Ce travail s'inscrit dans le cadre de recherche sur les maladies vectorielles de Lyme et Virus du Nil au sein de l'Agence de Santé Publique du Canada (ASPC) ayant pour finalité d'évaluer et de cartographier les risques sanitaires associés à ces maladies infectieuses liées au climat aux échelles municipales, provinciales et fédérale. Dans ce contexte, cette recherche vise à démontrer la faisabilité, la pertinence et les enjeux de recourir aux méthodes de réduction d'échelle pour obtenir à une haute résolution spatio-temporelle (100/30 m et 1 jour) avec au plus des marges d'erreur de 2 unités, des déterminants climatiques et microclimatiques (DCMC) en milieu hétérogène du Canada. Un cadre méthodologique d'application des méthodes de réduction d'échelle, Random Forest Regression (RFR), Thermal sharpening (TsHARP), Pixel block intensity modulation (PBIM), a été proposé pour estimer la température de surface (LST) de MODIS 1000 m à 100/30 m. Des expérimentations basées sur cette approche ont été effectuées sur trois sites au Québec à différentes époques. Les résultats, spatialement représentatifs, ont été validés avec les températures de l'air et celles prises par de Landsat 08 avec des marges d'erreur autour de 2°C. L'analyse des résultats démontre la capacité effective des méthodes de réduction d'échelle à discriminer la LST dans l'espace. Toutefois, dans le contexte du projet de l'ASPC, ces résultats sont non concluants à 100/30 m en l'absence d'une plus-value significative au plan spatial de LST. Cette analyse a conduit à discuter des enjeux temporels, spatiaux, méthodologiques et de gestion de gros volumes de données en lien avec la réduction d'échelle dans le contexte du projet. / This research is part of the Public Health Agency of Canada's (PHAC) research on Lyme and West Nile Virus vector-borne diseases, which aims to assess and map the health risks associated with these climate-related infectious diseases at the municipal, provincial and federal levels. In this context, this research aims to demonstrate the feasibility, relevance and challenges of using downscaling methods to obtain high spatial and temporal resolution (100/30 m and 1 day), with margins of error of no more than 2 units, of climatic and microclimatic determinants (CMDs) in a heterogeneous Canadian environment. A methodological framework for the application of downscaling methods, Random Forest Regression (RFR), Thermal sharpening (TsHARP), Pixel block intensity modulation (PBIM), has been proposed to estimate the surface temperature (LST) from MODIS 1000 m to 100/30 m. Experiments with our approach were carried out at three sites in Quebec at different times. The spatially representative results were validated with air and Landsat 08 temperatures with error margins around 2°C. The analysis of our results demonstrates the effective capacity of downscaling methods to discriminate LST in space. However, in the context of the ASPC project, these results are inconclusive at 100/30 m in the absence of a significant, expected increase in the spatial accuracy of LST. This analysis led to a discussion of the temporal, spatial, methodological and large data volume management issues related to downscaling in the context of the project.

This work is motivated by the question: how much complexity is appropriate for a cloud parameterization used in general circulation models (GCM). To approach this question, cloud parameterizations across the complexity range are explored using general circulation models and theoretical Monte-Carlo simulations. Their results are compared with high-resolution satellite observations and simulations that resolve the GCM subgrid-scale variability explicitly. A process-orientated evaluation is facilitated by GCM forecast simulations which reproduce the synoptic state. For this purpose novel methods were develop to a) conceptually relate the underlying saturation deficit probability density function (PDF) with its saturated cloudy part, b) analytically compute the vertical integrated liquid water path (LWP) variability, c) diagnose the relevant PDF-moments from cloud parameterizations, d) derive high-resolution LWP from satellite observations and e) deduce the LWP statistics by aggregating the LWP onto boxes equivalent to the GCM grid size. On this basis, this work shows that it is possible to evaluate the sub-grid scale variability of cloud parameterizations in terms of cloud variables. Differences among the PDF types increase with complexity, in particular the more advanced cloud parameterizations can make use of their double Gaussian PDF in conditions, where cumulus convection forms a separate mode with respect to the remainder of the grid-box. Therefore, it is concluded that the difference between unimodal and bimodal PDFs is more important, than the shape within each mode. However, the simulations and their evaluation reveals that the advanced parameterizations do not take full advantage of their abilities and their statistical relationships are broadly similar to less complex PDF shapes, while the results from observations and cloud resolving simulations indicate even more complex distributions. Therefore, this work suggests that the use of less complex PDF shapes might yield a better trade-off. With increasing model resolution initial weaknesses of simpler, e.g. unimodal PDFs, will be diminished. While cloud schemes for coarse-resolved models need to parameterize multiple cloud regimes per grid-box, higher spatial resolution of future GCMs will separate them better, so that the unimodal approximation improves.

L'acquisition de paramètres marins à partir des données spatiales de la couleur de l'eau nécessite l'élimination de la contribution de l'atmosphère au signal mesuré par le capteur. En effet, la majorité du rayonnement solaire mesuré par les instruments optiques dans les longueurs d'ondes qui intéressent la couleur de l'eau provient de la diffusion par les molécules de l'air et les aérosols atmosphériques. L'élimination de la contribution de l'atmosphère est appelée correction atmosphérique (CA). Pour les eaux claires, les méthodes de CA supposent une réflectance marine nulle dans le proche infra-rouge (PIR). Ceci permet d'estimer la réflectane de l'atmosphère et de l'extrapoler vers les bandes du visible, et donc de déterminer le signal marin qui contient les informations sur les propriétés optiques des eaux marines. Cette hypothèse n'est cependant pas vérifiée pour les eaux turbides, qui représentent la quasi totalité des eaux côtières. Par conséquent, de nombreux algorithmes de CA ont été développés pour les eaux côtières incluant des hypothèses alternatives. L'objectif de ce travail de thèse est de valider et d'améliorer ces méthodes de CA pour les images MODIS Aqua. Pour cela, diverses approches de CA développées pour les eaux cotières ont été comparées et validées : (1) l'algorithme standard de la NASA, (2) le "NIR Similary spectrum algorithm" qui inclut des hypothèes d'homogénéité spatiale des réflectances marines et atmosphériques, (3) l'algorithme qui utilise les bandes dans l'infrarouge moyen pour la CA dans les eaux très turbides, et (4) un algorithme utilisant un réseau de neurones artificiels. L'exercice de validation à partir de données in situ, et en fonction des types d'eaux, a permis d'identifier différentes pistes d'amélioration pour l'estimation du signal marin. L'un d'entre elles comprend l'utilisation de relations spectrales pour forcer les modèles de réflectances marines utilisés par les algorithmes CA pour estimer le signal marin dans le PIR. Des modifications ont été apportées aux modèles de réflectances marines de l'algorithme standard de la NASA et du "NIR Similarity spectrum algorithm". Chacun des modèles a été forcé avec des relations spectrales préalablement validées grâce à des données globales. Une étude de sensibilité et une validation de ces algorithmes modifiés à partir de données MODIS-Aqua dans la Manhe Orientale/Mer du Nord et la Guyane Française ont démontré que les modifications suggérées amélioraient les estimations du signal marin dans les eaux côtières optiquement complexes. / To acquire marine parameters from remote sensing ocean color data, the sensor-measured signal needs to be corrected for the atmospheric contribution. Indeed, the solar radiation reflected by air molecules and atmospheric aerosols is significant in the sensor bands of interest for ocean color applications. The removal of the atmospheric contribution is called the atmospheric correction (AC). In open ocean waters, the AC relies on the assumption that the water is totally absorbent in the near infrared (NIR) part of the spectral region, allowing to retrieve the atmospheric contribution and to extrapolate it to the visible spectral range, and thus to determine the marine signal that contains the information on the optical properties of seawaters. However, this assumption is not valid in highly productive and turbid coastal waters. Hence, AC approaches for coastal waters need to rely on alternative assumptions. This Ph. D. thesis has as main objective to validate and improve these AC methods developed for contrasted coastal waters, with a focus on MODIS Aqua images. First, a validation and comparison of existing AC methods, relying on diverse assumptions and methods, is performed. Therefore, four commonly used AC methods are selected, (1) the standard NIR AC approach of NASA, (2) the NIR similarity spectrum AC approach including assumptions of spatial homogeneity in the water and aerosol reflectance, (3) the switching algorithm using the short wave infrared bands for AC in highly turbid waters, (4) an Artificial Neural Network algorithm. With the help of a validation exercise based on in situ data and as a function of the water type, several areas of improvement are delineated, including the use of spectral relationships to constrain NIR-modelling schemes. Modified NIR-modelling schemes are suggested for the standard NASA and NIR similarity spectrum AC methods. Both are forced with globally valid spectral relationships. Sensitivity studies and validation exercises, using MODIS-Aqua images in the Eastern English Channel/North Sea and French Guiana waters, are conducted showing that the suggested modified NIR-modelling schemes improve the estimations of the marine signal in contrasted coastal waters.

Made available in DSpace on 2017-07-10T19:24:19Z (GMT). No. of bitstreams: 1 Clovis_Cechim_MC.pdf: 6987482 bytes, checksum: c33db297dd7ec8aaf8bfde9e1e56c2cc (MD5) Previous issue date: 2016-02-04 / Sugarcane has been cropped and produced in Brazil for a long time, so, it deserves mention because it makes the country as the largest producer, with also representativeness in sugar and ethanol production. The knowledge of reliable estimates concerning their cropped areas is essential for Brazilian agribusiness, as they help in determining prices to producers by power plants as well as allow establishing logistics flow of production. The cropped areas estimates are made by official agencies. Therefore, in order to reduce this subjectivity, geotechnology use comes as an alternative since it has been widely used in mappings agricultural crops. Thus, this study aimed at developing a methodology for mapping sugarcane crop in Paraná State with satellite images as LANDSAT, IRS and spectrum-temporal series of vegetation indexes from MODIS sensor, for 2010/2011 to 2014/2015 harvesting season. The carried out mappings indicated a strong positive correlation concerning Canasat and official IBGE. The developed method was based on Fuzzy ARTMAP classification and was efficient to map and estimate the sugarcane cropped area using vegetation index in Paraná State. / A cana-de-açúcar como cultura cultivada e produzida no Brasil merece destaque, pois torna o País o maior produtor mundial, com representatividade também na produção de açúcar e etanol. O conhecimento de estimativas confiáveis de suas áreas cultivadas é imprescindível para o agronegócio brasileiro, por auxiliar na determinação dos preços aos produtores pelas usinas e permitir estabelecer a logística de escoamento da produção. As estimativas de área cultivada são realizadas de forma subjetiva pelos órgãos oficiais. Com a finalidade de diminuir tal subjetividade, surge como alternativa o uso de geotecnologias, as quais têm sido muito utilizadas em mapeamentos de culturas agrícolas. Diante disto, o objetivo deste trabalho foi o desenvolvimento de uma metodologia para o mapeamento da cultura de cana-de-açúcar para o Estado do Paraná usando imagens dos satélites LANDSAT, IRS e de séries espectro-temporais de índices de vegetação, provenientes do sensor MODIS, para as safras de 2010/2011 a 2014/2015. O mapeamento da cultura foi realizado a partir do modelo de classificação supervisionada Fuzzy ARTMAP, tendo como variáveis de entrada, termos harmônicos de amplitude e fase e as métricas fenológicas da cultura. Os mapeamentos realizados indicaram forte correlação positiva com relação aos dados do Canasat e oficiais IBGE. O método desenvolvido com base na classificação Fuzzy ARTMAP demonstrou ser eficiente para mapear e estimar a área cultivada da cultura de cana-de-açúcar utilizando índices de vegetação no Estado do Paraná.

Made available in DSpace on 2017-05-12T14:47:35Z (GMT). No. of bitstreams: 1 Clovis_Cechim_MC.pdf: 6987482 bytes, checksum: c33db297dd7ec8aaf8bfde9e1e56c2cc (MD5) Previous issue date: 2016-02-04 / Sugarcane has been cropped and produced in Brazil for a long time, so, it deserves mention because it makes the country as the largest producer, with also representativeness in sugar and ethanol production. The knowledge of reliable estimates concerning their cropped areas is essential for Brazilian agribusiness, as they help in determining prices to producers by power plants as well as allow establishing logistics flow of production. The cropped areas estimates are made by official agencies. Therefore, in order to reduce this subjectivity, geotechnology use comes as an alternative since it has been widely used in mappings agricultural crops. Thus, this study aimed at developing a methodology for mapping sugarcane crop in Paraná State with satellite images as LANDSAT, IRS and spectrum-temporal series of vegetation indexes from MODIS sensor, for 2010/2011 to 2014/2015 harvesting season. The carried out mappings indicated a strong positive correlation concerning Canasat and official IBGE. The developed method was based on Fuzzy ARTMAP classification and was efficient to map and estimate the sugarcane cropped area using vegetation index in Paraná State. / A cana-de-açúcar como cultura cultivada e produzida no Brasil merece destaque, pois torna o País o maior produtor mundial, com representatividade também na produção de açúcar e etanol. O conhecimento de estimativas confiáveis de suas áreas cultivadas é imprescindível para o agronegócio brasileiro, por auxiliar na determinação dos preços aos produtores pelas usinas e permitir estabelecer a logística de escoamento da produção. As estimativas de área cultivada são realizadas de forma subjetiva pelos órgãos oficiais. Com a finalidade de diminuir tal subjetividade, surge como alternativa o uso de geotecnologias, as quais têm sido muito utilizadas em mapeamentos de culturas agrícolas. Diante disto, o objetivo deste trabalho foi o desenvolvimento de uma metodologia para o mapeamento da cultura de cana-de-açúcar para o Estado do Paraná usando imagens dos satélites LANDSAT, IRS e de séries espectro-temporais de índices de vegetação, provenientes do sensor MODIS, para as safras de 2010/2011 a 2014/2015. O mapeamento da cultura foi realizado a partir do modelo de classificação supervisionada Fuzzy ARTMAP, tendo como variáveis de entrada, termos harmônicos de amplitude e fase e as métricas fenológicas da cultura. Os mapeamentos realizados indicaram forte correlação positiva com relação aos dados do Canasat e oficiais IBGE. O método desenvolvido com base na classificação Fuzzy ARTMAP demonstrou ser eficiente para mapear e estimar a área cultivada da cultura de cana-de-açúcar utilizando índices de vegetação no Estado do Paraná.

Inner Mongolian grasslands are part of the vast Eurasian steppe belt and were used for nomadic pastoralism for thousands of years. As a result of political and economic changes in China in the last century, this mobile grazing management has been replaced by a sedentary and intensified livestock production. Stocking rates have increased substantially, overshooting the carrying capacity of the grasslands. These land use changes have induced severe grassland degradation. The impact and causes of grassland degradation have been investigated by the Sino-German joint research group MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate) in the Xilin River catchment of Inner Mongolia since 2004. This work is part of subproject P6, which amongst others pursues the goal of quantifying water balance exchange by micrometeorology and remote sensing. The dominating process of water balance losses in Inner Mongolian grasslands is evapotranspiration (ET), whereby water vapour is released into the lower atmosphere. ET is highly variable in both time and space in this semi-arid environment, as it is coupled with the typically fluctuating amount of precipitation (P). However, despite ET being the key output process of the hydrological cycle of Inner Mongolian grasslands and despite its important role as an indicator for ecosystem functioning, little is known about its spatiotemporal distribution and variability in this remote area. Recent studies on ET have demonstrated variations due to phenology, soil moisture and land use, but these studies have been limited to short periods and have been conducted on a few field sites in close proximity with debatable representativeness for the 2600 km² of grasslands in the Xilin River catchment. The development of a number of remote sensing methods in the last decades has introduced various approaches to determining spatial ET from space, but the application of remotely sensed ET in regional long-term studies is still problematic. Nevertheless, a variety of surface parameters are provided by the sensor MODIS (moderate resolution imaging spectroradiometer) at a resolution of approx. 1km. The aim of this work was (1) to close the gap between the limitations of available local ET measurements and the need for long-term studies on spatial ET in Inner Mongolian grasslands and (2) to analyse the spatiotemporal variability of ET and its implications on livestock management in this area. Therefore, micrometeorological data, remote sensing products and hydrological modelling with BROOK90 were integrated to model spatial ET for the grasslands of the Xilin River catchment over 10 years. The hydrological model BROOK90 calculates ET based on a modified Penman-Monteith approach including the separation of energy into transpiration and soil evaporation. The spatial application of the model was based on a land use classification restricted to the land use unit typical steppe. BROOK90 was parameterised from eddy covariance measurements, soil characteristics and MODIS leaf area index (LAI). Location and canopy parameters were provided individually, as well as the essential daily model input, including P and air temperatures for each pixel. Minimum and maximum air temperatures were calculated based on a relationship between measured air temperatures and MODIS surface temperatures (R²=0.92 and R²=0.87, n=81). Spatial P was estimated from a relationship found between the measured cumulative P of six rain gauges within the grasslands and the increase of MODIS LAI around these measurements (R²=0.80, n=270). Modelled ET is plausible and fits in the range of published results. ET was demonstrated to be highly variable in both time and space: the high spatiotemporal variability of eight-day ET is reflected by the coefficients of variation, which varied between 25% and 40% for the whole study area and were up to 75% for individual pixels. Soil evaporation reacts considerably more sensitively to precipitation pulses than transpiration. Modelled annual ET sums approached or exceeded precipitation sums in general; however, P exceeded ET in 2003, when exceptionally high precipitation occurred. The strong dynamics and the high spatiotemporal variability of ET clearly demonstrate that the current static livestock management is not adapted to the conditions of Inner Mongolian grasslands. New concepts for a sustainable livestock management could be developed in consideration of the intrinsic long-term patterns of spatial ET distribution and spatiotemporal variability identified in this work. Moreover, as this method for modelling spatial ET is not restricted to the grasslands of the Xilin River catchment, livestock management in other semi-arid grasslands could benefit from it as well. / Die Grasländer der Inneren Mongolei sind Teil des riesigen eurasischen Steppengürtels und wurden seit Tausenden von Jahren für die nomadische Weidewirtschaft genutzt. Als Folge der politischen und wirtschaftlichen Veränderungen in China im letzten Jahrhundert ist diese mobile Weidewirtschaft durch eine ortsgebundene und intensivierte Tierhaltung ersetzt worden. Besatzdichten wurden erheblich erhöht und die Tragfähigkeit der Grasländer wurde deutlich überschritten. Diese Landnutzungsänderungen haben schwerwiegende Degradationserscheinungen der Grasländer induziert. Die Ursachen und Auswirkungen der Degradation sind von der Deutsch-Chinesischen-Forschungsgruppe MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate) im Einzugsgebiet des Xilin-Flusses in der Inneren Mongolei seit 2004 untersucht worden. Diese Arbeit wurde im Rahmen des Teilprojektes P6 erstellt, welches unter anderem das Ziel verfolgt, Wasserhaushaltsprozesse mit Mikrometeorologie und Fernerkundung zu quantifizieren. Der dominierende Prozess der Wasserbilanz-Verluste in den Grasländern der Inneren Mongolei ist die Verdunstung (ET), wobei Wasserdampf in die untere Atmosphäre freigesetzt wird. ET ist in diesem semi-ariden Ökosystem in Zeit und Raum sehr variabel, da an die in der Regel schwankenden Niederschläge (P) gekoppelt. Trotz der Schlüsselrolle, die ET im Wasserkreislauf der Inneren Mongolei einnimmt, und der wichtigen Rolle als Indikator für die Funktionsweise des Ökosystems, ist wenig über die raum-zeitliche Verteilung und Variabilität von ET in dieser abgelegenen Region bekannt. Neuere Studien haben ET-Schwankungen aufgrund von Phänologie, Bodenfeuchte und Bodennutzung dargestellt, aber diese Studien sind auf kurze Zeiträume beschränkt und wurden auf nur wenigen Standorten, die sich in unmittelbarer Nähe befinden, durchgeführt. Dies stellt ihre Repräsentativität für die 2600 km² an Grasland im Xilin-Einzugsgebiet in Frage. Die Entwicklung von Fernerkundungsmethoden in den letzten Jahrzehnten hat verschiedene Ansätze zur Bestimmung der räumlichen ET hervorgebracht, jedoch ist die Anwendung von ET aus Fernerkundungsdaten in regionalen Langzeitstudien immer noch problematisch. Dennoch werden eine Vielzahl von Oberflächenparametern durch den Sensor MODIS (Moderate Resolution Imaging Spectroradiometer) bei einer Auflösung von ca. 1km zur Verfügung gestellt. Das Ziel dieser Arbeit war (1) die Lücke zwischen den verfügbaren lokalen ET-Messungen und dem Bedarf an langfristigen Untersuchungen zu räumlicher ET im Grasland der Inneren Mongolei zu schließen und (2) die räumlich-zeitliche Variabilität von ET vor dem Hintergrund des Beweidungsmanagements zu analysieren. Daher wurden mikrometeorologische Daten, Fernerkundungsprodukte und hydrologische Modellierungen mit BROOK90 integriert, um die räumliche ET für die Grasländer des Xilin-Einzugsgebietes über 10 Jahre zu modellieren. Das hydrologische Modell BROOK90 berechnet ET auf Basis eines modifizierten Penman-Monteith-Ansatzes einschließlich der Aufteilung in Transpiration und Bodenverdunstung. Die räumliche Anwendung des Standortmodells basiert auf einer Landnutzungsklassifikation und wurde für die Landnutzungsklasse typical steppe durchgeführt. Eddy-Kovarianz-Messungen, Bodeneigenschaften und MODIS-Blattflächenindex (LAI) wurden zur Parametrisierung von BROOK90 verwendet. Sowohl Lage- und Pflanzenparameter, als auch die notwendigen Modelleingangsdaten (Tageswerte von P und Lufttemperaturen), wurden für jeden Pixel individuell zur Verfügung gestellt. Minimum- und Maximum-Lufttemperaturen wurden mittels einer Beziehung zwischen gemessenen Lufttemperaturen und MODIS-Oberflächentemperaturen berechnet (R²=0.92 und R²=0.87, n=81). Räumliche P wurden aus einem Zusammenhang zwischen gemessenen kumulierten P von sechs Niederschlagsmessern im Untersuchungsgebiet und der Erhöhung des MODIS-LAI im Bereich dieser Messungen abgeleitet (R²=0.80, n=270). Die modellierte räumliche ET ist plausibel und liegt im Wertebereich der publizierten Ergebnisse. Es wurde gezeigt, das ET sehr variabel in Raum und Zeit ist: die raum-zeitlichen Schwankungen der achttägigen ET wurden durch den Variationskoeffizienten dargestellt, welcher zwischen 25% und 40% für das gesamte Untersuchungsgebiet variiert und für einzelne Pixel bis auf 75% ansteigt. Die Bodenverdunstung reagiert wesentlich empfindlicher auf Niederschlagsereignisse als die Transpiration. Modellierte Jahres-ET-Summen erreichen oder überschritten die Niederschlagssummen in der Regel, jedoch übertraf P die ET im Jahre 2003, als außergewöhnlich hohe Niederschläge aufgetreten sind. Die starke Dynamik und die hohe raum-zeitliche Variabilität der ET zeigen deutlich, dass die aktuelle statische Tierhaltung nicht an die Bedingungen in den Innermongolischen Grasländern angepasst ist. Neue Konzepte für eine nachhaltige Viehwirtschaft könnten unter Berücksichtigung der inhärenten langfristigen Muster der räumlichen Verteilung von ET und ihrer raum-zeitlichen Variabilität, die in dieser Arbeit identifiziert wurden, entwickelt werden. Außerdem ist die Anwendung der entwickelten Methode für die Modellierung räumlicher ET nicht auf die Grasländer des Xilin-Einzugsgebietes beschränkt; die Weidewirtschaft in anderen semi-ariden Grasländern könnte ebenfalls davon profitieren.

No description available.

Cette thèse analyse (i) la variabilité pluviométrique contemporaine en Nouvelle-Calédonie et ses téléconnexions avec les températures de surface océanique (TSO) du Pacifique tropical et (ii) l'impact des anomalies atmosphériques sur l'activité des incendies estimés par satellites. L'objectif est de construire un modèle permettant de prévoir l'intensité de la saison des feux entre septembre et décembre (SOND). Le croisement de trois bases de données de feux détectés par satellites avec le réseau des stations météorologiques montre de forts déficits pluviométriques jusqu'à trois mois avant les feux. Ces déficits pluviométriques sont partiellement liés aux phases chaudes du phénomène El Niño Southern Oscillation (ENSO) et plus particulièrement à celles durant lesquelles les anomalies thermiques se situent à proximité de la ligne de changement de date équatoriale lors du printemps austral. Ces anomalies renforcent la circulation moyenne de Hadley et la subsidence au niveau des latitudes néo-calédoniennes. La téléconnexion entre les TSO du Pacifique central et les précipitations du Pacifique SW s'affaiblit à partir du mois de décembre au moment où l'ENSO atteint, paradoxalement, son intensité maximale. Cette modulation saisonnière est le produit d'une interaction entre (i) le cycle saisonnier des TSO brutes dans le Pacifique central, (ii) le cycle de vie des anomalies thermiques des épisodes chauds et (iii) l'intensité du gradient zonal des TSO le long de l'équateur. Une analyse en ondelettes montre que les pluies néo-calédoniennes sont également sensibles à des modes de variations plus lents (> 8 ans) du Pacifique central entre septembre et novembre. / This PhD analyses (i) New Caledonian rainfall variability and its relationships with sea surface temperature (SST) in the tropical Pacific ocean and (ii) the impacts of atmospheric variability on fire activity. Our main goal is to build an empirical statistical scheme for predicting the September to December fires. We examined the relationships between fires detected by ATSR and MODIS sensors and local-scale atmospheric conditions. While the signal in maximum temperature is weak and not robust among the fire records, the local-scale anomalies of rainfall are always clearly negative for at least 3 months before the fires. These rainfall anomalies are related to warm El Niño Southern Oscillation (ENSO) events and specially to those exhibiting highest SST anomalies in the central Pacific during the austral spring. The warm central Pacific events strengthen the southern Hadley cell around New Caledonian longitudes, with positive rainfall anomalies in the equatorial Pacific leading to an anomalous release of latent heat in the upper troposphere and an increased subsidence in the SW Pacific. Atmospheric anomalies are strongest in September–November because of a combination of a rather strong zonal SST gradient with the warmest SST in the equatorial Pacific just west of the dateline. Squared wavelet coherence between New Caledonia rainfall and Niño 4 SST index shows that their negative correlations are mostly carried by two distinct timescales : the classical ENSO variability and a quasi-decadal one, mainly during the September-November season.

O presente trabalho teve por objetivo estudar o efeito do campo de ventos e do meandramento da Corrente do Brasil nas variabilidades hidrográfica e bioquímica ao largo da costa norte do Estado de São Paulo. Foram utilizados dados de temperatura, nutrientes e clorofila-a obtidos in situ mensalmente ao largo de Ubatuba entre dezembro de 2004 a abril de 2014, dados do campo de ventos do pacote Blended Sea Winds (NCDC/NOAA), além de Temperatura da Superfície do Mar e Clorofila-a da Superfície do Mar do sensor MODIS/AQUA. Os dados obtidos mostraram que na primavera o vento paralelo teve forte correlação com a temperatura em toda coluna de água, evidenciando a importância da intrusão remota nesta estação. No verão as altas correlações com o nitrato indicam a dominância de intrusão local. A correlação com a distância da Corrente do Brasil foi significativa com a clorofila-a, o nitrato e fosfato. Os resultados permitem inferir que o vento é o principal fator que determina a variabilidade hidrográfica e bioquímica na área de estudo, e que o meandramento da Corrente do Brasil teria papel secundário na dinâmica da plataforma continental interna. / The main goal of this work is to evaluate the effect of the wind field and Brazil Current meandering on hydrographic and biochemical variability off northern coast of Sao Paulo, Brazil. The dataset used were comprised of monthly samples of temperature, chlorophyll-a and nutrients acquired in situ in Ubatuba from December 2004 to April 2014, wind field derived from NCDC/NOAA Blended Sea Winds package, as well as sea surface temperature and sea surface chlorophyll remotely sensed by MODIS aboard Acqua satellite. Data analysis reveal a strong correlation of along-shore wind component with the water temperature in all depths at spring, pointing out the importance of remote intrusion and advection of South Atlantic Central Water at the sampling site. During summer, however, high correlation of said wind component with nitrate concentration show dominance of local intrusion processes. The distance between the sampling station and the Brazil Current front correlated significantly with chlorophyll-a, nitrate and phosphate. These results suggest that the wind is the main driver of biochemical and hydrographic variability at the study area, while the Brazil Current front meandering plays a secondary role in the internal shelf dynamics.

O presente trabalho teve por objetivo estudar o efeito do campo de ventos e do meandramento da Corrente do Brasil nas variabilidades hidrográfica e bioquímica ao largo da costa norte do Estado de São Paulo. Foram utilizados dados de temperatura, nutrientes e clorofila-a obtidos in situ mensalmente ao largo de Ubatuba entre dezembro de 2004 a abril de 2014, dados do campo de ventos do pacote Blended Sea Winds (NCDC/NOAA), além de Temperatura da Superfície do Mar e Clorofila-a da Superfície do Mar do sensor MODIS/AQUA. Os dados obtidos mostraram que na primavera o vento paralelo teve forte correlação com a temperatura em toda coluna de água, evidenciando a importância da intrusão remota nesta estação. No verão as altas correlações com o nitrato indicam a dominância de intrusão local. A correlação com a distância da Corrente do Brasil foi significativa com a clorofila-a, o nitrato e fosfato. Os resultados permitem inferir que o vento é o principal fator que determina a variabilidade hidrográfica e bioquímica na área de estudo, e que o meandramento da Corrente do Brasil teria papel secundário na dinâmica da plataforma continental interna. / The main goal of this work is to evaluate the effect of the wind field and Brazil Current meandering on hydrographic and biochemical variability off northern coast of Sao Paulo, Brazil. The dataset used were comprised of monthly samples of temperature, chlorophyll-a and nutrients acquired in situ in Ubatuba from December 2004 to April 2014, wind field derived from NCDC/NOAA Blended Sea Winds package, as well as sea surface temperature and sea surface chlorophyll remotely sensed by MODIS aboard Acqua satellite. Data analysis reveal a strong correlation of along-shore wind component with the water temperature in all depths at spring, pointing out the importance of remote intrusion and advection of South Atlantic Central Water at the sampling site. During summer, however, high correlation of said wind component with nitrate concentration show dominance of local intrusion processes. The distance between the sampling station and the Brazil Current front correlated significantly with chlorophyll-a, nitrate and phosphate. These results suggest that the wind is the main driver of biochemical and hydrographic variability at the study area, while the Brazil Current front meandering plays a secondary role in the internal shelf dynamics.