Extreme rainfall events in Catalonia. The case of 12 November 1988     

M. Carmen Llasat  Roberto Rodriguez 《Natural Hazards》1992,5(2):133-151

A study of the synoptic situation which produced the catastrophic floods of November 1988 in Catalonia (in the northeast of the Iberian Peninsula) is presented. Analyses of the vertical structure, potential instability, precipitable water, and instability index are made through the radiosounding data from Palma, Majorca. It is found that the 1988 situation is included in type I intense convective events in Catalonia (classification obtained from all the events since 1950, (Llasat, 1989)). It was characterized by:

(a)	-pattern in the middle and high troposphere, the ridge axis east of Catalonia.
(b)	High pressure over Europe.
(c)	South-easterly winds in the lower troposphere with warm and moist humid air advection and south-westerlies aloft over Catalonia.
(d)	Strong instability (convective and latent).
(e)	Penetration of Atlantic air.

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Chironomid-inferred temperature changes of the last century in anoxic Seebergsee,Switzerland: assessment of two calibration methods     

Isabelle Larocque-Tobler  Roberto Quinlan  Monique M. Stewart  Martin Grosjean 《Quaternary Science Reviews》2011,30(13-14):1770-1779

Chironomids (non-biting midges) can provide accurate climate reconstructions from the Late Glacial to the present. Until now, anoxic lakes have been avoided for temperature reconstructions since chironomid assemblages are sensitive to changes in oxygen concentrations in the hypolimnion. However, anoxic lakes may have varved sediments, providing the possibility for near-annual climate reconstructions. Here, we tested the applicability of two calibration methods to reconstruct mean July air temperatures from chironomid assemblages preserved in the sediments of the anoxic Seebergsee located in the northern Swiss Alps: a calibration-in-space approach and a calibration-in-time approach. The calibration-in-space approach (i.e. chironomid assemblages from surficial lake sediments (0–1 cm) calibrated against meteorological data) provided accurate inferences (i.e. similar temperature changes as measured at the closest meteorological station, and at regional stations) in the Seebergsee stratigraphy until anoxia increased in the lake. With the increase of anoxia, the chironomid-inferred temperatures were generally colder than measured temperatures. A calibration-in-time approach (i.e. calibration of chironomid assemblages in a time series against instrumental data from the closest meteorological station) provided accurate reconstructions (i.e. similar to the regional records) for the past 100 years, including the time period of inferred anoxia. However, its applicability should be further tested on longer temporal scales.  相似文献   

Applications of Bayesian model selection to cosmological parameters     

Roberto Trotta 《Monthly notices of the Royal Astronomical Society》2007,378(1):72-82

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The Millennium Galaxy Catalogue: the B-band attenuation of bulge and disc light and the implied cosmic dust and stellar mass densities     

Simon P. Driver  Cristina C. Popescu  Richard J. Tuffs  Jochen Liske  Alister W. Graham  Paul D. Allen  Roberto De Propris 《Monthly notices of the Royal Astronomical Society》2007,379(3):1022-1036

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Compositional and temporal investigation of exposed lunar basalts in the Mare Imbrium region   总被引：2，自引：0，他引：2  

Roberto Bugiolacchi  John E. Guest 《Icarus》2008,197(1):1-18

This paper presents an updated stratigraphical and compositional study of the exposed maria within the Imbrium basin on the Moon. Clementine multispectral data were employed to derive TiO₂ and FeO wt% abundance estimates of potentially distinct basaltic flows. Additionally, NASA Lunar Orbiter images were used to estimate flow ages using crater count statistics. Mare Imbrium shows evidence of a complex suite of low to high-Ti basaltic lava units infilling the basin over an 800 million year timescale. More than a third (37%) of identified mare basalts were found to contain 1-3 wt% TiO₂. Two other major mare lithological units (representing about 25% of the surface each) show TiO₂ values between 3-5 and 7-9 wt%. The dominant fraction (55%) of the sampled maria contain FeO between 16 and 18 wt%, followed by 27% of maria having 18-20 wt% and the remaining 18%, 14-16 wt% FeO. A crater frequency count (for diameters >500 m) shows that in three quarters of the sampled mare crater counts range between 3.5 and 5.5×¹⁰⁻² per km², which translates, according to a lunar cratering model chronology, into estimated emplacement ages between ∼3.3 and 2.5 Ga. A compositional convergence trend between the variations of iron and titanium oxides was identified, in particular for materials with TiO₂ and FeO content broadly above 5 and 17 wt%, respectively, suggesting a related petrogenesis and evolution. According to these findings, three major periods of mare infill are exposed in the Imbrium basin; despite each period showing a range of basaltic compositions (classified according to their TiO₂ content), it is apparent that, at least within these local geological settings, the igneous petrogenesis generally evolved through time towards more TiO₂- and FeO-rich melts.  相似文献   

The Australia Telescope 20-GHz (AT20G) Survey: the Bright Source Sample     

Marcella Massardi  Ronald D. Ekers  Tara Murphy  Roberto Ricci  Elaine M. Sadler  Sarah Burke  Gianfranco De Zotti  Philip G. Edwards  Paul J. Hancock  Carole A. Jackson  Michael J. Kesteven  Elizabeth Mahony  Christopher J. Phillips  Lister Staveley-Smith  Ravi Subrahmanyan  Mark A. Walker  Warwick E. Wilson 《Monthly notices of the Royal Astronomical Society》2008,384(2):775-802

The Australia Telescope 20-GHz (AT20G) Survey is a blind survey of the whole southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried out with the Australia Telescope Compact Array from 2004 to 2007.
The Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G Survey catalogue comprising 320 extragalactic     ) radio sources south of  δ=−15°  with      Jy. Of these, 218 have near simultaneous observations at 8 and 5 GHz.
In this paper we present an analysis of radio spectral properties in total intensity and polarization, size, optical identifications and redshift distribution of the BSS sources. The analysis of the spectral behaviour shows spectral curvature in most sources with spectral steepening that increases at higher frequencies (the median spectral index α, assuming   S ∝ν^α  , decreases from  α^8.6_4.8= 0.11  between 4.8 and 8.6 GHz to  α²⁰_8.6=−0.16  between 8.6 and 20 GHz), even if the sample is dominated by flat spectra sources (85 per cent of the sample has  α²⁰_8.6 > −0.5)  . The almost simultaneous spectra in total intensity and polarization allowed us a comparison of the polarized and total intensity spectra: polarized fraction slightly increases with frequency, but the shapes of the spectra have little correlation. Optical identifications provided an estimation of redshift for 186 sources with a median value of 1.20 and 0.13, respectively, for QSO and galaxies.  相似文献   

Analysis of surface circulation structures along a frequently repeated XBT transect crossing the Ligurian and Tyrrhenian Seas     

Tiziana Ciuffardi  Ernesto Napolitano  Roberto Iacono  Franco Reseghetti  Giancarlo Raiteri  Andrea Bordone 《Ocean Dynamics》2016,66(6-7):767-783

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Geometric Aspects of the Full Moment Tensors in the Gulf of California and the Mexican East Pacific Rise     

Roberto Ortega  Luis Quintanar  Eduardo Huesca-Pérez 《Pure and Applied Geophysics》2016,173(10-11):3595-3614

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Numerical study of circulation on the inner Amazon Shelf     

Roberto Fioravanti Carelli Fontes  Belmiro Mendes Castro  Robert C. Beardsley 《Ocean Dynamics》2008,58(3-4):187-198

We studied the circulation on the coastal domain of the Amazon Shelf by applying the hydrodynamic module of the estuarine and coastal ocean model and sediment transport. The first barotropic experiment aimed to explain the major bathymetric effects on tides and those generated by anisotropy in sediment distribution. We analyzed the continental shelf response of barotropic tides under realistic bottom stress parametrization (C _d ), considering sediment granulometry obtained from a faciologic map, where river mud deposits and reworked sediments areas are well distinguished, among others classes of sediments. Very low C _d values were set in the fluid mud regions off the Amapá coast (1.0 10^???4), in contrast to values around 3.5 10^???3 for coarser sediment regions off the Pará coast. Three-dimensional experiments represented the Amazon River discharge and trade winds, combined to barotropic tide influences and induced vertical mixing. The quasiresonant response of the Amazon Shelf to the M₂ tide acts on the local hydrodynamics by increasing tidal admittance, along with tidal forcing at the shelf break and extensive fluid mud regions. Harmonic analysis of modeled currents agreed well with the analysis of the AMASSEDS observational data set. Tidal-induced vertical shear provided strong homogenization of threshold waters, which are subject to a kind of hydraulic control due to the topographic steepness. Ahead of the hydraulic jump, the low-salinity plume is disconnected from the bottom and acquires negative vorticity, turning southeastward. Tides act as a generator mechanism and topography, via hydraulic control, acts as a maintainer mechanism for the low-salinity frontal zone positioning. Tidally induced southeastward plume fate is overwhelmed by northwestward trade winds so that they, along with background circulation, probably play the most important role on the plume fate and variability over the Amazon Shelf.  相似文献   

Evaluation of the measured seismic response of the Mexico City Cathedral     

Darío Rivera  Roberto Meli  Roberto Sánchez  Bernardo Orozco 《地震工程与结构动力学》2008,37(10):1249-1268

The seismic response of the Mexico City Cathedral built of very soft soil deposits is evaluated by using motions recorded in various parts of the structure during several moderate earthquakes. This unique set of records provides significant insight into the seismic response of this and other similar historic stone masonry structures. Free‐field ground motions are carefully compared in time and frequency domains with motions recorded at building basement. The dynamic characteristics of the structure are inferred from the earthquake records by using system identification techniques. Variation of seismic response for different seismic intensities is discussed. It is shown that, due to the soil–structure interaction, due to large differences between dominant frequencies of earthquake ground motions at the site and modal frequencies of vibration of the structure, and due to a particularly high viscous damping, seismic amplifications of ground motion in this and similar historic buildings erected on soft soil deposits are much smaller than that induced in most modern constructions. Nevertheless, earthquake records and analytical results show that several components of the structure such as its central dome and the bell towers may be subjected to local vibrations that significantly amplify ground motions. Overall, results indicate that in its present state the structure has an acceptable level of seismic safety. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献