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Influenza della densità della rete di pluviografi sulla modellazione idrologica delle piene. Analisi statistica attraverso campi di pioggia sintetici su bacini di differente dimensione e confronto con un caso reale
No full textAl fine di creare uno scenario di controllo non condizionato da errori di misura e di modellazione, è stata assunta come precipitazione di riferimento, un campo di precipitazione ad alta risoluzione spaziale e temporale (1.5 km x 1.5 km x 5 minuti, di durata pari a 80 anni) ottenuto attraverso un processo di downscaling, mentre come portata di riferimento è stato assunto il corrispondente idrogramma ottenuto attraverso due modelli afflussi-deflussi. Al fine di studiare la sensibilità della risposta idrologica in relazione alla densità della rete pluviografica, è stato supposto che la serie storica di pioggia estratta da una singola cella (1.5 km x 1.5 km) sia equivalente alla registrazione effettuata da un potenziale pluviografo fittizio, ed è stato considerato un numero variabile di potenziali pluviografi, distribuiti casualmente fra i punti del grigliato. Quindi per estensioni della rete variabili da 1 a 30 pluviografi (per ciascun bacino considerato), sono stati selezionati in modo casuale 100 combinazioni spaziali indipendenti di pluviografi, ottenendo altrettanti scenari di campi di precipitazione, che utilizzati come input dei due modelli afflussi-deflussi hanno consentito di realizzare 100 corrispondenti scenari di portata.
La qualità dei risultati è stata valutata confrontando gli scenari di portata (ottenuti attraverso un numero limitato di pluviografi) con la portata di riferimento (ottenuta attraverso l’intero campo di precipitazione ad alta risoluzione) applicando differenti metriche. Un’analisi critica dei vantaggi dell’utilizzo della modellazione distribuita rispetto a quella a parametri concentrati è stata eseguita considerando: variabilità delle performance dei modelli in relazione al numero di pluviografi utilizzati; relazione tra le performance dei modelli e l’entità dell’evento meteorico; numero minimo di pluviografi necessari per ottenere una risposta idrologica soddisfacente di ciascun modello e relazione con l’entità dell’evento; dipendenza rispetto alla dimensione del bacino.
Osservando la figura 1 possono essere illustrati alcuni dei risultati ottenuti. In particolare si nota come il numero minimo di pluviografi necessario a raggiungere un valore soddisfacente dell’efficienza di Nash Sutcliffe sia fortemente dipendente dall’entità dell’evento, questo comportamento è più accentuato per il modello a parametri concentrati. Con entrambi i modelli le simulazioni risultano migliori, a parità di pluviografi, per gli eventi di maggiore entità. Il modello a parametri concentrati presenta inoltre una marcata dipendenza con la dimensione del bacino, mentre il modello distribuito non ne risulta significativamente influenzato. In conclusione è importante notare che anche in bacini di piccole dimensioni sono necessari non meno di 5 pluviografi affinché il 50% degli eventi possa essere modellato con un’efficienza pari o maggiore di 0.5.
Infine è stato studiato un caso reale di 2 piccoli bacini provvisti di serie sufficientemente lunghe di osservazioni di precipitazione ad alta risoluzione (5 minuti) e di corrispondenti misure di portata. In particolare sono state valutate le performance dei due modelli afflussi-deflussi, confrontando la portata osservata con gli idrogrammi prodotti considerando le possibili combinazioni di pluviografi esistenti. Sebbene l’analisi sia limitata ad un numero massimo di tre pluviografi, risultano confermati i risultati ottenuti attraverso lo scenario sintetico sopra descritto
Influence of rain gauge network density on flood model prediction: a statistical investigation using synthetic rainfall fields on basins of different size and a comparison with a real case
No full textThe accuracy of simulation of the catchment hydrologic response is strongly affected by the reliable representation of the spatial rainfall pattern. The present work investigates the role of rainfall sampling and network density on the performance of a lumped and a distributed rainfall-runoff model in predicting extreme floods. The analysis is conducted on a suite of 12 basins of different size ranging from 15 to 1793 km2 , located in Sardinia, Italy.
In order to create a reference framework uncorrupted by errors of measure and of modelling, we assume as reference precipitation an high resolution rainfall field (1.5 km x 1.5 km x 5 min, 80 years long) derived through a downscaling procedure, and as reference discharge the corresponding hydrograph obtained by the two rainfall-runoff models. In order to investigate the sensitivity of the hydrological response to the rain gauge network density we assume that a rainfall series from a single cell (1.5 km x 1.5 km) is equivalent to a potential fictitious rain gauge record and consequently we activate a number of potential gauges ranging from 1 up to 30 (for each considered basin). Then for each fixed network size, we randomly select 100 independent spatial combinations of rain gauge positions providing the rainfall pattern scenarios which are used as input of the two rainfall-runoff models to produce an ensemble of 100 corresponding discharge scenarios.
Performances are evaluated by comparing the discharge scenarios (obtained by a limited number of potential rain gauges) with the reference discharge (obtained by the entire high resolution rainfall fields) and applying different metrics. A critical analysis of the advantage of using distributed vs lumped modelling is performed considering: model performance variability related to the number of rain gauges; model performance dependence on event magnitude; minimum number of rain gauges for a satisfying model performance and its relationship with event magnitude; dependence on the basin size.
Finally we analyse the real case of 2 small basins with a good record of hydrometric and high temporal resolution (5 min) pluviometric observations. Specifically we evaluate the performances by comparing the observed runoff with the hydrographic response produced by the rainfall-runoff models and considering as active a different number of rain gauges. Although this analysis is limited to a maximum of three rain gauges, it confirms the results obtained in the synthetic framework described above
Toward A Micrometeorological Assessment Of Agrivoltaic Farms: A Feature Tracking Velocimetry-Based Analysis
No full textWe investigate the flow dynamics around a model of an array of photovoltaic panels via laboratory experiments conducted in a water channel. The model farm consists of transparent polycarbonate panels with varying tilt angles, simulating different configurations typical of agrivoltaic systems. Velocities are measured using a feature tracking velocimetry technique. Results reveal distinct flow structures depending on the tilt angle of the panels and the distance between them, with varying numbers of recirculation regions observed. An increase in the distance between panels stretches the recirculation regions along the streamwise direction. Turbulent kinetic energy is more intense with negative tilt angles, and upstream turbulence penetrates more between panels. These findings suggest different transport and heat transfer properties, particularly relevant for tracker PV arrays that adjust tilt angles throughout the day. Understanding these dynamics is crucial for optimizing the design and operation of agrivoltaic farms to maximize energy production while minimizing impacts on agricultural productivity and the surrounding environment
A meteo-hydrological forecasting chain: performance of the downscaling and rainfall-runoff steps in a small catchment
Get PDFForecasting ground effects of severe meteorological events with an adequate lead time is fundamental for civil protection scopes and is therefore an important challenge for the scientific community. The paper focuses on the performance of some steps of a meteo-hydrological forecasting chain that can be applied in small watersheds to assess hydrological risk deriving by an intense storm predicted at the large meteorological scale. The proposed procedure integrates large-scale rainfall fields, as those produced by numerical weather prediction (NWP) models, with statistical rainfall downscaling and hydrological modelling. More in details, assuming a large scale rain rate as the input of the process, the forecasting chain produces an ensemble of hydrographs that are post-processed in order to give a probabilistic representation of mean streamflow maxima for different time windows. The outcome of this procedure can be thus applied to assess the risk that some critical streamflow thresholds may be exceeded. The procedure has been tested on more than one thousand recorded events in the Araxisi catchment in Sardinia, Italy. Results and performances are presented and discussed
The air quality in two-dimensional urban canyons with gable roof buildings: A numerical and laboratory investigation
No full textIn this work we compare two typical methods (numerical simulation and laboratory experiment) of modelling air flows at the urban scale to assess air quality in street canyons. We have investigated, both via numerical simulations and laboratory experiments, the effect of gable roofs, on the air quality in urban canyons with different aspect ratios. In particular, we have focused on the flow regimes, turbulence characteristics and air exchanges between the urban canyon and the outer flow. Results highlight how the choice of the roof shape can be meaningful for building design, planning strategies and regulatory purposes
Integrating hydrological and hydrodynamic models in river flooding simulation modelling system
No full textAccoppiamento di un modello idrodinamico ad un sistema probabilistico di previsione meteoidrologica
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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
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