1,720,958 research outputs found
Assessing storm surge model performance: what error indicators can measure the model's skill?
Get PDFA well-validated storm surge numerical model is crucial, offering precise coastal hazard information and serving as a basis for extensive databases and advanced data-driven algorithms. However, selecting the best model setup based solely on common error indicators like the root-mean-square error (RMSE) or Pearson correlation does not always yield optimal results. To illustrate this, we conducted 34-year high-resolution simulations for storm surge under barotropic (BT) and baroclinic (BC) configurations using atmospheric data from ERA5 and a high-resolution downscaling of the Climate Forecast System Reanalysis (CFSR) developed by the University of Genoa (UniGe). We combined forcing and configurations to produce three datasets: (1) BT-ERA5, (2) BC-ERA5, and (3) BC-UniGe. The model performance was assessed against nearshore station data using various statistical metrics. While RMSE and Pearson correlation suggest BT-ERA5, i.e., the coarsest and simplest setup, is the best model (followed by BC-ERA5), we demonstrate that these indicators are not always reliable for performance assessment. The most sophisticated model (BC-UniGe) shows worse values of RMSE or Pearson correlation due to the so-called "double penalty" effect. Here we propose new skill indicators that assess the ability of the model to reproduce the distribution of the observations. This, combined with an analysis of values above the 99th percentile, identifies BC-UniGe as the best model, while ERA5 simulations tend to underestimate the extremes. Although the study focuses on the accurate representation of storm surge by the numerical model, the analysis and proposed metrics can be applied to any problem involving the comparison between time series of simulation and observation
Análisis de la transferencia de oleaje producida en diferentestipologías de arrecife de coral en Recife (Brasil)
Get PDFABSTRACT: The coastal zone is one of the most dynamic, complex and productive systems that can be found in natural environments. These sectors favor the concentration of urban settlements, mainly due to industrial, fishing, tourism and transportation productivity. Specifically in Brazil, approximately 20% of the population is found in coastal municipalities and due to its location in the neotropical biogeographic region, its coastal zone is characterized by having varied ecosystems and natural environments, such as atolls, reefs, algae banks, estuaries, marshes, mangroves, among others. Ecosystems such as coral reefs have the ability to act as natural protection in the event of extreme waves, but strong urban pressure and climate change can degrade these environments, potentially causing a decrease in the protection service.
Based on information from bathymetric profiles, hydrodynamic conditions measured in the field and maritime climate databases at depths waters, in this work an analysis of wave transfer has been carried out in fringing and platform coral reef profiles, using the IH2VOF model. In the first place, field measurements (from Costa et al. (2015)) have been used to validate the performance of the detail model, obtaining that it manages to represent the waves transferred along the profiles under study, both for mean and storm conditions. Additionally, within the validation process the influence of infragravitational wave has been analyzed through the generation of irregular waves with secondorder components, obtaining that this type of waves is of greater importance in the fringing reef, which is mainly due to breaking wave process on the crest of the reef, dissipating the energy of short waves (low periods).
Subsequently, in order to characterize the energy transmission coefficient in the current maritime climate conditions, a description of mean and extreme conditions of the maritime climate in the area at depth water has been made. Thus, a set of sea states have been selected that have been propagated in front of the coral reef profiles. The results of this wave propagation process are used as initial conditions to carry out simulations with the IH2VOF, that allow obtaining the wave height transmitted in the fringing and platform reefs. In this way, the transmission coefficients for the current maritime climate conditions are determined. The analysis of the transmission coefficient under current conditions indicates that the two typologies considered have the capacity to attenuate the height of the incident wave. The fringing reef provides a greater protection service, being able to decrease the wave height by up to 94% at times of low tide, while the platform reef produces a maximum attenuation of 69% under the same conditions. The differences mentioned are mainly due to the fact that the fringing reef has a higher elevation at its crest, which causes the break of the waves at that point, while in the platform reef the dissipation of energy occurs as the waves propagates across the profile.
Finally, with the aim of evaluating the effects of climate change on transmission coefficients in the future, effects of an increase in mean sea level and a decrease in the elevation of the crest of the reefs have been incorporated, making new propagations for a storm condition and obtaining the variations of the transmission coefficient through simulations carried out with the IH2VOF. The results indicate that, when considering these two scenarios together, the wave height transmission coefficient increases by 40% in the fringing reef and by 69% in the platform reef. Furthermore, the values of the transmission coefficient under these scenarios cannot be described by the linear regression adjustment carried out for the current conditions, so it is considered that they must be analyzed independently to obtain adjustments that allow predicting future variations with a greater precision.RESUMEN: La zona costera es uno de los sistemas más dinámicos, complejos y productivos que se pueden encontrar en los ambientes naturales. Estos sectores favorecen la concentración de asentamientos urbanos, debido principalmente a la productividad industrial, pesquera, turismo y transporte. Específicamente en Brasil, aproximadamente el 20% de la población se encuentra en municipios costeros y debido a su ubicación en la región biogeográfica neotropical, su zona costera se caracteriza por poseer variados ecosistemas y ambientes naturales, como atolones, arrecifes, bancos de algas, estuarios, marismas, manglares, entre otros. Ecosistemas como arrecifes de coral tienen la capacidad de actuar como obras de protección naturales ante episodios de oleaje extremo, pero la fuerte presión urbana y el cambio climático pueden degradar estos ambientes, pudiendo provocar una disminución en el servicio de protección.
Con base en información de perfiles batimétricos, condiciones hidrodinámicas medidas en campo y bases de datos de clima marítimo en profundidades indefinidas en este trabajo se ha llevado a cabo un análisis de la transferencia de oleaje en perfiles de arrecife de coral tipo franja y plataforma, mediante el modelo IH2VOF. En primer lugar, las mediciones de campo (provenientes de Costa et al. (2015)) han sido utilizadas para validar el desempeño del modelo de detalle, obteniendo que éste logra representar el oleaje transferido a lo largo de los perfiles en estudio, tanto para condiciones medidas como de tormenta. Adicionalmente, dentro del proceso de validación se ha analizado la influencia de onda infragravitatoria mediante la generación de oleaje irregular con componentes de segundo orden, obteniendo que este tipo de ondas tiene mayor importancia en el arrecife tipo franja, lo que se debe principalmente a la rotura de oleaje en la cresta del arrecife, lo que disipa la energía de olas cortas (bajos periodos). Posteriormente, con el objetivo de caracterizar el coeficiente de transmisión de energía en las condiciones de clima marítimo actuales, se ha realizado una descripción de condiciones medias y extremas del clima marítimo en la zona en profundidades indefinidas. Así, se han seleccionado un conjunto de estados de mar que han sido propagados frente a los perfiles de arrecife de coral. Los resultados de este proceso de propagación del oleaje son utilizados como condiciones iniciales para la realización de simulaciones con el IH2VOF, que permiten obtener la altura de ola transmitida en los arrecifes tipo franja y plataforma. De esta forma, se determinan los coeficientes de transmisión para las condiciones de clima marítimo actuales.
El análisis del coeficiente de transmisión en condiciones actuales indica que las dos tipologías consideradas tienen capacidad para atenuar la altura de ola incidente. El arrecife tipo franja presta un mayor servicio de protección, pudiendo disminuir la altura de ola hasta en un 94% en instantes de bajamar, mientras que el arrecife plataforma produce una atenuación máxima del 69% bajo las mismas condiciones. Las diferencias mencionadas se deben principalmente a que el arrecife tipo franja posee una mayor elevación en su cresta, lo que produce la rotura del oleaje en dicho punto, mientras que en el arrecife tipo plataforma la disipación de la energía se produce a medida que el oleaje recorre el perfil.
Finalmente, con el objetivo de evaluar los efectos del cambio climático en los coeficientes de transmisión en el futuro, se han incorporado efectos de aumento del nivel medio del mar y la disminución en la elevación de la cresta de los arrecifes, realizando nuevas propagaciones frente a los perfiles para una condición de oleaje de tormenta y obteniendo las variaciones del coeficiente de transmisión mediante simulaciones realizadas con el IH2VOF. Los resultados indican que, al considerar estos dos escenarios de forma conjunta, el coeficiente de transmisión de altura de ola aumenta en un 40% en el arrecife franja y en un 69% en el arrecife plataforma. Además, los valores del coeficiente de transmisión bajo estos escenarios no logran ser descritos mediante el ajuste por regresión lineal realizado para las condiciones actuales, por lo que se considera que deben ser analizados de forma independiente para lograr obtener ajustes que permitan predecir variaciones futuras con una mayor precisión.Máster en Ingeniería costera y portuari
Análisis de marejadas históricas y recientes en las costas de Chile.
No full textLas marejadas son fenómenos que afectan frecuentemente las costas de Chile causando sobrepasos, cese de operaciones portuarias, daños a infraestructura costera, naufragios, lesiones y pérdida de vidas humanas. Conocer la información sobre las características oceanográficas, comportamiento de largo plazo, efectos y costos producidos por estos eventos extremos es de suma importancia para planificar futuras inversiones en infraestructura costera. En este estudio se entrega una recopilación exhaustiva en medios de prensa, publicaciones y organismos públicos de eventos de marejadas ocurridos en Chile a partir del año 1823. Con base a la información de eventos de marejadas proporcionada por la Armada de Chile, se realizaron búsquedas en prensa digital y archivos de periódicos de la Biblioteca Nacional de Chile y la Biblioteca Santiago Severín sobre los daños provocados por eventos de marejadas para las zonas costeras entre las regiones XV y XIV, entre los años 1979 y 2015. La cantidad de eventos anuales identificados fueron comparados con índices de las oscilaciones climáticas El Niño-Oscilación del Sur y el Modo Anular del Sur, obteniendo que los años en los cuales se supera la cantidad promedio de eventos anuales, están ligados a las fases positivas de las oscilaciones climáticas consideradas. Se analizaron daños, costos y parámetros oceanográficos asociados, identificando que los daños son mayores para marejadas de períodos y direcciones medias que se encuentran sobre el promedio de largo plazo de dichos parámetros, y, que marejadas de relativamente baja altura significativa tienen una incidencia importante en los daños registrados. Se propone una escala de magnitud de intensidad de daños por marejadas, la cual permite categorizar los eventos en base al nivel de daño registrado. Finalmente, se analizaron los comportamientos de largo plazo de los parámetros de oleaje y de los eventos identificados, obteniendo una tendencia al aumento del valor de la altura significativa y disminución de la dirección de incidencia del oleaje. De mantenerse este comportamiento, dentro de los próximos 100 años se producirían aumentos de 30 [cm] en la altura significativa y disminuciones de 20,5 [°] en la dirección media del oleaje. Adicionalmente, la cantidad anual de eventos de marejadas con registro de daños también presenta un aumento a lo largo del tiempo
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
Evaluación de caudal de sobrepaso en una defensa costera mediante un modelo basado en las ecuaciones de Navier-Stokes promediadas por Reynolds en el volumen (VARANS)
Get PDFThe calibration of the IH2VOF numerical model and a sensitivity analysis of wave overtopping in a coastal defense are presented in this study. Physical model tests are replicated at a reduced scale of 1:50 in the main breakwater of the port of Pòvoa de Varzim, Portugal (Neves et al., 2008). The parameters used in the calibration correspond to porosity, linear and non-linear friction coefficients characterizing a porous media, which in our model represent the defense’s armor and filter. For irregular waves and first-order generation in the numerical wavemaker (i.e., considering only waves as a boundary condition), overtopping is practically insensitive to the range of values used for the friction parameters, due to the relatively small volume of coastal defense. Porosity, in contrast, plays a significant role in the computation of overtopping. Once these parameters have been calibrated, the tests are repeated using a second-order generation, which incorporates both waves and the infragravity waves accompanying the former. Results show that the first-order generation overestimates the overtopping, especially in more intense wave conditions. For the second-order generation, results correspond fairly well with those reported by Neves et al. (2008). Finally, we recommend the use of secondorder generation both in the numerical and physical modelling of wave overtopping on coastal defenses to avoid unnecessarily conservative designs.En este trabajo se expone el proceso de calibración del modelo numérico IH2VOF y un análisis de sensibilidad del caudal de sobrepaso en una defensa costera. Para efectuar estos trabajos, se replican los ensayos de un modelo físico a escala reducida de 1:50 en el rompeolas principal del puerto de Pòvoa de Varzim, Portugal (Neves et al., 2008). Los parámetros analizados en el proceso de calibración corresponden a la porosidad y los coeficientes de fricción lineal y no-lineal , que caracterizan a los medios porosos. Para ensayos con oleaje irregular y generación de oleaje de primer orden, que incorpora sólo la banda espectral asociada al oleaje como condición de borde, los parámetros de fricción no tienen una gran incidencia en el cálculo del sobrepaso, pues actúan sobre un volumen relativamente pequeño de defensa costera. La porosidad, en contraste, juega un rol no despreciable en los resultados. Una vez calibrados estos parámetros, se repiten los ensayos usando un forzamiento de segundo orden, que incorpora tanto la banda del oleaje como las ondas infragravitatorias asociadas a los grupos de olas. Los resultados muestran que la generación de primer orden sobrestima el caudal de sobrepaso, lo que se hace más evidente para condiciones de oleaje de mayor intensidad. Para el forzamiento de segundo orden, en contraste, se obtienen resultados cercanos a los reportados por Neves et al. (2008). Finalmente, se recomienda utilizar el forzamiento de segundo orden tanto en la modelación numérica como física del sobrepaso de oleaje para evitar el sobredimensionamiento injustificado de defensas costeras
Developments in machine learning downscaling for storm surge in the northern Adriatic sea
No full textAccurate storm surge prediction is essential for coastal resilience and hazard mitigation, particularly as climate change increases the frequency and intensity of extreme events. While Machine Learning (ML) models have shown promise for downscaling storm surge predictions, they are often under-evaluated against high-resolution dynamical models and rarely tested on extreme conditions. This study addresses these limitations by integrating advanced dynamical modeling with ML approaches to evaluate storm surge prediction in the Northern Adriatic Sea. High-resolution simulations were developed using the SHYFEM hydrodynamic model with optimized configurations and high-quality forcing datasets. This provided a robust benchmark for assessing the performance of ML models ranging from simple Multivariate Linear Regression (MLR) to more complex Long Short-Term Memory (LSTM) networks. To improve model evaluation, a novel corrected mean absolute deviation (MADc) metric and a custom loss function (MADc2) were introduced, targeting improved performance on extreme events. Results show that while MLR offers computational efficiency, it lacks the ability to capture non-linear dynamics and extremes. In contrast, LSTM networks performed significantly better, particularly when trained using the MADc2 loss function. Training ML models on the output of the dynamical model led to strong consistency with observations, while direct training on tide gauge data at key locations (e.g., Punta della Salute and Trieste) revealed that some ML models could outperform the dynamical model in critical metrics. These findings highlight the potential of ML models, especially LSTM networks, as efficient and accurate alternatives to traditional numerical approaches. Given their lower computational demands and strong performance, ML techniques hold significant promise for operational storm surge forecasting, particularly in data-rich contexts or where computational resources are limited
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
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