Search NASA⌕ Search

SEARCH · Search NASA

Results for “SOUTHERN HEMISPHERE”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

MLS observations of lower stratospheric ClO and O3 in the 1992 Southern Hemisphere winter

UARS MLS measurements of ClO in the 1992 Southern Hemisphere winter are described. Lower stratospheric ClO abundances greater than 1 ppbv were observed in the vortex beginning 1 June. The enhanced ClO reached largest areal extent in mid-August, then retreated poleward. ClO abundances at 22 hPa decreased in early September while those at 46 hPa remained high. O3 decrease within the vortex was observed by mid-August, and was coincident with the enhanced ClO.

Waters, J. W.↗
NASA NTRS2018

Effect of Gravity Waves from Small Islands in the Southern Ocean on the Southern Hemisphere Atmospheric Circulation

The effect of small islands in the Southern Ocean on the atmospheric circulation in the Southern Hemisphere is considered with a series of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model in which the gravity wave stress generated by these islands is increased to resemble observed values. The enhanced gravity wave drag leads to a 2 K warming of the springtime polar stratosphere, partially ameliorating biases in this region. Resolved wave drag declines in the stratospheric region in which the added orographic gravity waves deposit their momentum, such that changes in gravity waves are partially compensated by changes in resolved waves, though resolved wave drag increases further poleward. The orographic drag from these islands has impacts for surface climate, as biases in tropospheric jet position are also partially ameliorated. These results suggest that these small islands are likely contributing to the missing drag near 60 degrees S in the upper stratosphere evident in many data assimilation products.

chemistry-climate models↗
NASA NTRS2013

Connections Between the Spring Breakup of the Southern Hemisphere Polar Vortex, Stationary Waves, and Air-sea Roughness

A robust connection between the drag on surface-layer winds and the stratospheric circulation is demonstrated in NASA's Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). Specifically, an updated parameterization of roughness at the air-sea interface, in which surface roughness is increased for moderate wind speeds (4ms to 20ms), leads to a decrease in model biases in Southern Hemispheric ozone, polar cap temperature, stationary wave heat flux, and springtime vortex breakup. A dynamical mechanism is proposed whereby increased surface roughness leads to improved stationary waves. Increased surface roughness leads to anomalous eddy momentum flux convergence primarily in the Indian Ocean sector (where eddies are strongest climatologically) in September and October. The localization of the eddy momentum flux convergence anomaly in the Indian Ocean sector leads to a zonally asymmetric reduction in zonal wind and, by geostrophy, to a wavenumber-1 stationary wave pattern. This tropospheric stationary wave pattern leads to enhanced upwards wave activity entering the stratosphere. The net effect is an improved Southern Hemisphere vortex: the vortex breaks up earlier in spring (i.e., the spring late-breakup bias is partially ameliorated) yet is no weaker in mid-winter. More than half of the stratospheric biases appear to be related to the surface wind speed biases. As many other chemistry climate models use a similar scheme for their surface layer momentum exchange and have similar biases in the stratosphere, we expect that results from GEOSCCM may be relevant for other climate models.

air-sea interaction↗
DOE OSTI2024

Concurrent Inter-Model Spread of Boreal Winter Westerly Jet Meridional Positions Between the Northern and Southern Hemispheres in CMIP6 Models

Here, this study investigates the inter-model spread of climatological extratropical westerly jets in boreal winter, using the historical simulation of 52 Coupled Model Intercomparison Project phase 6 (CMIP6) models from 1851 to 2014. The results show that there is a substantial spread in the latitude of the upper-tropospheric westerly jet across models, characterised by large inter-model standard deviations to both the poleward and equatorward sides of the jet axis, although the multi-model ensemble mean (MME) performs well in simulating meridional position of westerly jets. Furthermore, we detect the consistency of inter-model jet position spread between the Northern and Southern Hemispheres, based on the inter-model empirical orthogonal function (EOF) decomposition and correlation of regional-averaged zonal winds. Specifically, the models that simulate the westerly jets poleward/equatorward relative to the MME position in one hemisphere also tend to simulate the jets poleward/equatorward in the other hemisphere. Accordingly, we define a global jet spread index to depict the concurrence of jet shift in the two hemispheres. The results of inter-model regression analyses based on this index indicate that the models positioning the jets poleward than the MME tend to simulate a wider Hadley Cell, a poleward-shifted Ferrel Cell in the Southern Hemisphere, enhanced precipitation in the subtropics and suppressed precipitation in the tropics, and warmer sea surface temperatures in the subtropics and mid-latitudes. The present results suggest that improving the simulation of jet positions in climate models requires a comprehensive consideration of thermal states in the tropics and subtropics/mid latitudes.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1974

The 100 micron surveys in the Northern and Southern Hemispheres

Partial surveys in the far infrared in the Northern and Southern Hemispheres have covered 40% of the galactic equator and assorted regions away from the galactic plane. Approximately 120 100-micron objects are known. These are distributed extensively in galactic longitude and concentrated within + or - two degrees in galactic latitude. From this information, some general conclusions can be drawn about the sensitivity and coverage required for a general sky survey in the far infrared.

Hoffmann, W. F.↗
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 NTRS1977

Characteristics of southern hemisphere 200-mbar flow as determined from satellite data

Characteristics of southern hemisphere (SH) 200-mbar flow are examined by using geopotential height fields constructed with the aid of a satellite-based thermal structure. Similar northern hemisphere (NH) satellite-based fields are developed in order to make interhemispheric comparisons. Results indicate that both zonal and meridional components of the SH eddy kinetic energy are as large as their NH counterparts. The SH flow is in general more dependent on transient eddies, especially with regard to the meridional flow. In winter the difference in standing eddy magnitude is apparent only in the north-south component. In summer both zonal and meridional components have smaller standing eddy contributions in the SH. The meridional spectra show a preference for intermediate size (k = 4, 5) transient waves. Ratios of zonal to meridional energies indicate that, especially at intermediate wavelengths, the SH waves are 'more meridional' than those in the NH.

Adler, R. F.↗
NASA NTRS1986

Methane, carbon monoxide and methylchloroform in the Southern Hemisphere

New observational data on CH4, CO and CH3CCl3 in the Southern Hemisphere are reported. The data are analyzed for long term trends and seasonal cycles. CH3CCl3 data are used to scale the OH fields incorporated in a two-dimensional model, which in turn, is used to constrain the magnitude of a global CH4 source function. The possible causes of observed seasonality of CH3CCl3, CH4 and CO are identified, and several other aspects of observed CH4 variability are discussed. Possible future research directions are also given.

Fraser, P. J.↗
NASA NTRS2006

Cassini Imaging of Saturn: Southern Hemisphere Winds and Vortices

High-resolution images of Saturn's southern hemisphere acquired by the Cassini Imaging Science Subsystem between February and October 2004 are used to create maps of cloud morphology at several wavelengths, to derive zonal winds, and to characterize the distribution, frequency, size, morphology, color, behavior, and lifetime of vortices. Nonequatorial wind measurements display only minor differences from those collected since 1981 and reveal a strong, prograde flow near the pole. The region just southward of the velocity minimum at 40.7 deg S is especially active, containing numerous vortices, some generated in the proximity of convective storms. The two eastward jets nearest the pole display periodicity in their longitudinal structure, but no direct analogs to the northern hemisphere's polar hexagon or ribbon waves were observed. Characteristics of winds and vortices are compared with those of Saturn's northern hemisphere and Jupiter's atmosphere.

Saturn↗
NASA NTRS1999

SHADOZ (Southern Hemisphere ADditional OZonesondes): A New Ozonesonde Data Set for the Earth Science Community

In the past several years, new tropical tropospheric ozone data products have been developed from TOMS and other satellites. Global chemical-transport models have been developed for interpretation of satellite data and to predict future ozone levels in the troposphere and stratosphere. However, the lack of ozone profile measurements for validation and evaluation of these data sets and models is critical in regions like the tropics. In 1998 NASA/Goddard Space Flight Center, in partnership with NOAA/CMDL (Climate Monitoring and Diagnostics Lab) and other nations, began a 2-year project to collect weekly ozonesonde measurements at southern hemisphere tropical sites and make the data available to the scientific community at a single electronic location: http://code9lQ.gsfc.nasa.gov/Data services/Shadoz/shadoz hmpq2.htmi A summary of data from the SHADOZ sites will be presented: Ascension Island, Fiji, Tahiti, Galapagos, American Samoa, Natal (Brazil), Reunion Island, Watukosek (Java), Nairobi and Irene, South Africa. SHADOZ is designed to meet other needs: (1) Provide the first climatology of tropical ozone along the equatorial zone for the wave-one pattern in total ozone; (2) Supplement field project observations. (3) Guide algorithm development for future satellite instruments; (4) Train scientists and educators in southern hemisphere tropical locations. From time to time, intensive tropical campaigns are making data available to SHADOZ. Data from the first half of 1999 will include INDOEX (Indian Ocean Experiment), SOWER (Stratospheric Ozone and Water in the Equatorial Region) at Christmas Island (2N, 157W), and a cruise from Norfolk, Virginia to Cape Town and Mauritius on NOAA's RN 'Ronald H Brown.'

Witte, J. C.↗
NASA NTRS1984

Tropospheric methane in the mid-latitudes of the Southern Hemisphere

More than 800 methane concentration measurements have been obtained for the Southern Hemisphere's troposphere over the September 1980-March 1983 period. Concentrations are noted to increase throughout the troposphere during the study period, adding further support to the view that CH4 concentrations are currently increasing on a global scale. In the surface methane data, a seasonal cycle with a peak-to-peak amplitude of 28 ppbv is found. Maxima and minima are on September-October and March, respectively. The phase and amplitude of the cycle are qualitatively consistent with the concept that the major sink for methane is oxidation by hydroxyl radicals. Evidence is found for a positive vertical gradient in methane content.

Fraser, P. J.↗
NASA NTRS1986

UBV photometry of ten southern hemisphere active-chromosphere stars

High-precision UBV photometry of ten southern hemisphere active-chromosphere stars with strong Ca II H and K and/or H-alpha emission has been obtained. Eight of these stars showed variability during June 1985. Complete or partial light curves are presented for the stars, and these data, as well as mean V magnitudes and colors, are compared with the results of other investigators. In a number of cases, significant changes in photometric amplitude are found, which may serve to track the formation and evolution of active regions on these stars.

Bopp, Bernard W.↗
NASA NTRS1989

Dynamics of planetary-scale baroclinic waves during Southern Hemisphere winter

The characteristics of linear and finite amplitude baroclinic waves during Southern Hemisphere winter were investigated using a three-dimensional global primitive-equation spectral mode, with emphasis on the dynamics of planetary scale modes which propagate into the stratosphere. Linear stability computations showed that the winter zonally averaged basic state is baroclinically unstable, with the most unstable modes being Charney-type modes; however, the results showed that Green-type modes also exist; these give much larger relative amplitude in the stratosphere although they have smaller growth rates. The results suggest that the existence of both Charney and Green modes might explain certain observed properties of the eastward traveling waves, such as the lack of coherence between troposphere and stratosphere at zonal wavenumbers 1 and 2.

Young, Richard E.↗