1,721,180 research outputs found
Ocean response to the March 1997 Westerly Wind Event
No full textAn Ocean General Circulation Model is used to investigate the oceanic response to the March 1997 Westerly Wind Event that is suggested to have played an important role in the onset of the 1997–1998 El Niño. Our results point out three distinct impacts. First a strong wind-forced downwelling Kelvin wave propagates eastward generating sea surface temperature anomalies up to 1°C and large subsurface temperature and zonal current anomalies, mainly located in the core of the thermocline. Second the northward and westward extension of this wind event is responsible for a surface advection of cold waters from 130°E–5°N to the equator. Third it generates large zonal surface currents at the eastern edge of the warm and fresh pool by a nonlinear interaction between the wind-forced surface jet and the local thermohaline front. Salinity through both its contribution to the local zonal pressure gradient at the front and the barrier layer effect is crucial in the occurrence of this nonlinear mechanism. The fast displacement of the front (2000 km in a month) together with the cooling in the western Pacific is likely to be responsible for the eastward displacement of atmospheric deep convection and eastward winds observed in April–June 1997 and thus to have played a major role in initiating the El Niño of the century. <br/
Remote sensing and numerical modeling of the oceanic mixed layer salinity in the Bay of Bengal
No full textLe Golfe du Bengale (GdB), dans l'océan indien Nord, est sous l'influence d'intenses vents de mousson, qui se renversent saisonnièrement. Les fortes pluies et les apports fluviaux associés à la mousson de Sud-Ouest font du GdB l'une des régions les moins salées des océans tropicaux. La forte stratification haline proche de la surface qui en découle contribue à limiter le mélange vertical, ce qui maintient des températures de surface élevées et favorise la convection atmosphérique et les pluies. Cette stratification en sel a ainsi des implications profondes sur les échanges air-mer et sur le climat des pays riverains. L'objectif de ma thèse est d'améliorer la description de la variabilité de la salinité de surface (SSS) du GdB, et de comprendre ses mécanismes aux échelles de temps saisonnières à interannuelles. Les climatologies existantes ont permis de mettre en évidence un cycle saisonnier marqué de la SSS, avec un dessalement intense de la partie Nord du bassin pendant l'automne, suivi par une expansion de ces eaux dessalées le long du bord Ouest du bassin. Cette langue dessalée s'érode finalement pendant l'hiver, pour revenir à son extension minimale au printemps. Cependant, la rareté des observations in-situ de SSS ne permet d'observer les fluctuations interannuelles autour de ce cycle saisonnier que de manière parcellaire dans le GdB. Le développement récent de la télédétection spatiale de la SSS (missions SMOS et AQUARIUS) a ouvert de nouvelles opportunités à cet égard. Cette technologie reste toutefois délicate dans le cas d'un bassin de petite taille tel que le GdB, du fait des contaminations éventuelles du signal de SSS par les interférences radio et par les sources d'origine continentale. Une validation systématique des produits satellites par comparaison à un jeu de données in-situ exhaustif montre qu'Aquarius capture de façon réaliste les évolutions saisonnières et interannuelles de la SSS partout dans le GdB. A l'inverse, SMOS ne parvient pas à restituer une salinité meilleure que les climatologies existantes.Located in the Northern Indian Ocean, the Bay of Bengal (BoB) is forced by intense seasonally reversing monsoon winds. Heavy rainfall and strong river runoffs associated with the southwest monsoon makes the bay one of the freshest regions in the tropical ocean. This surface fresh water flux induces strong near surface salinity stratification, which reduces vertical mixing and maintains high sea surface temperatures and deep atmospheric convection and rainfall. This intense near surface haline stratification has therefore profound implications on the air-sea exchanges, and on the climate of the neighboring countries. The goal of my thesis is to improve the description of the Sea surface salinity (SSS) variability in the BoB and to understand the oceanic and atmospheric processes driving this variability at seasonal and interannual timescales. Existing climatologies reveal a marked seasonal cycle of SSS with an intense freshening of the northern part of the basin during fall that subsequently spreads along the western boundary. This fresh pool finally erodes during winter, to reach its minimal extent in spring. The paucity of in-situ SSS observations however prevented to monitor the interannual fluctuations around this seasonal picture with a good spatial coverage. The recent development of SSS remote-sensing capabilities (with SMOS and AQUARIUS satellites) may help with that regard. However this is particularly challenging for a small semi-enclosed basin such as the Bay of Bengal, because of the potential contamination of the SSS signal by radio frequency interferences and land effects in the near coastal environment. A thorough validation of these satellite products to an exhaustive gridded in-situ dataset shows that Aquarius reasonably captures the large-scale observed seasonal and interannual SSS evolution everywhere in the BoB while SMOS does not perform better than existing climatologies, advocating for improvements of its SSS retrieval algorithm there
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The influence of equatorial pacific westerly wind events on El Niño : atmospheric origins and oceanic impacts
No full textLes coups de vent d’ouest (WWEs) issu de la variabilité synoptique atmosphérique jouent un rôle crucial dans les irrégularités d’ENSO en contribuant au déclenchement et au développement de sa phase chaude, El Niño. Les WWEs sont des événements haute fréquence peu prévisibles et dont les origines atmosphériques restent encore débattues. Dans le but d’affiner la prévisibilité d’ENSO, cette thèse caractérise la part stochastique de la part prévisible des WWEs ainsi que de leur réponse océanique et couplée. Dans une première partie, j’ai relié l’occurrence et les caractéristiques des coups de vent à des phénomènes de grande échelle comme l'oscillation de Madden-Julian, les ondes de Rossby atmosphériques et ENSO, à partir d’analyse d’observations. Ensuite, la forte sensibilité de la réponse océanique des WWEs à l’état de l’océan a été mise en évidence grâce à une série de simulations océaniques forcées. Finalement, une simulation d’ensemble réalisée avec un modèle couplé océan-atmosphère a permis d'explorer le rôle des WWEs dans l’évolution contrastée des années 1997,2014 et 2015 qui présentaient des conditions similaires et favorables au déclenchement d'El Niño. Les résultats de ce travail montrent que la stochasticité des WWEs aboutit à une limitation intrinsèque de la prévisibilité des caractéristiques d’El Niño.Equatorial Pacific Westerly Wind Events (WWEs) impact ENSO evolution through their oceanic response and strongly contribute to its irregularities. WWEs are characterized by episodes of anomalous, short-lived, strong westerlies developing over the western Pacific warm pool. This thesis characterize the atmospheric origins and the oceanic and coupled impacts of these events in order to improve ENSO prediction. First, we show that, at intraseasonnal timescale, the Madden-Julian oscillation and the convectively coupled Rossby waves provide favourable conditions for the occurence of WWEs and confirm their modulation by ENSO at interannual timescale. Oceanic simulation with idealized forcing further allow characterizing and understanding the modulation of the SST response to WWE by the oceanic background state. Finally, The role of WWEs in the contrasted evolution of El Niño in 1997,2014 and 2015, which exhibited favourable conditions for El Niño to develop, is explored in ensemble simulations using a coupled ocean-atmosphere model. It is shown that the stochasticity of the WWEs acts as a strong limitation for ENSO predictability
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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