1,720,979 research outputs found
Future precipitation extremes: Differential changes from point to catchment scale revealed by a convection-permitting model ensemble
No full textUnderstanding spatial scale-dependent changes in extreme precipitation is crucial for flood risk adaptation in a warming climate. This study investigates how future changes in sub-daily to daily extreme precipitation can be transferred from point to catchment scales. We use the areal reduction factor (ARF) concept to quantify the impact of climate change on extremes at multiple scales from point (individual model grid cell) to catchment scales up to 3,751 km2 in the upper Adige River basin, eastern Italian Alps. We apply the Simplified Metastatistical Extreme Value (SMEV) framework to estimate extreme precipitation return levels (1–24 h durations, up to 100-year return periods) at multiple spatial scales using an ensemble of nine convection-permitting models from FPS-CORDEX. Models provide hourly precipitation data (remapped to 3 km grid) for historical (1996–2005) and future (2090–2099) periods under the RCP8.5 scenario. Our results show that ARFs derived by the models in the historical period align well with ARFs values obtained from observations. Under future scenarios, changes in ARFs cannot be in general deemed statistically significant, due to the important inter-model variability. ARFs slightly increase for short durations (1–3 h) and low-to-medium return periods (2–20 years) over small basins (<100km2), suggesting more spatially uniform extremes at these scales. Conversely, ARFs decrease for longer durations, larger basins and high return periods, implying that corresponding areal design precipitation will increase less than point precipitation under the same conditions. Our results highlight the need for high-resolution ensemble modeling to capture inter-model variability in extreme precipitation projections
Climatic oscillations influence the flooding of Venice
No full textA detailed analysis of the tidal regime in Venice, Italy,
7 during the last century shows that the frequency and
8 magnitude of high tides are correlated to interdecadal
9 climatic oscillations. The monthly high tide maxima and
10 the average elevation of all high tides are negatively
11 correlated to the North Atlantic Oscillation (NAO), to the
12 Arctic Oscillation (AO), to the East Atlantic – West Russian
13 oscillation (EA-WR), and to the Polar Eurasia
14 teleconnection (POL). The correlation is high during
15 winter months for all four indices, whereas in the fall,
16 when most of the city floods occur, the AO and the EA-WR
17 exert a stronger influence on the tidal regime. During
18 negative phases of the climate indices both the average
19 elevation of high tides and the frequency of flooding
20 increase consistently, with negative effects on the city and its
21 monuments
Orographic control on bias and uncertainty in extreme sub-daily precipitation simulations from a convection-permitting ensemble
Get PDFClimate change adaptation strategies and flood risk management in complex terrain rely on accurate projections of sub-daily precipitation extremes and on the realistic evaluation of the associated uncertainty. However, these aspects are still insufficiently analysed, especially concerning the most updated convection-permitting climate models (CPM). This study provides a comprehensive approach to assess the performance of CPMs in complex terrain by analysing bias and uncertainty of sub-daily extreme precipitation. We evaluate extreme sub-daily precipitation in the north-eastern Italian Alps using an ensemble of CPM simulations. We assess return levels for 2, 5, 10, 20, 50, and 100-year return periods across five durations (1, 3, 6, 12, and 24 h) and associated uncertainty. We compare estimates based on CPM simulations with the ones based on rain gauge observations. Our results show that CPM performance improves with longer durations, with underestimations in the lowlands and overestimations in the highlands, particularly for short durations. The CPM ensemble captures the orographic effect, although with a weaker magnitude with respect to what is observed. We quantify intra-model, inter-model, and total uncertainties, finding that inter-model uncertainty dominates, particularly at higher elevations for short durations. The normalised intra-model uncertainty ranges between 12% and 18% and matches well the observed uncertainty for the different elevation ranges, suggesting that the sampling uncertainties are, on average, roughly proportional to the return level values (and the relevant biases). This work provides critical insights into the performance of CPMs in complex terrain and has important implications for improving the accuracy of extreme precipitation estimations, which are crucial for climate change adaptation and flood risk management in mountainous regions
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
Elevation-Dependent Amplification of Rainfall Extremes: The Role of Rainfall/Snowfall Fraction in Convection-Permitting Models
No full textVariations 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
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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