Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-09-27T14:22:18Z No. of bitstreams: 1 Dissertac...pdf: 4004750 bytes, checksum: c28f16763d698bcdf286109327f4a3a0 (MD5) / Made available in DSpace on 2017-09-27T14:22:18Z (GMT). No. of bitstreams: 1 Dissertac...pdf: 4004750 bytes, checksum: c28f16763d698bcdf286109327f4a3a0 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A porção equatorial Oeste do Atlântico Sul é uma região-chave para o estudo das variabilidades climáticas, já que esta área é a principal saída de calor e sal para as altas latitudes do hemisfério norte através da Corrente Norte do Brasil. Esta transferência inter-hemisférica é um dos fatores cruciais para o funcionamento da circulação termohalina no oceano Atlântico, conhecida como Atlantic Meridional Overturning Circulation (AMOC). Baseado nisto, o objetivo deste trabalho é apresentar uma reconstrução da temperatura da superfície do mar (TSM) ao longo dos últimos 40.000 anos, em um intervalo que engloba o Ultimo Máximo Glacial (UMG) e o Holoceno. Para isto, foram empregados três testemunho sedimentares recuperados na margem Nordeste do Brasil. Dois destes testemunhos (MC 17/2 e MC 11/1) tiveram sua cronologia combinada, para juntos formarem um registro único do Holoceno. O terceiro testemunho (MC 10/3) enfoca o UMG e a fase de degelo até o início do Holoceno. Como proxies para a reconstrução paleoceanográfica da TSM foram empregados o isótopo estável de oxigênio (δ18Oc) do foraminífero planctônico Globigerinoides ruber (branco 250 – 300 μm), a Técnica do Análogo Moderno (TAM) e a análise faunística da assembleia de foraminíferos planctônicos na fração 150 μm. Os resultados para o UMG mostram a existência de dois cenários distintos que se separam em 21 k anos AP. Antes desta data condições mais frias na ordem de 2 ºC existiram na região, como ficou evidenciado pelos valores mais positivos do δ18Oc, pelas menores TSM reconstruídas pela TAM e pela maior abundância de foraminíferos planctônicos relacionados a produtividade e profundidade, como Globigerina glutinata, Neogloboquadrina dutertrei, Globorotalia truncatulinoides (dextral e sinistral) e Globorotalia inflata. Após 21 k anos AP uma forte transição ocorre no δ18Oc e na abundância absoluta de foraminíferos planctônicos, indicando a entrada de condições mais quentes na região, principalmente durante o evento Heinrich 1 (H1) e o Younger Dryas (YD). Este intervalo, que inclui a fase de degelo e parte do Holoceno é marcado pela redução das espécies relacionada a produtividade e profundidade e pelo aumento das espécies de águas quentes e superficiais. O retorno da espécie Globorotalia menardii em 21 k anos AP pode indicar a reativação do transporte de águas quentes do Oceano Índico para o Atlântico Sul realizado pela Corrente das Agulhas durante a fase de degelo. Os dados apresentados aqui demonstram que o Atlântico equatorial Oeste responde a entrada de água doce no Atlântico Norte e ao transporte de águas quentes via Corrente das Agulhas, e que o balanço destes dois fatores foi crucial para o retorno da AMOC no fim do UMG. Os resultados para o Holoceno mostraram que a região vem sofrendo um aumento progressivo da TSM da ordem de 1 ºC principalmente após o Holoceno médio, onde alterações nos padrões orbitais podem ter modificado a distribuição da energia solar no planeta. Análises espectrais sobre os dados mostram uma série de periodicidade quase cíclicas centradas em 4.1 – 3.8 kyr, 1.5 – 1.0 kyr, ~ 700 yr, 570 – 560 yr, ~ 390 yr, ~350 yr e ~ 330 yr e podem refletir a ação de forçantes climáticas externa (variabilidade solar) e internas (sistema oceano-atmosfera) transmitidas pela circulação termohalina globalmente. / The western equatorial Atlantic is a key region for the study of climate variability, as this area is the main source of heat and salt toward high latitudes of northern Atlantic through the North Brazil Current. This interhemispheric transfer is one of the crucial factors for the thermohaline circulation in the Atlantic Ocean, known as Atlantic Meridional Overturning Circulation (AMOC). Based on this, the aim of this work is to show a reconstruction of sea surface temperature (SST) over the last 40,000 years, into a range that comprises the Last Glacial Maximum (LGM) and Holocene. For this, we used three sedimentary records recovered in Northeast Brazilian margin. Two of these records (MC 17/2 e MC 11/1) were combined to generate a single record of Holocene. The last record comprises the LGM until the early Holocene. As proxies for the reconstruction of SST were employed the oxygen stable isotope (δ18Oc) of planktonic foraminifera Globigerinoides ruber (white 250 – 300 μm), the Modern Analogue Technique (MAT) and the assemblage of planktonic foraminifera in the size-fraction of 150 μm. The results for the LGM showed the existence of two different scenarios that were separated at 21 kyr BP. The heavier oxygen values recorded prior to 21 kyr BP demonstrated that the Last Glacial Maximum was up to 2ºC colder than Holocene. After 21 kyr BP, a strong shift to lighter values indicated the onset of warmer conditions during deglacial, especially during Heinrich event 1 and the Younger Dryas. The planktonic foraminifera assemblage as species related to productive or deep waters confirmed the conditions indicated by the oxygen composition; i.e., Globigerinita glutinata, Neogloboquadrina dutertrei, Globorotalia truncatulinoides (left and right coiling) and Globorotalia inflata were more abundant prior to 21 kyr BP. With the increase in the sea surface temperature after 21 kyr BP, the abundance of these species was reduced, particularly for G. glutinata and G. inflata, and the abundance of species found in warmer waters increased, especially for Globigerinella siphonifera. The species Globorotalia menardii, which was absent in the Last Glacial Maximum, reappeared after 21 kyr BP, which may have been a response to the Agulhas Leakage that released warmer waters into the South Atlantic at the beginning of deglacial. The data presented here indicate that the western equatorial Atlantic responded to the meltwater pulse at high latitudes of the northern Atlantic and to warm waters from the Indian Ocean. The balance between these two factors was crucial to the development of the Atlantic Meridional Overturning Circulation at the end of the LGM. The results of Holocene showed that the region has suffered a gradual increase in SST of around 1 ºC, mainly after the mid-Holocene, where changes orbital patterns may have changed the distribution of solar energy on the planet. Spectral analyzes on the data demonstrated a series of periodicities centered at 4.1 – 3.8 kyr, 1.5 – 1.0 kyr, ~ 700 yr, 570 – 560 yr, ~ 390 yr, ~350 yr e ~ 330 yr and can be related of climate forcing transmitted globally by the thermohaline circulation.

Le géothermomètre Δ47 est basé sur la relation entre l’abondance des liaisons 13C–18O des carbonates et la température de calcification. Ce proxy contourne potentiellement les limites des autres thermomètres (δ18O, Mg/Ca) pour reconstruire les paléo-températures des océans, expliquant son développement exponentiel depuis dix ans. Cette thèse teste pour la première fois le potentiel et les limites de la thermométrie Δ47 sur les coccolithes, des nannofossiles calcaires produits par des organismes calcifiants dans la zone photique. Ces biominéraux calcitiques et ubiquistes constituent une part importante de l’archive sédimentaire. Des cultures in vitro nous ont permis d’établir que trois espèces de coccolithes actuelles enregistrent la même relation Δ47 – T que la calcite inorganique, alors qu'elles présentent de très larges effets vitaux en δ18O (±5‰). Nous concluons que ces espèces de coccolithes d'importance géologique ne présentent pas d’effets vitaux en Δ47. Nous avons ensuite appliqué le Δ47 à l’étude des sédiments enregistrant l’événement d’anoxie océanique du Toarcien (–183 Ma) au cours duquel les reconstructions de températures restent encore ambigües, notamment du fait de la méconnaissance de la composition isotopique en oxygène de l’eau de mer. Sur la base des données Δ47 acquises, nous proposons des températures élevées (de l’ordre de 36°C), mais restant relativement stables sur l'intervalle d'étude. En couplant ces températures aux données de δ18O des carbonates, nous suggérons une variation importante du δ18O de l'eau de mer dans le Bassin de Paris lors de la mise en place des faciès black shales. Enfin, sur des sédiments pélagiques subactuels, l’une des espèces étudiées présente des déséquilibres isotopiques en Δ47 non observés en culture et explicables par d’autres paramètres environnementaux comme l’intensité lumineuse. Cette thèse illustre le potentiel du thermomètre Δ47 des coccolithes en différents contextes, ouvrant un vaste champ d’application de reconstruction des paléo-environnements sur le Méso-Cénozoïque / The Δ47 geothermometer relies on the relationship between the 13C–18O abundance in carbonateand temperature of calcification. This proxy has the potential to overcome limitations of other thermometers(δ18O, Mg/Ca) to reconstruct oceanic paleotemperatures. This thesis evaluates for the first time the potentialand the limitations of the Δ47 thermometry of the coccoliths, the calcareous nannofossils produced byorganisms calcifying in the photic zone. These calcitic and ubiquitous biominerals represent an importantpart of the sedimentary archive. In vitro cultures allow us to establish that three modern coccoliths speciesrecord the same Δ47–T relation than inorganic calcite, although exhibiting substantial δ18O vital effects(±5‰). We conclude that these coccoliths species do not present any Δ47 vital effect. We subsequentlyapplied the Δ47 proxy to sediments from the Toarcian oceanic anoxic events (–183 Ma) during which thetemperatures reconstructions are still elusive, mainly due to the unknown oxygen isotopic composition ofseawater. On the basis of our Δ47 data, we infer relatively high, yet steady temperatures (around 36°C) duringthe examined interval. By combining these Δ47-derived temperatures to carbonate δ18O data, we can suggestdrastic change in the seawater δ18O composition in the Paris Basin at the onset of black shale deposition. Acore top calibration of Δ47 of coccoliths revealed that one of the studied cultured species exhibits Δ47disequilibrium that is accountable by other environmental parameters, such as light irradiance in the naturalenvironment. Thus, this thesis illustrates the potential of the coccolith Δ47 thermometer in different settings,opening a wide range of application to reconstruct the palaeoenvironments over the Meso-Cenozoic Eras

In first part of the study we discuss impact of dynamical core in simulation of tropical rainfall. Over years many new dynamical cores have been developed for atmospheric models to increase efficiency and reduce numerical errors. CAM3.1 gives an opportunity to study the impact of the dynamical core on simulations with its three dynamical cores namely Eulerian spectral(EUL) , Semilagrangian dynamics(SLD) and Finite volume(FV) coupled to a single parametrization package. A past study has compared dynamical cores of CAM3 in terms on tracer transport and has showed advantages using FV in terms of tracer transport. In this study we compare the dynamical cores in climate simulations and at their optimal configuration, which is the intended use of the model. The model is forced with AMIP type SST and rainfall over seasonal, interannual scales is compared. The significant differences in simulation of seasonal mean exist over tropics and over monsoon regions with observations and among dynamical cores. The differences among EUL and SLD, which use spectral transform methods are lesser compared that of with FV clearly indicating role of numerics in differences. There exist major errors in simulation of seasonal cycle in all dynamical cores and errors in simulation of seasonal means over many regions are associated with errors in simulation of seasonal cycle such as over south china sea. Seasonal cycle in FV is weaker compared to SLD and EUL. The dynamical cores exhibit different interannual variability of rainfall over Indian monsoon region, the period of maximum power corresponding to a dynamical core differs substantially with another. From this study there seems no superiority associated with FV dynamical core over all climate scales as seen in tracer transport. The next part of the study deals with impact of diurnal ocean atmosphere coupling in an AGCM,CAM3.1. Due to relatively low magnitude of diurnal cycle of SST and lack of SST observations over diurnal scales current atmospheric models are forced with SSTs of periods grater than a day. CAM 3.1 standalone model is forced with monthly SSTs but the interpolation is linear to every time step between any two months and this linear interpolation implies a linear diurnal and intraseasonal variation of SST which is not true in nature. To test the sensitivity of CAM3.1 to coupling of SST on diurnal scales, we prescribed over tropics(20S20N) a diurnal cycle of SST over daily mean interpolated SST of different magnitudes and phase comparable to observations. This idea of using a diurnal cycle of SST retaining seasonal mean SST in an atmospheric model is novel and provides an interesting frame work to test sensitivity of model to interpolations used in coupling of boundary conditions. Our analysis shows a high impact of using diurnal cycle of SST on simulation of mean rainfall over tropics. The impact in a case where diurnal cycle of SST is fixed and retained to daily mean SST implies that changes associated with a coupled model are to some extent due to change in representation of diurnal cycle of SST. A decrease of excess rainfall over western coast of Bay of Bengal and an increase of rainfall over northern bay of Bengal in such case is similar to the improvement due to coupling atmospheric model to a slab ocean model. This also implies that problems with current AMIP models in simulation of seasonal mean Indian monsoon rainfall could be due to erroneous representation of diurnal cycle of SST in models over this region where the diurnal cycle of SST is high in observations. The high spatial variability of the impact in various cases over tropics implies that a similar spatial variation of diurnal cycle could be important for accurate simulation of rainfall over tropics. Preliminary analysis shows that impact on rainfall was due to changes in moisture convergence. We also hypothesized that diurnal cycle of SST could trigger convection over regions such as northern Bay of Bengal and rainfall convergence feedback sustains it. The impact was also found on simulation of internal interannual variability of rainfall

No description available.

Species must interact with air—aqueous interfaces in order to transport between either phase, however organic coated water surfaces are ubiquitous in the environment, and the physical and chemical processes that occur at organic coated aqueous surfaces are often different than those at pure air—water interfaces. Three studies were performed investigating the transport of species across air—aqueous interfaces with organic coatings in an effort to gain further insight into these processes. Gas and solution phase absorption spectroscopy were used to study the effect of octanol coatings on the formation of molecular iodine (I2) by the heterogeneous ozonation of iodide and its partitioning between phases. Compared to uncoated solutions, the presence of octanol monolayers had a minor effect on the total amount of I2 produced, however, it did significantly enhance the gas to solution partitioning of I2. Incoherent broadband cavity-enhanced absorption spectroscopy (IBBC-EAS) was used to measure the gas-phase nitrogen dioxide (NO2) evolved via photolysis of aqueous nitrate solutions either uncoated or containing octanol, octanoic acid and stearic acid monolayers. Both octanol and stearic acid reduced the rate of gaseous NO2 evolution, and octanol also decreased the steady-state amount of gaseous NO2. Alternatively, octanoic acid enhanced the rate of gaseous NO2 evolution. Finally, the loss of aqueous carbon dioxide (CO2) from aqueous solutions saturated with CO2 was measured using a CO2 electrode in the absence and presence of stearic acid monolayers and octanol coatings, and a greenhouse gas analyzer was used to measure the evolution of gaseous CO2 from solutios with octanol monolayers. Enhanced losses of aqueous and evolved gaseous CO2 were observed with organic coated solutions compared to those uncoated. The results of these studies suggest that organic coatings influence the transport of I2, NO2 and CO2 via one, or a combination of: barrier effects, surface tension effects, chemistry effects and aqueous – surface – gas partitioning effects. These results, particularly the enhanced partitioning of these species to octanol coated aqueous surfaces, have important implications for species transport at air—aqueous interfaces, and may provide useful insight for future studies and parameters for atmospheric models of these species.

Species must interact with air—aqueous interfaces in order to transport between either phase, however organic coated water surfaces are ubiquitous in the environment, and the physical and chemical processes that occur at organic coated aqueous surfaces are often different than those at pure air—water interfaces. Three studies were performed investigating the transport of species across air—aqueous interfaces with organic coatings in an effort to gain further insight into these processes. Gas and solution phase absorption spectroscopy were used to study the effect of octanol coatings on the formation of molecular iodine (I2) by the heterogeneous ozonation of iodide and its partitioning between phases. Compared to uncoated solutions, the presence of octanol monolayers had a minor effect on the total amount of I2 produced, however, it did significantly enhance the gas to solution partitioning of I2. Incoherent broadband cavity-enhanced absorption spectroscopy (IBBC-EAS) was used to measure the gas-phase nitrogen dioxide (NO2) evolved via photolysis of aqueous nitrate solutions either uncoated or containing octanol, octanoic acid and stearic acid monolayers. Both octanol and stearic acid reduced the rate of gaseous NO2 evolution, and octanol also decreased the steady-state amount of gaseous NO2. Alternatively, octanoic acid enhanced the rate of gaseous NO2 evolution. Finally, the loss of aqueous carbon dioxide (CO2) from aqueous solutions saturated with CO2 was measured using a CO2 electrode in the absence and presence of stearic acid monolayers and octanol coatings, and a greenhouse gas analyzer was used to measure the evolution of gaseous CO2 from solutios with octanol monolayers. Enhanced losses of aqueous and evolved gaseous CO2 were observed with organic coated solutions compared to those uncoated. The results of these studies suggest that organic coatings influence the transport of I2, NO2 and CO2 via one, or a combination of: barrier effects, surface tension effects, chemistry effects and aqueous – surface – gas partitioning effects. These results, particularly the enhanced partitioning of these species to octanol coated aqueous surfaces, have important implications for species transport at air—aqueous interfaces, and may provide useful insight for future studies and parameters for atmospheric models of these species.

Interannual variation of Indian summer (June-September: JJAS) monsoon rainfall (ISMR) depends on its relative intensity during early (June-July: JJ; contribution 52%) and late (August-September: AS; contribution 49%) phases. Apart from variations in sea surface temperature (SST), the primary reasons behind the variability during JJ and AS can be very different due to change in climatic conditions on account of post-onset processes. Here, using a high resolution general circulation model with seasonally varying climatological SST, mechanisms those govern the intensity of rainfall during JJ and AS are investigated. There is no significant relation-ship between intensity of precipitation over Indian region in JJ and AS. Moreover, the factors determining early monsoon (JJ) precipitation are different than that for late monsoon (AS). In absence of interannual SST variation, pre-monsoon soil moisture do not play a significant role for the interannual variation of monsoon precipitation over India. A large scale oscillation of the ITCZ is noticed on interannual time scale spanning from around 60◦E to 150◦E that brings spatially coherent flood and drought over this region. Early monsoon precipitation has a larger dependency on spring snow depth over Eurasia and phase of the upper tropospheric Rossby wave in May. However, late monsoon precipitation over India is mainly governed by the intensity and time scale of the intraseasonally varying convective cloud bands. This study suggests that early monsoon (JJ) precipitation over Indian region is more correlated with pre-monsoon signatures of land-atmosphere parameters. However, in later parts after the onset (AS), the monsoon intensity is primarily driven by its internal dynamics and characteristics of intraseasonal oscillation.

Made available in DSpace on 2014-08-20T14:25:45Z (GMT). No. of bitstreams: 1 dissertacao_catia_cristina_braga_rodrigues.pdf: 1202246 bytes, checksum: 0067166e90de2215d4ec858dba3e1ba5 (MD5) Previous issue date: 2012-04-18 / The periods of large variations in rainfall in the Mato Grosso do Sul State (centralwest region, Brazil), in particular the great floods or droughts, generate large economic losses to the state. The summer drought may further compromise the winter period, which often short rains occur. The main objective of this research is to verify bimonthly rainfall variation in the state of Mato Grosso do Sul during the summer (maximum variation) and the winter (minor variations) and their relationships with the bimonthly SST anomalies combined of the South Pacific and South Atlantic oceans. The combined anomalies were represented by Principal Oscillation Patterns (POPs), which represent the predominant patterns of ocean circulation. Monthly precipitation data from January to December (from 1981 to 2009) and monthly data of Sea Surface Temperature (SST) were used. From the rainfall climatology of the marking periods were selected two periods: December/January (rainier) and July/August (dry season). Homogeneous regions were generated by the K-means Method, three for December/January period and two for the July/August period. The regional accumulated rainfall presented no significant trend at 5% probability. The regional accumulated precipitation anomalies of two-month periods showed no significant correlations with SST anomalies in the Central Pacific (Niño 3.4) along the studied period. During the two months December/January, the largest excess precipitation in the region occurred with a predominance of strong El Nino events and droughts in major events La Niña and neutral. In regions 2 and 3 there is not a predominant sign of some events. During the July/ August period, the greatest excesses of precipitation occurred in the region with a predominance of La Niña events, with less relation respect region 2, both regions in a coherent signal (Neutral and La Niña). In cases of severe dry period, both regions have low relation with the events signals. The settings of multiple regressions of bi-monthly precipitation accumulated in homogeneous regions with the scores of the first six patterns of SST showed significant increase in both studied marking periods. The correlation coefficient between the bimonthly observed accumulated precipitation and regional estimates were significant at 1% probability in all regions. This occur especially in the region that represents the northwest quarter of the state in December/January and in the region that represents the major portion of Mato Grosso do Sul State in the July/August period. / Os períodos de grandes variações da precipitação no Mato Grosso do Sul, em especial as grandes cheias ou grandes estiagens, trazem grandes prejuízos financeiros ao Estado. As estiagens de verão podem comprometer ainda mais o período de inverno, no qual já é normal ocorrer poucas chuvas. Esta pesquisa tem por proposta principal verificar as variações bimensais da precipitação no estado de Mato Grosso do Sul nos períodos de verão (variações máximas) e inverno (variações mínimas) e suas relações com as anomalias bimensais de TSM combinadas dos oceanos Pacífico Sul e Atlântico Sul. As anomalias combinadas foram representadas pelos Padrões de Oscilação Principal (POP), os quais representam os padrões predominantes de circulação oceânica. Foram usados dados de precipitação mensal de janeiro a dezembro, período de 1981 a 2009 e dados médios mensais de Temperatura na Superfície do Mar (TSM). A partir da climatologia da precipitação foi selecionado os bimestres dezembro/janeiro (mais chuvoso) e julho/agosto (menos chuvoso) e geradas pelo método K-means regiões homogêneas, sendo três para o bimestre dezembro/janeiro e duas para o bimestre julho/agosto. As precipitações acumuladas regionais não apresentaram tendência temporal significativas a 5% de probabilidade. As anomalias de precipitação acumulada regionais dos bimestres não apresentaram correlações significativas com as anomalias de TSM na região do Pacífico Central (Niño 3.4) ao longo do período estudado, mas durante o bimestre dezembro/janeiro, os maiores excessos de precipitação da região 1 ocorreram com forte predomínio de eventos El Niño fortes e a maiores estiagens em Eventos La Niña e Neutros. Nas regiões 2 e 3 não existem um sinal predominante de alguns dos eventos. Durante o bimestre julho/agosto, os maiores excessos de precipitação ocorreram na região 1 com predomínio de eventos La Niña, com menor relação na região 2, mas ambas regiões com coerência do sinal (Neutro e La Niña). Nos casos de fortes estiagens, ambas as regiões apresentam baixa relação com os sinais dos eventos. Os ajustes das regressões múltiplas das precipitações acumuladas bimestrais nas regiões homogêneas com os escores dos seis primeiros padrões de TSM apresentaram aumento de significância em ambos bimestres estudados. O coeficiente de correlação entre as precipitações acumuladas regionais bimestrais observadas e estimadas foram significativas a 1% de probabilidade em todas as regiões, especialmente na região que representa o noroeste do Estado no bimestre dezembro/janeiro e a região que representa a maior parte do estado do Mato Grosso do Sul no bimestre julho/agosto.

La caractérisation des dynamiques de sous-mésoéchelle (<10km) à la surface de l'océan et leurs impacts sur les processus océaniques globaux sont des enjeux scientifiques majeurs. L'imagerie satellitaire est un outil essentiel dans ce contexte, qui présente toutefois des limitations liées aux instruments de télédétection. Dans le cas des images de température de surface des océans (SST), les mesures satellitaires des structures océaniques sont limitées par la résolution grossière des capteurs micro-ondes (~50km) d'une part, et par la sensibilité aux conditions climatiques (e.g., couverture nuageuse) des instruments de mesure infrarouge haute-résolution. Dans cette thèse, nous nous intéressons à l'analyse, la modélisation et la reconstruction des structures turbulentes haute-résolution capturées par imagerie satellitaire de SST, et proposons quatre contributions principales. Dans un premier temps, nous développons une méthode de filtrage conjointe Fourier-ondelettes pour le prétraitement d'artefacts géométriques dans les observations satellitaires infrarouges. Dans un deuxième temps, nous nous focalisons sur la caractérisation de la variabilité géométrique de champs de température de surface (SST) en utilisant des modèles de marches aléatoires appliqués aux lignes de niveaux. En particulier, nous considérons des processus aléatoires de type schramm Loewner (SLE). Nous nous intéressons ensuite à la modélisation stochastique des variabilités inter-échelles de champs de SST. Des modèles stochastiques de textures multivariées sont introduits. Ces modèles permettent de reproduire des propriétés statistiques et spectrales similaires à celles des données ayant servi à les calibrer. Nous développons ensuite des méthodes de super-résolution de champs de SST conditionnellement à une observation basse-résolution. Nous utilisons des modèles multivariés de textures formulés dans le domaine des ondelettes, en exploitant l'apprentissage d'à priori statistiques (i.e., covariances et covariances croisées) des différentes sous-bandes à partir d'images haute-résolution. Des contraintes supplémentaires imposées sur la phase de Fourier des différentes sous-bandes simulées permettent la reconstruction de structures géométriques marquées tels que les fronts. Nous démontrons la pertinence de la méthode proposée sur des images satellitaires de SST obtenues à partir du capteur Modis/Aqua. / The characterization of sub-mesoscale dynamics (<10 km) in the ocean surface and their impact on global ocean processes are major scientific issues. Satellite imagery is an essential tool within this framework. However, the use of remote sensing techniques still raise challenging. For instance, regarding Sea Surface Temperature (SST) images, satellite measurements of oceanic structures are limited by the coarse resolution of microwave sensors (~50km) on one hand, and by sensitivity to climatic conditions (eg., Cloud cover) of high-resolution infrared instruments on the other hand. In this thesis, we are interested in analysis, modeling and reconstruction of high-resolution turbulent structures captured by satellite SST imagery. In this context, we propose four main contributions. First, we develop a joint Fourier-Wavelet filtering method for the pre-processing of geometrical noises in satellite-based infrared observations, namely the striping noises. Secondly, we focus on the characterization of the geometric variability of sea surface temperature (SST) fields using random walk models applied to SST isolines. In particular, we consider the class of Schramm Loewner evolution curves (SLE). We then focus on the stochastic modeling of the cross-scale variabilities of SST fields. Stochastic multivariate texture-based models are introduced. These models are designed to reproduce several statistics and spectral properties that are observed on the data that are used to calibrate the model. We then develop our framework for stochastic super-resolution of SST fields conditionally to low-resolution observations. We use multivariate texture-based models formulated in the wavelet domain. These models exploit the formulation of statistical and spectral priors (i.e., covariances and cross-covariances) on wavelet subbands. These priors are directly learned from exemplar high-resolution images. Additional constraints imposed on the Fourier-phase of the different simulated subbands allow the reconstruction of coherent geometric structures such as the edge information. Our method is tested and validated using infrared high-resolution satellite SST images provided by Aqua Modis sensor.

Reconstruire des champs géophysiques à partir d'observations bruitées et partielles est un problème classique bien étudié dans la littérature. L'assimilation de données est une méthode populaire pour aborder ce problème, et se fait par l'utilisation de techniques classiques, comme le filtrage de Kalman d’ensemble ou des filtres particulaires qui procèdent à une évaluation online du modèle physique afin de fournir une prévision de l'état. La performance de l'assimilation de données dépend alors fortement de du modèle physique. En revanche, la quantité de données d'observation et de simulation a augmenté rapidement au cours des dernières années. Cette thèse traite l'assimilation de données d'une manière data-driven et ce, sans avoir accès aux équations explicites du modèle. Nous avons développé et évalué l'assimilation des données par analogues (AnDA), qui combine la méthode des analogues et des méthodes de filtrage stochastiques (filtres Kalman, filtres à particules, chaînes de Markov cachées). Des applications aux modèles chaotiques simplifiés et à des études de cas de télédétection réelle (température de surface de lamer, anomalies du niveau de la mer), nous démontrons la pertinence d'AnDA pour l'interpolation de données manquantes des systèmes dynamiques non linéaires et à haute dimension à partir d'observations irrégulières et bruyantes.Motivé par l'essor du machine learning récemment, la dernière partie de cette thèse est consacrée à l'élaboration de modèles deep learning pour la détection et de tourbillons océaniques à partir de données de sources multiples et/ou multi temporelles (ex: SST-SSH), l'objectif général étant de surpasser les approches dites expertes. / Reconstructing geophysical fields from noisy and partial remote sensing observations is a classical problem well studied in the literature. Data assimilation is one class of popular methods to address this issue, and is done through the use of classical stochastic filtering techniques, such as ensemble Kalman or particle filters and smoothers. They proceed by an online evaluation of the physical modelin order to provide a forecast for the state. Therefore, the performanceof data assimilation heavily relies on the definition of the physical model. In contrast, the amount of observation and simulation data has grown very quickly in the last decades. This thesis focuses on performing data assimilation in a data-driven way and this without having access to explicit model equations. The main contribution of this thesis lies in developing and evaluating the Analog Data Assimilation(AnDA), which combines analog methods (nearest neighbors search) and stochastic filtering methods (Kalman filters, particle filters, Hidden Markov Models). Through applications to both simplified chaotic models and real ocean remote sensing case-studies (sea surface temperature, along-track sea level anomalies), we demonstrate the relevance of AnDA for missing data interpolation of nonlinear and high dimensional dynamical systems from irregularly-sampled and noisy observations. Driven by the rise of machine learning in the recent years, the last part of this thesis is dedicated to the development of deep learning models for the detection and tracking of ocean eddies from multi-source and/or multi-temporal data (e.g., SST-SSH), the general objective being to outperform expert-based approaches.