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31.
Ana J. Abascal Sonia Castanedo Paula Núñez Adam Mellor Annika Clements Beatriz Pérez Mar Cárdenas Helios Chiri Raúl Medina 《Marine pollution bulletin》2017,114(1):302-314
This paper presents a high-resolution operational forecast system for providing support to oil spill response in Belfast Lough. The system comprises an operational oceanographic module coupled to an oil spill forecast module that is integrated in a user-friendly web application. The oceanographic module is based on Delft3D model which uses daily boundary conditions and meteorological forcing obtained from COPERNICUS and from the UK Meteorological Office. Downscaled currents and meteorological forecasts are used to provide short-term oil spill fate and trajectory predictions at local scales. Both components of the system are calibrated and validated with observational data, including ADCP data, sea level, temperature and salinity measurements and drifting buoys released in the study area. The transport model is calibrated using a novel methodology to obtain the model coefficients that optimize the numerical simulations. The results obtained show the good performance of the system and its capability for oil spill forecast. 相似文献
32.
Christian Wöhler Pablo d’Angelo Lars Krüger Annika Kuhl Horst-Michael Groß 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(6):529-540
In this article we propose a method for combining geometric and real-aperture methods for monocular three-dimensional (3D) reconstruction of static scenes at absolute scale. Our algorithm relies on a sequence of images of the object acquired by a monocular camera of fixed focal setting from different viewpoints. Object features are tracked over a range of distances from the camera with a small depth of field, leading to a varying degree of defocus for each feature. Information on absolute depth is obtained based on a Depth-from-Defocus approach. The parameters of the point spread functions estimated by Depth-from-Defocus are used as a regularisation term for Structure-from-Motion. The reprojection error obtained from bundle adjustment and the absolute depth error obtained from Depth-from-Defocus are simultaneously minimised for all tracked object features. The proposed method yields absolutely scaled 3D coordinates of the scene points without any prior knowledge about scene structure and camera motion. We describe the implementation of the proposed method both as an offline and as an online algorithm. Evaluating the algorithm on real-world data, we demonstrate that it yields typical relative scale errors of a few per cent. We examine the influence of random effects, i.e. the noise of the pixel grey values, and systematic effects, caused by thermal expansion of the optical system or by inclusion of strongly blurred images, on the accuracy of the 3D reconstruction result. Possible applications of our approach are in the field of industrial quality inspection; in particular, it is preferable to stereo cameras in industrial vision systems with space limitations or where strong vibrations occur. 相似文献
33.
Karin F. Helmens Jan Risberg Krister N. Jansson Jan Weckstrm Annika Berntsson Pivi Kaislahti Tillman Peter W. Johansson Stefan Wastegrd 《Quaternary Science Reviews》2009,28(19-20):1880-1894
Lake development at Sokli, northern Finland, is traced through the analysis of diatoms and other siliceous micro-fossils in a 2-meter thick minerogenic, laminated clay-silt deposit dated to the early part of Marine Isotope Stage (MIS) 3. Fluctuating water levels and changes in lake extent depicted by the siliceous micro-fossil record, together with lithology, suggest that an important part of the sediment sequence was deposited in a glacial lake. The proxy-based glacial lake evolution is tested using a Digital Elevation Model and geomorphologic evidence including eskers dated to the early MIS 3 Tulppio Interstadial at Sokli. Despite the apparent ice-dammed nature of the lake, the sediment is relatively rich in fossils and there are limited signs of re-deposition of older fossil material. The siliceous micro-fossil record together with data from other proxies previously analysed in the same sediment samples provides a coherent picture of past environmental changes around the Sokli site. This is most probably due to the sheltered position of the coring-site in a lake embayment. Quantitative climate reconstructions based on the diatom record show mean July air temperatures as high as present-day values at Sokli, and the temperature ranges indicated by the diatom record are in agreement with temperature reconstructions based on chironomids. The position of Sokli in the northeastern portion of the central area of the Scandinavian glaciations and the northern retreat pattern implies that an important part of eastern Fennoscandia was deglaciated during the early MIS 3 warming event. 相似文献
34.
A Wavelet-Based Correction Method for Eddy-Covariance High-Frequency Losses in Scalar Concentration Measurements 总被引：1，自引：1，他引：0
Eddy-covariance (EC) scalar-flux measurements suffer from unavoidable biases introduced by high-frequency losses in the sampled scalar concentration fluctuations. This bias alone leads to an underestimation of scalar fluxes by as much as 20% in some cases, especially when a closed-path gas analyzer is used to sample concentration far from the inlet location. A novel method that directly corrects for these high-frequency losses using only the sampled scalar-concentration time series is proposed and tested. The sampled concentration fluctuation time series is adjusted, point-by-point, in the wavelet half-plane for each EC averaging interval (??30?min). Similarity between scalars (and temperature) is not necessary and a pre-defined theoretical shape of the cospectrum is not required, making this method attractive at meteorologically non-ideal sites. When closed-path gas analyzers are used to measure H2O concentration fluctuations, the method is shown to reproduce the dependence of the attenuation on air relative humidity. Nevertheless, the method is not able to account for excessively large spectral attenuation that occurs close to the spectral peak, as might be the case with long tubes and high relative humidity. Since the method corrects the original scalar concentration time series and not the cospectrum, other flow statistics??such as variances and integral time scales??are also adjusted. The proposed method can be used synergistically with conventional high-frequency cospectral correction methods given the differences in assumptions and approaches among these methods. When the conventional and the proposed methods agree, added confidence to the estimate of the high frequency correction is gained, and vice versa. 相似文献
35.
Robust date for the Bronze Age Avellino eruption (Somma-Vesuvius): 3945 ± 10 calBP (1995 ± 10 calBC)
Jan Sevink Manfred J. van Bergen Johannes van der Plicht Hendrik Feiken Carmela Anastasia Annika Huizinga 《Quaternary Science Reviews》2011,30(9-10):1035-1046
We found Bronze Age lake sediments from the Agro Pontino graben (Central Italy) to contain a thin (2–3 cm) continuous tephra layer composed of lithics, crystals and minor volcanic glass. Tephrochronological and compositional constraints strongly suggest that this layer represents the Avellino pumice eruption, which has also been identified in Central Italian lake cores. Its provenance is corroborated by electron-microprobe analyses performed on juvenile pumice grains, showing that the tephra layer is probably the distal equivalent of the EU2 event of the Avellino eruption. We used multiple 14C age estimations of two lacustrine sequences with intercalated tephra layer, from the western border zone (Migliara 44.5) and the centre of the former lake (Campo Inferiore), for in tandem dating of this eruption, employing the OxCal code, which yielded a robust age of 3945 ± 10 calBP (1995 ± 10 calBC). To date, this is the only study providing both a terminus post and terminus ante quem of this precision, also demonstrating the advantage of dating distal tephra layers in a clear stratigraphic context over proximal deposits in sequences with major stratigraphic hiatuses. Our new results underscore the importance of the Avellino tephra layer as a precise time marker for studies on the Early Bronze Age of Central Italy. 相似文献
36.
I. Borgström Sara A. O. Cousins Annika C. Dahlberg & L.-O. Westerberg 《Geografiska Annaler: Series A, Physical Geography》1999,81(3):369-382
On 30-31 August 1997, extreme precipitation fell locally over parts of west central Sweden, causing flash floods on the eastern and southern slopes of Mount Fulufjället. Here we report from fieldwork carried out during the first year after the event. A survey map of the Stora Göljån flash flood channel is pre-sented. The geomorphic effects are described, as well as the general status of the recolonisation of vegetation. The erosional effects of the flash floods were extensive, and included the expansion of stream channels, mass movement, and the almost complete removal of vegetation in broad strips along the water-courses. Future work is presented in a theoretical context. 相似文献
37.
Annika M. V. Fain David A. Jay Doug J. Wilson Phil M. Orton Antonio M. Baptista 《Estuaries and Coasts》2001,24(5):770-786
We investigated seasonal and tidal-monthly, suspended particulate matter (SPM) dynamics in the Columbia River estuary from May to December 1997 using acoustic backscatter (ABS) and velocity data from four long-term Acoustic Doppler Profiler (ADP) moorings in or near the estuarine turbidity maximum (ETM). ABS profiles were calibrated and converted to total SPM profiles using pumped SPM samples and optical backscatter (OBS) data obtained during three seasonal cruises. Four characteristic settling velocity (W s) classes were defined from Owen Tube samples collected during the cruises. An inverse analysis, in the form of a non-negative least squares minimization, was used to determine the contribution of the four,W s-classes to each, total SPM profile. The outputs from the inverse analyses were 6–8 mo time-series ofW s-specific SPM concentration and transport profiles at each mooring. The profiles extended from the free surface to 1.8–2.7 m from the bed, with 0.25–0.50 m resolution. These time series, along with Owen Tube results and disaggregated size data, were used to investigate SPM dynamics. Three non-dimensional parameters were defined to investigate how river flow and tidal forcing affect particle trapping: Rouse numberP (balance between vertical mixing and settling) trapping efficiencyE (ratio of maximum SPM concentration in the estuary to fluvial source concentration), and advection numberA (ratio of height of maximum SPM concentration to friction velocity). The most effective particle trapping (maximum values ofE) occurs on low-flow neap tides. The location of the ETM and the maximal trapping migrated seasonally in a manner consistent with the increase in salinity intrusion length after the spring freshet. Maximum advection (high values ofA) occurred during highly stratified neap tides. 相似文献
38.
Esa Turunen Pekka T. Verronen Annika Seppälä Craig J. Rodger Mark A. Clilverd Johanna Tamminen Carl-Fredrik Enell Thomas Ulich 《Journal of Atmospheric and Solar》2009,71(10-11):1176-1189
Energetic particle precipitation couples the solar wind to the Earth's atmosphere and indirectly to Earth's climate. Ionisation and dissociation increases, due to particle precipitation, create odd nitrogen (NOx) and odd hydrogen (HOX) in the upper atmosphere, which can affect ozone chemistry. The long-lived NOx can be transported downwards into the stratosphere, particularly during the polar winter. Thus, the impact of NOx is determined by both the initial ionisation production, which is a function of the particle flux and energy spectrum, as well as transport rates. In this paper, we use the Sodankylä Ion and Neurtal Chemistry (SIC) model to simulate the production of NOx from examples of the most representative particle flux and energy spectra available today of solar proton events (SPE), auroral energy electrons, and relativistic electron precipitation (REP). Large SPEs are found to produce higher initial NOx concentrations than long-lived REP events, which themselves produce higher initial NOx levels than auroral electron precipitation. Only REP microburst events were found to be insignificant in terms of generating NOx. We show that the Global Ozone Monitoring by Occultation of Stars (GOMOS) observations from the Arctic winter 2003–2004 are consistent with NOx generation by a combination of SPE, auroral altitude precipitation, and long-lived REP events. 相似文献
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40.
The Precambrian Taratash complex (Middle Urals) is one of the rare windows into the Palaeoproterozoic and earlier history of the eastern margin of the East European Craton. Monazite from intensively deformed rocks within a major amphibolite-facies shear zone in the Taratash complex has been investigated by means of electron-probe microanalysis and laser-ablation SF-ICP-MS.Metamorphic and magmatic cores of monazite from metasedimentary and metagranitoid rocks yield U–Pb ages of 2244 ± 19 and 2230 ± 22 Ma (± 2 σ) and record a previously unknown pre-deformational HT-metamorphic event in the Taratash complex. Subsequent dissolution–reprecipitation of monazite, during shear zone formation under amphibolite-facies conditions, caused patchy zonation and chemical alteration of the recrystallised monazite domains, leading to higher cheralite and huttonite components. This process, which was mediated by a probable (alkali + OH)-bearing metamorphic fluid also caused a total resetting of the U–Pb-system. The patchy domains yield concordant U–Pb-ages between 2052 ± 16 and 2066 ± 22 Ma, interpreted as the age of the shear zone. In line with previously published ages of high grade metamorphism and migmatisation, the data may point to a Palaeoproterozoic orogenic event at the eastern margin of the East European Craton.Post-deformational fluid-induced greenschist-facies retrogression caused partial to complete breakdown of monazite to fluorapatite, REE + Y-rich epidote, allanite and Th-orthosilicate.The retrograde assemblages either form coronas around monazite, or occur as dispersed reaction zones, indicating that the REE, Y, and Th were mobile at least on the thin section scale. The greenschist-facies metamorphic fluid was aqueous and rich in Ca. Monazite affected by advanced breakdown responded to the retrogression by incorporating the cheralite or huttonite components during a fluid-induced dissolution–reprecipitation process. This event did not reset the U–Pb-system but caused partial Pb loss reflected by discordant U–Pb-dates. 相似文献