Severity–duration–frequency curves in the mitigation of drought impact: an agricultural case study     

F. Todisco  F. Mannocchi  L. Vergni 《Natural Hazards》2013,65(3):1863-1881

Severity–duration–frequency (SDF) curves are very useful in the analysis of drought phenomena. Station-level information obtained from SDF curves can be interpolated to obtain severity maps for fixed return period, in order to jointly analyse the spatial variability of drought characteristics (e.g. severity, duration and frequency). This approach is limited because the severity is usually quantified through indices that use hydrological and meteorological data, depending on the type of requirements. Therefore, drought indices can only reflect hydrological conditions, but are unable to quantify economic losses associated with droughts. In other words, SDF curves do not allow effective quantification of the impact expected with a certain return period. This paper proposes the methodology drought economic risk assessment (DERA) as an approach that emphasizes the importance of the relationship between a generic drought index (which quantifies water deficit) and the economic impact of the failure to meet water demand. Using integrated SDF curves, this relationship enables drought severity and corresponding impacts to be mapped. This procedure was applied to agricultural droughts (sunflower crop) in Umbria Region (central Italy). The agricultural drought impact variable was identified by sunflower yield (Y); the economic impact variable by net benefit depletion (EL); and the drought index by Relative Severity Index (RSI), which is quantifiable by a soil–water balance model. The relationships Y = g(RSI) and EL = f(Y) were specifically determined. Using DERA, it was possible to derive curves for SDF, impact–duration–frequency, and economic losses–duration–frequency (ELDF), which were then used to map severity, impact and economic losses for the assigned return period and duration. From the ELDF curves, further information was obtained by mapping critical drought durations for the assigned return period and economic loss threshold. The case study supports the potential of the proposed approach, both in the planning and real-time management of drought effects.  相似文献   

Influence of shear rate,organic matter content,pH and salinity on mud flocculation   总被引：5，自引：0，他引：5  

Francesca Mietta  Claire Chassagne  Andrew J. Manning  Johan C. Winterwerp 《Ocean Dynamics》2009,59(5):751-763

The purpose of this paper is to establish a relation between a few measurable quantities (the so-called ζ potential, organic matter content, and shear rate) and the flocculation behavior of mud. The results obtained with small-scale flocculation experiments (mixing jar) are compared to results of large-scale experiments (settling column). The mud used for all experiments has been collected in October 2007 in the lower Western Schelde, near Antwerp, Belgium. From this study, it was found that the mean floc size and the Kolmogorov microscale vary in a similar way with the shear rate for suspensions with different pH and salt concentrations. The size of flocs at a given shear rate depends on the properties of the suspension, which affect the electrokinetic properties of the sediment; these can be described by means of the ζ potential. The main findings of this paper are: (1) In saline suspensions at pH = 8, the mean floc size increases when the salt concentration and the ζ potential increase. (2) For a given ζ potential, the mean floc size at low pH is larger than observed at pH = 8 for any added salt. (3) The mean floc size increases with increasing organic matter content. (4) Mud with no organic matter at pH = 8 and no added salt flocculates very little. The response of mud suspensions to variations in salinity and pH is similar to that of kaolinite. This suggests that a general trend can be established for different and complex types of clays and mud. This systematic study can therefore be used for further development of flocculation models.  相似文献   

A reappraisal of shear wave splitting parameters from Italian active volcanic areas through a semiautomatic algorithm   总被引：1，自引：0，他引：1  

Francesca Bianco  Lucia Zaccarelli 《Journal of Seismology》2009,13(2):253-266

Shear wave splitting parameters represent a useful tool to detail the stress changes occurring in volcanic environments before impending eruptions. In the present paper, we display the parameter estimates obtained through implementation of a semiautomatic algorithm applied to all useful datasets of the following Italian active volcanic areas: Mt. Vesuvius, Campi Flegrei, and Mt. Etna. Most of these datasets have been the object of several studies (Bianco et al., Annali di Geofisica, XXXXIX 2:429–443, 1996, J Volcanol Geotherm Res 82:199–218, 1998a, Geophys Res Lett 25(10):1545–1548, 1998b, Phys Chem Earth 24:977–983, 1999, J Volcanol Geotherm Res 133:229–246, 2004, Geophys J Int 167(2):959–967, 2006; Del Pezzo et al., Bull Seismol Soc Am 94(2):439–452, 2004). Applying the semiautomatic algorithm, we confirmed the results obtained in previous studies, so we do not discuss in much detail each of our findings but give a general overview of the anisotropic features of the investigated Italian volcanoes. In order to make a comparison among the different volcanic areas, we present our results in terms of the main direction of the fast polarization (φ) and percentage of shear wave anisotropy (ξ).  相似文献   

Multi-wavelength observations of flares and eruptive filaments     

Francesca Zuccarello  Lidia Contarino  Paolo Romano  Viviana Battiato  Salvo L. Guglielmino 《Acta Geophysica》2009,57(1):24-30

In this paper we report some results obtained from multi-wavelength observations carried out to study the mechanisms operating in flares and filament eruptions. Most of these studies have given indication of the presence of phenomena that might be considered signatures of magnetic reconnection, while others have pointed out the important role played by magnetic helicity transport in corona before the eruptive phase.  相似文献   

Emergence and evolution of active and ephemeral regions: Comparison between observations and models     

Francesca Zuccarello  Salvatore L. Guglielmino  Viviana Battiato  Lidia Contarino  Daniele Spadaro  Pado Romano 《Acta Geophysica》2009,57(1):15-23

This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following legs of the flux tubes. These results are briefly discussed in the light of most recent models.  相似文献   

Paleoeskimo site taphonomy: An assessment of the integrity of the Tayara site,Qikirtaq Island,Nunavik, Canada     

Dominique Todisco  Najat Bhiry  Pierre M. Desrosiers 《Geoarchaeology》2009,24(6):743-791

A detailed taphonomic study was undertaken at the Tayara site in order to determine the impact of natural processes such as surface water flow on spatial patterning and site formation. The study focused on Paleoeskimo level II, which contains many lithics and significant faunal remains. Level II integrity was assessed through spatial analysis and by examining the size distribution of lithic artifacts and bone orientation. Experimental knapping aimed at replicating Paleoeskimo lithic technology was used to assess the possible size sorting of lithics. The study indicates that artifact burial by water‐laid sediments did not result in a selective impoverishment in small‐sized lithics. Statistically significant lithic concentrations and associations suggest that spatial distribution was not significantly modified by site formation processes. However, slight post‐depositional changes were presumably induced by water flows in the form of statistically significant horizontal bone reorientations. These occurred when gently flowing water inundated bone accumulations without inducing significant washing or sorting of smaller lithic debris. The spatial integrity evaluation of the level II assemblage reveals a low degree of spatial disturbance and disorganization of the material (i.e., limited entropy), which is likely related to low‐energy hydraulic forces and rapid burial soon after Paleoeskimo occupation. The grouping and deposition of much of the occupation debris is likely the result of Paleoeskimo activities (e.g., knapping and butchering), and the lithics and fauna specimens are probably at or very near their original location. These results show the behavioral significance of the grouping and deposition of debris in Tayara's level II. © 2009 Wiley Periodicals, Inc.  相似文献   

Natural and Anthropogenic Geohazards in Greater London Observed from Geological and ERS-1/2 and ENVISAT Persistent Scatterers Ground Motion Data: Results from the EC FP7-SPACE PanGeo Project     

Francesca Cigna  Hannah Jordan  Luke Bateson  Harry McCormack  Claire Roberts 《Pure and Applied Geophysics》2015,172(11):2965-2995

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A User-Oriented Methodology for DInSAR Time Series Analysis and Interpretation: Landslides and Subsidence Case Studies     

Davide Notti  Fabiana Calò  Francesca Cigna  Michele Manunta  Gerardo Herrera  Matteo Berti  Claudia Meisina  Deodato Tapete  Francesco Zucca 《Pure and Applied Geophysics》2015,172(11):3081-3105

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The ITalian ACcelerometric Archive (ITACA): processing of strong-motion data   总被引：1，自引：1，他引：0  

Marco Massa  Francesca Pacor  Lucia Luzi  Dino Bindi  Giuliano Milana  Fabio Sabetta  Antonella Gorini  Sandro Marcucci 《Bulletin of Earthquake Engineering》2010,8(5):1175-1187

The Italian strong-motion database was created during a joint project between Istituto Nazionale di Geofisica e Vulcanologia (INGV, Italian Institute for Geophysics and Vulcanology) and Dipartimento della Protezione Civile (DPC, Italian Civil Protection). The aim of the project was the collection, homogenization and distribution of strong motion data acquired in Italy in the period 1972–2004 by different institutions, namely Ente Nazionale per l’Energia Elettrica (ENEL, Italian electricity company), Ente per le Nuove tecnologie, l’Energia e l’Ambiente (ENEA, Italian energy and environment organization) and DPC. Recently the strong-motion data relative to the 23th December 2009, Parma (Mw = 5.4 and Mw = 4.9) and to the April 2009 L’Aquila sequences (13 earthquakes with 4.1 ≤ Mw ≤ 6.3) were included in the Italian Accelerometric Archive (ITACA) database (beta release). The database contains 7,038 waveforms from analog and digital instruments, generated by 1.019 earthquakes with magnitude up to 6.9 and can be accessed on-line at the web site . The strong motion data are provided in the unprocessed and processed versions. This article describes the steps followed to process the acceleration time series recorded by analogue and digital instruments. The procedures implemented involve: baseline removal, instrumental correction, band pass filtering with acausal filters, integration of the corrected acceleration in order to obtain velocity and displacement waveforms, computation of acceleration response spectra and strong motion parameters. This procedure is applied to each accelerogram and it is realised to preserve the low frequency content of the records.  相似文献   

Does cannibalism of larvae by adults affect settlement and connectivity of mussel populations?     

Francesca Porri  Tembisa Jordaan  Christopher D. McQuaid   《Estuarine, Coastal and Shelf Science》2008,79(4):687-693

Intertidal population dynamics are driven by a complex series of processes, including larval supply and the possibility of larval predation by benthic animals such as filter-feeders. We hypothesised that cannibalism by adults could play a major role in the population connectivity of mussel populations by removing larvae as they attempt to settle in the adult habitat. Specifically, we tested hypotheses that consumption of mussel larvae by adults removes a significant proportion of potential settlers and is influenced by both settlement intensity and tidal state (flooding or ebbing). Predation of mussel larvae by adult mussels was investigated on incoming and ebbing tides during four spring tides by analysing the gut contents of adult Perna perna and Mytilus galloprovincialis collected from the low intertidal mussel zone between October 2005 and January 2006. Consumption rates were then compared with estimates of successful settler densities on natural beds. The results showed that mortality of competent mussel larvae through adult ingestion removes up to 77% a of potential settlers. Rates of larval consumption were highest during months of intense settlement, suggesting that mussels feed opportunistically, filtering a relatively fixed volume of water and removing particles, including larvae, in proportion to their densities in the water. Rates of larviphagy were also higher during receding than incoming tides. We suggest that this is due to changes in larval density or, more probably, in adult filtration efficiency that are related to the state of the tide. Despite significant effects of both tidal state and settlement intensity on rates of larval ingestion, neither had a significant effect on the proportion of potential settlers removed. During settlement more than half of all potential settlers are lost through cannibalism, with potentially serious consequences for population maintenance. The results highlight the paradoxical nature of the evolution of settlement mechanisms in mussels, which must balance the advantages of settlement in habitats favourable to adults against the consumption of larvae by adults.  相似文献