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Journal articles on the topic "Atmospheric circulation Australia"

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McKay, Roseanna C., Julie M. Arblaster, and Pandora Hope. "Tropical influence on heat-generating atmospheric circulation over Australia strengthens through spring." Weather and Climate Dynamics 3, no. 2 (April 5, 2022): 413–28. http://dx.doi.org/10.5194/wcd-3-413-2022.

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Abstract. Extreme maximum temperatures during Australian spring can have deleterious impacts on a range of sectors from health to wine grapes to planning for wildfires but are studied relatively little compared to spring rainfall. Spring maximum temperatures in Australia have been rising over recent decades, and it is important to understand how Australian spring maximum temperatures develop in the present and warming climate. Australia's climate is influenced by variability in the tropics and extratropics, but some of this influence impacts Australia differently from winter to summer and, consequently, may have different impacts on Australia as spring evolves. Using linear regression analysis, this paper explores the atmospheric dynamics and remote drivers of high maximum temperatures over the individual months of spring. We find that the drivers of early spring maximum temperatures in Australia are more closely related to low-level wind changes, which in turn are more related to the Southern Annular Mode than variability in the tropics. By late spring, Australia's maximum temperatures are proportionally more related to warming through subsidence than low-level wind changes and more closely related to tropical variability. This increased relationship with the tropical variability is linked with the breakdown of the subtropical jet through spring and an associated change in tropically forced Rossby wave teleconnections. An improved understanding of how the extratropics and tropics project onto the mechanisms that drive high maximum temperatures through spring may lead to improved sub-seasonal prediction of high temperatures in the future.
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Ummenhofer, Caroline C., Alexander Sen Gupta, Andréa S. Taschetto, and Matthew H. England. "Modulation of Australian Precipitation by Meridional Gradients in East Indian Ocean Sea Surface Temperature." Journal of Climate 22, no. 21 (November 1, 2009): 5597–610. http://dx.doi.org/10.1175/2009jcli3021.1.

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Abstract This study explores the impact of meridional sea surface temperature (SST) gradients across the eastern Indian Ocean on interannual variations in Australian precipitation. Atmospheric general circulation model (AGCM) experiments are conducted in which the sign and magnitude of eastern Indian Ocean SST gradients are perturbed. This results in significant rainfall changes for western and southeastern Australia. A reduction (increase) in the meridional SST gradient drives a corresponding response in the atmospheric thickness gradients and results in anomalous dry (wet) conditions over Australia. During simulated wet years, this seems to be due to westerly anomalies in the thermal wind over Australia and anomalous onshore moisture advection, with a suggestion that the opposite occurs during dry conditions. Thus, an asymmetry is seen in the magnitude of the forced circulation and precipitation response between the dry and wet simulations. To assess the relative contribution of the SST anomalies making up the meridional gradient, the SST pattern is decomposed into its constituent “poles,” that is, the eastern tropical pole off the northwest shelf of Australia versus the southern pole in the central subtropical Indian Ocean. Overall, the simulated Australian rainfall response is linear with regard to the sign and magnitude of the eastern Indian Ocean SST gradient. The tropical eastern pole has a larger impact on the atmospheric circulation and Australian precipitation changes relative to the southern subtropical pole. However, there is clear evidence of the importance of the southern pole in enhancing the Australian rainfall response, when occurring in conjunction with but of opposite sign to the eastern tropical pole. The observed relationship between the meridional SST gradient in the eastern Indian Ocean and rainfall over western and southeastern Australia is also analyzed for the period 1970–2005. The observed relationship is found to be consistent with the AGCM results.
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Feng, Juan, Jianping Li, and Yun Li. "A Monsoon-Like Southwest Australian Circulation and Its Relation with Rainfall in Southwest Western Australia." Journal of Climate 23, no. 6 (March 15, 2010): 1334–53. http://dx.doi.org/10.1175/2009jcli2837.1.

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Abstract Using the NCEP–NCAR reanalysis, the 40-yr ECMWF Re-Analysis (ERA-40), and precipitation data from the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) and the Australian Bureau of Meteorology, the variability and circulation features influencing southwest Western Australia (SWWA) winter rainfall are investigated. It is found that the climate of southwest Australia bears a strong seasonality in the annual cycle and exhibits a monsoon-like atmospheric circulation, which is called the southwest Australian circulation (SWAC) because of its several distinct features characterizing a monsoonal circulation: the seasonal reversal of winds, alternate wet and dry seasons, and an evident land–sea thermal contrast. The seasonal march of the SWAC in extended winter (May–October) is demonstrated by pentad data. An index based on the dynamics’ normalized seasonality was introduced to describe the behavior and variation of the winter SWAC. It is found that the winter rainfall over SWWA has a significant positive correlation with the SWAC index in both early (May–July) and late (August–October) winter. In weaker winter SWAC years, there is an anticyclonic anomaly over the southern Indian Ocean resulting in weaker westerlies and northerlies, which are not favorable for more rainfall over SWWA, and the opposite combination is true in the stronger winter SWAC years. The SWAC explains not only a large portion of the interannual variability of SWWA rainfall in both early and late winter but also the long-term drying trend over SWWA in early winter. The well-coupled SWAC–SWWA rainfall relationship seems to be largely independent of the well-known effects of large-scale atmospheric circulations such as the southern annular mode (SAM), El Niño–Southern Oscillation (ENSO), Indian Ocean dipole (IOD), and ENSO Modoki (EM). The result offers qualified support for the argument that the monsoon-like circulation may contribute to the rainfall decline in early winter over SWWA. The external forcing of the SWAC is also explored in this study.
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Grose, Michael R., James S. Risbey, Aurel F. Moise, Stacey Osbrough, Craig Heady, Louise Wilson, and Tim Erwin. "Constraints on Southern Australian Rainfall Change Based on Atmospheric Circulation in CMIP5 Simulations." Journal of Climate 30, no. 1 (January 2017): 225–42. http://dx.doi.org/10.1175/jcli-d-16-0142.1.

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Atmospheric circulation change is likely to be the dominant driver of multidecadal rainfall trends in the midlatitudes with climate change this century. This study examines circulation features relevant to southern Australian rainfall in January and July and explores emergent constraints suggested by the intermodel spread and their impact on the resulting rainfall projection in the CMIP5 ensemble. The authors find relationships between models’ bias and projected change for four features in July, each with suggestions for constraining forced change. The features are the strength of the subtropical jet over Australia, the frequency of blocked days in eastern Australia, the longitude of the peak blocking frequency east of Australia, and the latitude of the storm track within the polar front branch of the split jet. Rejecting models where the bias suggests either the direction or magnitude of change in the features is implausible produces a constraint on the projected rainfall reduction for southern Australia. For RCP8.5 by the end of the century the constrained projections are for a reduction of at least 5% in July (with models showing increase or little change being rejected). Rejecting these models in the January projections, with the assumption the bias affects the entire simulation, leads to a rejection of wet and dry outliers.
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Wheeler, Matthew C., Harry H. Hendon, Sam Cleland, Holger Meinke, and Alexis Donald. "Impacts of the Madden–Julian Oscillation on Australian Rainfall and Circulation." Journal of Climate 22, no. 6 (March 15, 2009): 1482–98. http://dx.doi.org/10.1175/2008jcli2595.1.

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Abstract Impacts of the Madden–Julian oscillation (MJO) on Australian rainfall and circulation are examined during all four seasons. The authors examine circulation anomalies and a number of different rainfall metrics, each composited contemporaneously for eight MJO phases derived from the real-time multivariate MJO index. Multiple rainfall metrics are examined to allow for greater relevance of the information for applications. The greatest rainfall impact of the MJO occurs in northern Australia in (austral) summer, although in every season rainfall impacts of various magnitude are found in most locations, associated with corresponding circulation anomalies. In northern Australia in all seasons except winter, the rainfall impact is explained by the direct influence of the MJO’s tropical convective anomalies, while in winter a weaker and more localized signal in northern Australia appears to result from the modulation of the trade winds as they impinge upon the eastern coasts, especially in the northeast. In extratropical Australia, on the other hand, the occurrence of enhanced (suppressed) rainfall appears to result from induced upward (downward) motion within remotely forced extratropical lows (highs), and from anomalous low-level northerly (southerly) winds that transport moisture from the tropics. Induction of extratropical rainfall anomalies by remotely forced lows and highs appears to operate mostly in winter, whereas anomalous meridional moisture transport appears to operate mainly in the summer, autumn, and to some extent in the spring.
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Taschetto, Andréa S., Alex Sen Gupta, Harry H. Hendon, Caroline C. Ummenhofer, and Matthew H. England. "The Contribution of Indian Ocean Sea Surface Temperature Anomalies on Australian Summer Rainfall during El Niño Events." Journal of Climate 24, no. 14 (July 15, 2011): 3734–47. http://dx.doi.org/10.1175/2011jcli3885.1.

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Abstract This study investigates the impact of Indian Ocean sea surface temperature (SST) anomalies on the atmospheric circulation of the Southern Hemisphere during El Niño events, with a focus on Australian climate. During El Niño episodes, the tropical Indian Ocean exhibits two types of SST response: a uniform “basinwide warming” and a dipole mode—the Indian Ocean dipole (IOD). While the impacts of the IOD on climate have been extensively studied, the effects of the basinwide warming, particularly in the Southern Hemisphere, have received less attention. The interannual basinwide warming response has important implications for Southern Hemisphere atmospheric circulation because 1) it accounts for a greater portion of the Indian Ocean monthly SST variance than the IOD pattern and 2) its maximum amplitude occurs during austral summer to early autumn, when large parts of Australia, South America, and Africa experience their monsoon. Using observations and numerical experiments with an atmospheric general circulation model forced with historical SST from 1949 to 2005 over different tropical domains, the authors show that the basinwide warming leads to a Gill–Matsuno-type response that reinforces the anomalies caused by changes in the Pacific as part of El Niño. In particular, the basinwide warming drives strong subsidence over Australia, prolonging the dry conditions during January–March, when El Niño–related SST starts to decay. In addition to the anomalous circulation in the tropics, the basinwide warming excites a pair of barotropic anomalies in the Indian Ocean extratropics that induces an anomalous anticyclone in the Great Australian Bight.
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Troccoli, Alberto, Karl Muller, Peter Coppin, Robert Davy, Chris Russell, and Annette L. Hirsch. "Long-Term Wind Speed Trends over Australia." Journal of Climate 25, no. 1 (January 1, 2012): 170–83. http://dx.doi.org/10.1175/2011jcli4198.1.

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Abstract Accurate estimates of long-term linear trends of wind speed provide a useful indicator for circulation changes in the atmosphere and are invaluable for the planning and financing of sectors such as wind energy. Here a large number of wind observations over Australia and reanalysis products are analyzed to compute such trends. After a thorough quality control of the observations, it is found that the wind speed trends for 1975–2006 and 1989–2006 over Australia are sensitive to the height of the station: they are largely negative for the 2-m data but are predominantly positive for the 10-m data. The mean relative trend at 2 m is −0.10 ± 0.03% yr−1 (−0.36 ± 0.04% yr−1) for the 1975–2006 (1989–2006) period, whereas at 10 m it is 0.90 ± 0.03% yr−1 (0.69 ± 0.04% yr−1) for the 1975–2006 (1989–2006) period. Also, at 10 m light winds tend to increase more rapidly than the mean winds, whereas strong winds increase less rapidly than the mean winds; at 2 m the trends in both light and strong winds vary in line with the mean winds. It was found that a qualitative link could be established between the observed features in the linear trends and some atmospheric circulation indicators (mean sea level pressure, wind speed at 850 hPa, and geopotential at 850 hPa), particularly for the 10-m observations. Further, the magnitude of the trend is also sensitive to the period selected, being closer to zero when a very long period, 1948–2006, is considered. As a consequence, changes in the atmospheric circulation on climatic time scales appear unlikely.
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Ummenhofer, Caroline C., Peter C. McIntosh, Michael J. Pook, and James S. Risbey. "Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector." Journal of Climate 26, no. 21 (October 16, 2013): 8476–94. http://dx.doi.org/10.1175/jcli-d-12-00860.1.

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Abstract Characteristics of atmospheric blocking in the Southern Hemisphere (SH) are explored in atmospheric general circulation model (AGCM) simulations with the Community Atmosphere Model, version 3, with a particular focus on the Australia–New Zealand sector. Preferred locations of blocking in SH observations and the associated seasonal cycle are well represented in the AGCM simulations, but the observed magnitude of blocking is underestimated throughout the year, particularly in late winter and spring. This is related to overly zonal flow due to an enhanced meridional pressure gradient in the model, which results in a decreased amplitude of the longwave trough/ridge pattern. A range of AGCM sensitivity experiments explores the effect on SH blocking of tropical heating, midlatitude sea surface temperatures, and land–sea temperature gradients created over the Australian continent during austral winter. The combined effects of tropical heating and extratropical temperature gradients are further explored in a configuration that is favorable for blocking in the Australia–New Zealand sector with warm SST anomalies to the north of Australia, cold to the southwest of Australia, warm to the southeast, and cool Australian land temperatures. The blocking-favorable configuration indicates a significant strengthening of the subtropical jet and a reduction in midlatitude flow, which results from changes in the thermal wind. While these overall changes in mean climate, predominantly forced by the tropical heating, enhance blocking activity, the magnitude of atmospheric blocking compared to observations is still underestimated. The blocking-unfavorable configuration with surface forcing anomalies of opposite sign results in a weakening subtropical jet, enhanced midlatitude flow, and significantly reduced blocking.
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Taschetto, Andréa S., Reindert J. Haarsma, Alexander Sen Gupta, Caroline C. Ummenhofer, Khalia J. Hill, and Matthew H. England. "Australian Monsoon Variability Driven by a Gill–Matsuno-Type Response to Central West Pacific Warming." Journal of Climate 23, no. 18 (September 15, 2010): 4717–36. http://dx.doi.org/10.1175/2010jcli3474.1.

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Abstract The objective of this study is to investigate the mechanisms that cause the anomalous intensification of tropical Australian rainfall at the height of the monsoon during El Niño Modoki events. In such events, northwestern Australia tends to be wetter in January and February when the SST warming is displaced to the central west Pacific, the opposite response to that associated with a traditional El Niño. In addition, during the bounding months, that is, December and March, there is below-average rainfall induced by an anomalous Walker circulation. This behavior tends to narrow and intensify the annual rainfall cycle over northwestern Australia relative to the climatology, causing a delayed monsoonal onset and an earlier retreat over the region. Observational datasets and numerical experiments with a general circulation model are used to examine the atmospheric response to the central west Pacific SST warming. It is shown here that the increase of precipitation, particularly in February, is phased locked to the seasonal cycle when the intertropical convergence zone is displaced southward and the South Pacific convergence zone is strengthened. An interaction between the interannual SST variability associated with El Niño Modoki events and the evolution of the seasonal cycle intensifies deep convection in the central west Pacific, driving a Gill–Matsuno-type response to the diabatic heating. The westward-propagating disturbance associated with the Gill–Matsuno mechanism generates an anomalous cyclonic circulation over northwestern Australia, leading to convergence of moisture and increased precipitation. The Gill–Matsuno-type response overwhelms the subsidence of the anomalous Walker circulation associated with Modoki events over Australia during the peak of the monsoon.
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Weller, Evan, Ming Feng, Harry Hendon, Jian Ma, Shang-Ping Xie, and Nick Caputi. "Interannual Variations of Wind Regimes off the Subtropical Western Australia Coast during Austral Winter and Spring." Journal of Climate 25, no. 16 (August 15, 2012): 5587–99. http://dx.doi.org/10.1175/jcli-d-11-00324.1.

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Abstract Off the Western Australia coast, interannual variations of wind regime during the austral winter and spring are significantly correlated with the Indian Ocean dipole (IOD) and the southern annular mode (SAM) variability. Atmospheric general circulation model experiments forced by an idealized IOD sea surface temperature anomaly field suggest that the IOD-generated deep atmospheric convection anomalies trigger a Rossby wave train in the upper troposphere that propagates into the southern extratropics and induces positive geopotential height anomalies over southern Australia, independent of the SAM. The positive geopotential height anomalies extended from the upper troposphere to the surface, south of the Australian continent, resulting in easterly wind anomalies off the Western Australia coast and a reduction of the high-frequency synoptic storm events that deliver the majority of southwest Australia rainfall during austral winter and spring. In the marine environment, the wind anomalies and reduction of storm events may hamper the western rock lobster recruitment process.
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Dissertations / Theses on the topic "Atmospheric circulation Australia"

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Monges, Arnaud C. "Impact of the Madden-Julian oscillation over tropical South America During Austral summer." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/25784.

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Roquet, Fabien. "La circulation océanique autour du plateau de Kerguelen : de l'observation à la modélisation." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00431483.

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La grande extension méridienne et la faible profondeur du plateau de Kerguelen en font un obstacle majeur à l'écoulement zonal du Courant Circumpolaire Antarctique (CCA) dans le secteur indien de l'océan austral. Tandis que la majorité du transport du CCA est dévié au nord des îles Kerguelen, le reste (50 x 10 m3 s-1) doit passer plus au sud, probablement par les passages profonds du Fawn Trough (56°S, 77°E, 2650 m) et du Princess Elizabeth Trough (64°S, 82°E, 3650 m). Pourtant, le détail de la circulation autour du plateau est longtemps resté méconnu, en raison des difficultés à récolter des données dans cette région éloignée de toute route commerciale, d'un climat particulièrement rude et de la présence de la banquise recouvrant la moitié du plateau en hiver. L'objectif de cette thèse est d'améliorer notre connaissance de la circulation moyenne autour du plateau de Kerguelen. Pour cela, un large éventail d'outils allant de l'analyse d'observations récentes à l'utilisation de modèles numériques de circulation a été utilisé. Les données obtenues à l'aide d'éléphants de mer instrumentés sont présentées en détail. Une procédure de calibration et de validation de ces profils hydrologiques est proposée. Ce jeu de données, constitué d'un grand nombre de sections à haute résolution spatiale, est ensuite combiné avec d'autres observations plus conventionnelles (in situ et satellites) pour construire un nouveau schéma de circulation dans la région. L'existence d'un courant intense traversant le passage du Fawn Trough est alors mise en évidence. Les observations directes du courant du Fawn Trough pendant la campagne récente TRACK (resp.: Y.-H. Park) confirment l'importance de ce courant, qui concentre plus de 40 x 10 m3 s-1, soit 30 % du transport total du CCA. La connaissance de la circulation développée à partir des observations est ensuite utilisée pour valider une simulation au 1/4° de résolution. A l'aide de tests de sensibilité sur une configuration régionale de l'Océan Indien Sud, l'importance de la bonne représentation des caractéristiques des masses d'eau profonde et de la bathymétrie pour obtenir une simulation réaliste est mise en évidence. Finalement, une analyse dynamique de la simulation est menée, montrant comment la circulation résulte d'une combinaison des effets de la bathymétrie et du vent au travers de la balance de Sverdrup topographique. L'extension méridienne du CCA est maximale dans la région du plateau de Kerguelen, augmentant régionalement le forçage du vent. En permettant le passage de la partie sud du CCA près de la divergence antarctique (entre 60°S et 65°S), où le pompage d'Ekman est très intense, le plateau de Kerguelen pourrait favoriser indirectement l'accélération du CCA.
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Barbara, Loïc. "Reconstruction des conditions océaniques de surface et de la productivité en Péninsule Antarctique au cours de l'Holocène et du réchauffement récent." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14540/document.

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Durant les dernières décennies, la Péninsule Antarctique a été identifiée comme étant la région où le réchauffement récent est le plus marqué dans l’Hémisphère Sud. Cependant, au-delà de la période instrumentale, la variabilité climatique Holocène de cette partie du globe est en grande partie inconnue. Cette absence de données limite notre capacité à évaluer les l’amplitude des changements actuels dans le contexte de la variabilité historique ainsi que les mécanismes de forçage sous-jacents. Nous avons ainsi ciblé nos analyses sur des enregistrements sédimentaires prélevés à l’Est et à l’Ouest de la Péninsule Antarctique, avec pour objectif d’étendre les connaissances spatiales et temporelles des conditions de l’océan de surfaces dans ce secteur de l’Antarctique au cours du dernier siècle, du dernier millénaire ainsi que durant l’Holocène. La méthodologie de cette thèse est basée sur une comparaison multi-proxies qui inclut, comme outils principaux, les assemblages des diatomées et les biomarqueurs spécifiques de diatomées (HBIs). Nous avons pu ainsi documenter la réponse régionale environnementale aux variations climatiques à différentes échelles de temps, et définir les mécanismes forçant sur la variabilité des conditions d’océan de surface ainsi que la formation du couvert de banquise en Péninsule Antarctique. La comparaison de nos enregistrements avec des données issues des carottes de glace, a permis de mettre en évidence le rôle important des changements d’intensité des cellules atmosphériques sur la dynamique de la circulation océanique, la durée du cycle saisonnier de banquise et la productivité siliceuse
The Antarctic Peninsula has been identified during the last decades as the region from the Southern Hemisphere which is the most affected by the recent warming. However, beyond the instrumental period, the Holocene climate variability of this area is largely unknown, limiting our ability to evaluate the current changes within the context of historical variability and underpin the underlying forcing mechanisms. We focused our analysis on sedimentary sequences from the Eastern and Western side of the Antarctic Peninsula, in order to expand the spatial and temporal knowledge of sea-surface conditions over the last century, the last millennium and throughout the Holocene in this Antarctic area. The inferences are based on a multi-proxy comparison mainly using diatom assemblages and diatom specific biomarkers (HBIs). We documented the regional environmental response to climate changes at different time scales and described the forcing mechanisms on the sea-surface conditions and sea ice cover variability in Antarctic Peninsula. Comparing our results with ice core data allowed us to highlight the large impact of atmospheric forcings on the oceanic circulation, the seasonal sea ice dynamics and the siliceous productivity
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Sallée, Jean-Baptiste. "Les eaux modales de l'Océan Austral." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00193791.

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Les eaux modales Subantarctiques (SAMW) sont formées dans la profonde couche de mélange au nord du front Subantarctique (SAF) dans l'Océan Austral. Elles influencent le climat à des échelles décennales et inter-annuelles et jouent un rôle fondamental dans la ventilation de la thermocline de l'Océan Austral. Nous étudions la formation des SAMW en nous fondant sur les récents flotteurs profilants ARGO et sur les dériveurs de surface GDP. Ces jeux de données fournissent une très bonne couverture spatio-temporelle des processus à l'oeuvre dans les couches supérieures de l'Océan Austral. Depuis le lancement du programme international ARGO, le nombre de profils hydrographiques a augmenté de façon considérable dans l'Océan Austral. Une analyse de ces données a montré que les flux air-mer et les flux d'Ekman sont les forçages dominants dans la formation des SAMW. Nous avons trouvé une transition rapide, autour de 70°E, des couches de mélange peu profondes en amont vers des couches de mélange très profondes en aval. Cette transition est associée à un changement de signe de la diffusion tourbillonnaire horizontale dans les couches de surface, et à l'extension méridionale de l'ACC lorsqu'il passe autour du plateau de Kerguelen. Ces effets sont directement liés à la bathymétrie et laissent place à une région de formation des SAMW au Sud-Ouest de l'Australie.

La formation des SAMW est intimement liée à la dynamique océanique Australe et à la position des principaux fronts polaires. Une deuxième étude concerne la circulation de l'ACC et la variabilité frontale. Dans cette étude, nous avons tiré parti de la complémentarité des données in situ et altimétriques afin de suivre l'évolution des deux principaux fronts de l'ACC pendant la période 1993-2005. Nous avons comparé leurs mouvements avec les deux principaux modes de variabilité atmosphérique de l'Hémisphère Sud, le mode annulaire Austral (SAM) et l'Oscillation Australe El-Niño (ENSO). La position moyenne des fronts est déterminée avant tout par les fonds océaniques. Cependant, nous avons trouvé que dans les régions à fond plat, les fronts forment de grands méandres dus à l'activité tourbillonnaire et aux forçages atmosphériques.

En parallèle, nous avons développé une nouvelle estimation de la distribution circumpolaire de la diffusion dans l'Océan Austral. La diffusion n'a presque jamais été étudiée à partir de données in situ dans cet océan. Nous avons calculé une estimation du coefficient de diffusion tourbillonnaire à partir d'une analyse statistique de dix années de trajectoires de dériveurs de surface. Nous avons cartographié ce coefficient dans l'Océan Austral, puis nous l'avons paramétré à partir de données altimétriques pour pouvoir en étudier l'évolution inter-annuelle et en faciliter l'utilisation dans le futur. Cette étude montre que l'Océan Austral est fortement diffusif au nord de l'ACC, et particulièrement près des courants de bord Ouest, c'est à dire dans la Rétroflexion des Aiguilles, dans la région du plateau de Campbell, et dans le courant de Brésil-Malouines.

Ces résultats nous ont menés à une analyse circumpolaire de la formation des SAMW, et à une meilleure conception du lien entre la dynamique océanique Australe et la formation des SAMW. La croissance constante des données hydrologiques du programme ARGO dans l'Océan Austral nous a également permis de mieux représenter la répartition des régions de formation des SAMW. Nous avons trouvé que la diffusion tourbillonnaire joue un rôle majeur dans les budgets de chaleur locaux. Au Sud des courants de bord Ouest, et au nord du SAF, la diffusion tourbillonnaire apporte de la chaleur, équilibrant et même dominant les refroidissements hivernaux dus aux flux d'Ekman et aux flux air-mer. Elle réduit en particulier la déstabilisation de la couche de mélange au nord du SAF dans l'Ouest du bassin Indien, en aval de la Rétroflexion des Aiguilles, et dans l'Ouest du bassin Pacifique, en aval du Plateau de Campbell.
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Morse, Danielle M. Fuelberg Henry E. "A chemical and meteorological analysis of long-range transport from Africa during austral spring." Diss., 2005. http://etd.lib.fsu.edu/theses/available/etd-07142005-174734.

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Thesis (M.S.)--Florida State University, 2005.
Advisor: Dr. Henry E. Fuelberg, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 27, 2005). Document formatted into pages; contains ix, 42 pages. Includes bibliographical references.
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Books on the topic "Atmospheric circulation Australia"

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Whetton, Peter. Australian Region intercomparison of the results of some general circulation models used in enhanced greenhouse experiments. Australia: CSIRO, 1991.

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Behera, Swadhin, and Toshio Yamagata. Climate Dynamics of ENSO Modoki Phenomena. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.612.

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The El Niño Modoki/La Niña Modoki (ENSO Modoki) is a newly acknowledged face of ocean-atmosphere coupled variability in the tropical Pacific Ocean. The oceanic and atmospheric conditions associated with the El Niño Modoki are different from that of canonical El Niño, which is extensively studied for its dynamics and worldwide impacts. A typical El Niño event is marked by a warm anomaly of sea surface temperature (SST) in the equatorial eastern Pacific. Because of the associated changes in the surface winds and the weakening of coastal upwelling, the coasts of South America suffer from widespread fish mortality during the event. Quite opposite of this characteristic change in the ocean condition, cold SST anomalies prevail in the eastern equatorial Pacific during the El Niño Modoki events, but with the warm anomalies intensified in the central Pacific. The boreal winter condition of 2004 is a typical example of such an event, when a tripole pattern is noticed in the SST anomalies; warm central Pacific flanked by cold eastern and western regions. The SST anomalies are coupled to a double cell in anomalous Walker circulation with rising motion in the central parts and sinking motion on both sides of the basin. This is again a different feature compared to the well-known single-cell anomalous Walker circulation during El Niños. La Niña Modoki is the opposite phase of the El Niño Modoki, when a cold central Pacific is flanked by warm anomalies on both sides.The Modoki events are seen to peak in both boreal summer and winter and hence are not seasonally phase-locked to a single seasonal cycle like El Niño/La Niña events. Because of this distinction in the seasonality, the teleconnection arising from these events will vary between the seasons as teleconnection path will vary depending on the prevailing seasonal mean conditions in the atmosphere. Moreover, the Modoki El Niño/La Niña impacts over regions such as the western coast of the United States, the Far East including Japan, Australia, and southern Africa, etc., are opposite to those of the canonical El Niño/La Niña. For example, the western coasts of the United States suffer from severe droughts during El Niño Modoki, whereas those regions are quite wet during El Niño. The influences of Modoki events are also seen in tropical cyclogenesis, stratosphere warming of the Southern Hemisphere, ocean primary productivity, river discharges, sea level variations, etc. A remarkable feature associated with Modoki events is the decadal flattening of the equatorial thermocline and weakening of zonal thermal gradient. The associated ocean-atmosphere conditions have caused frequent and persistent developments of Modoki events in recent decades.
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Book chapters on the topic "Atmospheric circulation Australia"

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Fleming, James Rodger. "Introduction." In First Woman, 1–9. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198862734.003.0001.

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Joanne Simpson transformed the science of the tropical atmosphere and set a course in science for professional women to follow. She had a lifelong passion for clouds and severe storms, flying into and above them, measuring and modeling them, theorizing about the role of tropical clouds in the planetary circulation, and mentoring a generation of tropical meteorologists. In 1993, just shy of her seventieth birthday, Joanne commandeered a fully equipped NASA-owned DC8 research airplane during a field project to study El Niño, and flew several flights directly into tropical cyclone Oliver in the Coral Sea, some 500 km off the coast of Townsville, Australia. She and the crew did this on several consecutive days. The aircraft was equipped with radar being tested for use on a new satellite to measure tropical rainfall, and they wanted to use it to collect the best possible data on storm structure and dynamics. The third flight, directly into the storm, pushed the plane to its limits. The excessive humidity and turbulent shaking shorted out the experimental electronics and rendered the plane unusable for future missions. NASA was not pleased. Buffeted but invigorated by the successful but totally unauthorized flights, Joanne told the press that she felt fortunate to have seen meteorology develop from the “horse-and-buggy era” to the space age....
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Conference papers on the topic "Atmospheric circulation Australia"

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Babanin, Alexander V. "Wave-Induced Turbulence, Linking Metocean and Large Scales." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18373.

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Abstract Until recently, large-scale models did not explicitly take account of ocean surface waves which are a process of much smaller scales. However, it is rapidly becoming clear that many large-scale geophysical processes are essentially coupled with the surface waves, and those include ocean circulation, weather, Tropical Cyclones and polar sea ice in both Hemispheres, climate and other phenomena in the atmosphere, at air/sea, sea/ice and sea/land interface, and many issues of the upper-ocean mixing below the surface. Besides, the wind-wave climate itself experiences large-scale trends and fluctuations, and can serve as an indicator for changes in the weather climate. In the presentation, we will discuss wave influences at scales from turbulence to climate, on the atmospheric and oceanic sides. At the atmospheric side of the interface, the air-sea coupling is usually described by means of the drag coefficient Cd, which is parameterised in terms of the wind speed, but the scatter of experimental data with respect to such dependences is very significant and has not improved noticeably over some 40 years. It is argued that the scatter is due to multiple mechanisms which contribute into the sea drag, many of them are due to surface waves and cannot be accounted for unless the waves are explicitly known. The Cd concept invokes the assumption of constant-flux layer, which is also employed for vertical profiling of the wind measured at some elevation near the ocean surface. The surface waves, however, modify the balance of turbulent stresses very near the surface, and therefore such extrapolations can introduce significant biases. This is particularly essential for buoy measurements in extreme conditions, when the anemometer mast is within the Wave Boundary Layer (WBL) or even below the wave crests. In this presentation, field data and a WBL model are used to investigate such biases. It is shown that near the surface the turbulent fluxes are less than those obtained by extrapolation using the logarithmic-layer assumption, and the mean wind speeds very near the surface, based on Lake George field observations, are up to 5% larger. The dynamics is then simulated by means of a WBL model coupled with nonlinear waves, which revealed further details of complex behaviours at wind-wave boundary layer. Furthermore, we analyse the structure of WBL for strong winds (U10 > 20 m/s) based on field observations. We used vertical distribution of wind speed and momentum flux measured in Topical Cyclone Olwyn (April 2015) in the North-West shelf of Australia. A well-established layer of constant stress is observed. The values obtained for u⁎ from the logarithmic profile law against u⁎ from turbulence measurements (eddy correlation method) differ significantly as wind speed increases. Among wave-induced influences at the ocean side, the ocean mixing is most important. Until recently, turbulence produced by the orbital motion of surface waves was not accounted for, and this fact limits performance of the models for the upper-ocean circulation and ultimately large-scale air-sea interactions. While the role of breaking waves in producing turbulence is well appreciated, such turbulence is only injected under the interface at the vertical scale of wave height. The wave-orbital turbulence is depth-distributed at the scale of wavelength (∼10 times the wave height) and thus can mix through the ocean thermocline in the spring-summer seasons. Such mixing then produces feedback to the large-scale processes, from weather to climate. In order to account for the wave-turbulence effects, large-scale air-sea interaction models need to be coupled with wave models. Theory and practical applications for the wave-induced turbulence will be reviewed in the presentation. These include viscous and instability theories of wave turbulence, direct numerical simulations and laboratory experiments, field and remote sensing observations and validations, and finally implementations in ocean, Tropical Cyclone, ocean and ice models. As a specific example of a wave-coupled environment, the wave climate in the Arctic as observed by altimeters will be presented. This is an important topic for the Arctic Seas, which are opening from ice in summer time. Challenges, however, are many as their Metocean environment is more complicated and, in addition to winds and waves, requires knowledge and understanding of ice material properties and its trends. On one hand, no traditional statistical approach is possible since in the past for most of the Arctic Ocean there was limited wave activity. Extrapolations of the current trends into the future are not feasible, because ice cover and wind patterns in the Arctic are changing. On the other hand, information on the mean and extreme wave properties is of great importance for oceanographic, meteorological, climate, naval and maritime applications in the Arctic Seas.
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