A Simple Parametrization for the Concentration Variance Dissipation in a Lagrangian Single-Particle Model     

Enrico Ferrero  Luca Mortarini  Federico Purghè 《Boundary-Layer Meteorology》2017,162(1):91-116

A new quasi-analytical mixed-layer model is formulated describing the evolution of the convective atmospheric boundary layer (ABL) during cold-air outbreaks (CAO) over polar oceans downstream of the marginal sea-ice zones. The new model is superior to previous ones since it predicts not only temperature and mixed-layer height but also the height-averaged horizontal wind components. Results of the mixed-layer model are compared with dropsonde and aircraft observations carried out during several CAOs over the Fram Strait and also with results of a 3D non-hydrostatic (NH3D) model. It is shown that the mixed-layer model reproduces well the observed ABL height, temperature, low-level baroclinicity and its influence on the ABL wind speed. The mixed-layer model underestimates the observed ABL temperature only by about 10 %, most likely due to the neglect of condensation and subsidence. The comparison of the mixed-layer and NH3D model results shows good agreement with respect to wind speed including the formation of wind-speed maxima close to the ice edge. It is concluded that baroclinicity within the ABL governs the structure of the wind field while the baroclinicity above the ABL is important in reproducing the wind speed. It is shown that the baroclinicity in the ABL is strongest close to the ice edge and slowly decays further downwind. Analytical solutions demonstrate that the \(\mathrm{e}\)-folding distance of this decay is the same as for the decay of the difference between the surface temperature of open water and of the mixed-layer temperature. This distance characterizing cold-air mass transformation ranges from 450 to 850 km for high-latitude CAOs.  相似文献   

Subduction polarity reversal at the junction between the Western Alps and the Northern Apennines, Italy     

Gianluca Vignaroli  Claudio Faccenna  Laurent Jolivet  Claudia Piromallo  Federico Rossetti 《Tectonophysics》2008,450(1-4):34-50

The controversial relationship between the orogenic segments of the Western Alps and the Northern Apennines is here explored integrating recently published 3D tomographic models of subduction with new and re-interpreted geological observations from the eclogitic domain of the Voltri Massif (Ligurian Alps, Italy), where the two belts joint each other. The Voltri Massif is here described as an extensional domain accommodating the opposing outward migration of the Alpine and Apennine thrust fronts, since about 30–35 Ma. Using tomographic images of the upper mantle and paleotectonic reconstructions, we propose that this extensional setting represents the surface manifestation of an along strike change in polarity of the subducted oceanic slab whose polarity changed laterally in space and in time. Our tectonic model suggests that the westward shift of the Alpine thrust front from the Oligocene onward was the consequence of the toroidal asthenospheric flow induced by the retreat of the Apenninic slab.  相似文献   

<Emphasis>A</Emphasis> probability index for surface zonda wind occurrence at Mendoza city through vertical sounding principal components analysis     

Federico?OteroEmail author  Federico?Norte  Diego?Araneo 《Theoretical and Applied Climatology》2018,131(1-2):213-225

The aim of this work is to obtain an index for predicting the probability of occurrence of zonda event at surface level from sounding data at Mendoza city, Argentine. To accomplish this goal, surface zonda wind events were previously found with an objective classification method (OCM) only considering the surface station values. Once obtained the dates and the onset time of each event, the prior closest sounding for each event was taken to realize a principal component analysis (PCA) that is used to identify the leading patterns of the vertical structure of the atmosphere previously to a zonda wind event. These components were used to construct the index model. For the PCA an entry matrix of temperature (T) and dew point temperature (Td) anomalies for the standard levels between 850 and 300 hPa was build. The analysis yielded six significant components with a 94 % of the variance explained and the leading patterns of favorable weather conditions for the development of the phenomenon were obtained. A zonda/non-zonda indicator c can be estimated by a logistic multiple regressions depending on the PCA component loadings, determining a zonda probability index \( \widehat{c} \) calculable from T and Td profiles and it depends on the climatological features of the region. The index showed 74.7 % efficiency. The same analysis was performed by adding surface values of T and Td from Mendoza Aero station increasing the index efficiency to 87.8 %. The results revealed four significantly correlated PCs with a major improvement in differentiating zonda cases and a reducing of the uncertainty interval.  相似文献   

The at-rest earth pressure coefficient prediction using simple elasto-plastic constitutive models     

Antonio Federico  Gaetano Elia  Agnese Murianni 《Computers and Geotechnics》2009,36(1-2):187-198

The paper deals with the theoretical prediction of the at-rest earth pressure coefficient for normally consolidated soils (k_0(NC)) using simple elasto-plastic constitutive models. In the first part of the work, the k_0(NC) expressions derived from critical state soil mechanics models are critically discussed. It is shown that, adopting typical values of the models parameters, the experimental k_0(NC) values are usually over-predicted. In the second part, a possible modification of the critical state model formulation, which allows to predict lower k_0(NC) values for a fixed angle of shearing resistance, is considered. Finally, a discussion of the results and some brief conclusions are proposed.  相似文献   

Managing coastal erosion: A management proposal for a littoral cell in Todos Santos Bay,Ensenada, Baja California,Mexico     

Carlos Peynador  Federico Méndez-Sánchez 《Ocean & Coastal Management》2010,53(7):350-357

A diagnostic of coastal erosion and shoreline retreat occurring at a 7-km long sandy beach (Littoral Cell III) located in Todos Santos Bay (Baja California, Mexico) is performed trough the analysis of aerial photographs. Around 82,000 m² of this sandy beach have been lost in a 20 year period (1985–2005), at a beach loss rate of 2,100 m² per year. This indicates that coastal erosion is becoming a hazard to human lives and coastal infrastructure. Due to the latter, the implementation of a Shoreline Erosion Management Plan (SEMP) is proposed as the best management approach to deal with the problem. The Littoral Cell III SEMP considers four core policies, eight management strategies and a group of specific measures.  相似文献   

Field investigation and rockfall hazard zonation at the Shijing Mountains Sutra caves cultural heritage (China)   总被引：2，自引：0，他引：2  

Xueliang Wang  Luqing Zhang  Sijing Wang  Federico Agliardi  Paolo Frattini  Giovanni B. Crosta  Zhifa Yang 《Environmental Earth Sciences》2012,66(7):1897-1908

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Prediction of time to slope failure: a general framework   总被引：4，自引：1，他引：3  

A. Federico  M. Popescu  G. Elia  C. Fidelibus  G. Internò  A. Murianni 《Environmental Earth Sciences》2012,66(1):245-256

The prediction of time to slope failure (TSF) is a goal of major importance for both landslide researchers and practitioners. A reasonably accurate prediction of TSF allows human losses to be avoided, damages to property to be reduced and adequate countermeasures to be designed. A pure “phenomenological” approach based on the observation and interpretation of the monitored data is generally employed in TSF prediction. Such an approach infers TSF mainly from the ground surface displacements using regression techniques based on empirical functions. These functions neglect the rheological soil parameters in order to reduce the prediction uncertainties. This paper presents an overlook of the methods associated with this approach and proposes a unique expression encompassing most of the previously proposed equations for TSF prediction, thus offering a general framework useful for comparisons between different methods. The methods discussed in this paper provide an effective tool, and sometimes the only tool, for TSF prediction. The fundamental problem is always one of data quality. A full confidence in all assumptions and parameters used in the prediction model is rarely, if ever, achieved. Therefore, TSF prediction models should be applied with care and the results interpreted with caution. Documented case studies represent the most useful source of information to calibrate the TSF prediction models.  相似文献   

Numerical modeling and mechanical analysis of an innovative soil anchoring system     

Claudio di Prisco  Federico Pisanò 《Acta Geotechnica》2014,9(6):1013-1028

In this paper, the pull-out performance of an innovative system for soil anchoring is mechanically interpreted on the basis of a preliminary finite element investigation. The system consists of a tie rod equipped with thick steel sockets, extruding into the soil to increase the overall pull-out bearing capacity. The effectiveness of the anchorage is shown to be mainly due to the steel sockets, producing two correlated strength mechanisms: a direct one, associated with the shear/flexural strength of the sockets themselves; and an indirect one, in the form of a remarkable increase in the normal confinement on the tie rod and hence in the mobilizable shear stresses. The numerical results are finally exploited to conceive a simplified mechanical model for the interpretation/prediction of the pull-out anchor performance.  相似文献   

Interaction between ultrapotassic magmas and carbonate rocks: Evidence from geochemical and isotopic (Sr, Nd, O) compositions of granular lithic clasts from the Alban Hills Volcano, Central Italy     

Angelo Peccerillo  Marcella Federico  Mauro Brilli 《Geochimica et cosmochimica acta》2010,74(10):2999-95

Magma-carbonate rock interaction is investigated through a geochemical and Sr-Nd-O isotope study of granular lithic clasts (ejecta) from the Alban Hills ultrapotassic volcano, Central Italy. Some samples (Group-1) basically represent intrusive equivalents of Alban Hills magmas. A few samples (Group-2) are ultramafic, have high MgO (∼30 to 40 wt%) and δ¹⁸O‰, and originated by accumulation of mafic phases that crystallised from ultrapotassic melts during assimilation of dolomitic rocks. Group-3 ejecta consist of dominant K-feldspar, and show major element compositions similar to phonolites, which, however, are absent among the Alban Hills volcanics. Finally, another group (Group-4) contains corroded K-feldspars, surrounded by a microgranular to porphyritic matrix, made of igneous minerals (K-feldspar, foids, clinopyroxene, phlogopite) plus wollastonite, garnet, and some cuspidine. Group-4 ejecta are depleted in SiO₂ and enriched in CaO with respect to Group-3.The analysed ejecta have similar ¹⁴³Nd/¹⁴⁴Nd (0.51204-0.51217) as the Alban Hills lavas, whereas ⁸⁷Sr/⁸⁶Sr (0.70900-0.71067) is similar to lower. Whole rocks δ¹⁸O‰ ranges from +7.0 to +13.2, reaching maximum values in ultramafic samples. A positive correlation with CaO is observed in single rock groups. Large Ion Lithophile Element (LILE) abundances and REE fractionation are generally high, and extreme values of Th, U and LREE are found in some Group-3 and Group-4 rocks.Mineralogical, petrological and geochemical data reveal extensive interaction between magma and carbonate wall rocks, involving both dolostones and limestones. These processes had dramatic effects on magma compositions, especially on phonolites, which were transformed to foidites. Evidence of such a process is found in Group-4 samples, in which K-feldspar is observed to react with a matrix that represents strongly undersaturated melts formed by interaction between silicate magma and carbonates. Trace element data also testify to a very important role for F-CO₂-H₂O-S fluids during magma-wall rock interaction. Fluid transfer was responsible for extreme enrichments in Th, U, and LREE especially observed in Group-3 and Group-4 rocks. Implications of these processes for potassic magma evolution in Central Italy are discussed.  相似文献   

The Prestige oil spill: a scientific response     

Albaigés J  Morales-Nin B  Vilas F 《Marine pollution bulletin》2006,53(5-7):205-207

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