1,720,963 research outputs found
Climate change impact on the cryosphere: from local to global scale
Full text linkLa criosfera, la porzione della superficie terrestre dove l'acqua è immagazzinata allo stato solido, svolge un ruolo di fondamentale importanza nella regolazione del bilancio energetico terrestre e del ciclo idrologico, fornendo risorse idriche a molte regioni del pianeta. La criosfera, regolando ed allo stesso tempo essendo influenzata dalle condizioni climatiche, è una importante sentinella dei cambiamenti climatici, subendone gli effetti e scaturendone ulteriori a scala globale e locale. In questo studio vengono analizzate diverse tematiche legate alla criosfera, dalle Alpi italiane alla Groenlandia. Viene studiata in primo luogo la climatologia di altezza ed equivalente in acqua del manto nevoso (SWE) tramite l'analisi statistica di altezza e densità della neve raccolte tra il 1967 ed il 2020 in un'ampia regione delle Alpi italiane. Dall'analisi statistica è emerso che l'altezza neve è diminuita di 12 cm e lo SWE di 37 mm per decade dal 1967. L'altezza media della neve si è ridotta del 33\% nel periodo 1994-2020 rispetto al periodo 1967-1993, mentre lo SWE del 37\%. Gli effetti del cambiamento climatico risultano essere più intensi a basse altitudini, con una riduzione dell'altezza del manto nevoso del 63\% al di sotto dei 1500 m. Questi risultati sono ulteriormente confermati dal change-point trovato a fine anni 1980. L'analisi del dataset HISTALP mostra la forte dipendenza dell'evoluzione del manto nevoso dalla temperatura, influenzando lo stato di precipitazione e regolando l'inizio della fusione. Gli effetti del manto nevoso a scala locale sono stati studiati analizzando il contributo della fusione nivale nel caso di eventi di precipitazione intensa con presenza di neve al suolo. L'analisi è stata limitata alle stazioni di Aprica e Pantano d'Avio, in Lombardia, dove sono stati raccolti i dati di temperatura, precipitazione ed altezza neve dal 1996. Con i dati osservati è stato calibrato un modello gradi-giorno tramite il quale è stato possibile ricostruire la serie temporale della somma di precipitazione e fusione nivale per le durate di 1, 3, 6, 12 e 24 ore. L'analisi degli annual maxima ha mostrato che la fusione nivale contribuisce ad un incremento medio dei quantili di circa il 2.2\%, aumentando con la durata fino a raggiungere, in un solo caso, il 10\%. Ad una più larga scala, lo studio della fusione superficiale della Groenlandia è di fondamentale importanza nella stima del contributo della calotta di ghiaccio all'innalzamento del livello medio degli oceani. Sono stati raccolti ed intercalibrati i dati satellitari a microonde passive raccolti da sensori montati su cinque diversi satelliti tra il 1979 ed il 2019. Il confronto con dati misurati da stazioni meteorologiche e con simulazioni del modello climatico regionale MAR hanno mostrato che un algoritmo basato sul modello di emissione elettromagnetica MEMLS riesce a cogliere l'evoluzione spaziale e temporale della fusione superficiale. L'analisi dei trend di lungo periodo ha mostrato che la superficie di fusione è aumentata tra il 3.6 ed il 6.9\% dell'intera area della Groenlandia per decennio durante il periodo di osservazione. Inoltre, la stagione di fusione è iniziata tra i 3 ed i 4 giorni prima e si è conclusa tra i 3 ed i 7 giorni dopo ogni decennio. Il numero totale medio di giorni di fusione è aumentato di circa 3-5 giorni per decennio. Per l'area della Groenlandia è stato poi implementato un algoritmo di downscaling statistico per il modello MAR. Il confronto con le misure di temperatura delle stazioni meteorologiche e con i dati di temperatura superficiale rilevati dal satellite Lansat-8 mostra come il dataset ad elevata risoluzione riesca meglio a cogliere la distribuzione spaziale della temperatura, senza perdere accuratezza a livello locale. Il confronto con le misure di bilancio di massa superficiale mostra invece un sostanziale miglioramento rispetto all'output originale a bassa risoluzioneThe cryosphere, the region of the Earth where water is stored in its solid form, plays a crucial role in regulating Earth’s energy balance and contributes to moisture fluxes and freshwater storage and release, providing water resources to many regions of the world. The cryosphere affects and is affected by climate conditions, being a driver and a sentinel of climate change, and playing a role of paramount importance from global to local scale processes. Here, different topics related to the cryosphere are investigated, spanning from the Greenland ice sheet to the Italian alps. A climatology of snow depth and snow water equivalent is carried out using a dataset of snow depth and snow density measurements collected at 299 sites between 1967 and 2020 over a wide portion of the Italian Alps. By performing different statistical analyses, a decrease of 12 cm every decade in snow depth and 37 mm every decade in SWE has been found since 1967. Average snow depth in the period 1994-2020 has been 33% lower than in the period 1967-1993, with stronger effects at low altitudes (reduction of 63% below 1500 m asl). The average SWE in 1994-2020 has been 36% lower than in 1967-1993. These results are confirmed by the increased elevation of the computed null snow depth elevation and the detected change-points at the end of the 1980s. The analysis of the HISTALP dataset confirmed the strong dependency of snow accumulation and melt on air temperature, impacting liquid/solid precipitation separation and timing of melt onset. The influence of snow on ground at local scale has been investigated evaluating the contribution of snowmelt to intense rain-on-snow events in Lombardy. By means of measured temperature, precipitation and snow depth data and the calibration of a snowmelt model, the timeseries of the combination of precipitation and melt has been obtained for the fixed durations 1, 3, 6, 12 and 24 h. The annual maxima analysis revealed that snowmelt increases the quantiles obtained from the selected extreme values distributions of about 2.2%, with stronger impacts for longer durations, up to 10%. At a larger scale, the analysis of surface melting over the Greenland ice sheet is of paramount importance to better estimate the ice sheet contribution to sea level rise. The cross-calibration of five different sensors collecting satellite data over the Greenland ice sheet between 1979 and 2019 has been performed. The comparison with in-situ observation and the output of the regional climate model MAR revealed that a threshold-based melt detection algorithm based on the electromagnetic emission model MEMLS shows the best performances in capturing surface melting evolution. The long-term trends analysis showed an increase of surface melting areal extension of about 3.6-6.9% of the Greenland ice sheet every decade. The melting season has started between 3 and 4 days earlier and between 3 and 7 days later every decade. The total number of melting days has increase by 3-5 days every decade. A statistical downscaling algorithm for the regional climate model MAR has been implemented. The comparison with in-situ observations and satellite measurements revealed that the downscaled dataset can well capture temperature temporal evolution and spatial distribution. It better captures at local scale the cumulated surface mass balance, exhibiting lower errors when compared with measured surface mass balance with respect to the original modelled outpu
A method to assess the uncertainty of Benfratello's estimate of the irrigation deficit in a semiarid area and its GIS based application for anthropogenic and climate change scenarios
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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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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