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Registros recuperados: 42
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AN INTERACTIVE SOFTWARE PACKAGE FOR VALIDATING SATELLITE DATA Gayana
Muraleedharan,P.M.; Pankajakshan,T..
Earth observation satellite launched in the last three decades have made vital contributions to the understanding of the planet. The earth system consisting of land, oceans and atmosphere is linked together by a number of complicated processes. Potential of microwave sensors in studying the boundary layer dynamics of the ocean-atmosphere system is well documented. Technology has revolutionized the application of such sensors and several missions are planned to take off in near future for meeting specific objectives. Launching of such sensors need to be followed by an extensive validation campaign for providing accurate and reliable information to the users. A PC-based interactive system has been developed and presented here for validating satellite mounted...
Tipo: Journal article Palavras-chave: Validation; Microwave sensor; Autocorrelation; Sea surface temperature; Wind speed; Columnar water vapor.
Ano: 2004 URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-65382004000300018
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Analyse de la variation de la température de surface de la mer (SST) aux stations côtières de Côte d'Ivoire. OceanDocs
Mahan, N. Claude; Bamba, S. Barthélémy; Aman, Angora.
Depuis 1977, le Centre de Recherches Océanologiques (CRO) a entrepris des mesures quotidiennes de température de la mer le long des côtes ivoiriennes. Les remontées d'eaux froides qui affectent la côte ivoirienne présentent une forte variabilité à différentes échelles de temps et d'espace. Ces processus environnementaux complexes, irréguliers et difficiles à appréhender ont une grande influence sur un écosystème pélagique instable et par nature changeant (Arfi et al., 1995). Ces mesures répondent à un double objectif concernant l'étude saisonnière de l'upwelling côtier ivoiro-ghanéen pour prévoir les périodes et les zones favorables à la pêche sur le plateau continental ivoirien et à l'alimentation du projet GOOS (Global Ocean Observing System) de la...
Tipo: Journal Contribution Palavras-chave: Sea surface temperature; Sea level variations; Inshore stations.
Ano: 2008 URL: http://hdl.handle.net/1834/5748
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Association between bluefin tuna schools and oceanic features in the western Mediterranean ArchiMer
Royer, Francois; Fromentin, Jean-marc; Gaspar, P.
We present an analysis of the distribution of bluefin tuna Thunnus thynnus schools spotted during aerial surveys in the Gulf of Lions, in relation to oceanographic features. Bio-optical and thermal properties of the sea surface derived from high-resolution sensors (AVHRR and SeaWiFS) were studied on a daily basis, and an edge-detection technique was applied to detect frontal zones. Geostatistics and point-process analyses were used to evaluate the role of the environment in structuring the spatial pattern of bluefin tuna (BFT). The distribution of schools spotted was strongly non-stationary both in space and time; this is believed to be an effect of the survey design (transect sampling) and the influence of transient oceanographic structures (surface...
Tipo: Text Palavras-chave: Thunnus thynnus; Gulf of Lions; Point process analysis; Front detection; Sea surface temperature; Ocean colour; Aggregation.
Ano: 2004 URL: http://archimer.ifremer.fr/doc/00000/10786/7585.pdf
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Atmospheric response to sea surface temperature mesoscale structures ArchiMer
Lambaerts, J.; Lapeyre, Guillaume; Plougonven, R.; Klein, Patrice.
Recent studies have revealed that strong sea surface temperature (SST) fronts, on the scale of a Western Boundary Current, significantly affect not just the Marine Boundary Layer but the entire troposphere. This has aroused renewed interest in air-sea interactions. The present study investigates the atmospheric response to fixed SST anomalies associated with mesoscale oceanic eddies and submesoscale filaments, using idealized simulations. Our main result is that in weak wind conditions, the vertical velocity in the planetary boundary layer (PBL) is linearly proportional to the SST Laplacian. This is established by a quantitative analysis in the spatial space as well as in the spectral space. Comparing the responses to two different SST fields shows that...
Tipo: Text Palavras-chave: Air-sea interactions; Boundary layer; Sea surface temperature.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00169/28047/26247.pdf
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Causes of Low Frequency North Atlantic SST Variability in a Coupled GCM OceanDocs
Schneider, E.K.; Kirtman, B.P.; Wu, Z..
The low frequency sea surface temperature (SST) variability in the North Atlantic is studied using the Center for Ocean-Land-Atmosphere Studies (COLA) anomaly coupled general circulation model. The main focus is placed on the relative roles of stable and unstable coupled feedbacks in inducing the low frequency SST variability in various regions of the North Atlantic. To examine this question, a recently developed coupling technique, interactive ensembles, is applied to reduce the strength of “weather noise” in the model and isolate the atmospheric feedback to boundary forcing.
Tipo: Journal Contribution Palavras-chave: Sea surface temperature.
Ano: 2004 URL: http://hdl.handle.net/1834/508
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Characterizing and Comparing the Spawning Habitats of Sardine (Sardinops sagax) and Anchovy (Engraulis encrasicolus) in the Northern Benguela Region OceanDocs
Tjizoo,Mbeurora Beau.
Spawning habitats of sardine and anchovy in eastern boundary current systems are characterized in an attempt to understand the fluctuations observed in their abundance. The northern Benguela, as an eastern boundary current system, is characterized by turbulent conditions that seem to govern the variability observed in the abundance of these species. Sardine and anchovy have developed mechanisms that enable them to maximize productivity. In the northern Benguela, spawning intensity is historically known to be high in periods and vicinities where turbulence is reduced. However, it is believed that selection of conditions for spawning by these species may change withfluctuations in abundance of fish.
Tipo: Theses and Dissertations Palavras-chave: Sardine fisheries; Spawning; Anchovy fisheries; Habitat; Ecosystems; Sea surface temperature; Salinity; Spatial distribution; Climatic changes; Anthropogenic factors; Pelagic environment; Circulation; Coastlines.
Ano: 2008 URL: http://hdl.handle.net/1834/5231
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Detection of mesoscale thermal fronts from 4km data using smoothing techniques: Gradient-based fronts classification and basin scale application ArchiMer
Roa Pascuali, Liliana; Demarcq, Herve; Nieblas, Anne-elise.
In order to optimize frontal detection in sea surface temperature fields at 4 km resolution, a combined statistical and expert-based approach is applied to test different spatial smoothing of the data prior to the detection process. Fronts are usually detected at 1 km resolution using the histogram-based, single image edge detection (SIED) algorithm developed by Cayula and Cornillon in 1992, with a standard preliminary smoothing using a median filter and a 3 × 3 pixel kernel. Here, detections are performed in three study regions (off Morocco, the Mozambique Channel, and north-western Australia) and across the Indian Ocean basin using the combination of multiple windows (CMW) method developed by Nieto, Demarcq and McClatchie in 2012 which improves on the...
Tipo: Text Palavras-chave: Mesoscale thermal fronts; Preliminary smoothing; Sea surface temperature; 4 km resolution; Gradient intensity classification; Expert-based approach; Detection efficiency; Indian Ocean.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00269/37998/42023.pdf
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Determining bluefin tuna habitat through frontal features in the Mediterranean sea ArchiMer
Royer, Francois; Fromentin, Jean-marc; Farrugio, Henri; Gaspar, Philippe.
The distribution patterns of bluefin tuna schools observed during the STROMBOLI EU project (2000-2002) were analysed in relation to oceanographic conditions. High-resolution radiometers (AVHRR and SeaWiFS) were used on a daily basis to derive maps of environmental variability. An edge detection technique was especially applied to estimate the position of frontal features. Using a variety of geostatistical and point process techniques, we were able to show that the distribution of bluefin schools was partially driven by the occurrence of transient fronts in the Gulf of Lions. This is believed to be mainly a trophic association, since enhanced convergence and retention processes occur at fronts, possibly leading to higher prey densities (e.g. anchovies). The...
Tipo: Text Palavras-chave: Thunnus thynnus; Aerial survey; Gulf of Lions; Sea surface temperature; Ocean colour; Fronts.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/00194/30504/28914.pdf
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Diagnosis of high-resolution upper ocean dynamics from noisy sea surface temperatures ArchiMer
Isern-fontanet, J.; Hascoet, Erwan.
The noise present in infrared satellite measurements of sea surface temperature (SST) hampers the use of surface quasi-geostrophic (SQG) equations to diagnose ocean dynamics at high resolutions. Here we propose a methodology to reduce the contribution of noise when diagnosing surface vorticity, divergence, and vertical velocity from SST able to retain the dynamics at scales of a few kilometers. It is based on the use of denoising techniques with curvelets as basis functions and the application of a selective low-pass filters to improve the reconstruction of surface upwelling/downwelling patterns. First, it is tested using direct numerical simulations of SQG turbulence and then applied to diagnose low-frequency vertical velocity patterns from real MODIS...
Tipo: Text Palavras-chave: Sea surface temperature; Surface quasi-geostrophy; Remote sensing; Vertical velocity; Ocean submesoscales; Image denoising.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00170/28162/26391.pdf
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Effect of subjective choices on the objective analysis of sea surface temperature data in the tropical Atlantic and Pacific oceans ArchiMer
Molinari, Rl; Festa, Jf.
Many subjective choices are required to perform an objective interpolation (OI) analysis of environmental variables. Herein, we consider the effects on the statistical analysis of sea surface temperature (SST) using (1) a structure function or covariance analysis, (2) different analytical expressions to represent the statistics of the raw data, and (3) different historical SST data sets. The historical data sets are the well-sampled Comprehensive Ocean-Atmospheric Data Set (COADS) and the poorly sampled historical expendable bathythermograph (XBT) data set. Results from these analyses are used to generate error maps for a poorly-sampled, two month XBT array and a proposed well-sampled profiling float array. For the relatively data-rich GOADS analysis,...
Tipo: Text Palavras-chave: Analyse objective; Température superficielle; Fonction de structure; Analyse statistique; Interpolation objective; Objective analysis; Sea surface temperature; Structure function; Statistical analysis; Objective interpolation.
Ano: 2000 URL: http://archimer.ifremer.fr/doc/00325/43573/44041.pdf
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Environmental noise in spawning areas: the case of Atlantic bluefin tuna (Thunnus thynnus) ArchiMer
Royer, Francois; Fromentin, Jean-marc.
This paper provides an exploratory analysis aiming to seek whether the colour of environmental noise theory could help in understanding the intriguing reproductive strategy of Atlantic bluefin tuna (BFT). A frequency-based approach based on spectral exponents, f(beta) with beta < 0, is chosen and applied on 10 biogeographical provinces covering the North Atlantic. The major BFT spawning area, i.e. the Mediterranean Sea, was the only one to display a pink power spectrum, whereas open ocean regions displayed more reddened fluctuations, i.e. greater variance at low frequencies. Environmental noise in the Mediterranean could, thus, offer more favourable characteristics on the long-term than the open ocean. The implications of these findings are discussed in...
Tipo: Text Palavras-chave: Thunnus thynnus; Spectral analysis; Spawning; Sea surface temperature; Environmental noise.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2437.pdf
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Exploring Machine Learning to Correct Satellite-Derived Sea Surface Temperatures ArchiMer
Picart, Stephane Saux; Tandeo, Pierre; Autret, Emmanuelle; Gausset, Blandine.
Machine learning techniques are attractive tools to establish statistical models with a high degree of non linearity. They require a large amount of data to be trained and are therefore particularly suited to analysing remote sensing data. This work is an attempt at using advanced statistical methods of machine learning to predict the bias between Sea Surface Temperature (SST) derived from infrared remote sensing and ground “truth” from drifting buoy measurements. A large dataset of collocation between satellite SST and in situ SST is explored. Four regression models are used: Simple multi-linear regression, Least Square Shrinkage and Selection Operator (LASSO), Generalised Additive Model (GAM) and random forest. In the case of geostationary satellites for...
Tipo: Text Palavras-chave: Machine learning; Systematic error; Sea surface temperature; Random forest.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00426/53797/54721.pdf
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Group for High Resolution Sea Surface Temperature (GHRSST) analysis fields inter-comparisons-Part 2: Near real time web-based level 4 SST Quality Monitor (L4-SQUAM) ArchiMer
Dash, Prasanjit; Ignatov, Alexander; Martin, Matthew; Donlon, Craig; Brasnett, Bruce; Reynolds, Richard W.; Banzon, Viva; Beggs, Helen; Cayula, Jean-francois; Chao, Yi; Grumbine, Robert; Maturi, Eileen; Harris, Andy; Mittaz, Jonathan; Sapper, John; Chin, Toshio M.; Vazquez-cuervo, Jorge; Armstrong, Edward M.; Gentemann, Chelle; Cummings, James; Piolle, Jean-francois; Autret, Emmanuelle; Roberts-jones, Jonah; Ishizaki, Shiro; Hoyer, Jacob L.; Poulter, Dave.
There are a growing number of level 4 (L4; gap-free gridded) sea surface temperature (SST) products generated by blending SST data from various sources which are available for use in a wide variety of operational and scientific applications. In most cases, each product has been developed for a specific user community with specific requirements guiding the design of the product. Consequently differences between products are implicit. In addition, anomalous atmospheric conditions, satellite operations and production anomalies may occur which can introduce additional differences. This paper describes a new web-based system called the L4 SST Quality Monitor (L4-SQUAM) developed to monitor the quality of L4 SST products. L4-SQUAM intercompares thirteen L4...
Tipo: Text Palavras-chave: Sea surface temperature; Intercomparison; Climate data; Sea ice; Data centers.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00101/21188/19798.pdf
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Internal Atmospheric Dynamics and Tropical Indo-Pacific Climate Variability OceanDocs
Kinter, S.M.; Pegion, K.; Kirtman, B.P..
One possible explanation for tropical sea surface temperature (SST) interannual variability is that it can be accurately described by a linear auto-regressive model with damped coupled feedbacks and stochastic forcing. This auto-regressive model can be viewed is a “null hypothesis” for tropical SST variability. This paper advances a new coupled general circulation model (CGCM) coupling strategy, called an interactive ensemble as a method to test this null hypothesis. The design of the interactive ensemble procedure is to reduce the stochastic variability in the air-sea fluxes applied to the ocean component while retaining the deterministic component of the coupled feedbacks. The interactive ensemble procedure uses multiple realizations of the atmospheric...
Tipo: Working Paper Palavras-chave: Sea surface temperature; Atmospheric conditions.
Ano: 2005 URL: http://hdl.handle.net/1834/512
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Linear Gaussian state-space model with irregular sampling: application to sea surface temperature ArchiMer
Tandeo, Pierre; Ailliot, Pierre; Autret, Emmanuelle.
Satellites provide important information on many meteorological and oceanographic variables. State-space models are commonly used to analyse such data sets with measurement errors. In this work, we propose to extend the usual linear and Gaussian state-space to analyse time series with irregular time sampling, such as the one obtained when keeping all the satellite observations available at some specific location. We discuss the parameter estimation using a method of moment and the method of maximum likelihood. Simulation results indicate that the method of moment leads to a computationally efficient and numerically robust estimation procedure suitable for initializing the Expectation-Maximisation algorithm, which is combined with a standard numerical...
Tipo: Text Palavras-chave: State-space model; Irregular sampling; Ornstein-Uhlenbeck process; EM algorithm; Sea surface temperature.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00039/15047/12441.pdf
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Linking wind and interannual upwelling variability in a regional model of the southern Benguela - art. no. 2188 ArchiMer
Blanke, Bruno; Roy, Claude; Penven, Pierrick; Speich, Sabrina; Mcwilliams, James; Nelson, Greville.
We quantify the wind contribution to the development of interannual sea surface temperature (SST) anomalies along the shelf of southern Africa. We compare numerical simulations that differ only in the amount of variability kept in the ERS1/2-derived surface wind forcing. Surprisingly, most of the cold and warm episodes over the Agulhas Bank are strictly related to local fluctuations of the forcing, whereas the shelf of the west coast extending 400 km north of Cape Columbine is equally sensitive to open-sea wind fluctuations. We diagnose the respective role of mesoscale eddy activity and of low frequency and intra-monthly wind fluctuations in generating interannual SST variability. The fair degree of correlation obtained at a few locations between the model...
Tipo: Text Palavras-chave: Numerical simulation; Wind fluctuation; Sea surface temperature; Upwelling.
Ano: 2002 URL: https://archimer.ifremer.fr/doc/2002/publication-770.pdf
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Mangrove increases resiliency of the French Guiana shrimp fishery facing global warming ArchiMer
Diop, Bassirou; Blanchard, Fabian; Sanz, Nicolas.
This paper deals with the biological, ecological and economic impact of global warming and mangrove habitat availability on the French Guiana shrimp fishery. A dynamic bio-economic model is built by employing a shrimp stock's growth function depending on Sea Surface Temperature (SST) and on mangrove surface. The model is empirically calibrated for the French Guiana shrimp fishery using time series collected over 1995–2011. First, two Cobb-Douglas functions, which describe shrimp's natural growth and harvest, are estimated. Then, a Maximum Economic Yield (MEY) harvest rule, based on the optimization of the net present value derived from fishing, is computed. Three management strategies are compared (Closure, Status Quo management, and MEY) under three...
Tipo: Text Palavras-chave: Renewable resources; Fishery bio-economic model; Global warming; Shrimp; Sea surface temperature; Mangrove.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00455/56672/58537.pdf
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Modelling the tides and their impacts on the vertical stratification over the Sofala Bank, Mozambique ArchiMer
Chevane, C. M.; Penven, Pierrick; Nehama, F. P. J.; Reason, C. J. C..
The Sofala Bank, a wide shelf located along the central coast of Mozambique, hosts tides with high amplitudes. The Regional Ocean Modelling System (ROMS) was used to analyse the tidal currents on the bank and to investigate their effects on the stratification and generation of tidal fronts. During spring tides, barotropic tidal currents with maximum values ranging from 40 cm s–1 to 70 cm s–1 are found on the central bank. The major axis of the tidal ellipses for M2 and S2 follow a cross-shelf direction with mainly anticlockwise rotation. Similar to observations, three distinct regimes occur: (i) a warm well-mixed region on the inner shelf where the depths are <30 m; (ii) a wellmixed colder region above the shelf edge; and (iii) a stratified region...
Tipo: Text Palavras-chave: Barotropic tidal currents; ROMS; Sea surface temperature; Shallow seas; Tidal front.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00362/47276/47852.pdf
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Near-Sea Surface Temperature Stratification from SVP Drifters ArchiMer
Reverdin, Gilles; Morisset, S.; Bellenger, H.; Boutin, J.; Martin, N.; Blouch, P.; Rolland, Jean; Gaillard, Fabienne; Bouruet-aubertot, P.; Ward, B..
This study describes how the hull temperature (Ttop) measurements from multisensor surface velocity program (SVP) drifters can be combined with other measurements to provide quantitative information on near-surface vertical temperature stratification during large daily cycles. First, Ttop is compared to the temperature measured at 17 -cm depth from a float tethered to the SVP drifter. These 2007-12 SVP drifters present a larger daily cycle by 1%-3% for 1 degrees-2 degrees C daily cycle amplitudes, with a maximum difference close to the local noon. The difference could result from flow around the SVP drifter in the presence of temperature stratification in the top 20 cm of the water column but also from a small influence of internal drifter temperature on...
Tipo: Text Palavras-chave: Sea surface temperature; Buoy observations.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00155/26589/24720.pdf
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Observed atlantification of the Barents Sea causes the Polar Front to limit the expansion of winter sea ice ArchiMer
Barton, Benjamin I.; Lenn, Yueng-djern; Lique, Camille.
Barents Sea Water (BSW) is formed from Atlantic Water that is cooled through atmospheric heat loss and freshened through seasonal sea ice melt. In the eastern Barents Sea, the BSW and fresher, colder Arctic Water meet at the surface along the Polar Front (PF). Despite its importance in setting the northern limit of BSW ventilation, the PF has been poorly-documented, mostly eluding detection by observational surveys that avoid seasonal sea ice. In this study, satellite sea surface temperature (SST) observations are used in addition to a temperature and salinity climatology to examine the location and structure of the PF, and characterise its variability over the period 1985 – 2016. It is shown that the PF is independent of the position of the sea ice edge...
Tipo: Text Palavras-chave: Arctic; Sea ice; Fronts; Sea surface temperature; Satellite observations.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00448/56003/57509.pdf
Registros recuperados: 42
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