Monitoring Etna volcanic plumes using a scanning LiDAR     

Simona Scollo  Antonella Boselli  Mauro Coltelli  Giuseppe Leto  Gianluca Pisani  Nicola Spinelli  Xuan Wang 《Bulletin of Volcanology》2012,74(10):2383-2395

In this paper, we use data obtained from LiDAR measurements during an ash emission event on 15 November 2010 at Mt. Etna, in Italy, in order to evaluate the spatial distribution of volcanic ash in the atmosphere. A scanning LiDAR system, located at 7?km distance from the summit craters, was directed toward the volcanic vents and moved in azimuth and elevation to analyse different volcanic plume sections. During the measurements, ash emission from the North East Crater and high degassing from the Bocca Nuova Crater were clearly visible. From our analysis we were able to: (1) evaluate the region affected by the volcanic plume presence; (2) distinguish volcanic plumes containing spherical aerosols from those having non-spherical ones; and (3) estimate the frequency of volcanic ash emissions. Moreover, the spatial distribution of ash mass concentration was evaluated with an uncertainty of about 50?%. We found that, even during ash emission episodes characterised by low intensity like the 15 November 2010 event, the region in proximity of the summit craters should be avoided by air traffic operations, the ash concentration being greater than 4?×?10^?3?g/m³. The use of a scanning permanent LiDAR station may usefully monitor the volcanic activity and help to drastically reduce the risks to aviation operations during the frequent Etna eruptions.  相似文献   

Do alternate bars affect sediment transport and flow resistance in gravel‐bed rivers?     

Simona Francalanci  Luca Solari  Marco Toffolon  Gary Parker 《地球表面变化过程与地形》2012,37(8):866-875

  相似文献   

Rapid and reliable seismic source characterization in earthquake early warning systems: current methodologies,results, and new perspectives     

Simona Colombelli  Aldo Zollo 《Journal of Seismology》2016,20(4):1171-1186

In the present paper, we provided a review of the main principles and methodologies on which the current earthquake early warning systems are grounded and will also provide a perspective view for next future developments and improvements. First, we introduce the standard methodologies for the source characterization in earthquake early warning, with a special focus on the real-time earthquake magnitude determination. We discuss the suitability of existent methodologies and empirical regression laws for very large events. We then present the different approaches for the rapid prediction of the ground shaking and of the potential damaged zone, both based on traditional seismic data and on the use of continuous GPS data. Finally, the last part of the paper provides the perspective view toward a next generation of early warning systems, linking new research achievements about the earthquake rupture nucleation and the development of new methods/technologies aimed at a fast and high-resolution, real-time modeling of the ongoing source process and accurate prediction of the quake shaking at the regional and local scale.  相似文献   

Electron accepting capacity of dissolved organic matter as determined by reaction with metallic zinc   总被引：2，自引：0，他引：2  

Christian Blodau  Markus Bauer  Simona Regenspurg  Donald Macalady 《Chemical Geology》2009,260(3-4):186-195

Information about the chemical electron accepting capacity (EAC) of dissolved organic matter (DOM) is scarce owing to a lack of applicable methods. We quantified the electron transfer from metallic Zn to natural DOM in batch experiments at DOC concentrations of 10–100 mg-C L^− 1 and related it to spectroscopic information obtained from UV-, synchronous fluorescence, and FTIR- spectroscopy. The electron donating capacity of DOM and pre-reduced DOM was investigated using Fe(CN)₆³⁻ as electron acceptor. Presence of DOM resulted in release of dissolved Zn, consumption of protons, and slower release of hydrogen compared to reaction of metallic Zn with water at pH 6.5. Comparison with reaction stoichiometry confirmed that DOM accepted electrons from metallic Zn. The release of dissolved Zn was dependent on pH, DOC concentration, ionic strength, and organic matter properties. The reaction appeared to be completed within about 24 h and was characterized by pseudo first order kinetics with rate constants of 0.5 to 0.8 h^− 1. EAC per mass unit of carbon ranged from 0.22 mmol g^− 1 C to 12.6 mmol g^− 1 C. Depending on the DOM, a calculated 28–127% of the electrons transferred from metallic Zn to DOM could be subsequently donated to Fe(CN)₆³⁻. EAC decreased with DOC concentration, and increased with aromaticity, carboxyl, and phenolic content of the DOM. The results indicate that an operationally defined EAC of natural DOM can be quantified by reaction with metallic Zn and that DOM properties control the electron transfer. Shortcomings of the method are the coagulation and precipitation of DOM during the experiment and the production of hydrogen and dissolved Zn by reaction of metallic Zn with water, which may influence the determined EAC.  相似文献   

Hazard assessment at volcanic fields: the Campi Flegrei case history     

Lucio Lirer  Paola Petrosino  Ines Alberico 《Journal of Volcanology and Geothermal Research》2001,112(1-4)

Volcanological analysis of the 10 000 yr –1538 explosive activity at Campi Flegrei shows that the most common explosive eruptions are characterized by the emplacement of flow or surge deposits, originating from the interaction between magma and shallow and/or sea water. The minimum volumes of pyroclastic products range between 0.04 and 0.7 km³; the proximal areas covered by these products range from 3–4 to 40–50 km². The pyroclastic flow and surge deposits occurring inside the caldera have been strongly controlled by pre-existent morphology; because of this, the area of present Napoli city was blanketed by approximately 5 m of pyroclastic deposits, during the last 5000 yr.Previous analysis suggests that the presence of even very low topographic obstacles may influence pyroclastic density current run out such that future eruptive deposits would mainly be confined inside the caldera rim. We suggest that a future eruption at Campi Flegrei would not seriously involve the urbanized area of Napoli city located on the hills. On the contrary, the plains located on the eastern side of the caldera (Fuorigrotta, Bagnoli) would be the most damaged area.  相似文献   

Shallow velocity model of the Northern Flank of Stromboli Volcano, deduced by high frequency surface wave dispersion     

Simona Petrosino  Mario La Rocca  Edoardo del Pezzo 《Journal of Seismology》1999,3(1):83-94

The wavefield produced by the Stromboli volcano explosion quakes shows a significant amount of surface waves. Rayleigh waves recorded by a linear array have been investigated to infer the shear-wave velocity model of the Stromboli northern flank. The group velocity dispersion curve was obtained using the multiple filter technique, while the phase velocity dispersion curve was calculated both by phase-matched filtering and performing a p– stack on the observed waveforms. Through the inversion of these curves we were able to recover the shear-wave structure to a depth of about 190 m.  相似文献   

Records of environmental and climatic changes during the late Holocene from Svalbard: palaeolimnology of Kongressvatnet   总被引：2，自引：0，他引：2  

Piero Guilizzoni  Aldo Marchetto  Andrea Lami  Achim Brauer  Luigi Vigliotti  Simona Musazzi  Leonardo Langone  Marina Manca  Federico Lucchini  Natale Calanchi  Enrico Dinelli  Alceo Mordenti 《Journal of Paleolimnology》2006,36(4):325-351

A multi-core, multidisciplinary palaeolimnological study of the partially varved sediment of a deep, meromictic, arctic lake, Kongressvatnet (Svalbard, Western Spitsbergen), provides a record of environmental and climatic changes during last ca. 1800 years. The chronology of sedimentation was established using several dating techniques (¹³⁷Cs, ²¹⁰Pb, varve counts, palaeomagnetic correlation). A multiproxy record of palaeolimnological variability was compiled based on sedimentation rates, magnetic properties, varve thickness, organic matter, geochemistry, pigments from algal and photosynthetic bacteria, mineralogy and biological assemblages (diatoms, Cladocera). The major features recognised in our master core K99-3 include a shift in sediment source and supply (magnetic measurements, geochemistry) probably caused by glaciological changes in the catchment around 38–32 cm core depth (AD 700–820). Additional environmental changes are inferred at 20–18, 8–4.5 and 3–2 cm (AD ca. 1160–1255; 1715–1880; 1940–1963, respectively). During the past ca. 120 years a prominent sedimentological change from brownish-grey, partly laminated silt-clay (varves) to black organic-rich deposits was observed. From AD 1350 to AD1880 the sediment is comprised of a continuous sequence of varves, whereas the earlier sediments are mostly homogeneous with only a few short intercalated laminated sections between AD 860 and 1350. Sedimentation and accumulation rates increased during the last 30 years (modern warming). Pigment concentrations are very low in the lower ca. 32 cm of the core (AD 820) probably because of the high turbidity high energy environment. The high sulphur content in the uppermost 32 cm of sediment has given rise to two horizontally stratified populations of sulphur anaerobic photosynthetic bacteria, as inferred from their specific carotenoids. These bacteria populations are much more abundant during the Little Ice Age (LIA) than during warmer periods (e.g., during the Medieval Warm Period and 20th century). Diatoms are lacking from the core base up to 18 cm (ca. AD 1255); at this level, species indicative of mesotrophic water are present, whereas from 17 cm to the top of the core, oligotrophic taxa such as Staurosira construens/S. pinnata complex dominate, indicating extended ice coverage and more oligotrophic waters during the LIA. The concentration of Cladocera subfossil remains (dominated by Chydorus) are relatively high in the deepest sections (54–32 cm), whereas the upper 32 cm are characterized by a very low concentration of remains, possibly because of the strongly anoxic conditions, and in this upper sediment section rotifer resting eggs become prevalent. We interpret these changes as responses to climate forcing through its impact on glacial melt water, lake ice cover duration and mainly redox conditions in deep water. The observed changes suggest that at least some of our recorded changes may parallel the Greenland Ice core, although our study added more details about the inferred climatic changes. Further aspects are discussed, such as catchment processes, glacial activity, duration of the Medieval Warm Period, the Little Ice Age, local human activity, and limnology.  相似文献   

Fluidization and de-aeration of pyroclastic mixtures: The influence of fines content,polydispersity and shear flow     

Piero Bareschino  Teresita Gravina  Lucio Lirer  Antonio Marzocchella  Paola Petrosino  Piero Salatino 《Journal of Volcanology and Geothermal Research》2007

Fluidization of pyroclastic solids has long been indicated as one key to explain the enhanced mobility of dense pyroclastic gravity currents and their associated hazard. However there is a lack of characterization of the actual pattern and extent of fluidization establishing in real pyroclastic flows and some authors still raise arguments about the relevance of fluidization to the mobility of dense pyroclastic gravity currents. The present paper addresses the fluidization of pyroclastic granular solids with a specific focus on the analysis of factors that may promote homogeneous fluidization and retard solids de-aeration and consolidation. These factors include fines content, particle polydispersity and the establishment of shear flow.  相似文献   

Adaptive POD model reduction for solute transport in heterogeneous porous media     

Calogero B. Rizzo  Felipe P. J. de Barros  Simona Perotto  Luca Oldani  Alberto Guadagnini 《Computational Geosciences》2018,22(1):297-308

We study the applicability of a model order reduction technique to the solution of transport of passive scalars in homogeneous and heterogeneous porous media. Transport dynamics are modeled through the advection-dispersion equation (ADE) and we employ Proper Orthogonal Decomposition (POD) as a strategy to reduce the computational burden associated with the numerical solution of the ADE. Our application of POD relies on solving the governing ADE for selected times, termed snapshots. The latter are then employed to achieve the desired model order reduction. We introduce a new technique, termed Snapshot Splitting Technique (SST), which allows enriching the dimension of the POD subspace and damping the temporal increase of the modeling error. Coupling SST with a modeling strategy based on alternating over diverse time scales the solution of the full numerical transport model to its reduced counterpart allows extending the benefit of POD over a prolonged temporal window so that the salient features of the process can be captured at a reduced computational cost. The selection of the time scales across which the solution of the full and reduced model are alternated is linked to the Péclet number (P e), representing the interplay between advective and dispersive processes taking place in the system. Thus, the method is adaptive in space and time across the heterogenous structure of the domain through the combined use of POD and SST and by way of alternating the solution of the full and reduced models. We find that the width of the time scale within which the POD-based reduced model solution provides accurate results tends to increase with decreasing P e. This suggests that the effects of local-scale dispersive processes facilitate the POD method to capture the salient features of the system dynamics embedded in the selected snapshots. Since the dimension of the reduced model is much lower than that of the full numerical model, the methodology we propose enables one to accurately simulate transport at a markedly reduced computational cost.  相似文献   

Temperature changes in the North-Western Italian Alps from 1961 to 2010     

Fiorella Acquaotta  Simona Fratianni  Diego Garzena 《Theoretical and Applied Climatology》2015,122(3-4):619-634

  相似文献