1,720,959 research outputs found
Understanding Convective Organization and Seeking it Through Observations
No full textThis study pursues two main objectives: firstly, to unravel the sensitivity of convective self-aggregation (SA) to diverse physical parameterizations, and secondly, to comprehend the characteristics of convective organization in observations, shedding light on associated physical mechanisms. Studying organization is of profound significance due to its impact on the radiation budget, climate feedbacks, hydrological cycle, and extreme precipitation patterns, impacting society and climate. Addressing the first objective, radiative-convective equilibrium simulations explore the effects of 24 parameterization combinations on aggregated and random convective patterns. Key to our analysis is understanding the role of maximum free convection distance dclr, found crucial for SA, and its modulation by parameterizations. SA predominantly emerges in scenarios with limited convective cores and extensive dclr values (since they are anticorrelated), influenced by sub-grid scale mixing, planetary boundary layer (PBL), and microphysics. Horizontal mixing primarily influences SA by determining the size of convective cores, which is tight to their number and spacing. On the other hand, the influence of microphysics primarily stems from rain evaporation and its subsequent effects on CPs. Surprisingly, perturbations to ice cloud microphysics had a notably limited effect. Non-local PBL mixing schemes enhance SA by reducing PBL heights and increasing entrainment at the PBL top, facilitated by stronger vertical moisture gradients. This heightened entrainment to the CPs gust fronts, diminishing CPs sizes and intensities. This reduction hampers efficient moisture redistribution and convective triggering, as strong entrainment limits gust front convergence, constraining convective initiation, increasing dclr and fostering the formation of dry patches that drive SA. For our second objective, we move beyond idealized models, utilizing state-of-the-art observations, reanalysis data, advanced numerical models, and machine learning techniques. Applying multivariate analysis typically used for SA, we examine convective organization and its impact on total column water vapor variability in three mesoscale sized domains within the tropical western Pacific warm pool region, lying either north of the equator (2-9N or 3-10N), or directly straddling the equator 3S-4N). During periods with limited SST gradients (boreal summer/autumn), convection tends to be random, with small horizontal humidity gradients. In periods with a weak zonal SST gradient (> 10^-3 K/km, boreal winter/spring), aggregated convection prevails, exhibiting larger humidity gradients, stronger outgoing longwave radiation, and a drier atmosphere. Intermittent episodes of random convection and smaller humidity gradients disrupt this pattern. A composite analysis of such events associates them with westward propagating convectively coupled wave-like modes in the three regions, suggesting these modes play a key role in mesoscale water vapor variability during boreal winter and spring, potentially influencing long-term variations in convective organization. To further understand the mechanisms that lead and prevent the development of convection organization. Our study leverages on realistic simulations, underscoring the important role of humidity advection in orchestrating the organization and disorganization of convection, with wind shear playing a dual role in either organizing or disorganizing convection, contingent on its strength and direction. In terms of its characteristics, when convection is organized, the atmosphere is significantly drier compared to the random state. Diabatic feedbacks consistently works to cluster convection, but large-scale dynamics play a more important role in instigating and disrupting organization over the warm pool region, since the large-scale dynamics can export moist gross static energy from moist to dry regions, disallowing organization.This study pursues two main objectives: firstly, to unravel the sensitivity of convective self-aggregation (SA) to diverse physical parameterizations, and secondly, to comprehend the characteristics of convective organization in observations, shedding light on associated physical mechanisms. Studying organization is of profound significance due to its impact on the radiation budget, climate feedbacks, hydrological cycle, and extreme precipitation patterns, impacting society and climate. Addressing the first objective, radiative-convective equilibrium simulations explore the effects of 24 parameterization combinations on aggregated and random convective patterns. Key to our analysis is understanding the role of maximum free convection distance dclr, found crucial for SA, and its modulation by parameterizations. SA predominantly emerges in scenarios with limited convective cores and extensive dclr values (since they are anticorrelated), influenced by sub-grid scale mixing, planetary boundary layer (PBL), and microphysics. Horizontal mixing primarily influences SA by determining the size of convective cores, which is tight to their number and spacing. On the other hand, the influence of microphysics primarily stems from rain evaporation and its subsequent effects on CPs. Surprisingly, perturbations to ice cloud microphysics had a notably limited effect. Non-local PBL mixing schemes enhance SA by reducing PBL heights and increasing entrainment at the PBL top, facilitated by stronger vertical moisture gradients. This heightened entrainment to the CPs gust fronts, diminishing CPs sizes and intensities. This reduction hampers efficient moisture redistribution and convective triggering, as strong entrainment limits gust front convergence, constraining convective initiation, increasing dclr and fostering the formation of dry patches that drive SA. For our second objective, we move beyond idealized models, utilizing state-of-the-art observations, reanalysis data, advanced numerical models, and machine learning techniques. Applying multivariate analysis typically used for SA, we examine convective organization and its impact on total column water vapor variability in three mesoscale sized domains within the tropical western Pacific warm pool region, lying either north of the equator (2-9N or 3-10N), or directly straddling the equator 3S-4N). During periods with limited SST gradients (boreal summer/autumn), convection tends to be random, with small horizontal humidity gradients. In periods with a weak zonal SST gradient (> 10^-3 K/km, boreal winter/spring), aggregated convection prevails, exhibiting larger humidity gradients, stronger outgoing longwave radiation, and a drier atmosphere. Intermittent episodes of random convection and smaller humidity gradients disrupt this pattern. A composite analysis of such events associates them with westward propagating convectively coupled wave-like modes in the three regions, suggesting these modes play a key role in mesoscale water vapor variability during boreal winter and spring, potentially influencing long-term variations in convective organization. To further understand the mechanisms that lead and prevent the development of convection organization. Our study leverages on realistic simulations, underscoring the important role of humidity advection in orchestrating the organization and disorganization of convection, with wind shear playing a dual role in either organizing or disorganizing convection, contingent on its strength and direction. In terms of its characteristics, when convection is organized, the atmosphere is significantly drier compared to the random state. Diabatic feedbacks consistently works to cluster convection, but large-scale dynamics play a more important role in instigating and disrupting organization over the warm pool region, since the large-scale dynamics can export moist gross static energy from moist to dry regions, disallowing organization
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
Tropospheric ozone prediction in Bogotá: a machine learning approach
No full textilustraciones, diagramasEl ozono troposférico es una preocupación ambiental que tiene repercusiones tanto en la salud humana como en los ecosistemas, aún más, cuando su producción depende directamente de factores tanto ambientales como antropogénicos. En los últimos años, en Bogotá, el ozono ha tenido una tendencia de aumento en su concentración. Por ello, es imperativo estudiar la razón por la cual este incremento se está presentando, así como realizar avances en modelos que permitan realizar alertas tempranas y reducir el riesgo. La predicción es crucial para concientizar sobre la salud pública y la implementación de estrategias de gestión de la calidad del aire. Se realiza un estudio general del comportamiento y evolución del ozono (O3) en las diferentes zonas de Bogotá. Este proyecto tiene como objetivo diseñar un modelo predictivo de aprendizaje automático (machine learning) de los niveles de O3 en Bogotá utilizando datos de la Red de Monitoreo de Calidad del Aire de Bogotá (RMCAB), incluyendo mediciones de precursores de ozono y variables meteorológicas. Los modelos de aprendizaje automático utilizados fueron redes convolucionales y capas de memoria bireccional a largo plazo (LSTM) de la biblioteca Tensor Flow Keras y el paquete Python Sklearn, para facilitar la categorización de técnicas de inteligencia artificial. Esto da como resultado un modelo que destaca por su capacidad de ofrecer pronósticos altamente precisos al considerar y cuantificar la influencia de los precursores. Los resultados del modelo determinaron una correlación de Spearman mayor a 0.6, la raíz del error cuadrático medio se mantuvo por debajo de 10 µg/m³ en todos los casos y el Índice de Ajuste superó el valor de 0.5 en todos los casos, categorizados como bueno, excelente y bueno respectivamente, lo cual sugiere que el modelo replica con precisión y exactitud el comportamiento y la tendencia del ozono. Se espera que la metodología aplicada sirva como referencia para continuar con la predicción de otros contaminantes atmosféricos de interés y de esta forma dar apoyo a la toma de decisiones que permitan minimizar los impactos ambientales enfocados a la calidad del aire. (Texto tomado de la fuente).Tropospheric ozone is an environmental concern has repercussions on both human health and ecosystems, even more so when its production depends directly on both environmental and anthropogenic factors. In recent years, in Bogotá, ozone has had a trend of increasing concentration. Therefore, it is imperative to study the reason why this increase is occurring, as well as make advances in models that allow early warnings and risk reduction. The prediction is crucial for public health awareness and implementation of air quality management strategies. A general study of the behavior and evolution of ozone (O3) in the different areas of Bogotá is carried out. This project aims to create a predictive machine learning model for ozone levels in Bogotá using data from the air quality monitoring network, including measurements of O3 precursors and meteorological variables. Machine learning models used were Convolutional Networks and Birectional Long Short-Term Memory (LSTM) layers from the Tensor Flow Keras library, and the Python package Sklearn, to facilitate the categorization of artificial intelligence techniques. This results in a model that stands out for its ability to offer highly accurate forecasts by considering and quantifying the influence of precursors. The results of the model determined a Spearman correlation greater than 0.6, the root mean square error remained below 10 µg/m³ in all cases and the Fit Index exceeded the value of 0.5 in all cases, categorized as good , excellent and good respectively, which suggests that the model accurately and precisely replicates the behavior and trend of ozone. It is expected that the applied methodology will serve as a reference to continue with the prediction of other atmospheric pollutants of interest and in this way provide support for decision-making that allows minimizing environmental impacts focused on air quality.MaestríaMagíster en Ingeniería - Ingeniería AmbientalCalidad del air
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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