Some Statistics of the Temperature Structure Parameter in the Convective Boundary Layer Observed by Sodar     

Igor Petenko  Giangiuseppe Mastrantonio  Angelo Viola  Stefania Argentini  Ilaria Pietroni 《Boundary-Layer Meteorology》2014,150(2):215-233

The characteristics of the temporal and height variations of the temperature structure parameter $C_\mathrm{T}^{2}$ in strongly convective situations derived from the sodar echo-signal intensity measurements were analyzed for the first 100 m. It was corroborated that the probability density function (pdf) of the logarithm of $C_\mathrm{T}^{2}$ in the lower convective boundary layer is markedly non-Gaussian, whereas turbulence theory predicts it to be normal. It was also corroborated that the sum of two weighted Gaussians, which characterize the statistics of $C_\mathrm{T}^{2}$ within convective plumes and in their environment and the probability of plume occurrence, well approximates the observed pdfs. It was shown that the height behaviour of the arithmetic mean of $ C_\mathrm{T}^{2}$ (both total and within plumes) follows well a power law $C_\mathrm{T}^{2} (z) \sim z^{-q}$ with the exponent $q$ close to the theoretically predicted value of 4/3. But for the geometrical means of $C_\mathrm{T}^{2}$ (both total and within the plumes), $q$ is close to 1. The difference between arithmetically and geometrically averaged $C_\mathrm{T}^{2}$ profiles was analyzed. The vertical profiles of the standard deviation, skewness and kurtosis of $\hbox {ln}C_\mathrm{T}^{2}$ pdfs were analyzed to show their steady behaviour with height. The standard deviations of the logarithm of $C_\mathrm{T}^{2}$ within the plumes and between them are similar and are 1.5 times less than the total standard deviation. The estimate of the variability index $F_\mathrm{T}$ and its height behaviour were obtained, which can be useful to validate some theoretical and modelling predictions. The vertical profiles of the skewness and kurtosis show the negative asymmetry of pdfs and their flatness, respectively. The spectra of variations in $\hbox {ln}C_\mathrm{T}^{2}$ are shown to be satisfactorily fitted by the power law $f^{-\gamma } $ in the frequency range 0.02 and 0.2 Hz, with the average exponent $\approx $ 1.27  $\pm $  0.22.  相似文献   

Observed and Modelled Convective Mixing-Layer Height at Dome C,Antarctica     

Giampietro Casasanta  Ilaria Pietroni  Igor Petenko  Stefania Argentini 《Boundary-Layer Meteorology》2014,151(3):597-608

The mixing-layer height is estimated using measurements from a high resolution surface-layer sodar run at the French-Italian station of Concordia at Dome C, Antarctica during the summer 2011–2012. The temporal and spatial resolution of the sodar allows the monitoring of the mixing-layer evolution during the whole diurnal cycle, i.e. a very shallow nocturnal boundary layer followed by a typical daytime growth. The behaviour of the summer mixing-layer height, variable between about 10- and 300 m, is analyzed as a function of the mean and turbulent structure of the boundary layer. Focusing on convective cases only, the retrieved values are compared with those calculated using a one-dimensional prognostic equation. The role of subsidence is examined and discussed. We show that the agreement between modelled and experimental values significantly increases if the subsidence is not kept fixed during the day. A simple diagnostic equation, which depends on the time-averaged integral of the near-surface turbulent heat flux, the background static stability and the buoyancy parameter, is proposed and evaluated. The diagnostic relation performance is comparable to that of the more sophisticated prognostic model.  相似文献   

Local Circulation Diurnal Patterns and Their Relationship with Large-Scale Flows in a Coastal Area of the Tyrrhenian Sea   总被引：1，自引：0，他引：1  

Igor Petenko  Giangiuseppe Mastrantonio  Angelo Viola  Stefania Argentini  Lucia Coniglio  Paolo Monti  Giovanni Leuzzi 《Boundary-Layer Meteorology》2011,139(2):353-366

In order to characterise the local low-level circulation in the Tyrrhenian Sea coastal area near Rome, the wind field observed by conventional anemometers, Doppler sodar, and rawinsonde has been analysed. The prevailing diurnal behaviour of wind speed and direction as a function of season was highlighted, and the existence of two different patterns of the local circulation, mainly due to land and sea breezes and to the drainage flow from the mouth of the Tiber valley, revealed. The comparison between the low-level circulation and synoptic flow allowed us to determine the influence of the large-scale flow on nocturnal currents that are observed at the Pratica di Mare site and the way that wind direction evolves during the day. Numerical simulations are consistent with experimental data and depict the main features of the low-level wind field in the area.  相似文献   

Development and testing of subsurface sampling devices for the Beagle 2 lander   总被引：3，自引：0，他引：3  

L Richter  P CosteV.V Gromov  H KochanR Nadalini  T.C NgS Pinna  H.-E RichterK.L Yung 《Planetary and Space Science》2002,50(9):903-913

For planetary landing missions, the capability to acquire samples of soil and rock is of high importance whenever complex analyses (e.g. isotopic studies) on these materials are to be carried out, or when samples are to be returned to Earth. Not only surface samples are of relevance, but in recent concepts at least for Mars landing missions also subsurface samples are required. Subsurface material on Mars is believed to have been protected from the inferred oxidants at the immediate surface while also being protected from the UV influx. Therefore, there is considerable hope that in subsurface soil samples on Mars, at least organic matter delivered by meteorites may be detected, and possibly also relics of earlier simple microbial life on the planet. Likewise, samples from the inside of Martian surface rocks promise to have been protected from weathering and for the same reason they are important for organic chemistry studies. In this paper, an overview is given of the development and science of two different subsurface sampling devices for the Beagle 2 lander of ESA's Mars Express mission, being a “Mole” subsurface soil sampler and a small rock coring and sampling mechanism. Besides their sampling function, both the Mole and the Corer/Grinder will provide data on physical properties of Martian soils and rock, respectively, through the way they interact with the sampled materials. Details of the Mole and Corer/Grinder design are presented, along with results of recent tests with prototypes in the laboratory on physically analogous sample materials.  相似文献   

Ground motion amplification due to shallow cavities in nonlinear soils   总被引：2，自引：0，他引：2  

Stefania Sica  Angelo Dello Russo  Federica Rotili  Armando Lucio Simonelli 《Natural Hazards》2014,71(3):1913-1935

Subsurface cavities or stiff inclusions represent mechanical discontinuities for seismic waves propagating in soils. They modify the propagation pattern of seismic waves and alter soil response in correspondence to the ground level or building foundations. In the literature, different analytical and numerical solutions have been proposed to account for the effect of underground cavities or inclusions on the motion generated by P, S or R waves. In these former studies, the subsoil was assimilated to a homogeneous, isotropic and linear elastic halfspace containing one or more cavities. In the present study, the effect of subsurface cavities on ground motion amplification has been analysed accounting for soil stiffness degradation and associated damping increase with increasing levels of shear strains, a fundamental aspect of soil behaviour under earthquakes. The analysed model was inspired to a real case represented by the village of Castelnuovo (Italy), which during the 2009 Abruzzo earthquake suffered huge damage. The main shock (6 April 2009) caused the collapse of 50 % of the whole built environment. The historical centre of Castelnuovo rises on a hill. In its subsoil, there are many cavities with roofs 2–3 m below the ground level. The longitudinal NW–SE section of the hill has been investigated by 2D nonlinear site response analyses. A preliminary site response analysis was performed without modelling cavities, to identify ground motion amplification due to mere stratigraphic and topographic factors. The numerical model was later refined inserting: (1) a single cavity below the hilltop, (2) multiple cavities placed below the ground surface of the hill and (3) multiple cavities filled with concrete (inclusions). The performed study highlights the important role exerted by underground cavities on the ground motion computed at the hill surface. This effect should be properly considered for both microzonation studies and the correct determination of the seismic actions on specific buildings.  相似文献   

HASSET: a probability event tree tool to evaluate future volcanic scenarios using Bayesian inference     

Rosa Sobradelo  Stefania Bartolini  Joan Martí 《Bulletin of Volcanology》2014,76(1):1-15

Event tree structures constitute one of the most useful and necessary tools in modern volcanology for assessment of hazards from future volcanic scenarios (those that culminate in an eruptive event as well as those that do not). They are particularly relevant for evaluation of long- and short-term probabilities of occurrence of possible volcanic scenarios and their potential impacts on urbanized areas. In this paper, we introduce Hazard Assessment Event Tree (HASSET), a probability tool, built on an event tree structure that uses Bayesian inference to estimate the probability of occurrence of a future volcanic scenario and to evaluate the most relevant sources of uncertainty from the corresponding volcanic system. HASSET includes hazard assessment of noneruptive and nonmagmatic volcanic scenarios, that is, episodes of unrest that do not evolve into volcanic eruption but have an associated volcanic hazard (e.g., sector collapse and phreatic explosion), as well as unrest episodes triggered by external triggers rather than the magmatic system alone. Additionally, HASSET introduces the Delta method to assess precision of the probability estimates, by reporting a 1 standard deviation variability interval around the expected value for each scenario. HASSET is presented as a free software package in the form of a plug-in for the open source geographic information system Quantum Gis (QGIS), providing a graphically supported computation of the event tree structure in an interactive and user-friendly way. We also include further in-depth explanations for each node together with an application of HASSET to Teide-Pico Viejo volcanic complex (Spain).  相似文献   

The lentic–lotic character of Mediterranean rivers and its importance to aquatic invertebrate communities     

Andrea Buffagni  Stefania Erba  David G. Armanini 《Aquatic Sciences - Research Across Boundaries》2010,72(1):45-60

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Antioxidant efficiency and detoxification enzymes in spotted dogfish Scyliorhinus canicula     

Stefania Gorbi  David Pellegrini  Sara Tedesco  Francesco Regoli   《Marine environmental research》2004,58(2-5):293

Although elasmobranchs are widely distributed species, commonly found on sandy, gravely or muddy bottoms, several biological aspects of their metabolism still remain poorly investigated. In this work the efficiency of antioxidant system and detoxification enzymes were investigated in the coastal spotted dogfish Scyliorhinus canicula and in the red mullet Mullus barbatus for comparison with a teleost species.Organisms were sampled during a bottom trawl survey and analyzed for the biotransformation activity (EROD), levels of metallothioneins, catalase, glutathione S-transferases and total oxyradical scavenging capacity (TOSC) toward peroxyl radicals and hydroxyl radicals.EROD activity in the elasmobranchs was more than one order of magnitude lower than in the red mullets, while similar levels of metallothioneins were measured in these species. S. canicula showed significantly lower antioxidant enzymes and a more reduced efficiency in neutralizing ^√OH; on the other hand the scavenging capability toward ROO^√ was comparable in S. canicula and M. barbatus.  相似文献   

Induction of cytochrome P4501A and biliary PAH metabolites in European eel Anguilla anguilla: Seasonal, dose- and time-response variability in field and laboratory conditions     

Stefania Gorbi  Francesco Regoli   《Marine environmental research》2004,58(2-5):511

Induction of cytochrome P4501A in fish is a well-known indicator of exposure to polycyclic aromatic hydrocarbons (PAHs) and determination of PAH metabolites in bile by fixed wavelength fluorescence (FF) or synchronous fluorescence spectroscopy (SFS), has become an useful method in monitoring programs. In this work the relationship between cytochrome P4501A (EROD activity) and levels of biliary PAH metabolites was measured in the European eel Anguilla anguilla, in both field and laboratory conditions: organisms were sampled on a seasonal basis from the Orbetello lagoon (Tuscany) to characterize the natural variability of these biological parameters, while in laboratory eels were intraperitoneally injected with benzo[a]pyrene to investigate temporal and dose-dependent induction patterns. Results showed that induction of cytochrome P450 and accumulation of PAHs metabolites in bile are not necessarily correlated either in field, or in laboratory investigations; different seasonal changes were measured in natural conditions and slight variations in dose and time response patterns were also obtained in laboratory exposures.  相似文献   

Induction of cytochrome P4501A and biliary PAH metabolites in European eel Anguilla anguilla: Seasonal, dose- and time-response variability in field and laboratory conditions   总被引：3，自引：0，他引：3  

Gorbi S  Regoli F 《Marine environmental research》2004,58(2-5):511-515

Induction of cytochrome P4501A in fish is a well-known indicator of exposure to polycyclic aromatic hydrocarbons (PAHs) and determination of PAH metabolites in bile by fixed wavelength fluorescence (FF) or synchronous fluorescence spectroscopy (SFS), has become an useful method in monitoring programs. In this work the relationship between cytochrome P4501A (EROD activity) and levels of biliary PAH metabolites was measured in the European eel Anguilla anguilla, in both field and laboratory conditions: organisms were sampled on a seasonal basis from the Orbetello lagoon (Tuscany) to characterize the natural variability of these biological parameters, while in laboratory eels were intraperitoneally injected with benzo[a]pyrene to investigate temporal and dose-dependent induction patterns. Results showed that induction of cytochrome P450 and accumulation of PAHs metabolites in bile are not necessarily correlated either in field, or in laboratory investigations; different seasonal changes were measured in natural conditions and slight variations in dose and time response patterns were also obtained in laboratory exposures.  相似文献