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International audience; Changes in terrestrial tropical carbon stocks have an important role in the global carbon budget. However, current observational tools do not allow accurate and large-scale monitoring of the spatial distribution and dynamics of carbon stocks'. Here, we used low-frequency L-band passive microwave observations to compute a direct and spatially explicit quantification of annual aboveground carbon (AGC) fluxes and show that the tropical net AGC budget was approximately in balance during 2010 to 2017, the net budget being composed of gross losses of -2.86 PgC yr(-1) offset by gross gains of -2.97 PgC yr(-1) between continents. Large interannual and spatial fluctuations of tropical AGC were quantified during the wet 2011 La Nina year and throughout the extreme dry and warm 2015-2016 El Nino episode. These interannual fluctuations, controlled predominantly by semiarid biomes, were shown to be closely related to independent global atmospheric CO2 growth-rate anomalies (Pearson's r = 0.86), highlighting the pivotal role of tropical AGC in the global carbon budget.

2 ficheros .pdf, copias de la Presentación original (41 Pags.) y del Resumen ampliado (1 Pag.) en Libro de Actas del Congreso., This communication will present the main results of a series of airborne campaigns conducted at the Valencia Anchor Station (VAS) and Los Monegros site using the CAROLS (Combined Airborne Radio-instruments for Ocean and Land Studies) radiometer on board the ATR 42 aircraft from M¶et¶eo-France. The main objective was to contribute to the implementation of the SMOS emission model L-MEB (L-band Microwave Emission model of the Biosphere) in the framework of the validation of SMOS land data and products. Speci¯cally, the objectives of the CAROLS campaigns were the following, Soil Moisture Validation Studies: Previous °ights at the VAS area took place in 2008 in the context of the ESA SMOS Validation Rehearsal Campaign 2008 (EMIRAD radiometer, L-band) over a control area of 10km£10km where intensive soil moisture data was acquired concurrently to airborne L-band measurements. One of the objectives of that campaign was to establish homogeneous units to characterize the average soil moisture of that area, and to investigate the possibility of extending the methodology to the whole SMOS validation pixel at the VAS site. The `homogeneous units' characterisation was studied and extended further in the context of CAROLS 2009, and validated during the CAROLS 2010 campaign., Radiometric Characterisation & SMOS Data Validation: The 10km £ 10km mentioned above is part of a larger area of » 50km £ 50km within the VAS SMOS validation pixel. For CAROLS 2009, °ights were performed over a 30km £ 50km area in order to examine the ra- diometric signature of other surfaces that are present in the VAS SMOS pixel but not in the 10km £ 10km control area examined in 2008 (mostly dense forests, matorral, and non-°at sur- faces). Main results of CAROLS 2009 will be presented in this communication, and the emphasis will be on comparing local to regional scale results given that CAROLS °ights were performed at 4000m above the surface. For 2010, lower altitude °ights (» 2200m a.s.l.) over an area of 20km£20km containing a large number of homogeneous units (`environmental units'), were used for validation of SMOS microwave model L-MEB. The preliminary results of this campaign will be presented in this communication, and the emphasis will be on the validation of the L-MEB model., In addition to the activities at the VAS site, °ights over Los Monegros' salt pans near Zaragoza were performed in the 2010 CAROLS Campaign to study their emissivity at L-band. Three playa-lakes (Guallar, La Playa, and Salineta) were sampled to measure gravimetric soil moisture and electrical conductivity.

1 copia .pdf con Figs., Poster presentado en la European Geophysical Union. General Assembly 2011 celebrada en Viena del 03 al 08 de abril 2011. Session GI-1 on Geoscience Instrumentation., This communication will present the main results of a series of airborne campaigns conducted at the Valencia Anchor Station (VAS) and Los Monegros site using the CAROLS (Combined Airborne Radio-instruments for Ocean and Land Studies) radiometer on board the ATR 42 aircraft from M¶et¶eo-France. The main objective was to contribute to the implementation of the SMOS emission model L-MEB (L-band Microwave Emission model of the Biosphere) in the framework of the validation of SMOS land data and products. Speci¯cally, the objectives of the CAROLS campaigns were the following: Soil Moisture Validation Studies: Previous °ights at the VAS area took place in 2008 in the context of the ESA SMOS Validation Rehearsal Campaign 2008 (EMIRAD radiometer, L-band) over a control area of 10km£10km where intensive soil moisture data was acquired concurrently to airborne L-band measurements. One of the objectives of that campaign was to establish homogeneous units to characterize the average soil moisture of that area, and to investigate the possibility of extending the methodology to the whole SMOS validation pixel at the VAS site. The `homogeneous units' characterisation was studied and extended further in the context of CAROLS 2009, and validated during the CAROLS 2010 campaign. Radiometric Characterisation & SMOS Data Validation: The 10km £ 10km mentioned above is part of a larger area of » 50km £ 50km within the VAS SMOS validation pixel. For CAROLS 2009, °ights were performed over a 30km £ 50km area in order to examine the ra- diometric signature of other surfaces that are present in the VAS SMOS pixel but not in the 10km £ 10km control area examined in 2008 (mostly dense forests, matorral, and non-°at sur- faces). Main results of CAROLS 2009 will be presented in this communication, and the emphasis will be on comparing local to regional scale results given that CAROLS °ights were performed at 4000m above the surface. For 2010, lower altitude °ights (» 2200m a.s.l.) over an area of 20km£20km containing a large number of homogeneous units (`environmental units'), were used for validation of SMOS microwave model L-MEB. The preliminary results of this campaign will be presented in this communication, and the emphasis will be on the validation of the L-MEB model. In addition to the activities at the VAS site, °ights over Los Monegros' salt pans near Zaragoza were performed in the 2010 CAROLS Campaign to study their emissivity at L-band. Three playa-lakes (Guallar, La Playa, and Salineta) were sampled to measure gravimetric soil moisture and electrical conductivity.

Known as ESAs 'Water Mission', SMOS will improve our understanding of Earth's water cycle, providing much-needed data for modelling of the weather and climate, and increasing the skill in numerical weather and climate prediction.

Optical remote sensing has been widely used for diagnostics of land surface atmosphere exchanges, including evapotranspiration (ET). Estimating ET now benefits from modeling maturity at local scale, while ongoing challenges include both spatial and temporal issues: influences of spatial heterogeneities on non-linear behavior when upscaling and extrapolation of instantaneous estimates at satellite overpass to the daily scale. Both issues are very important when using remote sensing for managing water resources, especially in agriculture. The two main contributions of the current study are first the examination of the diurnal behavior of evaporative fraction (EF) and available energy (AE) over heterogeneous agricultural land surfaces, and second presenting a simple approach to derive area-averaged daily ET under such conditions. Area-averaged fluxes are expressed using the same equations as those used over homogeneous areas, but whose arguments are effective expressions of the local parameters involved. Next, heuristic formulations are proposed to estimate the diurnal courses of EF and AE, by combining diurnal meteorological information available from observation networks (or weather forecasts) with instantaneous estimates at satellite overpass obtained from a simple energy balance model. These investigations were conducted using ground based data collected in the semi-arid Yaqui valley, north-western Mexico, over three adjacent agricultural fields which different crops and soil moisture conditions. This approach accurately reproduced the diurnal course of ET. However, these promising results have to be confirmed using actual satellite and operational meteorological data. This work is the subject of ongoing investigations.

This thesis deals with optical coupling systems and is divided in two parts. The first one is concerned with directional coupling between two graded index fibres made by a diffusion process. The theory and physics of ion exchange is studied, providing a theoretical description of the refractive index change. A mathematical method of solving the concentration dependent diffusion equation is given. Theoretical index distributions are thus obtained for circular waveguides. To compare theory with experiment, a device directly measuring the index profile of a circular fibre is described. The theory of propagation in round graded index fibres, is reviewed and a simplified coupling coefficient derived in order to determine the coupling efficiency. The coupling arrangement is described and the results discussed. It is shown that efficient tapping of power can be done with the high order modes, and eventually, at a much lower efficiency with the low order ones. The second part describes a theoretical study of optical contradirectional coupling between a single mode sandwich ribbon fibre and a thin film planar waveguide, longitudinal phase matching being achieved by means of a periodic corrugation, which is typically a grating etched into the film. Film-fibre couplers were tested and achieved an estimated efficiency of only due to the poor quality of the gratings. With several improvements in the set-up and specimens, an efficiency of over 60 is quite feasible. The application of the method for linking integrated optical devices is considered as well as a possible demultiplexer. The study presented provides the ground work for future development of integrated optical devices links and an active device.

International audience; L’agriculture est aujourd’hui le secteur d’activité le plus consommateur d’eau, environ 70% dela ressource. Dans un contexte de changement global et de raréfaction la ressource (etd’appauvrissement de sa qualité), les travaux sur la gestion de l’eau prennent une importancecruciale. Dans le continuum d’échelles en jeu du global au local, l'homme interagit trèsfortement et rapidement (par les pratiques agricoles, l’organisation de l’espace...) de l’échellelocale (typiquement la parcelle agricole) à l’échelle du paysage (typiquement le petit bassinversant ou le bassin de production 100 km2).L’intérêt des travaux soutenus par le TOSCA pour la gestion de la ressource en eau sera dansun premier temps évoqué et illustré par des exemples de projets dont les finalités sont ladétection du stress hydrique, l’amélioration de l’estimation de l’évapotranspiration réelle, ladétermination des surfaces irriguées, l’estimation du pompage, les liens avec l’hydrologie desnappes.Dans un deuxième temps seront passés en revue les développements méthodologiquesrécents : amélioration et mise en œuvre de modèles (SAMIR, SAT-IRR…), développementd’algorithmes de cartographie de l’évapotranspiration (EVASPA), mise au point d’indices destress et caractérisation de l’état hydrique des surfaces, travaux sur la désagrégation dedonnées spatiales pour accéder à l’échelle du parcellaire, etc… Le développement de chaînesde traitement de données satellitaires (IRT Landsat) sera également évoqué ici. Les liens avecle pôle de données et de services ‘Surfaces Continentales’ THEIA - en particulier les Centresd’Expertise ‘Evapotranspiration‘ et ‘Occupation des Sols’ - seront discutés.La valorisation de l’ensemble de ces travaux afin d’accéder au bilan hydrique fin à l’échelle dela parcelle agricole et d’optimiser la gestion de la ressource en eau se heurte encore à uneabsence de données spatiales adaptées. Celles-ci sont attendues de la mission infrarougethermique (IRT) combinant la haute résolution spatiale (la cinquantaine de mètres) et unefréquence de revisite élevée (de 1 à 3 jours) en cours d’étude dans le cadre d’un partenariatCNES - ISRO avec l’Inde. Le TOSCA soutient très activement un ensemble d’activités spécifiquesorientées sur la mesure de la température de surface avec pour objectif de consolider lesspécifications de la mission (résolution, heure de passage, orbite, etc…) et de préciser laprécision attendue sur les produits finaux.

The availability of satellite-derived global surface soil moisture products during the last decade has opened up great opportunities to incorporate these observations into applications in hydrology, meteorology, and climatic modeling. This study evaluates a new global soil moisture product developed under the framework of the European Space Agency (ESA) climate change initiative (CCI), using finer spatial resolution synthetic aperture radar (SAR) and ground-based measurements of soil moisture. The analysis is carried out over selected in situ networks over Ireland, Spain, and Finland with the aim of assessing the temporal representativeness of the coarse-scale CCI essential climate variable (ECV) soil moisture (ECV SM) product in these different areas. A good agreement (correlation coefficient (R) values between 0.53 and 0.92) was observed between the three soil moisture data sets for the Irish and Spanish sites while a reasonable agreement (R values between 0.41 and 0.52) was observed between the SAR and ECV SM soil moisture data sets at the Finnish sites. Overall, the two different satellite-derived products captured the soil moisture temporal variations well and were in good agreement with each other, highlighting the confidence of using the coarse-scale ECV SM product to track soil moisture variability in time.