On the developments of spectral wave models: numerics and parameterizations for the coastal ocean   总被引：1，自引：1，他引：0  

Aron Roland  Fabrice Ardhuin 《Ocean Dynamics》2014,64(6):833-846

The development of numerical wave models for coastal applications, including coupling with ocean circulation models, has spurred an ongoing effort on theoretical foundations, numerical techniques, and physical parameterizations. Some important aspects of this effort are reviewed here, and results are shown in the case of the French Atlantic and Channel coast using version 4.18 of the WAVEWATCH III ^R model. Compared to previous results, the model errors have been strongly reduced thanks to, among other things, the introduction of currents, coastal reflection, and bottom sediment types. This last item is described here for the first time, allowing unprecedented accuracy at some sites along the French Atlantic Coast. The adequate resolution, necessary to represent strong gradients in tidal currents, was made possible by the efficiency brought by unstructured grids. A further increase in resolution, necessary to resolve surf zones and still cover vast regions,will require further developments in numerical methods.  相似文献   

Fingerprinting feldspar phenocrysts using crystal isotopic composition stratigraphy: implications for crystal transfer and magma mingling in S-type granites   总被引：6，自引：0，他引：6  

Tod E. Waight  Roland Maas  Ian A. Nicholls 《Contributions to Mineralogy and Petrology》2000,139(2):227-239

 Microsampling of cm-scale feldspar crystals within an S-type granite from the Lachlan Fold Belt of southeastern Australia has revealed complex internal Sr and Nd isotopic variations. The observed isotopic zonations are in part interpreted as recording feldspar crystallisation in a dynamically mixing magma system, the isotopic composition of which was varying in response to the influx of more mafic and isotopically more mantle-like magmas, the latter stages of which are now represented in modified form by microgranular enclaves. Similar core to rim isotopic variations in feldspar megacrysts from a microgranular enclave and the adjacent host granite strongly suggest megacrysts in the enclave were transferred from the granitic magma during crystallisation. Feldspar rims have higher ⁸⁷Sr/⁸⁶Sr_i and lower ɛ_Nd(i) than adjacent whole rock analyses, but match those of mineral separates from the surrounding enclave matrix. This suggests that the final stages of megacryst growth occurred in the presence of a component that had previously interacted with a high ⁸⁷Sr/⁸⁶Sr, low ɛ_Nd(i) component such as metasedimentary wall rocks. Isotopic heterogeneities are also presererved within different mineral phases in the enclave matrix, suggesting that differing phases grew at differing stages of equilibration between the enclave magma and its host granitic magma. Our results reveal major isotopic heterogeneities on a single crystal and also inter-mineral scale in a pluton which shows well constrained evidence for magma mingling. These results indicate the suitability of feldspars as recorders of isotopic change in magmatic systems, even those which have cooled slowly in the plutonic environment and suggest that much heterogeneity in plutonic systems may be overlooked on a whole rock scale. Received: 28 September 1998 / Accepted: 29 December 1999  相似文献   

Science and User Needs for Observing Global Mass Transport to Understand Global Change and to Benefit Society     

Roland Pail  Rory Bingham  Carla Braitenberg  Henryk Dobslaw  Annette Eicker  Andreas Güntner  Martin Horwath  Eric Ivins  Laurent Longuevergne  Isabelle Panet  Bert Wouters  IUGG Expert Panel 《Surveys in Geophysics》2015,36(6):743-772

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Late quaternary sea‐level changes,crustal movements and coastal evolution in Northumberland,UK     

Ian Shennan  Ben Horton  Jim Innes  Roland Gehrels  Jerry Lloyd  Jenny McArthur  Mairead Rutherford 《第四纪科学杂志》2000,15(3):215-237

Northumberland lies in the transition between Holocene emergence and submergence and is thus a critical zone for testing models of isostatic rebound. We have collected data from this area to reconstruct relative sea‐level changes and lateral coastline movements for the last 14000 y. These are deposits from tidal marsh, back‐barrier wetland and terrestrial environments producing 47 sea‐level index points from 12 sites. There is no unequivocal evidence for Late Devensian sea levels above present and the reliable sea‐level index points are restricted between −6 m and +2.5 m relative to present and 9.0–2.5 kyr cal. BP. Analysis of these quantifies differential responses to glacio‐ and hydroisostatic rebound, with the northern sites recording a mid‐Holocene sea‐level maximum ca. 2.5 m above present, whereas the southern sites show a maximum ca. 0.5 m above present. These observations show a reasonable fit with the predictions from quantitative models of glacio and hydroisostatic rebound, but there is currently no unique solution of Earth and ice model parameters that will explain all the sea‐level observations. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Bayesian chemistry-assisted hydrograph separation (BACH) and nutrient load partitioning from monthly stream phosphorus and nitrogen concentrations     

Simon?J.?R.?WoodwardEmail author  Roland?Stenger 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(12):3475-3501

A Bayesian chemistry-assisted hydrograph separation (BACH) approach was developed, based on calibration of a three-component recursive digital filter, that requires monthly water quality data only. This enables BACH to be applied to the large number of rural catchments for which continuous flow records and monthly water chemistry time series exist from ‘state of environment’ monitoring programmes, but little supplementary data required for more sophisticated analysis techniques. As well as estimating fast, medium, and slow flow components, BACH also estimates for each flow component a time-invariant concentration of the chemical tracers chosen, allowing flow path-specific loads to be calculated. The method was demonstrated using 15 years of total phosphorus (TP) and total nitrogen (TN) data from eight mesoscale catchments in the Waikato region of New Zealand’s North Island. Calibration was done separately for three 5-year data periods, and validated against data from the following 5-year period. Flow path separation and concentration predictions were consistent between data periods, indicating that the TP–TN combination contained sufficient information to reliably identify three flow paths in each catchment; an event-response near-surface flow path with high concentrations of both phosphorus and nitrogen, a seasonal shallow groundwater flow path with lower concentrations of TP but high concentrations of TN, and a deeper slower groundwater flow path characterised by generally low concentrations of both TP and TN. Based on this analysis, the catchments were able to be grouped in three hydro-types. This shows that commonly available water quality data can support robust, objective flow separation and nutrient load apportionment, even in the absence of other supporting data, provided appropriate modelling methods are used.  相似文献   

Fault slip and identification of the second fault plane in the Varzeghan earthquake doublet     

Samar Amini  Roland Roberts  Mohammad Raeesi  Zaher Hossein Shomali  Bjorn Lund  Zoya Zarifi 《Journal of Seismology》2018,22(4):815-831

An intraplate earthquake doublet, with 11-min delay between the events, devastated the city of Varzeghan in northwestern Iran on August 11, 2012. The first Mw 6.5 strike-slip earthquake, which occurred after more than 200 years of low seismicity, was followed by an Mw 6.4 oblique thrust event at an epicentral separation of about 6 km. While the first event can be associated with a distinct surface rupture, the absence of a surface fault trace and no clear aftershock signature makes it challenging to identify the fault plane of the second event. We use teleseismic body wave inversion to deduce the slip distribution in the first event. Using both P and SH waves stabilize the inversion and we further constrain the result with the surface rupture extent and the aftershock distribution. The obtained slip pattern shows two distinct slip patches with dissimilar slip directions where aftershocks avoid high-slip areas. Using the estimated slip for the first event, we calculate the induced Coulomb stress change on the nodal planes of the second event and find a preference for higher Coulomb stress on the N-S nodal plane. Assuming a simple slip model for the second event, we estimate the combined Coulomb stress changes from the two events on the focal planes of the largest aftershocks. We find that 90% of the aftershocks show increased Coulomb stress on one of their nodal planes when the N-S plane of the second event is assumed to be the correct fault plane.  相似文献   

Data requirements for a 5-mm quasi-geoid in the Netherlands   总被引：1，自引：0，他引：1  

Hassan H. Farahani  Roland Klees  Cornelis Slobbe 《Studia Geophysica et Geodaetica》2017,61(4):675-702

We assess the surface gravity data requirements for a 5-mm quasi-geoid model for the Netherlands mainland and continental shelf in terms of omission and commission errors. The omission error critically depends on the roughness of the topography and bathymetry. For the Netherlands continental shelf, Central and Northern Netherlands, the omission error is well described by the model 0.32d mm, where d is the data spacing in km. For the more hilly Southern Netherlands, the omission error model is 0.92d mm. The commission error depends on the kernel modification, the data spacing, and the data accuracy. When using the spheroidal Stokes kernel, it is well described by 0.277 d σ_Δg mm, where σ_Δg is the noise standard deviation of surface gravity data in mGal. An upper bound of the commission error of the state-of-the-art satellite-only gravity model GOCO05S over the Netherlands is e^{0.03676L–11.419} mm, where L is the maximum degree up to which this model is used. Only if this model is truncated at a sufficiently low degree, e.g., at degree 100, its contribution to the total commission error can be neglected. We determine the total error as the sum of commission and omission errors. Hence, to realize a 5-mm quasi-geoid model for the Netherlands mainland and continental shelf, a data spacing of 3.5 km is needed when assuming a noise standard deviation of 1.5 mGal for surface gravity data. The currently available land-based gravity data fulfill this requirement. This does not apply to the situation at sea, where the density of the shipboard gravity data and the accuracy of the radar altimeter-derived data do not allow the realization of a 5-mm quasi-geoid model.  相似文献   

Definition and Proposed Realization of the International Height Reference System (IHRS)     

Johannes Ihde  Laura Sánchez  Riccardo Barzaghi  Hermann Drewes  Christoph Foerste  Thomas Gruber  Gunter Liebsch  Urs Marti  Roland Pail  Michael Sideris 《Surveys in Geophysics》2017,38(3):549-570

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Stand structure,floristic composition and species diversity along altitudinal gradients of a Bornean mountain range 30 years after selective logging     

Renee Sherna LAING  Kian Huat ONG  Roland Jui Heng KUEH  Nixon Girang MANG  Patricia Jie Hung KING  Muaish SAIT 《山地科学学报》2019,(6)

The mountain ecosystem is a hotspot of biodiversity and provides a significant contribution to the humans' livelihoods. However, there is still a lack of information regarding floral diversity and how it has been affected due to a logging operation in Sarawak. A study was conducted to determine vegetation recovery at the Heart of Borneo conservation area at different elevations: 750–1200 m(S1), 1200–1500 m(S2) and 1500 m(S3). A total of 891 trees were enumerated. The trees comprised 55 families, 98 genera and 203 species. The lowest elevation site, S1, contained the highest number of species(117) and families(42), while the highest elevation site, S3, contained the lowest diversity(25 families and 59 species). A similar forest structure was recorded, whereby diameter at breast height(dbh), basal area and height decreased as elevation increased. The most speciose families in S1 were Dipterocarpaceae(11 species) and Lauraceae(10 species), while Lauraceae and Fagaceae were the dominant tree families at S2 and S3. Secondary tree species are still abundantly found in the logged plots, especially at S2(45.5%), indicating that after 30 years, these stands are still in the recovery stages. The logged plots retained typical secondary forest appearances with lower canopy diameters and heights and dbh than the unlogged forest. Although the species richness approached that of the unlogged plots, especially at S1(90.9%) and S3(94.9%), there were still major differences in the floristic compositions between logged and unlogged plots(35.4%, 21.5% and 44.7% for S1, S2 and S3, respectively). Although potential seed sources were in close proximity, succession at S2 has proceeded much slower than at S1 and S3. Lower concentrations of soil nutrients, especially N, may be the main reason for the slow recovery. In conclusion, the results suggested that the selectively logged forest at the Payeh Maga Highland required more than three decades to recover and achieve a climate forest stage.  相似文献   

An algorithm to classify and monitor seasonal variations in vegetation phenologies and their inter-annual change   总被引：1，自引：0，他引：1  

Roland A. Geerken   《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(4):422-431

The algorithm presented in this paper classifies vegetation from annual Normalized Difference Vegetation Index (NVDI) time series according to the shape of the temporal cycle. Shape is described using the Fourier components’ magnitude and phase. The degree of an NDVI cycle’s similarity to a predefined reference cycle is measured by the similarity in their amplitude ratios and in their phase differences. Tolerable deviations from the ideal ratios and differences can be set by the user depending on individual accuracy requirements. Tolerable vegetation coverage variation within a shape class is another user defined variable. The algorithm is invariant to cycle modifications including temporal shifts, vertical displacements, and intensity variations, modifications that may be caused by differences in climate, soil (-type, -water, -fertility), or topography, but are unrelated to the vegetation type. The output is a highly consistent clustering of NDVI cycles according to their shapes, which can be linked to distinct vegetation types or land use practices. Intra-class coverage variations in the form of continuous fields measured relative to the reference cycle provide additional information about vegetation covers. Based on the same principles, inter-annual vegetation changes can be monitored with the possibility to distinguish between coverage fluctuations and phenological variations/changes.The algorithms are independent from scene statistics and can be used to create spatially and temporally comparable classifications. Their potential is demonstrated using a 250 m MODIS NDVI time series (version 4) from the Middle East.  相似文献