Application of the parabolic bay shape equation to sand and gravel beaches on Mediterranean coasts     

Chiara F. Schiaffino  Massimo BrignoneMarco Ferrari 《Coastal Engineering》2012,59(1):57-63

The equation most commonly used to describe the bay planform was proposed by Hsu and Evans (1989) and it was obtained through empirical analysis of sand beach planforms.In the last decade interest in gravel sediments increased owing to their greater stability on beaches, compared with sand sediments. Due to the differences between the morphodynamics of sand and gravel beaches, which is strictly influenced by their different hydraulic characteristics, it was necessary to create a predictive instrument for this beach type as well.Therefore, in this study the standard Hsu and Evans equation (1989) was modified in order to make it applicable not only to sand beaches but also to gravel beaches. The shoreline was computed according to a parabolic model in polar coordinates whose coefficients are considered linearly dependent on the wave direction and related to the beach type. The estimation of the free parameters of the model was performed according to a statistical analysis of a shorelines data set of Mediterranean sand and gravel embayed beaches.  相似文献   

Understanding the collapse–eruption link at Stromboli,Italy: A microanalytical study on the products of the recent Secche di Lazzaro phreatomagmatic activity     

Chiara M. Petrone  Eleonora Braschi  Lorella Francalanci 《Journal of Volcanology and Geothermal Research》2009

The Secche di Lazzaro (SDL) phreatomagmatic activity, with the associated Neostromboli sector collapse, represents the most powerful activity of the last 6 ky at Stromboli. As revealed by its present-day activity, Stromboli is one of the most eruptive volcanoes in Italy, and flank instability, along its NW flank, is a common process. Volcano instability is often dramatised by explosive eruptions, thus it is of crucial importance to understand the linking between volcano collapse and the plumbing system itself. The possible role of pre-eruptive magmatic processes as triggers of explosive eruptions can be mainly preserved by minerals and revealed by petrochemical studies. We studied the juvenile components (scoria and pumice) of the pyroclastic deposits from the SDL phreatomagmatic activity with the aim to understand the eruption–collapse link.  相似文献   

<Emphasis Type="Italic">Mesopithecus</Emphasis> (Primates: Cercopithecoidea) from Villafranca d’Asti (Early Villafranchian; NW Italy) and palaeoecological context of its extinction     

Chiara Pradella  Lorenzo Rook 《Swiss Journal of Geoscience》2007,100(1):145-152

Remains of the cercopithecid Mesopithecus monspessulanus are relatively rare. Two previously unpublished mandibles of M. monspessulanus (housed in the Basel Naturhistorisches Museum), from the Italian locality of Villafranca d’Asti are described. These remains belong to the assemblage of the Triversa Faunal Unit, dated to the Early Villafranchian, that is to the unit MN16a (Middle Pliocene) of the European mammal biochronology. According to this recently revised biochronological attribution, Villafranca d’Asti records the last Mesopithecus occurrence in Europe. The NOW (Neogene Old World) database has been used as a basis to evaluate both the mammalian faunal and the palaeoenvironmental context at the time surrounding this last occurrence of Mesopithecus. The comparison (taxonomical composition and ungulate hypsodonty), between the Villafranca d’Asti assemblage and other Plio-Pleistocene mammal communities of Europe, shows that the extinction of Mesopithecus is related to a faunal turnover and a change toward more open landscapes during the Early–Middle Villafranchian transition. This is consistent with the “Elephant-Equus event”, that occurred in Europe at 2.5 Ma. Furthermore, the co-occurring but more terrestrial cercopithecid Macaca crossed this faunal turnover. This strengthens the assumption that the latest Mesopithecus species, M. monspessulanus, had woodland-oriented adaptations. Editorial handling: J.-P. Billon-Bruyat & M. Chiari (Guest)  相似文献   

Cooling history of lunar Mg-suite gabbronorite 76255, troctolite 76535 and Stillwater pyroxenite SC-936: The record in exsolution and ordering in pyroxenes     

I. Stewart McCallum  M. Chiara Domeneghetti  Jeffrey M. Schwartz  Emily K. Mullen  Michele Zema  Fernando Cmara  Catherine McCammon  Jibamitra Ganguly 《Geochimica et cosmochimica acta》2006,70(24):6068-6078

We have determined cooling rates of orthopyroxene crystals from two Mg-suite lunar samples (gabbronorite 76255 and troctolite 76535) and one terrestrial sample (orthopyroxenite SC-936 from the Stillwater Complex), on the basis of their Fe–Mg ordering states. In addition, a cooling rate of 76255 was determined by modeling the formation of exsolution lamellae in pyroxenes. The M1–M2 site occupancies of the orthopyroxene crystals were determined by single crystal X-ray diffraction and the rate constant for the ordering reaction was used along with calibrations of the equilibrium intracrystalline fractionation of Fe and Mg as a function of temperature to calculate cooling rates. The closure temperatures (T_C) of cation ordering are 525 °C for 76255, 500 °C for 76535 and 350 °C for SC-936 corresponding to cooling rates of 4 × 10⁻² °C/year at the closure temperature for the lunar samples and 10⁻⁶ °C/year for the Stillwater sample. A cooling rate for 76255, determined by simulating the exsolution process, is 1.7 × 10⁻² °C/year at a closure temperature for exsolution of 700 °C. The Fe–Mg ordering cooling rate determined for 76535 reflects a complex thermal history superimposed on the initial plutonic provenance established for this sample [McCallum, I.S., Schwartz, J.M., 2001. Lunar Mg suite: thermobarometry and petrogenesis of parental magmas. J. Geophys. Res. 106, 27969–27983]. The preservation of a crystallization age of 4.51 Ga and a metamorphic age of 4.25 Ga for 76535 is consistent with a model in which excavation of this sample from the lower lunar crust took place while the sample was at a temperature above the closure temperatures for the Sm–Nd, U–Pb and Ar–Ar isotopic systems. Temperatures in excess of the isotopic closure temperatures (i.e., >600 °C) in the lower lunar crust were maintained by heat diffusing from concentrations of U- and Th-rich KREEP material at the base of the crust. On the other hand, 76255 formed at a much shallower depth in the lunar crust (2 km) and was well below its isotopic closure temperatures at the time of excavation, most likely during the Serenitatis basin-forming impact event. Both lunar samples were reheated during transport to the surface and deposition in hot ejecta blankets. The reheating was short lived but apparently sufficient to redistribute Fe and Mg in M sites in orthopyroxenes. For the lunar samples, the cooling rates based on Fe–Mg ordering represent final stage cooling within an ejecta blanket.  相似文献   

Modeling groundwater/surface-water interactions in an Alpine valley (the Aosta Plain,NW Italy): the effect of groundwater abstraction on surface-water resources     

Gennaro A. Stefania  Marco Rotiroti  Letizia Fumagalli  Fulvio Simonetto  Pietro Capodaglio  Chiara Zanotti  Tullia Bonomi 《Hydrogeology Journal》2018,26(1):147-162

A groundwater flow model of the Alpine valley aquifer in the Aosta Plain (NW Italy) showed that well pumping can induce river streamflow depletions as a function of well location. Analysis of the water budget showed that ～80% of the water pumped during 2 years by a selected well in the downstream area comes from the baseflow of the main river discharge. Alluvial aquifers hosted in Alpine valleys fall within a particular hydrogeological context where groundwater/surface-water relationships change from upstream to downstream as well as seasonally. A transient groundwater model using MODFLOW2005 and the Streamflow-Routing (SFR2) Package is here presented, aimed at investigating water exchanges between the main regional river (Dora Baltea River, a left-hand tributary of the Po River), its tributaries and the underlying shallow aquifer, which is affected by seasonal oscillations. The three-dimensional distribution of the hydraulic conductivity of the aquifer was obtained by means of a specific coding system within the database TANGRAM. Both head and flux targets were used to perform the model calibration using PEST. Results showed that the fluctuations of the water table play an important role in groundwater/surface-water interconnections. In upstream areas, groundwater is recharged by water leaking through the riverbed and the well abstraction component of the water budget changes as a function of the hydraulic conditions of the aquifer. In downstream areas, groundwater is drained by the river and most of the water pumped by wells comes from the base flow component of the river discharge.  相似文献   

Al Huwaysah 010: The most reduced brachinite,so far     

Cristian Carli  Anna Barbaro  Mara Murri  Maria Chiara Domeneghetti  Antonio Langone  Enrico Bruschini  Alice Stephant  Matteo Alvaro  Stefania Stefani  Tiberio Cuppone  Martina Casalini  Alessandra Migliorini  Ted L. Roush  Giovanni Pratesi 《Meteoritics & planetary science》2023,58(6):855-874

Al Huwaysah 010 is an ungrouped achondrite meteorite, recently referred to as a brachinite-like meteorite. This meteorite, showing a fine-grained assemblage of low-Ca pyroxene and opaque phases, is strongly reduced in comparison to other reduced brachinites. The occurrence of some tiny plates of graphite and oldhamite in this meteorite suggests that a partial melt residue has experienced a further reduction process. Olivine, the most abundant phase, is compositionally homogeneous (Fo_83.3) as well as the clinopyroxene (En_45.5Fs_10.8Wo_43.7) and the plagioclase (Ab_69.5). Orthopyroxene (En_85.4Fs_13.9Wo_0.7) also occurs but only in a fine intergrowth. Other accessory phases are Fe metal grains (Ni-free or Cr-bearing Fe-Ni alloy), troilite, chlorapatite, pentlandite (as inclusions in chromite). The sample shows two different closure temperatures: the highest (≈900°C) is determined via the olivine–chromite intercrystalline geothermometer and the lowest temperature (≈520°C) is determined via the pyroxene-based intracrystalline geothermometer. These temperatures may represent, respectively, the closure temperature associated with the formation and a subsequent impact event excavating the sample from the parental body. The visible to near-infrared (VNIR) reflectance spectra of Al Huwaysah 010 exhibit low reflectance, consistent with the presence of darkening components, and weak absorptions indicative of olivine and pyroxene. Comparing the spectral parameters of Al Huwaysah 010 to potential parent bodies characterized by olivine–pyroxene mineralogy, we find that it falls within the field previously attributed to the SIII type asteroids. These results lead us to classify the Al Huwaysah 010 meteorite as the most reduced brachinite, whose VNIR spectral features show strong affinities with those of SIII asteroids.  相似文献   

Rainfall-derived growing season characteristics for agricultural impact assessments in South Africa   总被引：1，自引：0，他引：1  

Chiara Ambrosino  Richard E. Chandler  Martin C. Todd 《Theoretical and Applied Climatology》2014,115(3-4):411-426

Precipitation variability imposes significant pressure in areas where agricultural practice is dominated by smallholder farmers who are dependent on subsistence farming. Advances in the understanding of this variability, in both time and space, have an important role to play in increasing the resilience of agricultural systems. The need is particularly pressing in regions of the world such as the African continent, which is already affected by multiple stresses including poverty and economic and political instability. In this paper, we explore the use of generalised linear models (GLMs) for this purpose, via a case study from north-east South Africa. A GLM is used to link the local rainfall variability to large-scale climate drivers identified from previous subcontinental-scale analyses, and the ability of the resulting model to simulate precipitation features that are relevant in agricultural applications is evaluated. We focus in particular on a set of growing season indices, proposed for the investigation of intraseasonal characteristics relevant for maize production in the region. Seven indices were computed from spatially averaged daily rainfall series from nine stations in the study area. As a first attempt to use GLMs for this type of application, the results are encouraging and suggest that the models are able to reproduce a range of agriculture-relevant indices. However, further research into spatial correlation structure is recommended to improve the multisite generation of the rainfall-derived characteristics.  相似文献   

Extra-tropical atmospheric response to ENSO in the CMIP5 models     

Margaret M. Hurwitz  Natalia Calvo  Chaim I. Garfinkel  Amy H. Butler  Sarah Ineson  Chiara Cagnazzo  Elisa Manzini  Cristina Peña-Ortiz 《Climate Dynamics》2014,43(12):3367-3376

The seasonal mean extra-tropical atmospheric response to El Niño/Southern Oscillation (ENSO) is assessed in the historical and pre-industrial control CMIP5 simulations. This analysis considers two types of El Niño events, characterized by positive sea surface temperature (SST) anomalies in either the central equatorial Pacific (CP) or eastern equatorial Pacific (EP), as well as EP and CP La Niña events, characterized by negative SST anomalies in the same two regions. Seasonal mean geopotential height anomalies in key regions typify the magnitude and structure of the disruption of the Walker circulation cell in the tropical Pacific, upper tropospheric ENSO teleconnections and the polar stratospheric response. In the CMIP5 ensembles, the magnitude of the Walker cell disruption is correlated with the strength of the mid-latitude responses in the upper troposphere i.e., the North Pacific and South Pacific lows strengthen during El Niño events. The simulated responses to El Niño and La Niña have opposite sign. The seasonal mean extra-tropical, upper tropospheric responses to EP and CP events are indistinguishable. The ENSO responses in the MERRA reanalysis lie within the model scatter of the historical simulations. Similar responses are simulated in the pre-industrial and historical CMIP5 simulations. Overall, there is a weak correlation between the strength of the tropical response to ENSO and the strength of the polar stratospheric response. ENSO-related polar stratospheric variability is best simulated in the “high-top” subset of models with a well-resolved stratosphere.  相似文献   

European blocking and Atlantic jet stream variability in the NCEP/NCAR reanalysis and the CMCC-CMS climate model     

Paolo Davini  Chiara Cagnazzo  Pier Giuseppe Fogli  Elisa Manzini  Silvio Gualdi  Antonio Navarra 《Climate Dynamics》2014,43(1-2):71-85

The relationship between atmospheric blocking over Europe and the Atlantic eddy-driven jet stream is investigated in the NCEP/NCAR Reanalysis and in a climate model. This is carried out using a bidimensional blocking index based on geopotential height and a diagnostic providing daily latitudinal position and strength of the jet stream. It is shown that European Blocking (EB) is not decoupled from the jet stream but it is mainly associated with its poleward displacements. Moreover, the whole blocking area placed on the equatorward side of the jet stream, broadly ranging from Azores up to Scandinavia, emerges as associated with poleward jet displacements. The diagnostics are hence applied to two different climate model simulations in order to evaluate the biases in the jet stream and in the blocking representation. This analysis highlights large underestimation of EB, typical feature of general circulation models. Interestingly, observed blocking and jet biases over the Euro-Atlantic area are consistent with the blocking-jet relationship observed in the NCEP/NCAR Reanalysis. Finally, the importance of sea surface temperatures (SSTs) is investigated showing that realistic SSTs can reduce the bias in the jet stream variability but not in the frequency of EB. We conclude highlighting that blocking-related diagnostics can provide more information about the Euro-Atlantic variability than diagnostics simply based on the Atlantic jet stream.  相似文献   

Rainfall-induced landslide susceptibility zonation of Puerto Rico   总被引：9，自引：4，他引：5  

Chiara Lepore  Sameer A. Kamal  Peter Shanahan  Rafael L. Bras 《Environmental Earth Sciences》2012,66(6):1667-1681

Landslides are a major geologic hazard with estimated tens of deaths and $1–2 billion in economic losses per year in the US alone. The island of Puerto Rico experiences one or two large events per year, often triggered in steeply sloped areas by prolonged and heavy rainfall. Identifying areas susceptible to landslides thus has great potential value for Puerto Rico and would allow better management of its territory. Landslide susceptibility zonation (LSZ) procedures identify areas prone to failure based on the characteristics of past events. LSZs are here developed based on two widely applied methodologies: bivariate frequency ratio (FR method) and logistic regression (LR method). With these methodologies, the correlations among eight possible landslide-inducing factors over the island have been investigated in detail. Both methodologies indicate aspect, slope, elevation, geological discontinuities, and geology as highly significant landslide-inducing factors, together with land-cover for the FR method and distance from road for the LR method. The LR method is grounded in rigorous statistical testing and model building but did not improve results over the simpler FR method. Accordingly, the FR method has been selected to generate a landslide susceptibility map for Puerto Rico. The landslide susceptibility predictions were tested against previous landslide analyses and other landslide inventories. This independent evaluation demonstrated that the two methods are consistent with landslide susceptibility zonation from those earlier studies and showed this analysis to have resulted in a robust and verifiable landslide susceptibility zonation map for the whole island of Puerto Rico.  相似文献