Sabiia Seb
PortuguêsEspañolEnglish
Embrapa
        Busca avançada

Botão Atualizar


Botão Atualizar

Ordenar por: RelevânciaAutorTítuloAnoImprime registros no formato resumido
Registros recuperados: 19
Primeira ... 1 ... Última
Imagem não selecionada

Imprime registro no formato completo
A General formatting system for geo-referenced data. vol. 3: Standard subsets of GF3 OceanDocs
Tipo: Book Palavras-chave: Oceanography; Geophysical data; Sea level; Sea level measurement; Wave analysis; Wave data; Wave height; Wave measurement; Sea surface; Drifting data buoys; Bathymetric data; Bathymetry; Mean sea level; Sea level; Http://aims.fao.org/aos/agrovoc/c_34115.
Ano: 1996 URL: http://hdl.handle.net/1834/2798
Imagem não selecionada

Imprime registro no formato completo
An Ocean Wind Doppler Model Based on the Generalized Curvature Ocean Surface Scattering Model ArchiMer
Said, Faozi; Johnsen, Harald; Chapron, Bertrand; Engen, Geir.
A Doppler centroid D-C model based on the generalized curvature ocean surface scattering model (generalized curvature model or GCM) is presented. Two key features are included in this model: a skewness-related phase coefficient based on empirical skewness coefficients of sea-surface-slope probability density function (pdf) for wind speed less than 10 m/s and effects from wave breaking for wind speed greater than 10 m/s. Simulated D-c values are exclusively compared with the empirical geophysical Doppler model function named CDOP, for hh and vv polarizations, various wind conditions, and incidence angles. Good agreement is found overall between CDOP and simulated D-C values. The overall bias for simulated Dc-vv with and without skewness are 2.63 versus...
Tipo: Text Palavras-chave: Doppler measurements; Geophysical measurement techniques; Sea surface; Synthetic aperture radar (SAR).
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00283/39411/39116.pdf
Imagem não selecionada

Imprime registro no formato completo
Analysis of the SAR imaging process of the ocean surface using Volterra models ArchiMer
Le Caillec, Jm; Garello, R; Chapron, Bertrand.
In this paper, the synthetic aperture radar (SAR) process of the ocean surface mapping is studied using a decomposition based on a Volterra model. By a mathematical expansion of the complex exponential of the complete SAR transform, these models decompose the nonlinear distortion mechanisms of the SAR spectrum over different spectra of polynomial interactions. Thus, they offer an alternative modeling (to the exact SAR transform) giving a theoretical separation between the SAR Fourier components linearly derived from the sea surface elevation and the artifacts created by nonlinearities of. the SAR mapping of the. ocean surface. The main results of this paper consist of the systematic assessment of such an approximation of the ocean surface SAR imaging...
Tipo: Text Palavras-chave: Higher order statistics; Radar mapping; SAR; Sea surface; Volterra models.
Ano: 2002 URL: http://archimer.ifremer.fr/doc/00000/10606/9500.pdf
Imagem não selecionada

Imprime registro no formato completo
Analytical Techniques for the Doppler Signature of Sea Surfaces in the Microwave Regime-I: Linear Surfaces ArchiMer
Nouguier, Frederic; Guerin, Charles-antoine; Soriano, Gabriel.
This paper is the first in a series of two papers on the use of combined improved hydrodynamic and electromagnetic analytical models for the simulation of the ocean Doppler spectrum at microwave frequencies. Under a linear assumption for the sea surface, we derive statistical expression for the main Doppler characteristics according to asymptotic scattering models. We consider classical models such as the Kirchhoff approximation and the two-scale model, as well as the more recent weighted curvature approximation (WCA). We recover two salient features of Doppler signature in the microwave regime. First, the Doppler characteristics are very sensitive to polarization, with higher mean Doppler shift in horizontal polarization. This is correctly rendered by the...
Tipo: Text Palavras-chave: Doppler spectrum; Gravity waves; Microwave; Remote sensing; Rough surfaces; Scattering; Sea surface.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00054/16524/14379.pdf
Imagem não selecionada

Imprime registro no formato completo
Analytical Techniques for the Doppler Signature of Sea Surfaces in the Microwave Regime-II: Nonlinear Surfaces ArchiMer
Nouguier, Frederic; Guerin, Charles-antoine; Soriano, Gabriel.
This paper extends the results of a previous work by combining hydrodynamic and electromagnetic analytical models for the simulation of the ocean Doppler spectrum at microwave frequencies. We consider weakly nonlinear sea surfaces after the choppy wave model and incorporate them in classical and unified scattering models, namely, the Kirchhoff and weighted curvature approximations. We show that statistical expressions can be obtained for the Doppler spectrum in a way similar to the case of linear surfaces. As expected, the nonlinear nature of the sea surface dramatically impacts the Doppler spectrum at moderate to large incidence angles, with a shift of the central frequency and a broadening of the spectrum. Monte Carlo comparisons are performed with the...
Tipo: Text Palavras-chave: Doppler spectrum; Microwave; Nonlinear gravity waves; Remote sensing; Rough surfaces; Scattering; Sea surface.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00054/16555/14380.pdf
Imagem não selecionada

Imprime registro no formato completo
Atelier de formation sur le code de la pêche à kayar OceanDocs
Dioh, B.; Ndiaye, O.; Sané, K.; Diouf, P.S..
Dans le programme de conservation des écosystèmes marins et côtiers de I'Akique de I'Ouest du World Wide Fund for Nature (WWF), Kayar a été retenu comme site où des activités de terrain doivent être menées. Dans le but de former et de sensibiliser les acteurs chargés de I'application des lois et règlements relatifs à la pêche et ceux à qui cette réglementation s'applique, une séance de vulgarisation des lois et règlements régissant la pêche au Sénégal a été organisée le 26 juillet 2002 à Kayar. Aprés la cérémonie d'ouverture, Messieurs Ousmane NDIAYE, Chef de la division pêche artisanale à la Direction de l'océanographie et des pêches maritimes (DOPM) et Alassane Samba DIOP, Chef du secteur des pêches de Kayar, animateurs de la journée, ont fait une...
Tipo: Report Palavras-chave: Mackerel fisheries; Marine accidents; Fish; Legislation; Law of the sea; Sea surface; Fish; Legislation; Http://aims.fao.org/aos/agrovoc/c_15903; Http://aims.fao.org/aos/agrovoc/c_4253.
Ano: 2002 URL: http://hdl.handle.net/1834/1741
Imagem não selecionada

Imprime registro no formato completo
Guide to oceanographic and marine meteorological instruments and observing practices OceanDocs
Tipo: Book Palavras-chave: Oceanography; Marine technology; Meteorological instruments; Meteorological data; Meteorological observations; Oceanographic equipment; Oceanographic surveys; Sea surface; Temperature measurement; Salinity measuring equipment; Bathythermographs; Thermometers; Wave measuring equipment; Wave measurement; Wind measurement; Wind measuring equipment; Swell; Atmospheric pressure; Water colour; Water transparency; Meteorological instruments; Meteorological observations; Thermometers; Atmospheric pressure; Meteorological data; Http://aims.fao.org/aos/agrovoc/c_4779; Http://aims.fao.org/aos/agrovoc/c_4780; Http://aims.fao.org/aos/agrovoc/c_7721; Http://aims.fao.org/aos/agrovoc/c_693; Http://aims.fao.org/aos/agrovoc/c_34149.
Ano: 1975 URL: http://hdl.handle.net/1834/2676
Imagem não selecionada

Imprime registro no formato completo
IODE Steering Group for Global Ocean Surface Underway Data Pilot Project (SG-GOSUD) Third Session Monterey, USA, 3-4 November 2003 OceanDocs
The Third Session of the IODE Steering Group for Global Ocean Surface Underway Data (GOSUD) Pilot Project was held in Monterey, USA, from 3-4 November 2003. During this session the Steering Group reviewed the activities of the intersessional period and the accomplishments to date. The GOSUD Global Data Assembly Centre (GDAC) has been established at Coriolis, France, who will build the ftp structure to provide access to the underway data. It is also expected that http access will be developed. The Group also reviewed the tasks identified in the Project Plan and assigned leaders for the uncompleted tasks and established target dates. The project will seek to raise its profile within the scientific community during the next year.
Tipo: Report Palavras-chave: Oceanographic data; Sea surface.
Ano: 2003 URL: http://hdl.handle.net/1834/4328
Imagem não selecionada

Imprime registro no formato completo
Merging SeaWiFS and MODIS/Aqua Ocean Color Data in North and Equatorial Atlantic Using Weighted Averaging and Objective Analysis ArchiMer
Pottier, C; Garcon, V; Larnicol, G; Sudre, J; Schaeffer, P; Le Traon, Pierre-yves.
Two approaches of ocean color data merging were tested and compared in the North and Equatorial Atlantic Basin: the weighted averaging and the objective analysis. The datasets used were the daily level-3 binned data of chlorophyll-a from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer on the Aqua satellite over the year 2003, which is the first common full year of operation. Since they represent input for both approaches, matchups between the satellite and the in situ data from the SeaWiFS Bio-optical Archive and Storage System and the Atlantic Meridional Transect were first studied to compute a spatial map of the root mean-square error and of the bias. Because of the log distribution of the chlorophyll...
Tipo: Text Palavras-chave: Signal analysis; Sea surface; Marine vegetation; Biology.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-3631.pdf
Imagem não selecionada

Imprime registro no formato completo
Modelisation de la coherence spatiale du bruit genere par les vagues ArchiMer
Plaisant, M.
Empirical models already exist for ambient noise spectral density function of frequency, sea state or wind speed but they give no information on the spatial structure or coherence of the noise field which is essential as soon as array beamforming is involved. We have developed a model which computes the spatial coherence matrix of the noise field due to a continuous distribution of sources located at the sea surface, and also the noise power spectral density after classical beamforming on an equidistant hydrophones linear array. In this model, propagation effects like rays bending due to variations of index of refraction and multiple bottom and surface reflections are taken into account. Principles of the modeling are presented and results demonstrate that...
Tipo: Text Palavras-chave: Spectral analysis; Models; Wind speed; Sea surface; Surface water waves; Acoustic equipment; Sound waves; Underwater noise; Ambient noise.
Ano: 1990 URL: http://archimer.ifremer.fr/doc/1990/acte-1143.pdf
Imagem não selecionada

Imprime registro no formato completo
Modulation of Ka-Band Doppler Radar Signals Backscattered From the Sea Surface ArchiMer
Yurovsky, Yury Yu.; Kudryavtsev, Vladimir N.; Chapron, Bertrand; Grodsky, Semyon A..
This paper presents dual copolarized (VV and HH) Ka-band radar measurements of joint modulation of normalized radar crass section (NRCS) and Doppler velocity (DV) performed from a sea research platform. NRCS and DV modulations are well correlated. NRCS modulations exhibit a spiky structure. HH modulations are stronger than VV ones leading to modulations of the polarization ratio. This suggests that an important portion of NRCS modulations is produced by nonpolarized radar returns from modulated wave breaking facets. DV modulations reveal that at incidence angles <50 degrees, NRCS spikes are attributable to rather slow moving facets, which may he interpreted as short wave breaking disturbances embedded in the water at crests of modulating waves. Using...
Tipo: Text Palavras-chave: Doppler shift; Modulation transfer function (MTF); Radar backscattering; Sea surface; Spikes; Wave breaking.
Ano: 2018 URL: http://archimer.ifremer.fr/doc/00440/55156/56750.pdf
Imagem não selecionada

Imprime registro no formato completo
Ocean doppler anomaly and ocean surface current from Sentinel 1 tops mode ArchiMer
Johnsen, Harald; Nilsen, Vegard; Engen, Geir; Mouche, Alexis; Collard, Fabrice.
Processing and analysis of Doppler information from Sentinel 1A Interferometric Wide (IW) and Extra Wide (EW) modes are performed for assessing the capabilities of mapping ocean surface current field. Data from Agulhas (South-Africa) and Norwegian Coast are used in combination with numerical models, higher-order satellite products, and Lagrangian drifters. Results show strong Doppler signal and dynamics from coastal areas caused by a mixture of surface current and wind/wave induced drifts at a spatial resolution of around 2 km2 in IW mode and 4km2 in EW mode. Doppler values of up to 70 Hz are observed, corresponding to a surface drift velocity of 3.5 m/s. The Sentinel 1 retrieved surface current component is in reasonable agreement with the circulation...
Tipo: Text Palavras-chave: Doppler effect; Sea surface; Sea measurements; Ocean temperature; Surface treatment; Antennas.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00356/46713/46589.pdf
Imagem não selecionada

Imprime registro no formato completo
Onto a Skewness Approach to the Generalized Curvature Ocean Surface Scattering Model ArchiMer
Said, Faozi; Johnsen, Harald; Nouguier, Frederic; Chapron, Bertrand; Engen, Geir.
The generalized curvature ocean surface scattering model [general curvature model (GCM)] is extended and revisited. Two key steps are addressed in this paper, namely, a necessary sea surface spectrum undressing procedure and the inclusion of a skewness phase-related component. Normalized radar cross-section (NRCS) simulations are generated at C-band for various wind conditions, polarizations, and incidence angles. Results are compared with CMOD5.n. Although the sea surface spectrum undressing procedure is a necessary step, the overall NRCS dynamic is notably affected only in low wind conditions (<= 5 m/s). The inclusion of the skewness phase-related component makes the most impact to the NRCS dynamic where the upwind/downwind asymmetry is clearly...
Tipo: Text Palavras-chave: Geophysical measurements; Radar cross section; Remote sensing; Sea surface; Surface waves.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00409/52013/52725.pdf
Imagem não selecionada

Imprime registro no formato completo
Overview of the First SMOS Sea Surface Salinity Products. Part I: Quality Assessment for the Second Half of 2010 ArchiMer
Reul, Nicolas; Tenerelli, Joseph; Boutin, Jaqueline; Chapron, Bertrand; Paul, Frederic; Brion, Emilie; Gaillard, Fabienne; Archer, Olivier.
Multi-angular images of the brightness temperature (TB) of the Earth at 1.4 GHz are reconstructed from the Soil Moisture and Ocean Salinity (SMOS) satellite sensor data since end 2009. Sea surface salinity (SSS) products remote sensing from space is being attempted using these data over the world oceans. The quality of the first version of the European Space Agency operational Level 2 (L2) SSS swath products is assessed in this paper, using satellite/in situ SSS data match-ups that were collected over the second half of 2010. This database reveals that 95% of the SMOS L2 products show a global error standard deviation on the order of ∼1.3 practical salinity scale. Simple spatiotemporal aggregation of the L2 products to generate monthly SSS maps at 1◦ × 1◦...
Tipo: Text Palavras-chave: L-band; Microwave radiometry; Ocean salinity; Sea surface.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00072/18313/16109.pdf
Imagem não selecionada

Imprime registro no formato completo
Partially supervised oil-slick detection by SAR imagery using kernel expansion ArchiMer
Mercier, Grégoire; Ardhuin, Fanny.
Spaceborne synthetic aperture radar (SAR) is well adapted to detect ocean pollution independently from daily or weather conditions. In fact, oil slicks have a specific impact on ocean wave spectra. Initial wave spectra may be characterized by three kinds of waves, namely big, medium, and small, which correspond physically to gravity and gravity-capillary waves. The increase of viscosity, due to the presence of oil damps gravity-capillary waves. This induces not only a damping of the backscattering to the sensor but also a damping of the energy of the wave spectra. Thus, local segmentation of wave spectra may be achieved by the segmentation of a multiscale decomposition of the original SAR image. In this paper, a semisupervised oil-slick detection is...
Tipo: Text Palavras-chave: Water pollution; Synthetic aperture radar; Sea surface; Satellite applications; Oil spill; Image analysis.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1948.pdf
Imagem não selecionada

Imprime registro no formato completo
Statistical characterization of short wind waves from stereo images of the sea surface ArchiMer
Mironov, Alexey; Yurovskaya, M. V.; Dulov, V. A.; Hauser, D.; Guerin, C.a..
We propose a methodology to extract short-scale statistical characteristics of the sea surface topography by means of stereo image reconstruction. The possibilities and limitations of the technique are discussed and tested on a data set acquired from an oceanographic platform at the Black Sea. A validation is made with simultaneous in situ measurements as well as results from the literature. We show that one- and two-point properties of the short-scale roughness can be well estimated without resorting to an interpolation procedure or an underlying surface model. We obtain the first cumulants of the probability distribution of small-scale elevations and slopes as well as related structure functions. We derive an empirical parametrization for the skewness...
Tipo: Text Palavras-chave: Ocean field study; Radar backscattering modeling; Remote sensing; Sea surface; Short wind waves; Stereo photography.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00114/22511/20194.pdf
Imagem não selecionada

Imprime registro no formato completo
Statistical Descriptors of Ocean Regimes From the Geometric Regularity of SST Observations ArchiMer
Ba, Sileye O.; Autret, Emmanuelle; Chapron, Bertrand; Fablet, Ronan.
In this letter, we evaluate to which extent the activity of ocean fronts can be retrieved from the geometric regularity of ocean tracer observations. Applied to sea surface temperature (SST), we propose a method for the characterization of this geometric regularity from curvature-based statistics along temperature level lines in front regions. To assess the effectiveness of the proposed descriptors, we used six years (from 2003 to 2008) of daily SST observations of the regions of Agulhas in the South of Africa and of Malvinas off the southern Brazilian coast. These experiments stress the relevance of geometric regularity features of tracer observation at ocean surface to characterize seasonal variations in ocean regimes.
Tipo: Text Palavras-chave: Geosciences and remote sensing; Image analysis; Image classification; Image processing; Oceans; Ocean temperature; Sea surface.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00109/21993/20230.pdf
Imagem não selecionada

Imprime registro no formato completo
The airborne identification of oil films at the Caspian sea surface using CO2 lidar ArchiMer
Osadchy, Vu; Shifrin, Ks; Gurevich, Iy.
Contrast in the reflectivity between pure and contaminated sea surfaces is the result of two effects, namely: (1) the different reflectivity of sea water and oil films on sea water, and (2) the damping effect by the oil film on the sea waves. The problem is to estimate the contribution of these two effects on the total contrast, so that the substance effect can be calculated. Magnitude is related to the oil film thickness. The spectral behaviour of the contrast and its relationship with the film thickness were calculated for an undisturbed sea surface. The estimate of the damping effect was made using the Cox and Munk's slope distributions for pure and contaminated surfaces. The method chosen was verified by a series of tests conducted over the Caspian Sea...
Tipo: Text Palavras-chave: Hydrocarbure; Caractéristique optique; Pollution; Surface de la mer; Télédétection; Oil; Optical constant; Pollution; Sea surface; Remote sensing.
Ano: 1999 URL: http://archimer.ifremer.fr/doc/00325/43628/43255.pdf
Imagem não selecionada

Imprime registro no formato completo
Wave Breaking in Slicks: Impacts on C-Band Quad-Polarized SAR Measurements ArchiMer
Wergeland, Morten; Kudryavtsev, Vladimir; Chapron, Bertrand; Brekke, Camilla; Johannessen, Johnny A..
Radarsat-2 C-band quad-polarization SAR observations of crude oil, emulsion, and plant oil slicks acquired in the wind speed range from 4 to 8 m/s and incidence angles from 30 degrees to 50 degrees are analyzed to yield new insights into the attenuation of short waves and breaking waves by surface slicks in real conditions. To provide a direct quantitative assessment of the surface wave damping, the measurements are decomposed into polarization difference (PD), polarization ratio (PR), nonpolarized (NP), and cross-polarized (CP) components. The PD signals relate to the extent of Bragg damping in the slick areas, over which the PR is systematically higher than over the ambient sea surface. Attenuation of the breaking waves is revealed to affect both the CP...
Tipo: Text Palavras-chave: Oil pollution; Radar imaging; Sea surface; Surface waves.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00363/47460/47484.pdf
Registros recuperados: 19
Primeira ... 1 ... Última
 

Empresa Brasileira de Pesquisa Agropecuária - Embrapa
Todos os direitos reservados, conforme Lei n° 9.610
Política de Privacidade
Área restrita

Embrapa
Parque Estação Biológica - PqEB s/n°
Brasília, DF - Brasil - CEP 70770-901
Fone: (61) 3448-4433 - Fax: (61) 3448-4890 / 3448-4891 SAC: https://www.embrapa.br/fale-conosco

Valid HTML 4.01 Transitional