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41.
Implementation of a Single-Column Model for Fog and Low Cloud Forecasting at Central-Spanish Airports 总被引：1，自引：0，他引：1
Operations at Central-Spanish airports are often, especially in winter, affected by visibility reduction. The Instituto Nacional de Meteorología (INM), the Spanish Weather Service, has developed a single-column model (SCM) in order to improve short-term forecasts of
fog, visibility and low-clouds. The SCM, called H1D, is a one-dimensional version of the HIRLAM limited-area model. It is
operationally run for three airports in the region: Madrid-Barajas, Almagro and Albacete-Los Llanos. Since SCMs cannot deal
with horizontal heterogeneity, the terms that depend on the horizontal structure of the atmosphere are estimated from the
outputs of the three-dimensional (3-D) model and introduced into the SCM as external forcings. The systematic analysis of
the meteorological situations has evidenced the existence of a close relationship between fog formation and the presence of
drainage winds in the region. Since the 3-D model docs not have the necessary resolution to correctly simulate the main features
of the drainage flow caused by the complex topography in the proximity of Madrid-Barajas, it cannot provide the SCM with the
correct forcings. This problem has been partially overcome through the introduction of a module that, under certain conditions,
substitutes the values computed from the 3-D model outputs by others that are based on a conceptual model of the phenomenon
and have been empirically derived from climatological knowledge. This module improves the H1D verification scores for the
basic meteorological variables—wind, temperature and humidity—and reduces the false alarm rate in fog forecast. 相似文献
42.
Coastal regions are the areas most threatened by natural hazards, with floods being the most frequent and significant threat in terms of their induced impacts, and therefore, any management scheme requires their evaluation. In coastal areas, flooding is a hazard associated with various processes acting at different scales: coastal storms, flash floods, and sea level rise (SLR). In order to address the problem as a whole, this study presents a methodology to undertake a preliminary integrated risk assessment that determines the magnitude of the different flood processes (flash flood, marine storm, SLR) and their associated consequences, taking into account their temporal and spatial scales. The risk is quantified using specific indicators to assess the magnitude of the hazard (for each component) and the consequences in a common scale. This allows for a robust comparison of the spatial risk distribution along the coast in order to identify both the areas at greatest risk and the risk components that have the greatest impact. This methodology is applied on the Maresme coast (NW Mediterranean, Spain), which can be considered representative of developed areas of the Spanish Mediterranean coast. The results obtained characterise this coastline as an area of relatively low overall risk, although some hot spots have been identified with high-risk values, with flash flooding being the principal risk process. 相似文献
43.
When this article was originally published the author's 相似文献
44.
J. Acosta A. Muñoz P. Herranz C. Palomo M. Ballesteros M. Vaquero E. Uchupi 《Geo-Marine Letters》2001,21(3):123-130
Pockmarks ranging in width from <10 to 700 m, and with reliefs of 2 to 55 m were discovered in the Ibiza Channel and on the Balearic Promontory, Western Mediterranean, during a multibeam survey. In the Ibiza Channel the larger structures are found within a field of small craters less than 10 m wide and 5 m deep which give the seafloor an "orange peel" texture. The abundant 30 Ma-Present volcanic structures in the region suggests that most of the craters may have been formed by the escape of gases and associated waters via faults from a hydrothermal field beneath the surficial sediments. Others may be the result of neotectonism. 相似文献
45.
This paper focuses on some aspects of the motion of a small particle moving near the Lagrangian points of the Earth–Moon system.
The model for the motion of the particle is the so-called bicircular problem (BCP), that includes the effect of Earth and
Moon as in the spatial restricted three body problem (RTBP), plus the effect of the Sun as a periodic time-dependent perturbation
of the RTBP. Due to this periodic forcing coming from the Sun, the Lagrangian points are no longer equilibrium solutions for
the BCP. On the other hand, the BCP has three periodic orbits (with the same period as the forcing) that can be seen as the
dynamical equivalent of the Lagrangian points. In this work, we first discuss some numerical methods for the accurate computation
of quasi-periodic solutions, and then we apply them to the BCP to obtain families of 2-D tori in an extended neighbourhood
of the Lagrangian points. These families start on the three periodic orbits mentioned above and they are continued in the
vertical (z and ż) direction up to a high distance. These (Cantor) families can be seen as the continuation, into the BCP, of the Lyapunov
family of periodic orbits of the Lagrangian points that goes in the (z, ż) direction. These results are used in a forthcoming work [9] to find regions where trajectories remain confined for a
very long time. It is remarkable that these regions seem to persist in the real system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
46.
Ballesteros E Torras X Pinedo S García M Mangialajo L de Torres M 《Marine pollution bulletin》2007,55(1-6):172-180
Macroalgae is a biological key element for the assessment of the ecological status in coastal waters in the frame of the European Water Framework Directive (WFD, 2000/60/EC). Here we propose a methodology for monitoring water quality based on the cartography of littoral and upper-sublittoral rocky-shore communities (CARLIT, in short). With the use of spatial databases, GIS, and available information about the value of rocky-shore communities as indicators of water quality, it is possible to obtain an environmental quality index representative of the ecological status of rocky coasts. This index, which completely fulfils the requirements of the WFD, is expressed as a ratio between the observed values in the sector of shore that is being assessed and the expected value in a reference condition zone with the same substrate and coastal morphology (Ecological Quality Ratio, EQR). The application of this index to the coast of Catalonia (North-Western Mediterranean) is presented. 相似文献
47.
Antonio Rius Oleguer Nogués-Correig Serni Ribó Estel Cardellach Santi Oliveras Enric Valencia Hyuk Park José Miguel Tarongí Adriano Camps Hans van der Marel Roel van Bree Bas Altena Manuel Martín-Neira 《GPS Solutions》2012,16(2):231-241
The Global Navigation Satellite System Reflectometry (GNSS-R) concept was conceived as a means to densify radar altimeter measurements of the sea surface. Until now, the GNSS-R concept relied on open access to GNSS transmitted codes. Recently, it has been proposed that the ranging capability of the technique for ocean altimetric applications can be improved by using all the signals transmitted in the bandwidth allocated to GNSS, which includes open access as well as encrypted signals. The main objective of this study is to provide experimental proof of this enhancement through a 2-day experiment on the Zeeland Bridge (The Netherlands). In the experiment, we used a custom built GNSS-R system, composed of high gain GPS antennas, calibration subsystem, and an FPGA-based signal processor which implemented the new concepts, an X-band radar altimeter and a local geodetic network. The results obtained indicate that the new approach produces a significant improvement in GNSS-R altimetric performance. 相似文献
48.
E. Molina Ballesteros J. García Talegón A. C. I?igo I?igo M. González Sánchez H. Herrero Fernández 《Environmental Earth Sciences》2011,64(7):1741-1754
Some physical properties (bulk and free porosity, pore size distribution), and the chemical composition and mass balance of
two deeply weathered profiles one developed on Hercynian granodiorite and the other on pre-Cambrian slates were studied. Hydric
and mercury porosimetry, nitrogen adsorption techniques, chemical analyses and XRD techniques were used. On granodiorite,
weathering has created increased porosity with a pore diameter <5 μm, whereas on slates the weathering has produced of ca.
1 μm in diameter. These pore sizes have played an important role in the weathering processes. Assuming that weathering preserves
volumes, except in the uppermost part of the profiles, it brought about a loss of matter of more than 12% (~300 kg/m3) on granodiorite and ca. 30% (~800 kg/m3) on slates. These changes are related to shifts in the mineralogical evolution, with the appearance of new 2:1 and 1:1 phyllosilicates
and Fe oxy-hydroxides as the main authigenic minerals. The release of matter, at least since the upper Neogene until the present,
has led to the lowering of relief in a more or less homogeneous way, giving rise to gentle hillsides and flat surfaces below
which the current river networks are incised. Porosity studies have the potential to explain several specific landforms as
well as affecting landscape development in general. 相似文献
49.
V. Reglero F. Ballesteros P. Blay E. Porras F. Sánchez J. Suso 《Astrophysics and Space Science》2001,276(1):239-254
Two years after launch (04.21.97), LEGRI is operating on Minisat-01 in a LEO orbit. The LEGRI detector plane is formed by two type of gamma-ray solid state detectors: HgI2 and CdZnTe. Detectors are embedded in a box containing the FEE and DFE electronics. This box provides an effective detector passive shielding. Detector plane is multiplexed by a Coded Aperture System located at 54 cm and a Ta Collimator with a FCFOV of 22° and 2° angular resolution. The aim of this paper is to summarize the detector behaviour in three different time scales: before launch, during the in-orbit check-out period (IOC), and after two years of routine operation in space. Main results can be summarized as follows:A large fraction of the HgI2 detectors presented during LEGRI IOC very high count ratios from their first switch-on (May 1997). Therefore, they induced saturation in the on-board mass memory. After some unsuccessful attempts to reduce the count ratios by setting up different thresholds during LEGRI IOC, all of them were switched off except nine detectors in column 4, with a higher degree of stability.Oppositely, the 17 CdZnTe detectors present a remarkable stability in both their count-ratios and spectral shapes. Details about CdZnTe ground energy calibration, in-flight calibration (using the Crab) and detector stability are discussed hereafter. Detector efficiency function has been computed with the fixed flight threshold used within the calibrated energy range (20-80 KeV). It presents a maximum at 60 KeV, and decreasing efficiencies in the lower and upper energy range ends. Both, non-linear threshold cutting and the drop in the detector efficiency explain the CdZnTe computed operational efficiency response. 相似文献
50.
Fernando Jesús Ballesteros Roselló 《Astrophysics and Space Science》2001,276(1):291-298
-ray telescopes based on coded-mask techniques does not give adirect image of the sky sources but its correlation with the mask responsefunction. To obtain an image of the sky sources one has to treatmathematically the detected image, usually by correlating it with areconstruction array (correlation methods). Unfortunately this kindof methods, although quite fast, have some limitations in the reconstructedimage and in handling the real telescope response.To improve these results, several reconstruction methods have been developedand used. In the case of LEGRI (a -ray coded-mask telescopedeveloped for the University of Valencia) we have used the EM algorithm,an iterative maximum likelihood algorithm with very good response andwith good handling of the telescope response. 相似文献