Towards the evidence of a purely spatial spatial Einstein-Podolsky-Rosen paradox in images: measurement scheme and first experimental results

International audienceWe propose a scheme to evidence the Einstein-Podolsky-Rosen (EPR) paradox for photons produced by spontaneous down conversion, from measurement of purely spatial correlations of photon positions both in the near- and in the far-field. Experimentally, quantum correlations have been measured in the far-field of parametric fluorescence created in a type II BBO crystal. Imaging is performed in the photon counting regime with an electron-multiplying CCD (EMCCD) camera

Mathay – Site urbain d’Epomanduodurum (Les Champs des Isles, Les Oichottes), L’Essarté

Site urbain d’Epomanduodurum (Mandeure) Le faubourg de pont d’Epomanduodurum occupe tout entier une partie du territoire communal de Mathay. Les fouilles qui s’y déroulent depuis 1984, mettent en évidence l’organisation des quartiers et les activités qui y étaient exercées. Au lieu-dit Les Champs des Isles, la fouille du lotissement Rodeschini se poursuit sous la responsabilité de M. Lame et P. Mougin. La fin des recherches dans la parcelle 6 et celles effectuées dans les parcelles 5 et 7 ont..

Les risques environnementaux en 2020 : une feuille de route pour INRAE★

INRAE a mené une réflexion prospective collective sur les risques environnementaux dans une perspective inter- et transdisciplinaire inscrite dans le cadre des sciences de la durabilité. Les risques pour les sociétés, les écosystèmes et les milieux ont été considérés conjointement et de façon holistique. Cet article résume les quatre priorités scientifiques identifiées, exprimées de manière transverse. Une feuille de route pour atteindre ces objectifs est également proposée, incluant les ressources humaines, les infrastructures, l’animation scientifique et les partenariats. Ces conclusions devraient participer à la structuration de la recherche française et internationale, et constituer ainsi une contribution significative à l’effort requis par l’urgence environnementale actuelle

Using satellite scatterometers to monitor continental surfaces

International audienc

Characterization of west African land surface state autumn to summer evolution regarding Sahelian rainfall variability.

Avril 2005The ERS backscattering coefficient (0) and CMAP rainfall datasets are analyzed over period 1992-2000 to document the autumn to summer soil-vegetation water content evolution in West Africa regarding Sahelian rainfall variability. A composite analysis performed over 0 field averaged between longitudes 10°W- 10°E shows that the wettest (driest) July-September Sahelian rainy seasons have been preceded by negative (positive) anomalies of soil-vegetation water content over the Sudanian belt in June and positive (negative) ones over Guinea from winter to spring. While the former anomalies are linked to synchronous rainfall deficits, sign of delayed northward jump of the ITCZ, the latter do not coincide with any synchronous signal in precipitations. A 'Granger causality' analysis reveals that spring (March- May) anomalies of soil-vegetation water content are rather due to those recorded in rainfall during the preceding autumn (September-November) than to a persistence of winter 0 anomalies. These findings argue for inter-season memory effects in West Africa held by land surface state. Lastly, the positive anomalies of soil-vegetation water content from winter to spring over the Guinea belt induce a steeper (a flatter) meridional gradient over the subcontinent: it has been shown that the meridional arrangement of biosphere and soil water content over West Africa is critical for monsoon dynamics

Testing a sahelian grassland functioning model against herbage mass measurements

International audienceA simple grassland process model is tested against ground measurements collected during 15 years in the sahelian zone in Mali. The model uses standard daily meteorological variables and a limited number of site specific parameters to simulate herbage growth and canopy functioning. The model has two calibration parameters. Due probably to the strong interannual variation of both the herbaceous layer in terms of floristic composition and soil nutrient mineralization, the use of default values for the two calibration parameters leads to large errors in the prediction of herbage yields. In contrast, once the parameters have been optimised, a good concordance is found between the model outputs and the seasonal variation of the herbage standing mass in sites on sandy soils located along a north-south bioclimatic gradient

Estimation of Sahelian Aeolian Dust Emissions Based on Vegetation Modelling

International audienceThe amount of dust emitted by wind from semi-arid regions is estimated with a large degree of uncertainty, mainly due to the difficulty in accounting for the effects of the seasonal vegetation. The temporal change of the vegetation has been investigated over the Sahelian belt (12°N to 20°N and 20°W to 35°E) from 2004 to 2007 with a daily time resolution. The seasonal vegetation was simulated using the STEP model (Sahelian Transpiration Evaporation and Productivity model; [1] ; [2] ) at scales of 0.1° and 0.25°. The simulations have been compared to the MODIS Leaf Area Indexes (LAI). The comparisons between the simulated vegetation fields and the MODIS LAI have been performed by examining the field structure, the dynamics of the vegetation growth, and the amount of vegetation. The agreement with satellite LAI is very satisfying during the active growth period, both in terms of structure and amount. The period of vegetation growth appears as very sensitive to the initialization parameters of the STEP model, which therefore have been carefully constrained. Based on these vegetation fields, Sahelian dust emissions are simulated and the influence of the seasonal vegetation is estimated

Testing a sahelian grassland functioning model against herbage mass measurements

International audienceA simple grassland process model is tested against ground measurements collected during 15 years in the sahelian zone in Mali. The model uses standard daily meteorological variables and a limited number of site specific parameters to simulate herbage growth and canopy functioning. The model has two calibration parameters. Due probably to the strong interannual variation of both the herbaceous layer in terms of floristic composition and soil nutrient mineralization, the use of default values for the two calibration parameters leads to large errors in the prediction of herbage yields. In contrast, once the parameters have been optimised, a good concordance is found between the model outputs and the seasonal variation of the herbage standing mass in sites on sandy soils located along a north-south bioclimatic gradient

Characterization of west African land surface state autumn to summer evolution regarding Sahelian rainfall variability.

Avril 2005The ERS backscattering coefficient (0) and CMAP rainfall datasets are analyzed over period 1992-2000 to document the autumn to summer soil-vegetation water content evolution in West Africa regarding Sahelian rainfall variability. A composite analysis performed over 0 field averaged between longitudes 10°W- 10°E shows that the wettest (driest) July-September Sahelian rainy seasons have been preceded by negative (positive) anomalies of soil-vegetation water content over the Sudanian belt in June and positive (negative) ones over Guinea from winter to spring. While the former anomalies are linked to synchronous rainfall deficits, sign of delayed northward jump of the ITCZ, the latter do not coincide with any synchronous signal in precipitations. A 'Granger causality' analysis reveals that spring (March- May) anomalies of soil-vegetation water content are rather due to those recorded in rainfall during the preceding autumn (September-November) than to a persistence of winter 0 anomalies. These findings argue for inter-season memory effects in West Africa held by land surface state. Lastly, the positive anomalies of soil-vegetation water content from winter to spring over the Guinea belt induce a steeper (a flatter) meridional gradient over the subcontinent: it has been shown that the meridional arrangement of biosphere and soil water content over West Africa is critical for monsoon dynamics

The vegetation cycle in West Africa from AVHRR-NDVI data : horizons of predictability versus spatial scales

The predictability of the vegetation cycle is analyzed as a function of the spatial scale over West Africa during the period 1982-2004 The NDVI-AVHRR satellite data time series are spatially aggregated over windows covering a range of sizes from 8 x 8 km(2) to 1024 x 1024 km(2). The times series are then embedded in a low-dimensional pseudo-phase space using a system of time delayed coordinates. The correlation dimension (D-c) and entropy of the underlying vegetation dynamics, as well as the noise level (sigma) are extracted from a nonlinear analysis of the time series The horizon of predictability (H-P) of the vegetation cycle defined as the time interval required for an n% RMS error on the vegetation state to double (i e reach 2n% RMS) is estimated from the entropy production. Compared to full resolution, the intermediate scales of aggregation (in the range of 64 x 64 km(2) to 256 x 256 km(2)) provide times series with a slightly improved signal to noise ratio, longer horizon of predictability (about 2 to 5 decades) and preserve the most salient spatial patterns of the vegetation cycle Insights on the best aggregation scale and on the expected vegetation cycle predictability over West Africa are provided by a set of maps of the correlation dimension (D-c), the horizon of predictability (H-P) and the level of noise (sigma)