography, tropical heating, regional heating, and initial westerly flow are artificially modified. The effects of these changes on the stationary waves are discussed.

Kalnay, E.↗
NASA NTRS1987

Significance of the South Pacific Convergence Zone (SPCZ) in the energy budget of the Southern Hemisphere tropics

An in-depth investigation of the energetics, including boundary transports, was conducted on four equal-area regions in the tropical Southern Hemisphere during the SOP-1 period in 1979. The regions, each approximately centered on one of the wave axes of maximum warm rising air, include the SPCZ (115 deg W - 155 deg E) and the Australian (155-65 deg E), the African (65 deg E - 25 deg W), and the South American (25-115 deg W) regions. Daily variations of the energy conversions were examined, and time-averaged result of energy contents, conversions, and boundary transports were compiled for January 10-27. Results show that the eddy kinetic energy (KE) exceeds the eddy available potential energy (AE) in all four regions, with the largest excess being in the SPCZ. Of the conversion and flux terms, only the conversion of AE to KE is significant (again, with the greatest value in the SPCZ). An evaluation of boundary fluxes of KE indicates that the only significant transport between regions is a flow of KE from the SPCZ region into the South American region.

Hurrell, James W.↗
NASA NTRS1988

Geochemical comparison of K-T boundaries from the Northern and Southern Hemispheres

Closely spaced (cm-scale) traverses through the K-T boundary at Stevns Klint (Denmark), Woodside Creek (New Zealand) and a new Southern Hemisphere site at Richards Bay (South Africa) were subjected to trace element and isotopic (C, O, Sr) investigation. Intercomparison between these data-sets, and correlation with the broad K-T database available in the literature, indicate that the chemistry of the boundary clays is not globally constant. Variations are more common than similarities, both of absolute concentrations, and interelement ratios. For example, the chondrite normalized platinum-group elements (PGE) patterns of Stevns Klint are not like those of Woodside Creek, with the Pt/Os ratios showing the biggest variation. These differences in PGE patterns are difficult to explain by secondary alteration of a layer that was originally chemically homogeneous, especially for elements of such dubious crustal mobility as Os and Ir. The data also show that enhanced PGE concentrations, with similar trends to those of the boundary layers, occur in the Cretaceous sediments below the actual boundary at Stevns Klint and all three the New Zealand localities. This confirms the observations of others that the geochemistry of the boundary layers apparently does not record a unique component. It is suggested that terrestrial processes, eg. an extended period of Late Cretaceous volcanism can offer a satisfactory explanation for the features of the K-T geochemical anomaly. Such models would probably be more consistent with the observed stepwise, or gradual, palaeontological changes across this boundary, than the instant catastrophe predicated by the impact theory.

Tredous, M.↗
NASA NTRS1976

A numerical circulation model with topography for the Martian southern hemisphere

A two-level numerical model taking account of the observed planetary topography is applied to the general circulation of the Martian atmosphere in the southern hemisphere. The physics of this model is based on the assumption of a hydrostatic quasi-geostrophic ideal-gas atmosphere composed entirely of carbon dioxide; radiative transfer among the atmosphere, space, and the ground is included along with surface friction. The calculations indicate the development of near-equilibrium weather systems after about five model days, weather systems and velocity fields whose positions appear to be connected with topography, and a midlatitude jet stream strikingly similar to the terrestrial case. The results also suggest that the vertical and horizontal wind components in western Hellas and eastern Argyre produce copious amounts of suspendible dust each year, that both major and minor dust storms should be a common occurrence on Mars, and that the entire south circumpolar zone appears to be a dust sink in winter.

Mass, C.↗
NASA NTRS2017

Causes of Interannual Variability over the Southern Hemispheric Tropospheric Ozone Maximum

We examine the relative contribution of processes controlling the interannual variability (IAV) of tropospheric ozone over four sub-regions of the southern hemispheric tropospheric ozone maximum (SHTOM) over a 20-year period. Our study is based on hindcast simulations from the National Aeronautics and Space Administration Global Modeling Initiative chemistry transport model (NASA GMI-CTM) of tropospheric and stratospheric chemistry, driven by assimilated Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Our analysis shows that over SHTOM region, the IAV of the stratospheric contribution is the most important factor driving the IAV of upper tropospheric ozone (270 hectopascals), where ozone has a strong radiative effect. Over the South Atlantic region, the contribution from surface emissions to the IAV of ozone exceeds that from stratospheric input at and below 430 hectopascals. Over the South Indian Ocean, the IAV of stratospheric ozone makes the largest contribution to the IAV of ozone with little or no influence from surface emissions at 270 and 430 hectopascals in austral winter. Over the tropical South Atlantic region, the contribution from IAV of stratospheric input dominates in austral winter at 270 hectopascals and drops to less than half but is still significant at 430 hectopascals. Emission contributions are not significant at these two levels. The IAV of lightning over this region also contributes to the IAV of ozone in September and December. Over the tropical southeastern Pacific, the contribution of the IAV of stratospheric input is significant at 270 and 430 hectopascals in austral winter, and emissions have little influence.

Global Modeling Initiative chemistry transport mod↗
NASA NTRS1975

A numerical circulation model with topography for the Martian Southern Hemisphere

A quasi-geostrophic numerical model, including friction, radiation, and the observed planetary topography, is applied to the general circulation of the Martian atmosphere in the Southern Hemisphere at latitudes south of about 35 deg. Near equilibrium weather systems developed after about 5 model days. To avoid violating the quasi-geostrophic approximation, only 0.8 of the already smoothed relief was employed. Weather systems and velocity fields are strikingly tied to topography. A 2mb middle latitude jet stream is found of remarkably terrestrial aspect. Highest surface velocities, both horizontal and vertical, are predicted in western Hellas Planitia and eastern Argyre Planitia, which are observed to be preferred sites of origin of major Martian dust storms. Mean horizontal velocities and vertical velocities are found just above the surface velocity boundary layer.

Mass, C.↗
NASA NTRS1985

Significance of the South Pacific Convergence Zone in energy conversions of the Southern Hemisphere during FGGE, 10-27 January 1979

An attempt is made to relate the circulation features of the South Pacific Convergence Zone (SPCZ) to those of the Southern Hemisphere (SH) for the whole area and for three subsections. It is established that during the period of Jan. 10-24, 1979, when the SPCZ was convectively active, it played a significant role in the baroclinic energy conversion (CE) within the tropical SH. When the SPCZ dissipated the CE did likewise. A zonal wavenumber analysis shows that wavenumber four was dominant in the CE process in the SH topics when the SPCZ was active, but that it did not dominate when the SPCZ dissipated. It is shown that the most intense convective activity in the tropics occurred in the SPCZ and that its location corresponded favorably to maximum values of CE greater than zero.

Huang, H.-J.↗
NASA NTRS2002

Variability in Ozone in the Tropical Upper Troposphere-Lower Stratosphere from the 1998-2000 SHADOZ (Southern Hemisphere Additional Ozonesondes) Data

The first view of lower stratospheric and upper tropospheric structure from sondes is provided by a 3-year, 10-site record from the Southern Hemisphere ADditional OZonesondes (SHADOZ) network: . Observations covering 1998-2000 were made over Ascension Island; Nairobi, Kenya; Irene, South Africa; Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; Natal, Brazil. Taking the UT/LS (upper troposphere- lower stratosphere) as the region between 12 and 17 km, we examine ozone variability in this region on a week-to-week and seasonal basis. The tropopause is lower in September-October-November than in March-April-May, when ozone is a minimum at most SHADOZ stations. A zonal wave-one pattern (referring to ozone mixing ratios greater over the Atlantic and adjacent continents than over the Pacific and eastern Indian Ocean), persists all year. The wave, predominantly in the troposphere and with variable magnitude, appears to be due to general circulation - with subsidence over the Atlantic and frequent deep convection over the Pacific and Indian Ocean. The variability of deep convection most prominent at Java, Fiji, Samoa and Natal - is explored in time-vs-altitude ozone curtains. Stratospheric incursions into the troposphere are most prominent in soundings at Irene and Reunion Island.

Thompson, A. M.↗
NASA NTRS2002

The 1998-2000 SHADOZ (Southern Hemisphere ADditional OZonesondes) Tropical Ozone Climatology: Stratospheric and Tropospheric Ozone Variability and the Zonal Wave-One - 2

This is the second 'reference' or 'archival' paper for the SHADOZ (Southern Hemisphere Additional Ozonesondes) network and is a follow-on to the recently accepted paper with similar first part of title. The latter paper compared SHADOZ total ozone with satellite and ground-based instruments and showed that the equatorial wave-one in total ozone is in the troposphere. The current paper presents details of the wave-one structure and the first overview of tropospheric ozone variability over the southern Atlantic, Pacific and Indian Ocean basins. The principal new result is that signals of climate effects, convection and offsets between biomass burning seasonality and tropospheric ozone maxima suggest that dynamical factors are perhaps more important than pollution in determining the tropical distribution of tropospheric ozone. The SHADOZ data at ( ) are setting records in website visits and are the first time that the zonal view of tropical ozone structure has been recorded - thanks to the distribution of the 10 sites that make up this validation network.

Thompson, Anne M.↗
NASA NTRS1991

Identification of widespread pollution in the Southern Hemisphere deduced from satellite analyses

Vertical profiles of ozone obtained from ozonesondes in Brazzaville (Congo) and Ascension Island show that large quantities of tropospheric ozone are present over southern Africa and the adjacent eastern tropical South Atlantic Ocean. The origin of this pollution is widespread biomass burning in Africa. These measurements support satellite-derived tropospheric ozone data that demonstrate that ozone originating from this region is transported throughout most of the Southern Hemisphere. Seasonally high levels of CO2 and methane observed at middle- and high-latitude stations in Africa, Australia, and Antarctica likely reflect the effects of this distant biomass burning. These data suggest that even the most remote regions on this planet may be significantly more polluted than previously believed.

Fishman, J.↗
NASA NTRS1979

Southern Hemisphere measurements of the anisotropy in the cosmic microwave background radiation

A recent airborne measurement of the large-angular-scale anisotropy in the cosmic background radiation from the Southern Hemisphere (Lima, Peru) is in essential agreement with previous measurements from the northern hemisphere. The net anisotropy from the combined data can be described by a first-order spherical harmonic (Doppler) anisotropy of amplitude 3.1 plus or minus 0.4 mK with a quadrupole component of less than 1 mK. Additional ground-based measurements of the linear polarization yield an upper limit of l mK, or one part in 3000, at 95% confidence level for the amplitudes of any spherical harmonic through third order.

Smoot, G. F.↗
NASA NTRS2021

The 2019 Southern Hemisphere Stratospheric Polar Vortex Weakening and Its Impacts

This study offers an overview of the low-frequency (i.e., monthly to seasonal) evolution, dynamics, predictability, and surface impacts of a rare Southern Hemisphere (SH) stratospheric warming that occurred in austral spring 2019. Between late August to mid- September 2019, the stratospheric circumpolar westerly jet weakened rapidly, and Antarctic stratospheric temperatures rose dramatically. The deceleration of the vortex at 10 hPa was as drastic as that of the first ever observed major sudden stratospheric warming in the SH during 2002, while the mean Antarctic warming over the course of spring 2019 broke the previous record of 2002 by ~50% in the mid-stratosphere. This event was preceded by a poleward shift of the SH polar night jet in the uppermost stratosphere in early winter, which was then followed by record-strong planetary wave-one activity propagating upward from the troposphere in August that acted to dramatically weaken the polar vortex throughout the depth of the stratosphere. The weakened vortex winds and elevated temperatures moved downward to the surface from mid-October to December, promoting a record strong swing of the Southern Annular Mode (SAM) to its negative phase. This record-negative SAM appeared to be a primary driver of the extreme hot and dry conditions over subtropical eastern Australia that accompanied the severe wildfires that occurred in late spring 2019. State-of-the-art dynamical seasonal forecast systems skillfully predicted the significant vortex weakening of spring 2019 and subsequent development of negative SAM from as early as late July.

Antarctic Oscillation↗
NASA NTRS1992

Do large impact basins in the Southern Hemisphere of Mars control the distribution of polar structures and deposits?

Among the problems in Martian geology are the cause of the off-axis and asymmetric distribution of the southern polar layered terrain and residual ice deposits and the cause of the orientation of scarps, valleys, and reentrant canyons that occur. A problem region is the small number of large (D greater than 500) impact basins seen in the relatively well preserved cratered terrain of the south polar region. This region was mapped in detail, searching for evidence of ancient, highly degraded impact basins for two reasons: To determine whether the apparent absence of large impact basins is due to incomplete mapping and recognition or a fundamental characteristic of the Martian crust related to the origin of the Martian crustal dichotomy, and whether ancient impact basins exert some control on the distribution of volcanic and polar deposits in the Southern Hemisphere and on the topography on which these deposits lie. The possible influence is examined of the candidate basins in localizing the asymmetric distribution of polar deposits and in controlling the orientation of structures found within these deposits.

Frey, Herbert↗
NASA NTRS1993

Do large impact basins in the southern hemisphere of Mars control the distribution of polar structures and deposits?

Among the outstanding problems in Martian geology are the cause of the off-axis and asymmetric distribution of the southern polar layered terrain and residual ice deposits and the cause of the orientation of scarps, valleys, and re-entrant canyons which occur there. A perhaps related problem region is the apparently small number of large (D greater than 500 km) impact basins seen in the relatively well-preserved cratered terrain of the south polar region. Previously only the 850 km wide South Polar Basin was easily recognized. The south polar region was mapped in detail, searching for evidence of ancient, highly degraded impact basins that may have escaped earlier notice, for two reasons: (1) to determine whether the apparent absence of large impact basins is due to incomplete mapping and recognition or a fundamental characteristic of the Martian crust related to the origin of the Martian crustal dichotomy, and (2) to determine whether ancient impact basins, if they exist, exert some control on the distribution of volcanic and polar deposits in the southern hemisphere and on the topography on which these deposits lie. Several promising candidates, including a large pre-Hellas basin in the Malea Planum region and an older but comparably sized basin overlapping South Polar, were previously described. Concentration is on the possible influence of the candidate basins in localizing the asymmetric distribution of polar deposits and in controlling the orientation of structures found within these deposits.

Frey, Herbert↗