Sabiia Seb
PortuguêsEspañolEnglish
Embrapa
        Busca avançada

Botão Atualizar


Botão Atualizar

Ordenar por: RelevânciaAutorTítuloAnoImprime registros no formato resumido
Registros recuperados: 49
Primeira ... 123 ... Última
Imagem não selecionada

Imprime registro no formato completo
A model of sea-foam thickness distribution for passive microwave remote sensing applications ArchiMer
Reul, Nicolas; Chapron, Bertrand.
[1] Foam formations at the sea surface significantly contribute to microwave brightness temperature signatures over the ocean for moderate to high wind speeds. The thickness of foam layers generated by breaking waves follows a specific distribution due to unsteadiness of breaking and the large range of wave scales involved in the phenomenon. Although the effect of a distributed thickness-parameter on the foam-induced microwave brightness temperature may be comparable to or larger than the fractional whitecap coverage, it is not yet included in brightness models. To fill this gap, we develop a dynamical model for the conditional fraction of sea-surface covered by whitecaps with given thickness, as a function of wind speed. It is an integrated function of...
Tipo: Text Palavras-chave: Sea foam; Breaking waves; Thickness; Fractional coverage; Microwave brightness temperature.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/00000/10693/9320.pdf
Imagem não selecionada

Imprime registro no formato completo
A new generation of Tropical Cyclone Size measurements from space ArchiMer
Reul, Nicolas; Chapron, Bertrand; Zabolotskikh, E.; Donlon, C.; Mouche, Alexis; Tenerelli, Joseph; Collard, F.; Piolle, Jean-francois; Fore, A.; Yueh, S.; Cotton, J.; Francis, P.; Quilfen, Yves; Kudryavtsev, V..
Combined microwave brightness temperature measurements from recent L- and dual C-band satellite radiometers provide new estimates of surface wind speed structure in Tropical Cyclones which enhances temporal sampling capability for gale (34-knots), damaging (50-knots) and destructive (64-knots) wind radii. Wind radii estimates in Tropical Cyclones (TC) are crucial to help determine the TC wind structure for the production of effective warnings and to constrain initial conditions for a number of applications. In that context, we report on the capabilities of a new generation of satellite microwave radiometers operating at L-band frequency (~1.4 GHz) and dual C-band (~6.9 and 7.3 GHz). These radiometers provide wide swath (> 1000 km) coverage at a spatial...
Tipo: Text
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00376/48758/49151.pdf
Imagem não selecionada

Imprime registro no formato completo
A revised L-band radio-brightness sensitivity to extreme winds under tropical cyclones: The 5 year SMOS-Storm database ArchiMer
Reul, Nicolas; Chapron, Bertrand; Zabolotskikh, E.; Donlon, C.; Quilfen, Yves; Guimbard, Sebastien; Piolle, Jean-francois.
Five years of SMOS L-band brightness temperature data intercepting a large number of tropical cyclones (TCs) are analyzed. The storm-induced half-power radio-brightness contrast (ΔI) is defined as the difference between the brightness observed at a specific wind force and that for a smooth water surface with the same physical parameters. ΔI can be related to surface wind speed and has been estimated for ~ 300 TCs that intercept with SMOS measurements. ΔI, expressed in a common storm-centric coordinate system, shows that mean brightness contrast monotonically increases with increased storm intensity ranging from ~ 5 K for strong storms to ~ 24 K for the most intense Category 5 TCs. A remarkable feature of the 2D mean ΔI fields and their variability is that...
Tipo: Text
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00324/43542/43178.pdf
Imagem não selecionada

Imprime registro no formato completo
A satellite altimeter model for ocean slick detection - art. no. C04004 ArchiMer
Tournadre, Jean; Chapron, Bertrand; Reul, Nicolas; Vandemark, D.
[1] About 5% of Ku-band altimeter ocean data are degraded by the occurrence of high radar return cross sections (sigma(0)), usually called sigma(0) blooms. During blooms, which occur during no or low wind conditions, the mean altimeter waveform can significantly depart from the expected shape. In about 60% of the cases the waveforms are distorted to such an extent that either the range tracker loses lock or the off-nadir angle estimate becomes unrealistic. The analysis of high data rate altimeter waveforms during bloom events reveals the presence of V-shaped patterns similar to the ones observed during rain events. These patterns trace small-scale (i.e., smaller than the altimeter footprint) changes in surface backscatter. Such variations of surface...
Tipo: Text Palavras-chave: Slick; Sigma blooms; Altimeter waveforms.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1353.pdf
Imagem não selecionada

Imprime registro no formato completo
A simplified asymptotic theory for ocean surface electromagnetic wave scattering ArchiMer
Mouche, Alexis; Chapron, Bertrand; Reul, Nicolas.
The normalized radar cross-section ( NRCS) expression of the Local Curvature Approximation (LCA-1) is derived to first order. The polarization sensitivity of this model is compared to the Kirchhoff Approximation ( KA), Two-Scale Model (TSM), Small Slope Approximation (SSA-1) and Small Perturbation Method (SPM-1) to first order in the backscattering configuration. Analytical comparisons and numerical simulations show that LCA-1 and TSM could be rewritten with the same formulation and that their polarization sensitivities are comparable. Comparisons with experimental data acquired in C- and Ku-band reveal that the polarization sensitivities of these models are not adequate. However, the NRCS azimuth modulation predicted by LCA-1 is found to be dependent on...
Tipo: Text
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3001.pdf
Imagem não selecionada

Imprime registro no formato completo
Assimilation of SMOS L-band Wind Speeds: Impact on Met Office Global NWP and Tropical Cyclone Predictions ArchiMer
Cotton, J.; Francis, P.; Heming, J.; Forsythe, M.; Reul, Nicolas; Donlon, C..
A new generation of L-band sensors, such as ESA's Soil Moisture Ocean Salinity (SMOS) mission, have the capability to provide information on the ocean-surface wind speed under high wind and rain conditions. In this study we evaluate the use of SMOS wind speeds within Met Office numerical weather prediction (NWP). Observation minus model background (O-B) departure statistics are used to investigate SMOS error characteristics, quality flags, and develop a quality control method. Observation errors and spatial correlation distances are estimated using a statistical method. Observing system experiments are performed to diagnose the impact of SMOS on NWP forecasts and analyses, including tropical cyclone (TC) predictions. The quality of SMOS retrievals appears...
Tipo: Text Palavras-chave: SMOS; L-band wind speed; Data assimilation; Tropical cyclones; NWP.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00417/52868/53782.pdf
Imagem não selecionada

Imprime registro no formato completo
Comparison of spaceborne measurements of sea surface salinity and colored detrital matter in the Amazon plume ArchiMer
Fournier, Severine; Chapron, Bertrand; Salisbury, J.; Vandemark, Douglas; Reul, Nicolas.
Large rivers are key hydrologic components in oceanography, particularly regarding air-sea and land-sea exchanges and biogeochemistry. We enter now in a new era of Sea Surface Salinity (SSS) observing system from Space with the recent launches of the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius/Sac-D missions. With these new sensors, we are now in an excellent position to revisit SSS and ocean color investigations in the tropical northwest Atlantic using multi-year remote sensing time series and concurrent in situ observations. The Amazon is the world's largest river in terms of discharge. In its plume, SSS and upper water column optical properties such as the absorption coefficient of colored detrital matter (acdm) are strongly...
Tipo: Text Palavras-chave: Amazon-Orinoco river plume; SMOS SSS; Conservative mixing; Ocean color; Salinity; Satellite oceanography.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00255/36610/35742.pdf
Imagem não selecionada

Imprime registro no formato completo
Demonstration of ocean surface salinity microwave measurements from space using AMSR-E data over the Amazon plume ArchiMer
Reul, Nicolas; Saux Picart, Stephane; Chapron, Bertrand; Vandemark, D.; Tournadre, Jean; Salisbury, J..
Microwave Sea Surface Salinity (SSS) measurements can be performed by isolating the emissivity response to salinity changes from numerous geophysical effects, including surface temperature and wind waves. At L-band frequencies (1 to 2 GHz), the sensitivity to SSS is sufficient but it falls off quickly as frequency is increased. Nevertheless, methods using higher microwave frequencies with much lower SSS sensitivity than at L band, can already be tested. In particular, combining 6 and 10 GHz data in vertical polarization efficiently minimizes sea surface roughness and thermal impacts. Using AMSR-E data, the retrieved bi-monthly maps of SSS at 0.5 degrees resolution over the region of the Amazon plume show relative accuracy in-line with the future L-band...
Tipo: Text
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6620.pdf
Imagem não selecionada

Imprime registro no formato completo
Earth-viewing L-band radiometer sensing of sea surface scattered celestial sky radiation - Part I: General characteristics ArchiMer
Tenerelli, Joseph; Reul, Nicolas; Mouche, Alexis; Chapron, Bertrand.
The "galactic glitter" phenomenon at L-band, i.e., the scattering of celestial sky radiation by the rough ocean surface, is examined here as a potential source of error for sea surface salinity (SSS) remote sensing. We begin by considering the transformations that must be applied to downwelling celestial noise in order to compute the eventual impact on the antenna temperature. Then, outside the context of any particular measurement system, we use approximate scattering models along with a model for the equilibrium wind wave spectrum to examine how the scattered signal at the surface might depend on the geophysical conditions and scattering geometry. It is found that, when the specular point lies far away from the galactic plane, where the incident...
Tipo: Text Palavras-chave: Scattering; Remote sensing; Radiometry.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-3922.pdf
Imagem não selecionada

Imprime registro no formato completo
Earth-Viewing L-Band Radiometer Sensing of Sea Surface Scattered Celestial Sky Radiation—Part II: Application to SMOS ArchiMer
Reul, Nicolas; Tenerelli, Joseph; Floury, N; Chapron, Bertrand.
We examine how the rough sea surface scattering of L-band celestial sky radiation might affect the measurements of the future European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. For this purpose, we combined data from several surveys to build a comprehensive all-sky L-band celestial sky brightness temperature map for the SMOS mission that includes the continuum radiation and the hydrogen line emission rescaled for the SMOS bandwidth. We also constructed a separate map of strong and very localized sources that may exhibit L-band brightness temperatures exceeding 1000 K. Scattering by the roughened ocean surface of radiation from even the strongest localized sources is found to reduce the contributions from these localized strong sources...
Tipo: Text Palavras-chave: Sea surface electromagnetic scattering; Microwave radiometry.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-3636.pdf
Imagem não selecionada

Imprime registro no formato completo
First Assessment of SMOS Data Over Open Ocean: Part II-Sea Surface Salinity ArchiMer
Boutin, J.; Martin, N.; Yin, X.; Reul, Nicolas; Spurgeon, P..
We validate Soil Moisture and Ocean Salinity (SMOS) sea surface salinity (SSS) retrieved during August 2010 from the European Space Agency SMOS processing. Biases appear close to land and ice and between ascending and descending orbits; they are linked to image reconstruction issues and instrument calibration and remain under study. We validate the SMOS SSS in conditions where these biases appear to be small. We compare SMOS and ARGO SSS over four regions far from land and ice using only ascending orbits. Four modelings of the impact of the wind on the sea surface emissivity have been tested. Results suggest that the L-band brightness temperature is not linearly related to the wind speed at high winds as expected in the presence of emissive foam, but that...
Tipo: Text Palavras-chave: L-Band; Microwave Radiometry; Ocean Salinity; Sea Surface.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00074/18557/16108.pdf
Imagem não selecionada

Imprime registro no formato completo
Geophysical Model Function for the AMSR2 C-Band Wind Excess Emissivity at High Winds ArchiMer
Zabolotskikh, Elizaveta V.; Reul, Nicolas; Chapron, Bertrand.
Measurements of the Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard GCOM-W1 satellite at 6.925 and 7.3 GHz and both linear polarizations over tropical cyclones (TCs) during 2012 – 2014 are used to derive a new geophysical function relating the brightness temperature to the sea surface wind speed (SWS) in extreme conditions. . Similar sensitivity to SWS at close C-band frequencies allowed to correct for the atmospheric contributions to the microwave radiance and estimate the brightness temperature (TB) at the surface under the TCs, combining theoretical modeling and measured TB analyses. Estimated oceanic TBs were regressed against the wind speeds from the Best Track Archive to derive the new geophysical model function (GMF) for the wind speed...
Tipo: Text Palavras-chave: Atmosphere; Geophysical measurements; Oceans; Passive microwave remote sensing; Tropical cyclones (TCs).
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00300/41094/40267.pdf
Imagem não selecionada

Imprime registro no formato completo
Haline hurricane wake in the Amazon/Orinoco plume: AQUARIUS/SACD and SMOS observations ArchiMer
Grodsky, Semyon A.; Reul, Nicolas; Lagerloef, Gary; Reverdin, Gilles; Carton, James A.; Chapron, Bertrand; Quilfen, Yves; Kudryavtsev, Vladimir N.; Kao, Hsun-ying.
At its seasonal peak the Amazon/Orinoco plume covers a region of 10^6 km2 in the western tropical Atlantic with more than 1m of extra freshwater, creating a near-surface barrier layer (BL) that inhibits mixing and warms the sea surface temperature (SST) to >29oC. Here new sea surface salinity (SSS) observations from the Aquarius/SACD and SMOS satellites help elucidate the ocean response to hurricane Katia, which crossed the plume in early fall, 2011. Its passage left a 1.5psu high haline wake covering >10^5 km2 (in its impact on density, the equivalent of a 3.5oC cooling) due to mixing of the shallow BL. Destruction of this BL apparently decreased SST cooling in the plume, and thus preserved higher SST and evaporation than outside. Combined with SST,...
Tipo: Text
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00094/20540/18943.pdf
Imagem não selecionada

Imprime registro no formato completo
How Can Present and Future Satellite Missions Support Scientific Studies that Address Ocean Acidification? ArchiMer
Salisbury, Joseph; Vandemark, Douglas; Joensson, Bror; Balch, William; Chakraborty, Sumit; Lohrenz, Steven; Chapron, Bertrand; Hales, Burke; Mannino, Antonio; Mathis, Jeremy T.; Reul, Nicolas; Signorini, Sergio R.; Wanninkhof, Rik; Yates, Kimberly K..
Space-based observations offer unique capabilities for studying spatial and temporal dynamics of the upper ocean inorganic carbon cycle and, in turn, supporting research tied to ocean acidification (OA). Satellite sensors measuring sea surface temperature, color, salinity, wind, waves, currents, and sea level enable a fuller understanding of a range of physical, chemical, and biological phenomena that drive regional OA dynamics as well as the potentially varied impacts of carbon cycle change on a broad range of ecosystems. Here, we update and expand on previous work that addresses the benefits of space-based assets for OA and carbonate system studies. Carbonate chemistry and the key processes controlling surface ocean OA variability are reviewed. Synthesis...
Tipo: Text
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00271/38234/36417.pdf
Imagem não selecionada

Imprime registro no formato completo
Impact on sea surface salinity retrieval of different auxiliary data within the SMOS mission ArchiMer
Sabia, Roberto; Camps, A; Vall Ilossera, M; Reul, Nicolas.
Aiming to provide sea surface salinity (SSS) maps with a spatiotemporal averaged accuracy of 0.1 psu (practical salinity units), the Soil Moisture and Ocean Salinity (SMOS) community is increasingly focusing on the determination of a robust inversion scheme to enable SSS retrieval from L-band brightness temperature data. In the framework of the Synergetic Aspects and Auxiliary Data Concepts for Sea Surface Salinity Measurements from Space project, efforts have been oriented toward a quantitative analysis of SSS retrieval using different auxiliary data sets. This paper aims to contribute to the assessment of the SMOS salinity retrieval error budget in view of the upcoming SMOS mission ground segment development. Aiming to do that, different models and...
Tipo: Text Palavras-chave: Spatiotemporal averaging; Sea salinity; Microwave radiometry; Auxiliary data.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2011.pdf
Imagem não selecionada

Imprime registro no formato completo
Importance of the Equatorial Undercurrent on the Sea Surface Salinity in the Eastern Equatorial Atlantic in boreal spring ArchiMer
Da-allada, Casimir Yelognisse; Jouanno, J.; Gaillard, Fabienne; Kolodziejczyk, Nicolas; Maes, C.; Reul, Nicolas; Bourles, B..
The physical processes implied in the sea surface salinity (SSS) increase in the equatorial Atlantic Cold Tongue (ACT) region during boreal spring and the lag observed between boreal spring SSS maximum and sea surface temperature (SST) summer minimum are examined using mixed-layer salinity budgets computed from observations and model during the period 2010-2012. The boreal spring SSS maximum is mainly explained by an upward flux of high salinity originating from the core of the Equatorial Undercurrent (EUC) through vertical mixing and advection. The vertical mixing contribution to the mixed-layer salt budget peaks in April-May. It is controlled primarily by i) an increased zonal shear between the surface South Equatorial Current and the subsurface EUC and...
Tipo: Text Palavras-chave: Atlantic Cold Tongue; SMOS SSS; Model; EUC salinity maximum; Vertical processes.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00363/47396/47388.pdf
Imagem não selecionada

Imprime registro no formato completo
Importance of the sea surface curvature to interpret the normalized radar cross section - art. no. C10002 ArchiMer
Mouche, Alexis; Chapron, Bertrand; Reul, Nicolas; Hauser, D; Quilfen, Yves.
[1] Asymptotic models ( small perturbation and small slope approximation at first-order, Kirchhoff approximation or two-scale model) used to predict the normalized radar cross section of the sea surface generally fail to reproduce in detail backscatter radar measurements. In particular, the predicted polarization ratio versus incidence and azimuth angles is not in agreement with experimental data. This denotes the inability of these standard models to fully take into account the roughness properties with respect to the sensor's configuration of measurement ( frequency, incidence, and polarization). On the basis of particular assumptions, to decompose the scattered electromagnetic field between zones covered with freely propagating waves and others where...
Tipo: Text
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3577.pdf
Imagem não selecionada

Imprime registro no formato completo
Interannual surface salinity in Northwest Atlantic shelf ArchiMer
Grodsky, Semyon A.; Reul, Nicolas; Chapron, Bertrand; Carton, James A.; Bryan, Frank O..
Sea surface salinity (SSS) from the Aquarius and SMOS satellite missions displays a steady increase of ~1psu over the entire northwestern Atlantic shelf south of Nova Scotia during the 2011-2015. Put in the context of longer ocean profile data the results suggest that mixed layer salinity and temperature north of the Gulf Stream experience positively correlated shelf-wide interannual oscillations (1psu/2degC). Salty and warm events occur coincident with anomalous easterly-southeasterly winds and Ekman transport counteracting the mean southwestward shelf currents. They are coincident with the weakening of both branches of the Scotian Shelf Current (SSC), but only moderately correlate with shifts of the Gulf Stream North Wall. This suggests that salt...
Tipo: Text Palavras-chave: Salinity; Interannual; Satellite.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00376/48736/49100.pdf
Imagem não selecionada

Imprime registro no formato completo
Modeling sun glitter at L-band for sea surface salinity remote sensing with SMOS ArchiMer
Reul, Nicolas; Tenerelli, Joseph; Chapron, Bertrand; Waldteufel, P.
Since the sun is an extremely strong radiation source at L-band, accounting for sun glint over the ocean, i.e., solar radiation reflected by the sea surface toward downward-looking radiometers, raises a significant challenge for the remote sensing of sea surface salinity. This paper describes a dedicated physical model for sun glint at L-band frequencies and provides quantitative and qualitative estimates of the sun glint contamination impinging the antenna of the Microwave Imaging Radiometer with Aperture Synthesis interferometer onboard the future European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission, The sun brightness temperature expected during the mission period is first estimated from past solar flux data with an expected range of...
Tipo: Text Palavras-chave: Sun glitter; Sea surface salinity SSS; Rough surface scattering; Ocean remote sensing; Microwave radiometry.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3565.pdf
Imagem não selecionada

Imprime registro no formato completo
Multisensor observations of the Amazon-Orinoco river plume interactions with hurricanes ArchiMer
Reul, Nicolas; Quilfen, Yves; Chapron, Bertrand; Fournier, Severine; Kudryavtsev, Vladimir; Sabia, Roberto.
An analysis is presented for the spatial and intensity distributions of North Atlantic extreme atmospheric events crossing the buoyant Amazon-Orinoco freshwater plume. The sea surface cooling amplitude in the wake of an ensemble of storm tracks traveling in that region is estimated from satellite products for the period 1998-2012. For the most intense storms, cooling is systematically reduced by approximate to 50% over the plume area compared to surroundings open-ocean waters. Historical salinity and temperature observations from in situ profiles indicate that salt-driven vertical stratification, enhanced oceanic heat content, and barrier-layer presence within the plume waters are likely key oceanic factors to explain these results. Satellite SMOS surface...
Tipo: Text Palavras-chave: Hurricanes; Amazon-Orinocco river plume; SMOS SSS; Cooling inhibition; Barrier-layer; Haline stratification.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00252/36326/34855.pdf
Registros recuperados: 49
Primeira ... 123 ... 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