1,720,960 research outputs found
Spatial and temporal variability of the frequency of extreme daily rainfall regime in the La Plata Basin during the 20th century
Full text linkWe analyzed trends, interdecadal variability, and the quantification of the changes in the frequency of daily rainfall for two thresholds: 0.1 mm and percentile 75th, using high quality daily series from 52 stations in the La Plata Basin (LPB). We observed increases in the annual frequencies in spatially coherent areas. This coherence was more marked in austral summer, autumn, and spring, during which the greatest increases occurred in southern Brazil, especially during extreme events. In winter, the low and middle basins of the Río Uruguay and Río Paraná showed negative trends, some of which were significant. Interdecadal variability is well defined in the region with more pronounced positive jumps west of the basin between 1950 and 2000. This variability was particularly more marked during periods of extreme rainfall in summer, autumn, and spring, unlike in winter when extreme daily rainfall in the lower Rio Paraná basin decreased by up to 60%. The changes in the past century during extreme rainfall produced modifications in the annual rainfall cycle. The annual cycle of both indices was broader during the last period which is mainly explained by the strong decreases in winter.Fil: Penalba, Olga Clorinda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; ArgentinaFil: Robledo, Federico Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentin
Influence of the large-scale climate variability on daily rainfall extremes over Argentina
Full text linkA singular value decomposition (SVD) analysis was performed jointly on the daily intensity of extreme rainfall (DIER) over Argentina and sea surface temperature (SST) anomalies from 17.5∘N?90∘S to describe and understand the influence of the large-scale variability of the SSTs on the regional extreme rainfall events for spring summer, autumn and winter. Three main leading modes were identified in agreement with previous works. Mode 1 activity is strongly related to El Niño-Southern Oscillation (ENSO). Warm anomalies in the central-eastern tropical Pacific and western Indian Ocean induce circulation anomalies extended along the South Pacific and the development of a continental-scale circulation gyre in South America promoting moisture convergence, and in turn favouring DIER positive anomalies, in eastern Argentina. The combined influence of SST anomalies in the tropical Atlantic and western tropical Pacific characterizes Mode 2 activity, which induces an anticyclonic (cyclonic) circulation gyre in southeastern South America promoting anomalous moisture convergence (divergence) and thus positive (negative) DIER anomalies in eastern Argentina in spring and fall (summer and winter). Finally, Mode 3 activity is also influenced by SST anomalies in tropical central-eastern Pacific from winter to summer. The associated teleconnections contribute to the development of a cyclonic circulationmainly influencing southeastern SouthAmerica (SESA) circulation to the north of 30∘S from summer to winter, and further south in spring.Fil: Robledo, Federico Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Vera, Carolina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Penalba, Olga Clorinda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentin
Teleconnections between tropical-extratropical oceans and the daily intensity of extreme rainfall over Argentina
Full text linkA Singular value decomposition (SVD) analysis was performed jointly on the daily intensity of extreme rainfall (DIER) over Argentina and the sea surface temperature (SST) of all the oceans from 17.5 °N to 90 °S in order to identify the large-scale variability of the SSTs related to extreme rainfall, in the period 1962–2005. The main objective of the article is to objectively recognize regions of the tropical and subtropical oceans that could be related with the extreme rainfall over Argentina. Spring is the season that is best represented by the first mode, accounting for up to 45% of the covariance between the DIER and SST. The first SVD mode of spring, summer and autumn presents a pattern of SST relating to the El Nino-Southern Oscillations (ENSO) phenomena with an enhanced DIER in different zones of centre and ˜ east of Argentina. In the second SVD mode of spring and summer, the SST patterns show cold conditions in the tropical and subtropical Atlantic and near Indonesia with an enhancement of the DIER in the centre and east of Argentina. These modes show a significant decadal variability. In the third SVD mode of spring and summer, the SST patterns present warm and cold conditions in the Indian Ocean and the centre and western Pacific Ocean (PO) with decreased rainfall in the northern and eastern portion of Argentina, respectively. This mode shows a significant period of temporal variability of around 14 years. The third mode of autumn presents warm conditions in the tropical Atlantic and the southwest PO with a low DIER in the centre and east of Argentina. This mode also presents temporal variability of around 14 years. The correlation between each mode derived from analysis of SVD and climate indices related with SST were computed.Fil: Robledo, Federico Ariel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Penalba, Olga Clorinda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bettolli, Maria Laura. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Multi‐scale features of the co‐variability between global sea surface temperature anomalies and daily extreme rainfall in Argentina
No full textThe goal of this study is to provide a better understanding of the trends and dominant oscillations characterizing the co-variability between global sea surface temperature (SST) anomalies and daily extreme rainfall in Argentina. A singular value decomposition was performed between daily extreme rainfall monthly index in Argentina and global SST without removing the trends. The three leading modes explain 70.5% of the co-variability, while the two leading modes explain more than 66% of the variability. The two leading modes exhibit significant variability on inter-annual timescales related to tropical Pacific and Indian oceans, and specifically with El Niño–Southern Oscillation and the Indian Ocean Dipole. On decadal timescales, the leading mode activity is related to the Pacific Decadal Oscillation, whereas the second leading mode is associated with the Atlantic Multi-decadal Oscillation (AMO). The third leading mode show co-variability between the SST of the tropical Atlantic and the Indian ocean and extreme rainfall in the eastern-centre of Argentina; this mode distinguishes phases of AMO. In addition, the two leading modes show positive trends, being largely non-linear for leading one. The fact that extreme rainfall changes in Argentina observed in the last decades, are significantly influenced by the combination of the multi-decadal variability and long-term trends associated with the tropical oceans, is valuable knowledge to assess them in the future.Fil: Robledo, Federico Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Vera, Carolina Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Penalba, Olga Clorinda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Instituto Franco-argentino sobre Estudios del Clima y sus Impactos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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
Extreme daily precipitation in Argentina: changes observed in the second half of the twentieth century and association with the tropical ocean surface temperature
Full text linkEsta tesis presenta un estudio de la variabilidad espacio-temporal de la intensidad diaria de precipitación que excede el percentil 75 (DIER75). Este índice permitió evaluar la frecuencia y la intensidad de los extremos diarios de precipitación, explicando el 70% de los acumulados mensuales de lluvia. En el periodo 1962-2005, la región subtropical de Argentina muestra una disminución en el DIER75, en cambio en el centro del país, se registran incrementos en los primeros meses del año. Junio, es el único mes que presenta una señal significativa (disminución) con coherencia espacial, en el centro de Argentina. Asimismo, la región subtropical presenta variabilidades de mayor frecuencia (2 años) que las zonas del centro-este de Argentina (de 3 a 8 años), y hacia el oeste, se evidencian ciclos de variabilidad de entre 10 y 14 años. La tesis avanza en el conocimiento sobre la relación entre la anomalía de temperatura superficial del mar (TSM) de los océanos tropicales y subtropicales y la intensidad de precipitación diaria extrema en la Argentina, con el fin de encontrar las regiones fuentes en los océanos y describir los mecanismos dinámicos asociados a escala planetaria y regional. Se realizó un análisis de descomposición en valores singulares y se identificó que la influencia del Pacífico, ligada al ENOS y Niño Modoki, aquella del Índico, relacionado al IOD, y aquella del Atlántico, asociada al AMO y el TSA, se combinan en los tres primeros modos que resultan del análisis de SVD. Aunque la relación de cada una de las regiones oceánicas identificadas con el DIER75 no es la misma. En especial se encontró que la influencia de las regiones oceánicas tropicales sobre los extremos de precipitación diaria en Argentina, se asocia con diferentes trenes de ondas de Rossby que emanan del Pacífico central y oeste e Índico este en dirección a Sudamérica, que promueven la convergencia o divergencia de humedad en el Sudeste de Sudamérica. Se realizó un trabajo exploratorio con el fin de evaluar cómo la señal global de calentamiento de las TSM repercute en la covariabilidad observada entre las anomalías de TSM y del DIER75 en Argentina. Se encontró que este calentamiento debilita la influencia de la TSM en el Pacífico central asociadas al ENOS, mientras que la asociación se intensifica con los océanos el Indico y el Atlántico tropical.This thesis presents a study of the spatiotemporal variability of extreme daily rainfall in Argentina using a monthly index of daily precipitation intensity based on the 75th percentile (DIER75). The index allowed the evaluation of frequency and intensity of extreme daily rainfall, which accounts for 70% of the monthly accumulated rainfall. In the period 1962-2005, the subtropical region of Argentina shows a decrease in DIER75, while there are increases in the Midwest during the summer months. On the other hand, June is the only month that shows a significant decrease with large spatial coherence in central Argentina. Also, the subtropical region exhibits higher frequency variability (2 years) than those observed over central-eastern Argentina (3 to 8 years), while to the west, cycles of variability are detected between 10 and 14 years. This thesis studied the relationship between the anomaly of sea surface temperature (SST) at the tropical and subtropical oceans and extreme daily rainfall in Argentina. We also explore the dynamical mechanisms associated with regional and global scale. An analysis of singular value decomposition (SVD) was made that shows that a combined influence of the Pacific (linked to ENSO, Niño Modoki) the Indian Ocean (related to the IOD), and the Atlantic (associated with the AMO and the TSA), influence the variability the three leading modes resulting from the SVD analysis. Although, the influence of each identified ocean region over the DIER75 activity is not the same. Moreover, it was found that the influence of tropical ocean regions on the extremes of daily precipitation in Argentina is associated with Rossby wave trains emanating from the central and western Pacific and Indian Oceans extending towards South America, promoting the convergence or divergence of moisture in southeastern South America. Exploratory work was carried out on how global warming signal as described by global SSTs affects the observed covariability between SST anomalies and DIER75 in Argentina. We found that global warming weakens the influence of SSTs in the central Pacific associated with ENSO. Conversely, the magnitude of the correlations with the tropical Indian and Atlantic intensify.Fil:Robledo, Federico Ariel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
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
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