Cloud thermodynamic phase inferred from merged POLDER and MODIS data

International audienceThe global spatial and diurnal distribution of cloud properties is a key issue for understanding the hydrological cycle, and critical for advancing efforts to improve numerical weather models and general circulation models. Satellite data provides the best way of gaining insight into global cloud properties. In particular, the determination of cloud thermodynamic phase is a critical first step in the process of inferring cloud optical and microphysical properties from satellite measurements. It is important that cloud phase be derived together with an estimate of the confidence of this determination, so that this information can be included with subsequent retrievals (optical thickness, effective particle radius, and ice/liquid water content). In this study, we combine three different and well documented approaches for inferring cloud phase into a single algorithm. The algorithm is applied to data obtained by the MODIS (MODerate resolution Imaging Spectroradiometer) and POLDER3 (Polarization and Directionality of the Earth Reflectance) instruments. It is shown that this synergistic algorithm can be used routinely to derive cloud phase along with an index that helps to discriminate ambiguous phase from confident phase cases. The resulting product provides a semi-continuous confidence index ranging from confident liquid to confident ice instead of the usual discrete classification of liquid phase, ice phase, mixed phase (potential combination of ice and liquid particles), or simply unknown phase clouds. This approach is expected to be useful for cloud assimilation and modeling efforts while providing more insight into the global cloud properties derived from satellite data

Comparison of PARASOL Observations with Polarized Reflectances Simulated Using Different Ice Habit Mixtures

Insufficient knowledge of the habit distribution and the degree of surface roughness of ice crystals within ice clouds is a source of uncertainty in the forward light scattering and radiative transfer simulations required in downstream applications involving these clouds. The widely used MODerate Resolution Imaging Spectroradiometer (MODIS) Collection 5 ice microphysical model assumes a mixture of various ice crystal shapes with smooth-facets except aggregates of columns for which a moderately rough condition is assumed. When compared with PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) polarized reflection data, simulations of polarized reflectance using smooth particles show a poor fit to the measurements, whereas very rough-faceted particles provide an improved fit to the polarized reflectance. In this study a new microphysical model based on a mixture of 9 different ice crystal habits with severely roughened facets is developed. Simulated polarized reflectance using the new ice habit distribution is calculated using a vector adding-doubling radiative transfer model, and the simulations closely agree with the polarized reflectance observed by PARASOL. The new general habit mixture is also tested using a spherical albedo differences analysis, and surface roughening is found to improve the consistency of multi-angular observations. It is suggested that an ice model incorporating an ensemble of different habits with severely roughened surfaces would potentially be an adequate choice for global ice cloud retrievals

Cloud thermodynamic phase inferred from merged POLDER and MODIS data

The global spatial and diurnal distribution of cloud properties is a key issue for understanding the hydrological cycle, and critical for advancing efforts to improve numerical weather models and general circulation models. Satellite data provides the best way of gaining insight into global cloud properties. In particular, the determination of cloud thermodynamic phase is a critical first step in the process of inferring cloud optical and microphysical properties from satellite measurements. It is important that cloud phase be derived together with an estimate of the confidence of this determination, so that this information can be included with subsequent retrievals (optical thickness, effective particle radius, and ice/liquid water content). In this study, we combine three different and well documented approaches for inferring cloud phase into a single algorithm. The algorithm is applied to data obtained by the MODIS (MODerate resolution Imaging Spectroradiometer) and POLDER3 (Polarization and Directionality of the Earth Reflectance) instruments. It is shown that this synergistic algorithm can be used routinely to derive cloud phase along with an index that helps to discriminate ambiguous phase from confident phase cases. The resulting product provides a semi-continuous index ranging from confident liquid to confident ice instead of the usual discrete classification of liquid phase, ice phase, mixed phase (potential combination of ice and liquid particles), or simply unknown phase clouds. The index value provides simultaneously information on the phase and the associated confidence. This approach is expected to be useful for cloud assimilation and modeling efforts while providing more insight into the global cloud properties derived from satellite data

Networking Axelera "hydrogène décarboné" (en virtuel)

SSCI-VIDE+CARE+VMLInternational audienceNon

Ethoxy and silsesquioxane derivatives of antimony as dopant precursors: unravelling the structure and thermal stability of surface species on SiO2

International audienceWe report here the controlled preparation of SiO2 supported Sb-(mono)layers and their thorough characterization by in situ IR, solid-state NMR and elemental analyses. This study allows for the molecular understanding of the surface Sb species derived from the grafting of ethoxy and polyhedral oligomeric silsesquioxane antimony derivatives as mono- or bi-podal Sb(III) surface species depending on the number of surface SiOH groups. This result is different from what was observed with the phosphorus analogue (POSS-P) that yielded P(V) species. A monolayer coverage of Sb species onto silica was also obtained using both POSS-Sb and the [Sb(OEt)3]2 derivative with surface densities ranging from ∼0.3 Sb nm−2 to 1.8 Sb nm−2, respectively. It is noteworthy that under optimized conditions, a layer of antimony species or suboxides on silica was produced using POSS-Sb without significant Sb loss, highlighting the protective properties of the POSS cage. These results open new perspectives for the controlled and non-destructive Sb-doping (Molecular Layer Doping) of semiconductors dedicated to nano-device applications

Remote sensing of aerosols over the oceans using MSG/SEVIRI imagery

The SEVIRI instrument on board Meteosat Second Generation (MSG) offers new capabilities to monitor aerosol transport over the Atlantic and the Mediterranean at high temporal and spatial resolutions, in particular, Saharan dust from North Africa, biomass-burning aerosols from subtropical Africa and pollution from Europe. An inversion technique was developed to estimate both aerosol optical thickness and Angström coefficients from SEVIRI measurements at 0.63 and 0.81 µm. This method relies on an optimized set of aerosol models to ensure a fast processing of full-resolution MSG images and to allow the processing of long time series. SEVIRI images for slots 45, 49 and 53 (11:15, 12:15, 13:15 UT) were processed for June 2003. The retrieved optical thicknesses and Angström coefficients are in good agreement with AERONET in-situ measurements in the Atlantic and in the Mediterranean. Monthly mean maps of both parameters are compared to that obtained with the polar orbiting sensor POLDER for June 2003. There is a good consistency between the two monthly means in terms of optical thickness, but the Angström coefficients show significant differences in the Atlantic zone which is affected by dust transport. These differences may be explained by the lack of specific non-spherical dust models within the inversion. The preliminary results presented in this paper demonstrate, nevertheless, the potential of MSG/SEVIRI for the monitoring of aerosol optical properties at high frequencies over the Atlantic and the Mediterranean

PROX reaction over Pt3Sn/Al2O3: Structural investigation by operando DRIFTS

International @ INGENIERIE+AMS:YSC:FRMInternational audiencePtxSn based catalysts have presented exhibit enhanced activities for preferential CO oxidation (PROX) as compared to analogous Pt catalysts. Yet, often ill-defined PtSn phases present on the catalyst prevent a full understanding of the reaction mechanism and active sites involved. Therefore we used for this study well-defined Pt and Pt3Sn catalysts, obtained by impregnation of pre-formed Pt or Pt3Sn nanoparticles [1]. Our 1% Pt3Sn/?-Al2O3 and 1% Pt/?-Al2O3 catalysts were used in the CO PROX. Experiments were carried out under controlled conditions to obtain intrinsic kinetics. Additionally an investigation of CO adsorption under the reaction mixture was carried out by operando DRIFTS over the samples. An unusual evolution of the adsorbed CO was noted while ramping up the temperature

Biodegradable polymer Biolimus-eluting stent (Nobori®) for the treatment of coronary artery lesions: review of concept and clinical results

Guillaume Schurtz,1,2 Cédric Delhaye,1 Christopher Hurt,1,2 Henri Thieuleux,1,2 Gilles Lemesle1–3 1Centre Hémodynamique et Unité des Soins Intensifs de Cardiologie, Hôpital Cardiologique, Centre Hospitalier Régional et Universitaire de Lille, Lille, France; 2Faculté de Médecine de Lille, Lille, France; 3Unité INSERM UMR744, Institut Pasteur de Lille, Lille, France Abstract: First-generation drug-eluting stents have raised concerns regarding the risk of late and very late stent thrombosis compared with bare metal stents and require prolonged dual antiplatelet therapy. Despite extensive investigations, the physiopathology of these late events remains incompletely understood. Aside from patient- and lesion-related risk factors, stent polymer has been cited as one of the potential causes. In fact, the persistence of durable polymer after complete drug release has been shown to be responsible for local hypersensitivity and inflammatory reactions. Third-generation drug-eluting stents with more biocompatible or biodegradable polymers have subsequently been developed to address this problem. In this article, we evaluate and discuss the concept and clinical results (safety and efficacy) of a third-generation drug-eluting stent with biodegradable polymer: the Nobori® stent. Keywords: percutaneous coronary intervention, stent thrombosis, antiplatelet therap

PROX reaction over Pt3Sn/Al2O3: Structural investigation by operando DRIFTS

International @ INGENIERIE+AMS:YSC:FRMInternational audiencePtxSn based catalysts have presented exhibit enhanced activities for preferential CO oxidation (PROX) as compared to analogous Pt catalysts. Yet, often ill-defined PtSn phases present on the catalyst prevent a full understanding of the reaction mechanism and active sites involved. Therefore we used for this study well-defined Pt and Pt3Sn catalysts, obtained by impregnation of pre-formed Pt or Pt3Sn nanoparticles [1]. Our 1% Pt3Sn/?-Al2O3 and 1% Pt/?-Al2O3 catalysts were used in the CO PROX. Experiments were carried out under controlled conditions to obtain intrinsic kinetics. Additionally an investigation of CO adsorption under the reaction mixture was carried out by operando DRIFTS over the samples. An unusual evolution of the adsorbed CO was noted while ramping up the temperature

Direct evidence of Pt-Sn alloy surface segregation at low temperatures by in situ IR of CO adsorption

National @ INGENIERIE+AMS:FRM:YSCInternational audienceIn the present study, a direct evidence of the surface segregation induced by CO adsorption on the structure of a Pt-Sn alloy supported on alumina is reported for the first time. The surface segregation was monitored by in situ diffuse reflectance FT-IR spectroscopy (DRIFTS) in a 2% CO/H2 atmosphere at various temperatures and showed to occur only below 175°C and was partly reversible following reduction at high temperature. The experiments are performed as well on a Sn-free sample for comparison and the behavior observed is typically to a Pt supported catalyst