Dissertations / Theses on the topic 'Southern Hemisphere'
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Anthony, Neville John. "Synthesis of the milbemycin southern hemisphere." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46940.
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Byrne, Nicholas. "Deterministic models of Southern Hemisphere circulation variability." Thesis, University of Reading, 2017. http://centaur.reading.ac.uk/74253/.
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Statistical models of atmospheric variability typically attempt to account for deterministic seasonal variations by constructing a long-term average for each day or month of the year. Year-to-year variability can then be treated as some form of stochastic process about this long-term average. In general, the stochastic processes are assumed to be statistically stationary (invariant under time translation). However, for a non-linear system such as the Earth’s atmosphere, multiple seasonal evolutions may be possible for the same external forcing. In the presence of such a multiplicity of solutions, the identification of a seasonal cycle with a long-term average may not be the optimal procedure. Previous research has suggested that multiple evolutions of the seasonal cycle of the Southern Hemisphere mid-latitude circulation may be possible. The central goal of this thesis is to build on this work and to present evidence for different seasonal evolutions of the Southern Hemisphere mid-latitude circulation. This evidence is initially presented by highlighting a low-frequency peak in an aspect of the Southern Hemisphere mid-latitude circulation that is viewed as a harmonic of the annual cycle (quasi-two year). Statistically stationary models of variability about a long-term average are argued to be unable to account for the presence of this harmonic. Following this, an alternative model of circulation variability is proposed that explicitly references various stages of the seasonal cycle in a deterministic manner. In particular, explicit reference is made to the downward shift and to the final breakdown of the stratospheric polar vortex. A re-interpretation of several previous results in the literature including Southern Annular Mode persistence timescales, Southern Hemisphere mid-latitude climate change and the semi-annual oscillation of the mid-latitude jet is subsequently presented using this alternative perspective.
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Lawrence, Bryan N. "The Southern Hemisphere middle atmosphere: climatology and waves." Thesis, University of Canterbury. Physics, 1990. http://hdl.handle.net/10092/7978.
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Data from a number of sources are used to examine the climatology of the southern hemisphere middle atmosphere. The stratospheric data used are winds and higher order quantities derived from stratospheric analyses provided by the U.S. National Meterological Center and the British Meteorological Office. Mesospheric winds are used from a number of years of continuous partial reflection radar observations at four southern hemisphere sites.
A comparison of the stratospheric analyses is used to highlight the regions of inadequacy in the data, and to assess its reliability.
A three year zonal mean climatology of the stratosphere is provided, and compared on an individual monthly basis with a time mean mesospheric climatology. This comparison highlights the importance of interannual variability in both the stratosphere and mesosphere, and emphasizes the mesospheric dependance on the stratospheric state below.
Wave motions are traced propagating through the stratosphere and tentatively identified in the mesospheric winds. One particular wave, the four day wave is examined in detail, and shown to exist on occasion in both the stratosphere and mesosphere.
Some suggestions for further work are presented, with respect to both data comparisons and stratosphere-mesosphere interactions.
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McKenny, Joy Martina. "Observations of southern hemisphere gamma ray emitting blazars." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/3695/.
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This thesis details observations of three Southern hemisphere blazars PKS 2155-304 PKS 2005-489 and PKS 0548-322 using the University of Durham Mark 6 Telescope between 1996 and 1999. The nature of blazars and the physical processes responsible for very high energy emission are also discussed. A signal above 700 GeV was observed from PKS 2155-304 between 1996 and 1997 but not in 1998 and 1999. One plausible explanation for this is a reduction in sensitivity of the Mark 6.Evidence for variability of high energy emission from PKS 2155-304 was search for but no firm conclusion was reached. Upper limits to emission from PKS 2005-489 and PKS 0548-322 were determined. Gamma ray observations for all three objects were tested for correlation with near simultaneous 2-10 keV X-ray emission (taken using the ASM onboard RXTE). No strong evidence for correlation was found. It is worth noting however that gamma ray emission from PKS 2155-304 was detected when the X-ray emission was greatest. No constraints could be made on models of gamma ray production from blazars. No models were excluded. Future observations with the new generation of gamma ray telescopes such as H.E.S.S. and CANGAROO will allow more detailed investigation of these objects and many others and their variability while multiwavelength observations will determine the nature of the acceleration processes at work.
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Marriage, Benjamin P. "Automatic detection and tracking of Southern Hemisphere cyclones." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/15271.
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The work contained in this thesis is toward producing an objective cyclone climatology of the extra-tropical regions of the Southern Hemisphere using observational data. The data identified as being the most appropriate for this task was the high resolution multi-spectral imagery produced by the Advanced Very High Resolution Radiometer (AVHRR) on board the National Oceanographic and Atmospheric Administration (NOAA) series of polar-orbiting satellites. A series of algorithms are presented to perform the automatic detection and tracking of cyclones in the Southern Hemisphere. Cloud detection was performed using a number of spectral and textural measures. Individual cloud objects were segmented using thresholding techniques. These cloud objects were pre-processed using an image normalisation algorithm to create an image (feature vector) which was invariant to rotation, translation, scaling and skew. Identification and tracking of cyclones was performed by finding the maximum cross-correlation between the normalised target images and a set of pre-defined normalised templates. Problems with automatically distinguishing between cloud and the surface near Antarctica still remain, and subsequently segmentation of the imagery into individual cloud objects was limited to certain cases. Identification of cyclones by matching with the pre-defined normalised templates was also shown to have only very limited ability to distinguish between cyclone cloud objects and non-cloud objects. Tracking of the cyclones once they have been manually identified and measured was shown to be promising, with the algorithm successfully tracking the cyclone in 16 out of 22 pairs of satellite images taken from 4 case studies of real Southern Hemisphere cyclones. Limitations of the tracking scheme were identified and improvements have been suggested.
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McGlue, Michael Matthew. "LATE QUATERNARY PALEOLIMNOLOGY IN THE SOUTHERN HEMISPHERE TROPICS." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/204064.
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Lake deposits are widespread throughout the Phanerozoic rock record and have long intrigued geologists and paleobiologists in search of natural resources or fossil biota. Low-energy lacustrine depositional environments, characterized by relatively rapid sediment influx rates and shallow zones of bioturbation, likewise produce highly-resolved archives of climate and ecosystems evolution. This dissertation describes four studies that use lake sediments for Quaternary environmental analysis. In East Africa, many decades of prior study provided the critical framework necessary for in-depth paleoenvironmental research at Lake Tanganyika (3° - 9°S). Seismic stratigraphic analysis integrated with radiocarbon-dated sediment cores from the Kalya horst and platform document a dramatic lake level lowstand prior to ~106 ka and a minor, short-lived regression during the Last Glacial Maximum (32 - 14 ka). Paleobathymetric maps reveal that Lake Tanganyika remains a large, connected water body even during episodes of extreme drought, which has implications for local and regional fauna. Over shorter timescales, geochronological, taphonomic and sedimentological analyses of shell beds around Kigoma (central Lake Tanganyika) document three distinct facies-types that are time-averaged over the latest Holocene. Lake level fluctuations associated with the termination of the Little Ice Age (~ 16th century CE) and subsequent encrustation played a key role in shell bed formation and persistence along high-energy littoral platforms, which has implications for structuring specialized communities of benthic fauna. In central South America (18° - 22°S), we studied the limnogeology of small lakes in the Puna and the Pantanal. Analyses of these sites were undertaken to: 1) ascertain how the lakes act as depositional basins; 2) assess sedimentation rates; and 3) construct limnogeological databases to guide future interpretations of ancient sediment cores. At Laguna de los Pozuelos (Argentine Puna), linear sedimentation rates approach 0.14 cm*y⁻¹ in the playa-lake center, and litho- and organo-facies development are dominantly controlled by basin hydrology, climate and biological feedbacks (both nutrient cycling and bioturbation) from waterbirds. At Lagoas Gaíva, Mandioré and Vermelha (Brazilian Pantanal), short-lived radioisotopes indicate uninterrupted depositional rates of 0.11 - 0.24 cm*y⁻¹, and hydrochemical and depositional patterns respond sensitively to changes in the seasonal flooding cycle of the Upper Paraguay River.
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Djurhuus, Anni. "Microbial oceanography of southern hemisphere seamounts and hydrothermal vents." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:727fb8de-a392-4030-bc86-6390143111fd.
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Microbial biogeography is being increasingly more studied, both in terms of genetic divisions and 'ecotype' variation. This thesis investigates the regional (100-1000s km) and local (10s m) distribution and diversity of microorganisms around hydrothermal vents and seamounts at the East Scotia Ridge and the Southwest Indian Ridge. Microbial communities were characterized using Illumina dye sequencing to de- termine taxon richness and diversity and flow cytometry to obtain cell counts. In addition I investigated the physicochemical environment (nutrients, organic carbon, salinity and temperature) in which the microorganisms persist. Typical deep-sea microorganisms were abundant at vents and below the euphotic zone on the seamounts. The surface layer of the seamounts contained typical open-ocean photoautotrophic organisms. Microbial communities were correlated to or- ganic carbon on both hydrothermal vents and seamounts. With microorganisms possi- bly having a large influence on carbon sequestration into the deep-sea from hydrothermal vents. On a local scale the hydrothermal vents had a relatively higher abundance of chemosynthetic Epsilonproteobacteria and the Gammaproteobacteria family SUP05, which were closely correlated to the redox potential in the vent effluent. This was prominent in both plumes from the East Scotia Ridge and the Southwest Indian Ridge, which also had distinct microbial community structures. Across the Southwest Indian Ocean the microbial communities were firstly segregated by depth. However, on a regional scale their physical environment primarily divided the microbial communities into three biological regimes the sub-tropical, con- vergence zone and the sub-Antarctic. The microbial community structure and biogeography is influenced by steep environmental gradients, displaying a distance-decay relationship between sampling locations. With environmental conditions persisting at different scales, from local (10s m) around the hydrothermal vents to regional (100-1000 km) between the seamounts, driving the microbial community patterns. The same horizontal and vertical patterns for microorganisms and metazoans points to fundamental differences throughout all parts of the ecosystem/food web.
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Engels, Ryland Peter Antonij. "Linked Hemispheres: American Literary Transcendentalism and the Southern Continents." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23143.
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This thesis examines relationships that formed between US Transcendentalism and the Southern Hemisphere in the nineteenth century. It argues that the works of Ralph Waldo Emerson, Walt Whitman and Henry David Thoreau are relevant to the literary histories of regions including Latin America, Southern Africa and Australasia, and that this fact has been inadequately addressed by criticism. The introduction serves to situate this claim within ongoing debates in fields such as American Studies and World Literature. I contend that the inclusion of Southern Hemispheric literature within these discussions has the potential to enrich our interpretations of both US and world literary texts, particularly by enabling new approaches to be taken to long-standing, transnational questions of race, settler colonialism, globalization and Romantic nationalism. Each chapter centres on a different continental region in the Southern Hemisphere. In each, North American literary perceptions of that region are put into dialogue with nineteenth-century Southern Hemispheric responses to US Transcendentalism. The first chapter is devoted to Latin America; it concerns Edward and Alexander Everett, Sophia Peabody, Mary Mann, Domingo Faustino Sarmiento and José Martí. The second chapter focuses on South Africa in the late colonial period and highlights aspects of the thought and work of figures such as Olive Schreiner, Jan Smuts and Mahatma Gandhi. The final chapter considers Australia and the Pacific Islands. It begins with a discussion of the US philosopher Josiah Royce’s tour of Australasia and, thereafter, gives an account of Australian poetry’s response to Transcendentalism. Four poets are included in this section: Charles Harpur, Henry Kendall, William Gay and Bernard O’Dowd. The chapter concludes by drawing parallels between Charles Warren Stoddard’s correspondence with Whitman, his writings about the Pacific Islands and the strains of Primitivism that can be identified in Transcendentalist texts more generally.
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Hamacher, Duane Willis Physics Faculty of Science UNSW. "A search for transiting extrasolar planets from the southern hemisphere." Publisher:University of New South Wales. Physics, 2008. http://handle.unsw.edu.au/1959.4/40943.
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To date, more than 300 planets orbiting stars other than our sun have been discovered using a range of observing techniques, with new discoveries occuring monthly. The work in this thesis focused on the detection of exoplanets using the transit method. Planets orbiting close to their host stars have a roughly 10 per cent chance of eclipsing (transiting) the star, with Jupiter?sized planets causing a one per cent dip in the flux of the star over a few hours. A wealth of orbital and physical information on the system can be extracted from these systems, including the planet density which is essential in constraining models of planetary formation. To detect these types of planets requires monitoring tens of thousands of stars over a period of months. To accomplish this, we conduct a wide-field survey using the 0.5-meter Automated Patrol Telescope (APT) at Siding Spring Observatory (SSO) in NSW, Australia. Once candidates were selected from the data?set, selection criteria were applied to separate the likely planet candidates from the false?positives. For this thesis, the methods and instrumentation used in attaining data and selecting planet candidates are discussed, as well as the results and analysis of the planet candidates selected from star fields observed from 2004?2007. Of the 65 planet candidates initially selected from the 25 target fields observed, only two were consistent with a planet transit. These candidates were later determined to be eclipsing binary stars based on follow up observations using the 40-inch telescope, 2.3-m telescope, and the 3.9-m Anglo-Australian Telescope, all located at SSO. Additionally, two planet candidates from the SuperWASP-North consortium were observed on the 40-inch telescope. Both proved to be eclipsing binary stars. While no planets were found, our search methods and results are consistent with successful transit surveys targeting similar fields with stars in a similar magnitude range and using similar methods.
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Chan, Agnes Chi-Man. "Baroclinic instability and the summer Southern Hemisphere wavenumber 5 circulation." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63967.
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Dickinson, Mark R. "Very high energy gamma ray observations of southern hemisphere blazars." Thesis, Durham University, 1997. http://etheses.dur.ac.uk/4705/.
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This thesis is concerned with very high energy γ-ray observations of blazars observable from the southern hemisphere. The data presented were obtained using the recently deployed University of Durham Mark 6 high sensitivity Čerenkov telescope. Chapters 1 and 2 are introductory; the subjects of γ-ray astronomy, extensive air showers, Čerenkov light production, the development of the atmospheric Čerenkov technique and the current status of TeV astronomy are discussed. Chapter 3 introduces the telescopes operated by the University of Durham. The Mark 6 telescope, designed to have a low threshold energy and a high resolution imaging system, is discussed in detail. Chapter 4 presents the calibration and analysis techniques routinely applied to data obtained with the Mark 6 telescope. The chapter concludes with a set of moment parameter selections designed to reject a significant fraction of the cosmic ray cascades, while retaining the majority of γ-rays cascades. These selections have resulted in a 5σ detection of PSR 1706-44. Chapter 5 discusses active galactic nuclei and in particular blazars. Topics included are recent high energy observations; the differences between the radio/X-ray selected BL Lacs and flat spectrum radio quasars; the infrared background; high energy flux variability and γ-ray production mechanisms within these objects. The chapter concludes with a list of possible very high energy γ-ray emitting blazars observable with the Mark 6 Čerenkov telescope. Chapter 6 presents the results from four of these very high-energy γ-ray blazar candidates; PKS 0548-322, PKS 1514-24, PKS 2005-489 and PKS 2155-304. There is no evidence for γ-ray emission from these sources, either in the form of a steady flux or variable activity. Three sigma integral flux upper limits above 300 GeV are produced for these objects and the implications of these observations are discussed. The conclusions are presented in Chapter 7 as well as ideas for future work.
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Van, Der Wiel Karin. "Mechanisms for the existence of diagonal Southern Hemisphere Convergence Zones." Thesis, University of East Anglia, 2015. https://ueaeprints.uea.ac.uk/53448/.
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This thesis considers the northwest-southeast, diagonal, orientation of the South Pacific and South Atlantic Convergence Zones (SPCZ and SACZ, respectively) which provide vital precipitation locally and influence mean climate globally. Their basic formation mechanism is not fully understood. A conceptual framework is developed to explain the mechanism responsible for the SPCZ diagonal orientation. Wind shear and Rossby wave refraction cause vorticity centres in the subtropical jet to develop a diagonal orientation and propagate equatorward towards the eastern Pacific upper-tropospheric westerlies. Ascent ahead of cyclonic vorticity anomalies in the wave then triggers deep convection parallel to the vorticity centre. Latent heat from condensation forces additional ascent and upper-tropospheric divergence; through vortex stretching this leads to an anticyclonic vorticity tendency. The calculation of a vorticity budget shows this tendency is strong enough to dissipate the wave. A similar sequence of events triggers diagonal bands of convection in the SACZ, though the vortex stretching feedback is not strong enough to dissipate the Rossby wave. An atmospheric general circulation model is used to investigate this mechanism. In an experiment the parametrisation of convection is modified: dynamic Rossby wave forcing is decoupled from the usual thermodynamic response. Consequently, Rossby waves over the SPCZ region are not dissipated, confirming the feedback in the framework. Furthermore, it is shown that SPCZ convective events decrease the strength of the eastern Pacific upper-tropospheric westerlies. Further experiments show which surface boundary conditions support the SPCZ diagonal orientation. Continental configuration, orography and absolute Sea Surface Temperatures (SST) do not have a significant influence. The key boundary condition is the zonally asymmetric component of the SST distribution. This leads to a strong subtropical anticyclone over the southeast Pacific that transports and supplies moisture to the SPCZ. Convection is triggered when the dynamical forcing from Rossby waves is present.
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Russell, Andrew. "Southern Hemisphere atmospheric circulation impacts on eastern Antarctic Peninsular precipitation." Thesis, University of Birmingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419512.
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Banks, Maria Elaine. "Glacial Processes and Morphologies in the Southern Hemisphere of Mars." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/193842.
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Understanding the history of ice on Mars provides important insight into Martian geologic and climatic history. A model capable of ice reconstruction that requires few input parameters, and a detailed analyses of landforms in an area with hypothesized glacial modification, Argyre Planitia, provide further understanding of Martian ice.A threshold-sliding model was developed to model perfectly-plastic deformation of ice that is applicable to ice bodies that deform when a threshold basal shear stress is exceeded. The model requires three inputs describing bed topography, ice margins, and a function defining the threshold basal shear stress. The model was tested by reconstructing the Greenland ice sheet and then used to reconstruct ice draping impact craters on the margins of the Martian South Polar Layered Deposits using a constant basal shear stress of ~0.6 bars for the majority of Martian examples. This result is ~1/3 the value calculated for the Greenland ice sheet. Reasons for the lower Martian basal shear stress are unclear but could involve the strain-weakening behavior of ice. The threshold-sliding model can be used for ice reconstruction and forward modeling of erosion and deposition to provide further insight into the history of ice on Mars.To test the glacial hypothesis in the Argyre region, landforms are examined using images from the High Resolution Imaging Science Experiment (HiRISE) camera and other Martian datasets. Linear grooves and streamlined hills are consistent with glacial erosion. Deep semi-circular embayments in mountains resemble cirques. U-shaped valleys have stepped longitudinal profiles and tributary valleys have hanging valley morphology similar to terrestrial glacial valleys. Boulders blanketing a valley floor resemble ground moraine. Sinuous ridges cross topography, have layers, occur in troughs, and have variations in height that appear related to the surrounding surface slope; these are characteristics consistent with terrestrial eskers. At least portions of Argyre appear to be modified by ice accumulation, flow, erosion, stagnation and ablation. The type and amount of bedrock erosion and presence of possible eskers suggests the ice was, at times, wet-based.
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Li, Jinlong. "The seasonal variations of ozone in the stratosphere and their hemispheric asymmetries." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/25694.
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Ummenhofer, Caroline C. Mathematics & Statistics Faculty of Science UNSW. "Southern hemisphere regional precipitation and climate variability : extrems trends and prdictability." Awarded by:University of New South Wales. Mathematics & Statistics, 2008. http://handle.unsw.edu.au/1959.4/41253.
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This PhD thesis investigates the relative importance of oceanic and atmospheric influences on extremes, long-term trends, and seasonal to interannual variability of precipitation for different regions in the Southern Hemisphere in observations, reanalysis data, and output from general circulation models (GCM). Examination of interannual rainfall extremes over southwest Western Australia (SWWA) reveals a characteristic dipole pattern of Indian Ocean sea surface temperature anomalies (SSTA). This coincides with a large-scale reorganization of the wind field over the tropical/subtropical Indian Ocean changing SSTA, via anomalous Ekman transport in the tropical Indian Ocean and via anomalous air-sea heat fluxes in the subtropics, and altering moisture advection onto SWWA. The potential impact of these Indian Ocean SSTA in driving modulations of mid-latitude precipitation across southern and western regions of Australia is assessed in atmospheric GCM simulations. The SSTA give rise to changes in the thermal properties of the atmosphere, meridional thickness gradient, subtropical jet, thermal wind, and baroclinicity over southern regions of Australia, thus modulating precipitation. In addition, links between anomalous wet conditions over East Africa and these characteristic Indian Ocean SSTA are explored during the "short rain" season in October-November. Interannual extremes m New Zealand rainfall and their modulation by modes of Southern Hemisphere climate variability, namely the Southern Annular Mode (SAM) and El Nino-Southern Oscillation (ENSO), are investigated. Late twentieth Century trends in New Zealand precipitation are examined for the period 19792006 to quantify the relative impact of recent changes in the large-scale atmospheric circulation related to the SAM and ENSO. Increasingly drier conditions over much of New Zealand can be partially explained by the SAM and ENSO. Cool season rainfall variability in southeastern Australia is investigated via a classification and characterization of the predominant types of synoptic systems occurring in the region, focusing on frontal and cutoff low systems. Two definitions of the autumn break developed for northwestern Victoria are employed to produce a synoptic climatology of the break phenomenon. Trends in characteristics of the autumn break indicate that the most recent drought in southeastern Australia is comparable in severity with the two major droughts in the twentieth Century.
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Connolly, Charlotte J. "Causes of Southern Hemisphere climate variability in the early 20th century." Ohio University Honors Tutorial College / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1587217042363834.
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Roux, David Gerhardus. "An investigation of the structure of the Southern Hemisphere radio-meteor streams." Thesis, Rhodes University, 1988. http://hdl.handle.net/10962/d1004587.
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Our current knowledge of the Solar System, with a particular emphasis on the systems of interplanetary objects, is reviewed, and the theory of meteors and the reflection of radio waves from meteoric ionization is then discussed. A description of the meteor radar is given and a method of calibrating the antenna beam is developed. The main project comprises two parts: (a) A general survey of the radar echorate for 20 major and minor meteor streams and the sporadic meteor background, conducted from Grahamstown over the period 1986 April to 1988 January, is described. Definite shower activity was observed for all of the major and some of the minor showers. (b) Based on a scheme proposed by previous workers (Morton & Jones), a method of recovering meteor radiant distributions from the distribution of echo directions is developed. We devise a technique of compensating for possible distortions of the resulting radiant maps, which may arise due to the arisotropic antenna beam. This involves a system of echo-weighting. Radiant maps which showed considerably less distortion than those of the above workers were obtained without the weighting procedure. It is concluded that, although the method in its present form introduces spurious features into the maps, the principle is sound and should eventually be refined to produce the desired compensation
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Viola, D., and A. S. McEwen. "Geomorphological Evidence for Shallow Ice in the Southern Hemisphere of Mars." AMER GEOPHYSICAL UNION, 2018. http://hdl.handle.net/10150/627126.
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The localized loss of near-surface excess ice on Mars by sublimation (and perhaps melting) can produce thermokarstic collapse features such as expanded craters and scalloped depressions, which can be indicators of the preservation of shallow ice. We demonstrate this by identifying High Resolution Imaging Science Experiment images containing expanded craters south of Arcadia Planitia (25-40 degrees N) and observe a spatial correlation between regions with thermokarst and the lowest-latitude ice-exposing impact craters identified to date. In addition to widespread thermokarst north of 35 degrees N, we observe localized thermokarst features that we interpret as patchy ice as far south as 25 degrees N. Few ice-exposing craters have been identified in the southern hemisphere of Mars since they are easier to find in dusty, high-albedo regions, but the relationship among expanded craters, ice-exposing impacts, and the predicted ice table boundary in Arcadia Planitia allows us to extend this thermokarst survey into the southern midlatitudes (30-60 degrees S) to infer the presence of ice today. Our observations suggest that the southern hemisphere excess ice boundary lies at 45 degrees S regionally. At lower latitudes, some isolated terrains (e.g., crater fill and pole-facing slopes) also contain thermokarst, suggesting local ice preservation. We look for spatial relationships between our results and surface properties (e.g., slope and neutron spectrometer water ice concentration) and ice table models to understand the observed ice distribution. Our results show trends with thermal inertia and dust cover and are broadly consistent with ice deposition during a period with a higher relative humidity than today. Shallow, lower-latitude ice deposits are of interest for future exploration.
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Lerfald, Jennifer L. "Seasonal factors and birth weight, new evidence from the Southern Hemisphere." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57553.pdf.
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Flores, Marcos Froilán Andrade. "Stratospheric ozone trends as determined by regime analysis the southern hemisphere /." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2007.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Meteorology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Bird, David John. "Arrival directions of medium energy cosmic rays in the southern hemisphere /." Title page, contents and summary only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09pb6178.pdf.
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Hunt, Richard Jeffrey. "Ice-ocean-atmosphere interactions at high latitudes in the southern hemisphere." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307309.
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Steel, K. I. M. "Approaches to the synthesis of chrysothame and the avermectin southern hemisphere." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373925.
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Al-Ajmi, Dhari Nasser. "Wave activity in a stratospheric 'sudden warming' in the southern hemisphere." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/12178.
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Al-Shammary, Khalil Ibrahim Abbass. "Systematic studies of the Saxifragaceae S.L., chiefly from the southern hemisphere." Thesis, University of Leicester, 1991. http://hdl.handle.net/2381/34840.
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Engler's Saxifragaceae has long been recognised as a heterogeneous family. In particular, the southern hemisphere subfamily Escallonioideae is poorly known and its composition and relationships have not been established. The aim of this study was primarily to provide sufficient data in order to solve these problems, and secondly to examine the monophyletic nature (or otherwise) of the family. The present study therefore investigated the following genera from Engler's Escallonioideae: Cuttsia, Abrophyllum, Carpodetus, Corokla, Argophyllum, Forgesia, Choristylis, Quintinia, Escallonia, Valdivia, Tribeles, Polysoma and Anopterus, as well as southern hemisphere genera from other subfamilies (Vahlia, Montinia, Grevea, Eremosyne, Bauera, Tetracarpaea, Brexia, Ixerba, Roussea, Francoa, Tetilla, Lepuropetalon) and a few possibly related northern hemisphere genera (Ribes, I tea, Parnassia). The evidence gathered came from studies of leaf venation, leaf epidermal morphology and anatomy (including studies of trichomes), nodal anatomy, iridoid chemistry, SEM and TEM observations of pollen morphology and anatomy, and seed morphology and anatomy. This was amalgamated with other published data, e.g. on floral morphology, and cladistic analyses conducted using both Wagner and Camin-Sokal parsimony methods. The first set of analyses dealt with the genera listed above. A second set included other subfamilies and tribes from the Saxifragaceae, as well as other families, e.g. Celastraceae, Cornaceae, Cunoniaceae, Droseraceae, Pittosporaceae, and Ericaceae. The analyses indicated that the Escallonioideae comprise Cuttsia, Abrophyllum, Carpodetus, Corokia, Argophyllum, Forgesia, Quintinia, Escallonia and Valdivia; the Montinioideae contain Montinia and Grevea; Polyosma, Anopterus, Vahlia and Eremosyne are related to these two groups; and the whole would be best placed in Dahlgren's Cornales, along with the Hydrangeoideae, chiefly on account of the presence of iridoids. Family status is recommended for the Escallonioideae, Montinioideae, Hydrangeoideae, Vahlia and Eremosyne; further work is needed to establish the precise positions of Polyosma and Anopterus. Engler's concept of tribe Francoeae (Francoa and Tetilla) was supported; its relationships are not directly with the Saxifrageae but may lie with Lepuropetalon, Parnassia and Tribeles, not in the Cornales but possibly in the Saxifragales. Brexia, Ixerba and Roussea (Engler's Brexioideae) appeared to be monophyletic in the first analysis but a second one demonstrated that this heterogeneous group should be broken up; the relationships of the genera are still uncertain but may lie with the Celastraceae, along with Choristylis, Pottingeria, Ptersostemon, and Phyllonoma. Bauera and Tetracarpaea were confirmed as not belonging to the Escallonioideae; the former is related to and could be included in the Cunoniaceae, whilst the latter is best treated as a taxonomically isolated independent family. Ribes is closely allied to the tribe Saxifrageae (excluding Vahlia), and does not belong in the Escallonioideae. Engler's Saxifragaceae is therefore probably not monophyletic and should be broken up along the lines indicated above.
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Hudson, Debra Alison. "Antarctic sea-ice extent, Southern hemisphere circulation and South African rainfall." Doctoral thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/9682.
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Bibliography: p. 293-304.The study examines the response of an atmospheric general circulation model (OCM) to a reduction in Antarctic sea-ice extent during summer and winter, with emphasis on non-polar and southern African climates. Following an evaluation of the OCM, the control and perturbation simulations are analysed. The controls are forced by prescribed, observed sea surface temperatures (SSTs) and sea-ice extents, while in the perturbation simulations sea-ice is reduced and replaced with SSTs. The introduced anomalies are derived from an algorithm based on observed ice variability. The simulations are restarts of an AMIP (Atmospheric Model Intercomparison Project) configured simulation, and two summers (1979/80 and 1984185) and two winters (1980 and 1985) have been selected for the study. Three replicates have been performed for each time period for both the control and perturbation conditions.
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Ciampa, Dominic. "A southern hemisphere search for ultra-high-energy gamma ray sources." Title page, contents and summary only, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phc565.pdf.
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Cao, Jing. "An investigation of transport during minor stratospheric warmings in the Southern Hemisphere." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/25964.
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Grenfell, John Lee. "Southern hemisphere studies with a photochemical 3-dimensional model of the atmosphere." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388367.
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Eisenmann, Pascale. "Interpreting the Feeding Ecology of Southern Hemisphere Humpback Whales through Biochemical Assessment." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/365650.
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Southern hemisphere humpback whales are high-fidelity krill predators relying on high Antarctic krill biomass to survive and undergo successful reproduction. During the austral summer, humpback whales consume large quantities of krill and build up their blubber reserves. The rest of the year is spent migrating to temperate waters and back while relying on accumulated energy reserves. This expected reliance on Antarctic krill underpins our understanding of Southern hemisphere humpback populations. Their Northern hemisphere counterparts are however known to be more flexible in their feeding habits, and recent work has shown that the Southern hemisphere populations are capable of a certain feeding plasticity, with multiple visual reports of supplementary feeding during the migration, and evidence of anomalous feeding observed in baleen plates. Due to the dependency of Antarctic krill on sea-ice duration and extent for its larval recruitment, the entire Antarctic sea-ice ecosystem is expected to destabilise in a changing climate. The resulting effects on high-fidelity krill predators, such as humpback whales, are unknown. Detailed, long-term information regarding current and past diet, migration and metabolism of humpback whales are needed to successfully assess possible trophodynamic variability, and to differentiate between the natural feeding plasticity of this species and population responses to climate driven environmental change. This thesis aims to evaluate whether Australian humpback whale populations display feeding plasticity in their prey choice and/ or feeding locations.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Purich, Ariaan. "Investigating the influence of stratospheric ozone trends on Southern Hemisphere hydrological climate change." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104826.
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Changes in stratospheric ozone have previously been linked to Southern Hemisphere (SH) circulation changes. This study examines output from coupled climate models participating in the Climate Model Intercomparison Project 3 (CMIP3) for trends in precipitation and evaporation in the 20th and 21st centuries to assess whether stratospheric ozone influences the hydrological cycle and extreme precipitation in the SH extratropics, particularly during austral summer. Nineteen models are used, of which 10 incorporated ozone depletion (recovery) in the 20th (21st) century, whilst nine simply prescribed climatological ozone in both past and future climates. Trends in seasonal-mean precipitation are found to dominate overall changes in precipitation minus evaporation. For the 20th century, models with ozone depletion show a significant increase (decrease) in summer precipitation in high latitudes (mid-latitudes) compared to models without ozone depletion. In contrast, for the 21st century, models without ozone recovery show significantly larger changes in summer precipitation in these regions compared to models with ozone recovery. No significant differences, however, are found in the two sets of models during austral winter when stratospheric ozone is inactive. These results suggest that Antarctic ozone depletion and recovery significantly modulates hydrological climate change in the SH extratropics, in agreement with findings of previous studies. It is further found that stratospheric ozone primarily affects the frequency of light precipitation events (1–10 mm day^−1 ), indicating that an increase in mean precipitation over the Southern Ocean corresponds to an increase in the number of light precipitation days rather than extreme events. Implications of this finding to the SH surface climate and Southern Ocean circulation changes are discussed.Les changements de concentration d'ozone stratosphérique ont été déjà reliés aux changements de la circulation dans l'hémisphère sud (HS). Ce travail examine les tendances dans la précipitation et l'évaporation pendant les 20ième et 21ième siècles, dans des simulations produites par des modèles climatique couplés qui participent au Climate Model Intercomparison Project 3 (CMIP3). Le but est de déterminer si l'ozone stratosphérique influence le cycle hydrologique et la précipitation extrême aux latitudes extra-tropicales de l'HS, pendant l'été austral en particulier. Dix-neuf modèles sont utilisés, où 10 d'entre eux incorporent l'épuisement (le rétablissement) d'ozone au 20ième (21ième) siècle et les neuf autres prescrivent simplement l'ozone climatologique (du 20ième siècle) pendant le passé et le futur. Les tendances des moyennes saisonnières de précipitation dominent les changements de l'évaporation moins la précipitation, alors c'est cette variable qui est examinée plus en détail. Pour le 20ième siècle, il y a une augmentation (diminution) de précipitation significative en été aux latitudes subarctique (latitudes moyennes) dans les modèles avec l'épuisement d'ozone comparé à ceux avec l'ozone climatologique. En contraste, pour le 21ième siècle, les changements de précipitation sont considérablement plus grands dans les modèles sans le rétablissement d'ozone que dans les modèles avec le rétablissement d`ozone. Pour l'hiver austral, quand l'ozone est inactif, il n'y a pas de différences entre les deux groupes de modèles. Ces résultats suggèrent que la diminution et rétablissement d'ozone dans l'Antarctique a des implications considérables pour le changement de climat hydrologique dans l'HS hors tropique, une conclusion atteinte dans d'autres travaux. En plus, on trouve que l'ozone stratosphérique affecte principalement la fréquence des évènements de précipitation légère (1–10 mm jour^-1), ce qui indique qu'une augmentation de la précipitation moyenne correspond à une augmentation du nombre de jours de précipitation légère, plutôt que d'évènements extrêmes. Les implications de ces conclusions pour le climat à la surface ainsi que pour les changements de circulation dans l'océan de l'HS sont discutés.
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Rea, Gloria. "Role of the stratospheric dynamics in the southern hemisphere long-term climate change." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5946/.
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Il raffreddamento stratosferico associato alla riduzione dell’ozono nelle regioni polari induce un rafforzamento dei venti occidentali nella bassa stratosfera, uno spostamento verso il polo e un’intensificazione del jet troposferico delle medie latitudini. Si riscontra una proiezione di questi cambiamenti a lungo termine sulla polarità ad alto indice di un modo di variabilità climatica, il Southern Annular Mode, alla superficie, dove i venti occidentali alle medie latitudini guidano la Corrente Circumpolare Antartica influenzando la circolazione oceanica meridionale e probabilmente l’estensione del ghiaccio marino ed i flussi di carbonio aria-mare nell’Oceano Meridionale. Una limitata rappresentazione dei processi stratosferici nei modelli climatici per la simulazione del passato e la previsione dei cambiamenti climatici futuri, sembrerebbe portare ad un errore nella rappresentazione dei cambiamenti troposferici a lungo termine nelle rispettive simulazioni. In questa tesi viene condotta un’analisi multi-model mettendo insieme i dati di output derivati da diverse simulazioni di modelli climatici accoppiati oceano-atmosfera, che partecipano al progetto CMIP5, con l'obiettivo di comprendere come le diverse rappresentazioni della dinamica stratosferica possano portare ad una differente rappresentazione dei cambiamenti climatici alla superficie. Vengono utilizzati modelli “High Top” (HT), che hanno una buona rappresentazione della dinamica stratosferica, e modelli “Low Top” (LT), che invece non ne hanno. I risultati vengono confrontati con le reanalisi meteorologiche globali disponibili (ERA-40). Viene mostrato come la rappresentazione e l’intensità del raffreddamento radiativo iniziale e di quello dinamico nella bassa stratosfera, nei modelli, siano i fattori chiave che controllano la successiva risposta troposferica, e come il raffreddamento stesso dipenda dalla rappresentazione della dinamica stratosferica. Si cerca inoltre di differenziare i modelli in base alla loro rappresentazione del raffreddamento radiativo e dinamico nella bassa stratosfera e alla risposta del jet troposferico. Nei modelli, si riscontra che il trend del jet nell'intera troposfera è significativamente correlato linearmente al raffreddamento stesso della bassa stratosfera.
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Clokie, Martha Rebecca Jane. "Molecular studies of Southern Hemisphere disjunction in three plant genera, Eucryphia, Griselinia and Coriaria." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/29823.
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Three plant genera with South American-Australasian disjunctive distributions were studied: Eucryphia, Griselinia and Coriaria . The aims of the project were: a) to assess the utility of different chloroplast and nuclear DNA sequences for phylogenetic reconstruction and b) by means of molecular clocks to establish whether or not this distribution is due to vicariance (continental drift) or more recent dispersal events. DNA was extracted, and regions of interest were amplified and sequenced. These were rpoA, trnL-F and trnU-K from the chloroplast genome, and rDNA 5.8S and intergenic spacers 1 and 2, Adh and two loci of the G3pdh gene from the nuclear genome. In each of the three genera, a single trans-Antarctic disjunction was indicated. Molecular phylogenies were produced using parsimony. Individual base pair variation was analysed in detail, and graphs were drawn to highlight variable regions. Sequences providing the most resolution were trnL-F, ITS and the two loci of the G3pdh. Robust molecular phylogenies were produced which are consistent with morphological, fossil and biogeographical evidence. Constancy of mutation rate across the different branches of the trees was checked using the Tajima test. Where constancy was established, the rate of evolution for the different gene regions was used to estimate the divergence times within each genera. Calibrations were performed using fossil data for Eucryphia and Coriaria average mutation rates derived from Eucryphia were applied to the Griselinia data set, owing to the absence of fossils. New Zealand became separated from Antarctica (and therefore South America) 95 - 80 million years ago, whereas average divergence times for Coriaria and Griselinia were found to be around 3 and 50 million years respectively. Similiarly, with respect to Eucryphia, Australia split from Antarctica 40 million years ago but the divergence time is 23.23 million years. The disjunction therefore must have arisen by dispersal which may have occurred either in the water by rafting or floating, or in the air in wind currents ( Eucryphia has winged seeds) or by means of birds (Coriaria and Griselinia have fleshy diaspores). A review of similar disjunctions in other plants and animals revealed that vicariance explanations were more likely to apply to groups at the taxonomic ranks of genus and above, whereas dispersal explanations were more likely to apply at the level of genus and below. The generic level is consequently of great interest.
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Sudbury, Andrea. "Dialect contact and koineisation in the Falkland Islands : development of a southern hemisphere English?" Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313059.
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Hilgenbrink, Casey C. "Understanding the spatial distribution of the Southern Hemisphere near-surface westerlies and Its trends." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/114127.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 62-63).
In some experiments in which idealized general circulation models (GCMS) are used to study the tropospheric response to stratospheric perturbations, the tropospheric response is much stronger and longer-lived compared to observations (e.g., Polvani and Kushner 2002, Kushner and Polvani 2004). Chan and Plumb (2009) found that those experiments which exhibited particularly long tropospheric decorrelation times (and, by the fluctuation dissipation theorem, much stronger annular mode responses) were marked by bimodality in the distribution of the latitude of surface zonal-mean zonal winds. Here, ERA-Interim and NCEP/NCAR reanalysis data are used to establish if this bimodality exists in the Southern Hemisphere (SH) near-surface winds, which would predict the existence of an additional mode of tropospheric variability exhibiting stronger and longer-lived responses than what has previously been observed. Histograms of the latitudinal position of maximum near-surface zonal-mean zonal winds turn up no convincing evidence of jet bimodality, although they do reveal an interesting - but probably spurious trimodality in the NCEP/NCAR June-August 850-hPa distribution of jet latitude. A climatology of wintertime zonal winds reveals that there is a time-mean split jet over the South Pacific Ocean; furthermore, empirical orthogonal function analysis reveals that, over the South Pacific, the dominant mode of wintertime zonal wind variability is a splitting and un splitting of the jet. Ultimately, both the climatological split jet and its variability are determined not to be evidence of jet bimodality. The temporal trends in the distribution of near-surface jet latitude are also examined. Stratospheric ozone depletion has been implicated in surface circulation changes in the SH high latitudes; one of these changes has been a poleward shift of the jet in austral summer. In this thesis, it is found that a poleward shift of the December-February distribution of jet latitude has taken place from the pre-ozone-hole to ozone-hole eras, consistent with previous findings. The novel result is that there has also been a poleward shift of this distribution in May, which is consistent with a secondary maximum in ozone depletion near the tropopause in April-May as observed by other authors (Thompson et al. 2011), and would imply the occurrence of troposphere-stratosphere coupling in late fall. An in-depth investigation of these May zonal wind trends will be pursued in future work.
by Casey C. Hilgenbrink.
S.B.
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Harris, Leon Robert. "Detoxification of iron and oxygen radicals by the southern hemisphere lamprey Geotria australis Gray." Thesis, Harris, Leon Robert (1995) Detoxification of iron and oxygen radicals by the southern hemisphere lamprey Geotria australis Gray. PhD thesis, Murdoch University, 1995. https://researchrepository.murdoch.edu.au/id/eprint/52021/.
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The mechanisms whereby the Southern Hemisphere lamprey Geotria australis may minimise the potential toxicity of the extremely high tissue concentration of iron have been examined. Attention has focussed on elucidating mechanisms that prevent iron from interacting with oxygen free radicals and on those characteristics of lamprey ferritin which may allow its iron to be retained very efficiently.
The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase (SOD), have been measured in the livers of ammocoetes, metamorphosing and young adult (downstream migrating) G. australis. Total non-haem and ferritin iron concentrations in the liver rose significantly (p < 0.05) in the middle and later stages of metamorphosis. Hepatic SOD activity fell sharply immediately after the onset of metamorphosis, before rising significantly to high levels in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle.
The relationship between SOD activity and iron levels was further examined in the livers of adult upstream migrating G. australis that were naturally and artificially loaded with iron. A rise in iron levels over the 12 months of the upstream migration was tracked by the activity of SOD. Weekly intramuscular injections of iron as horse spleen ferritin into adult G. australis over ten weeks resulted in a progressive increase in that form of iron in the serum. However, as with control animals, the liver ferritin of injected lampreys consisted of one subunit type, whose Mr differed from horse spleen ferritin. The lampreys had thus converted horse spleen ferritin iron into endogenous ferritin iron, presumably in their liver. Marked rises in hepatic non-haem iron during the first two weeks and between weeks 8 and 10 of iron injections were accompanied by pronounced increases in SOD activity. A levelling off of iron concentration between weeks 2 and 8 was accompanied by a decline in SOD activity, even though non-haem iron levels were well above those of control animals. Enhanced SOD activity may therefore only be required when there is an elevated flux of iron in the liver through low molecular weight intermediates.
Ceruloplasmin activity in larval and adult lamprey plasma was negligible compared to that of human plasma, despite the fact that the copper content of plasma in lampreys and humans was comparable. This major antioxidant system found in higher vertebrates is thus apparently absent from lamprey plasma.
Adult lamprey liver ferritin is composed of two principal isoforms with isoelectric points of approximately 5.5, and appears to consist of a single type of subunit with a molecular mass of 20 300 Da, intermediate between the molecular mass of the heavy and light chains of higher vertebrates. The iron core contained within adult liver ferritin was predominantly (90%) crystalline, with about 10% in a non-crystalline phase and had a mean width of 7.0 nm. The ability of lamprey ferritin to resist the mobilisation of iron from its core by a superoxide-generating system was also examined and compared with those of other vertebrates. In contrast to ferritins from human, rat, and trout liver those of lamprey liver and horse spleen did not release iron in a predominantly superoxide-dependent manner.
The ability of G. australis to respond to elevated iron levels by enhancing the activity of the protective enzyme SOD, together with the resistance of lamprey ferritin to superoxide-mediated and superoxide-independent iron release, probably accounts for the tolerance of this species to iron levels that are well in excess of those considered to be toxic in humans and from which lampreys appear to suffer no harm.
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Botha, Ryno. "Variability and interannual trends in the climatology of radon-222 at two Southern Hemisphere coastal baseline sites." University of the Western Cape, 2021. http://hdl.handle.net/11394/8106.
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Philosophiae Doctor - PhDThis thesis characterises and discusses two continuous coastal Southern Hemispheric (SH) atmospheric radon (222Rn) signals. Large-scale atmospheric circulation patterns are important components of the climate system implicated in driving catastrophic events such as extreme droughts and mega-wildfires and radon measurements at coastal sites provide valuable information on interactions of terrestrial and oceanic air masses on regional to hemispheric scales. The main collaborating SH atmospheric observatories in this study are located at Cape Grim (CGO, Tasmania, 1992-2017) and Cape Point (CPO, South Africa, 1999-2017). The radon signal from a high-altitude remote island oceanic site in the Northern Hemisphere Mauna Loa Observatory (MLO, Hawaii, 2004-2015) is also incorporated for comparison purposes. The CGO radon signal is the longest and most sensitive in current existence. A variety of statistical, spectral, trend, back-trajectory and trajectory density methods are utilized in this study to illuminate features of the datasets on multiple scales. Strongly skewed radon distributions occur, with a large number of events falling into a compact range of low values (corresponding to marine air-masses) and a smaller number of events spread over a wide range of high-radon values (continental air-masses). Making use of Fast Fourier Transform power spectral analysis, prominent periodicities are identified on diurnal and annual scales. Inter-annual variations in seasonal and diurnal radon and meteorological characteristics, indicating changes in the continental/oceanic atmospheric mixing state, are evident especially during the period from 2012 to 2017, perhaps associated with the strong El-Niño southern oscillation centred on 2015. A slow but systematic decline in CGO and CPO radon levels is evident over the dataset, associated with fewer continental and more marine air-masses impacting the coastal stations. The long-term trends observed in the atmospheric radon signal may indicate changes in SH circulation patterns over time, perhaps associated with climate change effects.
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Clark, Logan N. "Southern Hemisphere Pressure Relationships during the 20th Century - Implications for Climate Reconstructions and Model Evaluation." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1586778291377432.
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Andrews, Allen Hia. "Lead-radium dating of two deep-water fishes from the southern hemisphere, Patagonian toothfish (Dissostichus eleginoides) and Orange Roughy (Hoplostethus atlanticus)." Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1005140.
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Patagonian toothfish (Dissostichus eleginoides) or "Chilean sea bass" support a valuable and controversial fishery, but the life history is little known and longevity estimates range from ~20 to more than 40 or 50 yr. In this study, lead-radium dating provided validated age estimates from juveniles to older adults, supporting the use of otoliths as accurate indicators of age. The oldest age groups were near 30 yr, which provided support for age estimates exceeding 40 or 50 yr from grow zone counts in otolith sections. Hence, scale reading, which rarely exceeds 20 years, has the potential for age underestimation. Lead-radium dating revealed what may be minor differences in age interpretation between two facilities and findings may provide an age-validated opportunity for the CCAMLR Otolith Network to reassess otolith interpretations. Orange roughy (Hoplostethus atlanticus) support a major deep-sea fishery and stock assessments often depend on age analyses, but lifespan estimates range from ~20 to over 100 yr and validation of growth zone counts remained unresolved. An early application of lead-radium dating supported centenarian ages, but the findings were met with disbelief and some studies have attempted to discredit the technique and the long lifespan. In this study, an improved lead-radium dating technique used smaller samples than previously possible and circumvented assumptions that were previously necessary. Lead-radium dating of otolith cores, the first few years of growth, provided ratios that correlated well with the ingrowth curve. This provided robust support for age estimates from otolith thin sections. Use of radiometric ages as independent age estimates indicated the fish in the oldest group were at least 93 yr. Lead-radium dating has validated a centenarian lifespan for orange roughy. To date, radium-226 has been measured in otoliths of 39 fish species ranging from the northern Pacific and Atlantic Oceans to the Southern Ocean. In total, 367 reliable radium-226 measurements were made in 36 studies since the first lead-radium dating study on fish in 1982. The activity of radium-226 measurements ranged over 3 orders of magnitude (<0.001 to >1.0 dpm.g⁻¹). An analysis revealed ontogenetic differences in radium-226 uptake that may be attributed to changes in habitat or diet. Radiometric age from otolith core studies was used to describe a radium-226 uptake time-series for some species, which revealed interesting patterns over long periods. This synopsis provides information on the uptake of radium-226 to otoliths from an environmental perspective, which can be used as a basis for future studies.
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Su, Lin 1966. "A diagnostic study of the summer southern hemisphere circulation of the CCC general circulation model /." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60493.
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The medium scale planetary wave regime, consisting largely of zonal wavenumbers 5-7, frequently dominate the summer Southern Hemisphere tropospheric circulation. We perform a diagnostic study of this circulation as simulated by the Canadian Climate Centre (CCC) general circulation model (GCM). The analysis of Hovmoller diagrams, space-time and zonal wavenumber spectra shows that the CCC GCM is able to simulate the observed medium scale wave regime.The zonally averaged meridional eddy heat and momentum transports and the associated baroclinic and barotropic energy conversions are also examined. The distributions of the transports on the vertical plane agree well with observations. When compared to the observed summer 1979 distributions, some quantitative differences remain: the vertical structure of the heat transport is too baroclinic, while the momentum transport tends to be too weak. The baroclinic and barotropic conversions all show a medium scale wave signal. The time evolution of the Richardson number of the mean flow suggests that the medium scale wave is due to a finite amplitude baroclinic instability.
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Al-Suwaidi, Aisha H. "A southern hemisphere record of the Toarcian Oceanic Anoxic Event from the Neuquén Basin, Argentina." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:4245fc05-416a-41c4-86ea-851005eca605.
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The Toarcian, Early Jurassic, Oceanic Anoxic Event (T-OAE: ~183 Ma) was characterized by globally synchronous deposition of sediments rich in organic carbon (black shales), and is associated with an abrupt negative carbon isotope excursion, disrupting a positive carbon-isotope excursion during the tenuicostatum–serpentinum ammonite Zone boundary. The T-OAE has been extensively studied in northern and southern Europe, but evidence from the southern hemisphere is limited. New geochemical data from the tenuicostatum–hoelderi (~serpentinum) Andean ammonite Zone, from the Neuquén Basin, Argentina provides evidence for the global imprint of the event. The event is recorded in bulk-sediment from Arroyo Lapa (North and South) and Arroyo Serrucho with δ13Corg values of -30‰ – -32.5‰ and δ13C values from fossil wood fall to -30.7 ‰, isotopic ratios that are comparable to those identified in Europe for the T-OAE. Hydrogen Index (HI) data for the T-OAE in Argentina give values ranging from 12 to 425 mg HC/ g TOC, indicating a mixture of terrestrial and marine organic components. Pristane/Phytane ratios and pyrite framboid distribution data indicative of anoxic conditions occur at some levels, and new δ98/95Mo data, with values ranging from ~ -0.2 to 0.78 ‰, which contrast with previously published molybdenum-isotope values from T-OAE black shales of northern Europe. Sedimentological data also reveals a marine transgression during the tenuicostatum–hoelderi Andean ammonite zone.
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Yuan, Kai. "Investigations of the Ionospheric Alfvén Resonator at high latitudes of both northern and southern hemisphere." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10074.
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In order to characterize the features of the Ionospheric Alfvén Resonator (IAR) at high latitudes in both northern and southern hemispheres, both data interpretation and numerical computation are presented. Four IAR events observed by the pulsation magnetometer at Sodankylä in a single month were statistically analysed. It was found that the IAR eigenfrequency separations fluctuate with time. The fluctuation was dominated by plasma density perturbation in the ionosphere. Also, a single IAR event observed by five pulsation magnetometers simultaneously was analysed. The analysis showed the eigenfrequencies of the single IAR detected at different locations are different. Additionally, the eigenfrequency shifts were found to differ at different locations. It indicates that the horizontal scale of a single IAR event could be up to thousands of kilometres. The horizontal structure of the IAR in a large scale is non-uniform. Also, the study has revealed that the visibility of the Spectrum Resonance Structure (SRS) strongly depends on the fluctuation rate of the eigenfrequency separations. Moreover, the first study of IARs in Antarctica was carried out. The IAR occurrence and the relation with the solar activities were investigated statistically. In addition, a numerical model was introduced in this thesis. Based on this model the boundary condition dependence of the IAR was investigated. According to the study the detected eigenfrequencies, the spatial structures of the field and the ratio between the intensities of the total current and the source current strongly depend on the ratio between the wave conductivity and the height integrated Pedersen conductivity in the E region. Also, the numerical study in this thesis has revealed that the eigenfrequency shifts respond to the different features of plasma density perturbations in different ways. The possibility of estimating the plasma density perturbation continuously from the IAR eigenfrequencies observed on the ground is illustrated.
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Hio, Yasuko. "Interannual Variations in the Structure and Interaction of Planetary Waves in the Southern Hemisphere Stratosphere." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147825.
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Chen, Sina. "Probing the population of narrow-line Seyfert 1 galaxies with a southern hemisphere extended sampling." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422848.
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During my Ph.D., I carried out a multi-wavelength study of narrow-line Seyfert 1 galaxies (NLS1s), with the aim of better understanding this peculiar class of AGN.
I present a new accurately selected catalog of NLS1s in the southern hemisphere from the Six-degree Field Galaxy Survey (6dFGS) final data release. The classification was based on their optical spectral properties. I further derived for the first time their flux-calibrated spectra that are not provided by the 6dFGS. By analyzing these spectra, I obtained strong luminosity correlations between continuum and optical emission lines. The central black hole masses were estimated with methods based on the reverberation mapping, confirming that NLS1s indeed host a relatively low-mass black hole compared to broad-line Seyfert 1 galaxies (BLS1s).
In addition, I present a detailed study of a limited number of NLS1s from the 6dFGS sample that both have optical and X-ray spectroscopic observations. There are five complex NLS1s (C-NLS1s) and six simple NLS1s (S-NLS1s). I propose a possible correlation between [O III] line asymmetry and X-ray complexity. The outflow or wind from the inner accretion disk is commonly present in NLS1s and mostly directed along the system axis. S-NLS1s are sources viewed at a small inclination, where the speed of the wind is high thus the blueshift of the blue wing is large. Such a strong wind could blow away the ionized material, therefore result in a simple X-ray spectrum. At a large inclination, instead, the speed of the wind is low, thus the blueshift is less prominent in C-NLS1s. The presence of ionized material in the weak wind could lead to the X-ray spectral complexity.
A fraction of NLS1s are detected at radio frequency. I studied their radio properties at 1.4 GHz and 5 GHz using the NRAO VLA Sky Survey (NVSS) and the Karl G. Jansky Very Large Array (JVLA) respectively. Radio-loud (RL) sources tend to reside in the more distant universe, host a large massive black hole, and have a higher radio and optical luminosity compared to radio-quiet (RQ) sources. To extend the spectral coverage, I generated the test statistic (TS) maps for each radio-emitting source using the Fermi-LAT ten years data set, finding no gamma-ray NLS1 in the sample.
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Oram, David Edward. "Trends of long-lived anthropogenic halocarbons in the Southern Hemisphere and model calculations of global emissions." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323346.
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Albuquerque, Cavalcanti Iracema Fonseca de. "Large scale disturbances in the southern hemisphere tropospheric circulation-model experiments and analyses of observed data." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305030.
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Hilliard, Robert William. "Aspects of feeding and digestion in the southern hemisphere lamprey Geotria Australis Gray: A comprehensive study." Thesis, Hilliard, Robert William (1987) Aspects of feeding and digestion in the southern hemisphere lamprey Geotria Australis Gray: A comprehensive study. PhD thesis, Murdoch University, 1987. https://researchrepository.murdoch.edu.au/id/eprint/52020/.
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The dentition, adult feeding mechanism, pancreatic tissue and intestine have been studied in the anadromous parasitic lamprey, Geotria australis (Geotriidae; Petrorryzoniformes). For coirparative purposes, the feeding structures of parasitic adults representing the two other families of extant lampreys (Petromyzontidae and Mordaciidae) have been examined, as have the pancreas of nordacia mordax and intestine of Lampetra spp. Wherever possible, the results of these studies on the feeding biology of lampreys are compared with those reported elsewhere. Conclusions drawn from these conparisons are used to elucidate phylogenetic relationships among the contenporary petromyzontiforms.
The unique oral disc teeth of G.australis appear well adapted to allow the oral disc to slide forwards over the surface of prey, yet restrict any tendency for the disc to slip backwards. The main cutting action results from a scissoring movement brought about by the rapid interlocking of the three sharp and stout cusps of the transverse lingual lamina with large grooves on the rear face of the supraoral lamina. The movement of excised flesh back through the oral passage to the pharynx would be facilitated by the action of the pair of strongly cuspid longitudinal lingual laminae. The results of this study have elucidated the feeding mechanism of G.australis, and support the view that this species removes considerable amounts of flesh rather than only blood from its prey.
The dentition of parasitic lanpreys representing the six genera of holarctic lanpreys (Petromyzontidae) and the other monogeneric Southern Hemisphere family (Mordaciidae) has also been studied. Attention was paid to coirparing the divergent dentitional characters, the locations of attack and the size of the oral disc and buccal glands of the blood-feeding Petromyzon marinus and those of the flesh-feeding Lampetra fluviatilis and Lanpetra ayresii. Conclusions drawn from these comparisons have been used to make suggestions regarding the feeding biology of those species for which less comprehensive data are available. It is also concluded that (a) blood-feeding preceded flesh-feeding in the modern lampreys, (b) endemic freshwater parasitic species typically ingest blood, (c) the ability to feed on flesh developed in populations which had access to estuarine and marine hosts. and (d) pre-Tertiary forms resembling contemporary Ichthyomyzon unicuspsis could have independently given rise to both genera of Southern Hemisphere lampreys.
The morphology of the pancreatic tissue has been examined in larval, metamorphosing and adult representatives of G.australis and in large larvae and recently metamorphosed adults of another Australian parasitic lamprey, M.mordax. The location of both the larval and adult pancreatic endocrine (islet) cells in both of these species differs markedly from that in comparable stages of holarctic lampreys. In larval G.australis, the main zone of islet cell proliferation is located laterally between the oesophagus and the inner edge of two large intestinal diverticula unique to this species, rather than dorsal and ventral to the oesophagus. The adult islet follicles of G.australis are packed into a single, discrete capsule adjacent to the oesophageal/intestinal junction, rather than separated into cranial, intermediate and caudal cords as in adult holarctic lampreys. In M.mordax, the larval islet cells are derived from the intestinal epithelium at the point where the anterior intestine is confluent with the oesophagous, but opposite the single intestinal diverticulum of this species. While adult islet follicles are also found en masse alongside the oesophageal/intestinal junction of M.mordax, they are not packed into a discrete capsule. The lack of separate intermediate and caudal cords in adults of the Southern Hemisphere lampreys is due to the lack of involvement of the bile duct in islet formation during metamorphosis. B cells are present in both larval and adult islet follicles of G.australis and M.mordax, and presumptive D cells were found in in all postlarval stages of G.australis after metamorphosing Stage 3, as well as in the young adults of M.mordax. While a further but less common u\ adult cell type was identified each Southern Hemisphere species, the shape and staining properties differed.
The exocrine pancreactic (zymogen) cells of larval G.australis are essentially restricted to the epithelium lining the two intestinal diverticula. The number of zymogen cells and digestive enzyme activity decline rapidly at the start of metamorphosis. While the diverticula are lost by metamorphosing Stage 4, zymogen cells reappear near the end of transformation in the mucosa lining the anterior intestine and de novo adult intestinal caecum. The latter structure, which is similar to that of adult holarctic lanpreys, develops alongside the new oesophageal/intestinal junction between Stages 4 and 6. In both larval and adult G.australis, tryptic, amylolytic and lipolytic activity were highest in those portions of the alimentary canal containing zymogen Differences cells. in the activity of the principal pancreatic enzymes within the gut of the larvae and adults have been related to the marked differences in the diet of the two divergent life cycle stages. While the exocrine pancreatic tissue of larval M.mordax is unique among lanpreys by being located within a single, large diverticulum containing an extensive network of mucosal folds, that of the adult is found in the same location as in those of other lanpreys. It is concluded that the different larval intestinal diverticula of Geotria and Mordacia represent independent specializations to increase and focus digestive enzyme activity at the front end of the intestine, possibly as a response to poor quality detritus in tenperate Australian streams. Such an explanation implies that the widely-dispersed populations of G.australis and the conteirporary fJordacia spp. radiated from stocks which evolved in Australia during the Tertiary.
Measurements have been made of those changes which lead to increases in the surface area of the intestine during the metamorphosis of G.australis, Lampetra fluviatilis and the nonparasitic brook lairprey. Lanpetra planeri. An account is also given of the pattern of intestinal fold formation, the fate of the typhlosolar pathway and the development of the typhlosolar vein in transforming G.australis. Although the intestine of G.australis increases in length by 12.5% and in diameter by 1.12 times during metamorphosis, the min cause of 5.71 times increase in surface area is the development of longitudinal folds. Except during Stages 3 and 4 of metamorphosis, the contribution of the typhlosole to the internal perimeter of the intestine is less in all life cycle stages of G.australis than in Lampetra spp. Metamorphic changes in the various intestinal measurements of the nonparasitic L.planeri parallel those of its presumed ancestral species, L.fluviatilis, between Stages 1 and 6. Subsequently, however, the longitudinal folds (but not the typhlosole) start regressing in the brook lairprey, just after the time when gonadal development is accelerated.
During the marine phase of G.australis, the external diameter of the intestine and the number and height of the longitudinal folds increase markedly, although the proportional contribution of the typhlosole to the internal perimeter of the anterior intestine falls from 12.2 to 7.5%. The intestine of fully grown adults of G.australis undergoes rapid atrophy when the animals leave the sea at the start of their upstream spawning migration, even though the gonads do not show any sign of accelerated development at this time.
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Thomson, Roberto F. "Response of temperate forest birds to habitat change in central Chile." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:1792418e-18e9-4344-96ce-3bad2aa03500.
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Despite the long time since the introduction and spread of pine plantations in southern hemisphere countries there has been no study of the suitability of this exotic and novel type of vegetation on the native avifauna. This thesis aims to add understanding of this habitat replacement and its effects on the forest bird community. This research included a series of studies to assess the quality of mature pine plantations for the forest avifauna in comparison to what is in native forests. The first two studies determine the effects on the forest bird community of the fragmentation and replacement of native forest in a gradient of substitution. The results showed a direct relationship between level of substitution and loss of functional diversity, and that fragmentation predicts the bird assemblage in pine stands. The next two studies used data from an intensive ringing season to assess differences in the condition of populations inhabiting each habitat. Birds, in general, were found in better condition in native fragments than in pine plantations. Moreover, a despotic distribution was determined for a migrant species and a gradient in habitat quality was found in relation to proximity to native forest. The next two studies used information from a nest-box survey set in a gradient of sites with substitution of native forest. The results showed that the type of forest cover and their proportion in the landscape may affect the breeding performance of some species. Finally, in the last study I evaluated the foraging niche of bird species in each habitat. Compared with native forest, niche breath reduced while the niche overlap increased in pine plantations for most species. The results suggest that pine plantations are poor quality habitat for the bird community and that the substitution of native forests increases selective pressure.
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Jacobi, Christoph, Friederike Liilienthal, T. Schmidt, and la Torre A. de. "Modeling the Southern Hemisphere winter circulation using realistic zonal mean gravity wave information in the lower atmosphere." Universität Leipzig, 2016. https://ul.qucosa.de/id/qucosa%3A16703.
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A mechanistic global circulation model is used to simulate the mesospheric and lower thermospheric circulation during austral winter. The model includes a gravity wave (GW) parameterization that is initiated by prescribed GW parameters in the troposphere. In standard configuration, these waves are described by a simple distribution with large amplitudes in the winter hemisphere and small ones in summer. Here we replace this distribution by a more realistic one, which is based on observations of potential GW energy using GPS radio occultations, but which is normalized to the same global mean amplitude. The model experiment shows that this new gravity wave distribution leads to weaker zonal winds in the mesosphere, a downward shift of the meridional poleward mesospheric wind jet, enhanced downwelling in the mid-to-high-latitude winter mesosphere and warming of the polar stratopause.Ein globales mechanistisches Zirkulationsmodell wird verwendet um die Dynamik der Mesosphäre und unteren Thermosphäre im Südwinter zu simulieren. Das Modell beinhaltet eine Schwerewellenparametrisierung die durch eine vorgeschriebene Schwerewellenverteilung in der oberen Troposphäre angetrieben wird. In der Standardkonfiguration besteht diese aus einer einfachen zonal gemittelten Verteilung mit größeren Amplituden im Winter als im Sommer. Wir ersetzen diese Verteilung durch eine realistischere, die auf der beobachteten globalen Verteilung der potentiellen Energie von Schwerewellen basiert und auf die gleiche global gemittelte Amplitude normiert wird. Das Modellexperiment zeigt, dass die neue Schwerewellenverteilung zu schwächeren zonalen Winden in der Mesosphäre, einer Verschiebung des meridionalen Jets nach unten, verstärkten Abwinden in der Mesosphäre mittlerer und höherer Breiten im Winter, und einer Erwärmung der polaren Winterstratopause führt.