The GTC: An Advanced 10m Telescope for the ORM     

J.M. Rodríguez Espinosa  P. Alvarez  F. Sánchez 《Astrophysics and Space Science》1998,263(1-4):355-360

The Gran Telescopio CANARIAS (GTC) is a high performance 10-m class telescope whose construction has been promoted by the IAC (Instituto de Astrofísica de Canarias). It will be installed at the Roque de los Muchachos Observatory (ORM), in the island of La Palma. First light is planned for end-2002. The key science drivers for the project are image quality, operational efficiency and reliability, as emphasized in the Conceptual Design Document which was finished in mid-97. The Preliminary Design is now proceeding on all aspects of the project. The GTC Project is presently funded at the 70% level by Spain. The scientific drives behind the GTC project are described here, as well as the current technical, managerial, and operational baseline. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Linking geomorphology and hydrodynamics: a case study from Península Valdés, Patagonia, Argentina   总被引：1，自引：0，他引：1  

María del Pilar Alvarez  Nilda E. Weiler  Mario A. Hernández 《Hydrogeology Journal》2010,18(2):473-486

A case study is presented to assess the relevance of geomorphology in hydrogeological phenomena in an arid coastal area in the Argentinean extra-Andean Patagonia (Península Valdés) with an average rainfall of 232 mm/year and a soil moisture deficit of about 472 mm/year. Various geomorphic units were identified by interpreting Landsat 7 satellite images processed with ER Mapper software and then surveyed in the field, as well as by geological characterization. The hydrodynamic analysis was based on a survey of 89 wells, the construction of equipotential maps, and the interpretation of pumping-test results by a non-equilibrium method. The hydrochemical characterization was based on chemical tests analyzed with the Easy_Quim 6.0 application. The combination of geomorphological, geological, hydrodynamic and hydrochemical elements allowed the definition of hydromorphological units that are typical of recharge, circulation and discharge areas, the latter both for coastal and inland areas in wetlands (salt pans) with elevations to ?40 m relative to sea level. These units and the criteria used for their definition allow immediate recognition of hydrogeological phenomena in arid regions such as the extra-Andean Patagonia, with low information density but with near-optimal satellite imaging of landforms due to the lack of vegetation cover.  相似文献   

Energy balance and evaporation loss of an irrigation reservoir equipped with a suspended cover in a semiarid climate (south‐eastern Spain)     

B. Gallego‐Elvira  A. Baille  B. Martin‐Gorriz  J. F. Maestre‐Valero  V. Martínez‐Alvarez 《水文研究》2011,25(11):1694-1703

The main objective of this study was to assess the impact of a suspended cover on the evaporation loss of an agricultural water reservoir (AWR). To this aim, a detailed data collection was carried out in a typical AWR located in south‐eastern Spain during 2 consecutive years. During the first year, the reservoir remained uncovered, while during the second year it was covered with a double black polyethylene (PE) shade cloth. On an annual scale, it was observed that the cover can provide a reduction of evaporation loss of 85%. Two approaches, energy balance and mass transfer, were used to analyse the effect of the cover on the evaporation process. Important modifications were observed on the magnitude, sign, annual trend and relative weight of the components of the energy balance. The changes were ascribed to the strong reduction of net radiation and to the substantial weight of the heat storage and sensible heat flux in the energy balance. A relevant finding was the contrast between the patterns of the annual evaporation curve for open‐water and covered conditions. The mass transfer approach allowed discriminating between the wind‐ and radiation‐shelter effects on the evaporation term. The reduction in water‐to‐air vapour deficit was the main factor explaining the high efficiency of the cover, whereas the reduction of the mass transfer coefficient was a modulating factor that accounted for the wind‐shelter effect. Overall, both approaches provided a sound basis to describe and explain the physical mechanisms underlying the high performance of the tested cover. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

44 years hindcast of sea level in the Atlantic Coast of Europe     

P. Sebastião  C. Guedes Soares  E. Alvarez 《Coastal Engineering》2008

The sea level of Northeast Atlantic Ocean is calculated for the period between 1958 and 2001 using a state-of-the-art barotropic model with a grid size of 10′ × 15′ (long × lat). The model includes astronomic effects, considering seven components of the tide, and the meteorological effects of wind and atmospheric pressure, allowing obtaining the astronomic tide, the atmospheric residuals and the non-linear addition of both components of sea level.  相似文献   

Assessment of WRF numerical model forecasts using different lead time initializations during extreme precipitation events over Macaé city,Rio de Janeiro (Brazil)     

da Silva  Fabricio Polifke  da Silva  Alfredo Silveira  da Silva  Maria Gertrudes Alvarez Justi  Pires  Gisele Dornelles 《Natural Hazards》2022,110(1):695-718

Natural Hazards - The ability to forecast extreme precipitation events has become increasingly important over the last decades due to their significant impacts on society and properties. In this...  相似文献   

Present warming within the context of cooling–warming cycles observed since 1854 in the Bay of Biscay     

M. deCastro  M. Gómez-Gesteira  I. Alvarez  J.L.G. Gesteira 《Continental Shelf Research》2009,29(8):1053-1059

The warming trend observed during the last decades in the Bay of Biscay is put within the context of sea surface temperature (SST) changes observed in the area since 1854. Macroscopically, two consecutive warming–cooling cycles were detected during this period of time: cooling from 1867 to 1910; warming from 1910 to 1945; cooling from 1945 to 1974; and warming from 1974 to nowadays. Warming rates of 0.17 and 0.22 °C per decade were measured during the warming sub-periods and cooling rates of ?0.14 and ?0.10 °C per decade were measured during the cooling sub-periods. The present warming period is on the same order of magnitude although slightly more intense than the one observed from 1910 to 1945, which is consistent with previous analysis carried for the North Atlantic. Finally, the thermal amplitude defined as the difference between the maximum and minimum annual values has increased since 1974 at a rate of 0.06 °C per decade due to the different increasing rates of the maximum (0.26 °C per decade) and minimum (0.20 °C per decade) SSTs.  相似文献   

Late Cretaceous geomagnetic polarity sequence: detailed rock and palaeomagnetic studies of the Scaglia Rossa limestone at Gubbio, Italy     

William Lowrie  Walter Alvarez 《Geophysical Journal International》1977,51(3):561-581

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Interplanetary scattering of fast solar electrons deduced from type III bursts observed at low frequencies     

H. Alvarez  R. P. Lin 《Solar physics》1976,46(2):477-481

Observations of low frequency solar type III radio bursts and the associated fast solar electrons show that the total path length traveled by the particles between the Sun and the Earth is significantly greater than the length of the smooth Archimedean spiral trajectory followed by the centroid of the type III exciter (Alvarez et al., 1975). Here we assume that the ratio of electron path length and the spiral length increases approximately as r ⁿ, where r is heliocentric distance, and then compute the radio bursts arrival time at 1 AU for different values of n. A comparison with the radio observations indicates that the best fit occurs for n = 1.5 ± 1.0. We interpret these results in terms of the variation of electron scattering with heliocentric distance.  相似文献   

Fast solar electrons,interplanetary plasma and km-wave type-III radio bursts observed from the IMP-6 spacecraft     

Hector Alvarez  Robert P. Lin  Samuel J. Bame 《Solar physics》1975,44(2):485-501

IMP-6 spacecraft observations of low frequency radio emission, fast electrons, and solar wind plasma are used to examine the dynamics of the fast electron streams which generate solar type-III radio bursts. Of twenty solar electron events observed between April, 1971 and August, 1972, four were found to be amenable to detailed analysis. Observations of the direction of arrival of the radio emission at different frequencies were combined with the solar wind density and velocity measurements at 1 AU to define an Archimedean spiral trajectory for the radio burst exciter. The propagation characteristics of the exciter and of the fast electrons observed at 1 AU were then conpared. We find that: (1) the fast electrons excite the radio emission at the second harmonic; (2) the total distance travelled by the electrons was between 30 and 70% longer than the length of the smooth spiral defined by the radio observations; (3) this additional distance travelled is the result of scattering of the electrons in the interplanetary medium; (4) the observations are consistent with negligible true energy loss by the fast electrons.  相似文献   

On final evolutions in the restricted planar parabolic three-body problem     

Martha Alvarez  Josep Maria Cors  Joaquin Delgado 《Celestial Mechanics and Dynamical Astronomy》2006,95(1-4):173-200

In this paper, we prove the existence of special type of motions in the restricted planar parabolic three-body problem, of the type exchange, emission–capture, and emission–escape with close passages to collinear and equilateral triangle configuration, among others. The proof is based on a gradient-like property of the Jacobian function when equations of motion are written in a rotating–pulsating reference frame, and the extended phase space is compactified in the time direction. Thus a phase space diffeomorphic to -coordinates (θ, ζ, ζ′) is obtained with the boundary manifolds θ = ± π/2 corresponding to escapes of the binaries when time tends to ± ∞. It is shown there exists exactly five critical points on each boundary, corresponding to classic homographic solutions. The connections of the invariant manifolds associated to the collinear configurations, and stable/unstable sets associated to binary collision on the boundary manifolds, are obtained for arbitrary masses of the primaries. For equal masses extra connections are obtained, which include equilateral configurations. Based on the gradient-like property, a geometric criterion for capture is proposed and is compared with a criterion introduced by Merman (1953b) in the fifties, and an example studied numerically by Kocina (1954).  相似文献