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11.
The role of the Madden–Julian Oscillation (MJO) in producing active and break periods of the South American (SA) monsoon and the performance of the ECMWF and NCEP models in predicting these periods at multiweek lead times are assessed. Two monsoon indices, based on precipitation and wind, are proposed to characterize these periods. The models represent well the observed association of active and break monsoon days with large scale convection and circulation anomalies. Although reproducing approximately the distribution of active and break days proportions in each phase of the MJO cycle, models produce a phase shift between observed and simulated distributions because they establish the teleconnection between Central Pacific and South America, as well as its impacts, sooner than in observations. The predictive skill of both rainfall and wind anomalies is limited to about 2 weeks, with the monsoon wind index displaying higher correlation score till week 3. The forecast performance is apparently not affected by initialization on active or break monsoon days. However, it is higher for prediction of lower precipitation in break days than heavier rainfall in active days. Wind is much better predicted than rainfall for active days, which could be used for extreme rainfall events forecast. Although relatively small at shorter lead times, the MJO contribution is the major source of rainfall predictability after week 3. To improve the multiweek prediction of SA monsoon, models need not only to predict correctly the MJO phase, but also to reproduce in the right phase the MJO-related SA rainfall anomalies.
相似文献12.
F. Battazza A. Coletta E. Lopinto C. Fiorentino L. Pietranera G. Valentini S. Zoffoli 《Journal of Geodynamics》2010,49(3-4):171-180
COnstellation of small Satellites for Mediterranean basin Observation (COSMO-SkyMed) is the largest Italian investment in Space Systems for Earth Observation, commissioned and funded by Italian Space Agency (ASI) and Italian Ministry of Defence (MoD). COSMO-SkyMed is a Dual-Use (Civilian and Defence) end-to-end Earth Observation System aimed at establishing a global service supplying provision of data, products and services compliant with well-established international standards and relevant to a wide range of applications, such as Risk Management, Scientific and Commercial Applications and Defence Applications. The system consists of a constellation of four LEO mid-sized satellites, each equipped with a multi-mode high-resolution SAR operating at X-band. Three out of four COSMO-SkyMed satellites have been successfully launched the 8th of June, the 9th of December 2007 and the 25th of October 2008 respectively, while the remaining satellite will be deployed within 2010. COSMO-SkyMed 1 and 2 completed their commissioning phase to test, verify and qualify the overall system and from the 1st of August 2008 both satellites are in the operational phase. The third satellite is still performing its commissioning and it is expected to enter in operation in the second half of 2009. The results of the commissioning phase of COSMO-SkyMed 1 and 2 are presented together with the Scientific Mission Exploitation strategy (i.e. Announcement of Opportunity, Background Mission). 相似文献
13.
The occurrence of micron to millimeter size globular heterogeneities in igneous rocks is frequently explained by processes of liquid immiscibility. However, such textures have also been documented in miscible magmatic pairs. In this study, the ability of miscible magmas to develop transient surface tensions and mimic the behavior of immiscible liquids is tested for the whole spectrum of magmatic compositions. We implemented a numerical model that includes the effect of gradient stresses (namely Korteweg stress) in order to investigate the role of such stresses in the evolution of diffusive interfaces. The results show that an initially elongated heterogeneity surrounded by a miscible and compositionally diverse magma will tend to minimize its contact surface by relaxing to a spherical shape, advected by a Korteweg stress driven flow. If the initial aspect ratio of the heterogeneity exceeds a critical value, surface minimization may be achieved by drop breakup. In addition, it is shown that two neighboring heterogeneities may coalesce to a single spherical drop. These results imply that even for fully miscible magmas, rheological barriers may prevent efficient mechanical intermingling and induce the formation of small-scale globular textures, analogous to those commonly observed in immiscible liquids. A better understanding of the role of Korteweg stress may be of the utmost importance for deciphering the textures generated by the interaction of compositionally diverse magmas. 相似文献
14.
A. Pastorello D. Sauer S. Taubenberger P. A. Mazzali K. Nomoto K. S. Kawabata S. Benetti N. Elias-Rosa A. Harutyunyan H. Navasardyan L. Zampieri T. Iijima M. T. Botticella G. Di Rico M. Del Principe M. Dolci S. Gagliardi M. Ragni G. Valentini 《Monthly notices of the Royal Astronomical Society》2006,370(4):1752-1762
Early-time optical observations of supernova (SN) 2005cs in the Whirlpool Galaxy (M51) are reported. Photometric data suggest that SN 2005cs is a moderately underluminous Type II plateau SN (SN IIP). The SN was unusually blue at early epochs ( U − B ≈−0.9 about three days after explosion) which indicates very high continuum temperatures. The spectra show relatively narrow P Cygni features, suggesting ejecta velocities lower than observed in more typical SNe IIP. The earliest spectra show weak absorption features in the blue wing of the He i 5876-Å absorption component and, less clearly, of Hβ and Hα. Based on spectral modelling, two different interpretations can be proposed: these features may either be due to high-velocity H and He i components, or (more likely) be produced by different ions (N ii , Si ii ). Analogies with the low-luminosity, 56 Ni-poor, low-velocity SNe IIP are also discussed. While a more extended spectral coverage is necessary in order to determine accurately the properties of the progenitor star, published estimates of the progenitor mass seem not to be consistent with stellar evolution models. 相似文献
15.
Francesco Visconti Luana Stefanon Carlo Camporeale Francesca Susin Luca Ridolfi Stefano Lanzoni 《地球表面变化过程与地形》2012,37(8):818-827
A new approach for the profiling of movable sediment beds in laboratory experiments is presented. It couples a triangulation laser sensor and an ultrasonic level transmitter, and allows a non‐intrusive, fast and accurate measurement of bed topography without stopping the experimental runs. The distortion of the laser beam due to the refraction at the water surface is corrected by contemporaneously measuring the elevation of the water surface through the ultrasonic level transmitter and taking advantage of geometrical relations involving the water depth, distance of the sensors from the water surface, and the angles that the emitted laser beam forms with the vertical before and after refraction. Several tests, under either still‐ or flowing‐water conditions, as well as increasing/decreasing water surface elevation, were carried out to evaluate the accuracy of the measurements. These tests indicate that good‐quality measurements are obtained for flow depths in the range 0 < D < 60 mm, typical of morphodynamic laboratory experiments. Finally, two relevant applications to movable bed experiments carried out under either lagoonal or fluvial conditions are presented that show the effectiveness of the proposed profiling technique. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
16.
Nico Valentini Alessandra Saponieri Matteo Gianluca Molfetta Leonardo Damiani 《Earth Science Informatics》2017,10(4):495-506
Video systems have become widely used all around the world in coastal monitoring strategies, allowing both high temporal and spatial sampling frequency, with low logistic and costs efforts. The present paper deals with a new tool for coastal images processing, aimed at the automatic shoreline detection and data analysis. The tool is composed by a shoreline detection routine implemented in a web-application, addressed at images processing (i.e. shoreline extraction and geo-rectification), data analysis and sharing results about beach actual state and shore evolution in quasi-real time. The Shoreline Detection Model (SDM) is based on a new algorithm, implementing image-processing procedures, which allows extracting the sea/land boundary from automatic segmented Timex images. The SDM calibration and validation has been performed on different coastal images derived from a video monitoring system installed at Alimini (Lecce, IT) in 2005, by comparing automatic shoreline contours with the manual detected ones. Moreover, in December 2015, new video monitoring systems were installed in South Italy (Porto Cesareo and Torre Canne, Apulia region), at sandy beaches affected by erosion phenomena. The application of the SDM on images recorded by the new systems has allowed testing the model feasibility at sites characterized by different morphological features and geographical exposition. The present describes in detail the SDM algorithm and the image processing procedures used. The results of the model calibration and validation performed at Alimini and the tests performed at Porto Cesareo on first images are reported. 相似文献
17.
For the first time, vertical fluxes of mineral dust measured by Eddy Covariance in two desert sites of Northern Asia have been used to test the performances of a wind erosion model in the field. Soil parameters required by the model were obtained through field and laboratory determinations. Model predictions and direct measurements have been compared. The main finding was that the direction of the horizontal wind relative to the orientation of nebkhas played a crucial role in determining the emission of particles in one of the investigated sites. Being unable to simulate such interaction, the model generally overestimated the actual emission. It provided, instead, reliable predictions (r2 = 0·87) when the wind direction was suitable in detaching loose erodible elements placed on nebkhas thanks to their normal orientation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
18.
Laura Valentini Bruno Capaccioni Piermaria Luigi Rossi Roberto Scandone Damiano Sarocchi 《Bulletin of Volcanology》2008,70(9):1087-1101
In order to provide new information about the source area and depositional mechanisms of the Upper Member of the Neapolitan
Yellow Tuff (NYT), a prominent pyroclastic deposit of the Campi Flegrei Volcanic District (southern Italy), statistics on
directional fabric, by means of computer-assisted image analysis on 32 rock samples, were compiled. Seventeen samples were
collected along vertical direction on two selected exposures and fifteen were taken from outcrops widely distributed all around
the Campi Flegrei Volcanic District. Fabric measurements within the investigated successions reveal a vertically homogeneous
direction of the mean particle iso-orientation, with considerable variability in the strength of particle iso-orientation
even at cm-scale. The existence of particle iso-orientation can be related to continuous sedimentation from a concentrated
bedload region beneath suspension currents, producing massive or inversely graded beds by traction carpet sedimentation. The
considerable vertical variability in the strength of iso-orientation is the result of very unstable flow regimes, up to the
extreme condition of discrete depositional events, with a variable combination of traction carpet and/or direct suspension
sedimentation. The vertical homogeneity in the mean orientation values, found in the investigated sections, may derive from
the sequential deposition of laminae to thin beds, whose relatively flat upper surfaces were unable to significantly deflect
the depositional system of the following currents. According to the observed homogeneous mean particle orientation values
along the investigated vertical profiles, samples collected through areal distribution are considered representative of the
local paleo-flow directions of the whole deposit. The mean directions of the samples collected areally show two different
coherent patterns which point to the existence of two different source areas. The first, which includes all samples from the
northern outcrops, appears to converge in a narrow area about 2 km NE of the town of Pozzuoli, largely in coincidence with
the inferred area on the basis of the pumice fall distribution. The second, which includes samples from Capo Miseno and Posillipo
areas, points to the central part of the Pozzuoli Bay, about 4 km offshore the town of Pozzuoli. 相似文献
19.
The analysis of the transition from the large-scale fluid regime to the short-scale kinetic range of wavelengths in the development of the turbulent cascade of energy is nowadays subject of fervent discussion in the space plasmas scientific community. We make use of Hybrid Vlasov-Maxwell simulations where the full kinetic dynamics of ions is taken into account, while electrons are treated as a fluid. We investigate the development of turbulence in the solar wind, in 1D-3V phase space configuration and in the frequency range across the ion cyclotron frequency. These simulations allow for the analysis of the role of kinetic effects in the short-scale region of the energy spectra in the direction parallel to the background magnetic field. Our numerical results show the presence of a significant electrostatic activity at small wavelengths, triggered by the resonant interaction of ions with longitudinal waves. Our model does not allow to take into account the evolution of the turbulent spectra in the plane perpendicular to the ambient field, due to limited dimensionality in phase space. On the other hand, this model permits to isolate and study the possibility of transferring the electromagnetic large-scale energy on the small-scale kinetic electrostatic component of the spectrum. Peculiar features observed in the spacecraft data in the solar wind are qualitatively reproduced within the hybrid-Vlasov model, such as the generation of perpendicular temperature anisotropy and accelerated longitudinal beams of ions in the distribution of particle velocities as well as the appearance of a marked peak of electrostatic activity in the short-scale termination of the turbulent spectra. 相似文献
20.
The nationalization of electoral change in a geographical perspective: the case of Italy (2006–2008)
Luana Russo 《GeoJournal》2014,79(1):73-87
This paper assesses the nationalization of electoral change in a setting of major changes at the party level. After discussing the theoretical difference between the configuration of the electorate and its movement, the Italian case is examined. In order to check whether strategic voting dynamics took place between the 2006 and 2008 Italian Parliamentary elections, the swing voters’ estimates are obtained. After having shown that the Italian electorate behaved strategically, we investigated whether the swing had a national or a territorial pattern. The findings show that the switching occurred in Italy between the 2006 and the 2008 elections can be considered national. 相似文献