Search results for "Clima"
showing 10 items of 6069 documents
Error propagation from line parameters to spectra simulations. Illustration on high temperature methane.
2010
Astrophysical investigations generally need both complete and accurate spectroscopic databases. Despite continuous efforts in experimental and theoretical spectroscopic investigations, the lack of data in some spectral regions of interest is one of the main limitation of the presently available spectroscopic databases. Unfortunately information about missing data relevant to specific experimental conditions is rarely directly accessible from spectroscopic databases (focusing naturally on available data). Such information relies essentially on theoretical investigations which are equally limited to the present state of the art of modelling. The purpose of the talk is to show how multi-resolu…
Titan's surface and atmosphere from Cassini/VIMS data with updated methane opacity
2013
International audience; We present an analysis of Titan data acquired by the Cassini Visual and Infrared Mapping Spectrometer (VIMS), making use of recent improvements in methane spectroscopic parameters in the region 1.3-5.2 μm. We first analyzed VIMS spectra covering a 8 × 10-km2 area near the Huygens landing site in order to constrain the single scattering albedo (ω0) of the aerosols over all of the VIMS spectral range. Our aerosol model agrees with that derived from Huygens Probe Descent Imager/Spectral Radiometer (DISR) in situ measurements below 1.6 μm. At longer wavelengths, ω0 steadily decreases from 0.92 at 1.6 μm to about 0.70 at 2.5 μm and abruptly drops to about 0.50 near 2.6 μm…
Evaluation of observed and modelled aerosol lifetimes using radioactive tracers of opportunity and an ensemble of 19 global models
2015
Abstract. Aerosols have important impacts on air quality and climate, but the processes affecting their removal from the atmosphere are not fully understood and are poorly constrained by observations. This makes modelled aerosol lifetimes uncertain. In this study, we make use of an observational constraint on aerosol lifetimes provided by radionuclide measurements and investigate the causes of differences within a set of global models. During the Fukushima Dai-Ichi nuclear power plant accident of March 2011, the radioactive isotopes cesium-137 (137Cs) and xenon-133 (133Xe) were released in large quantities. Cesium attached to particles in the ambient air, approximately according to their av…
Convective hydration in the tropical tropopause layer during the StratoClim aircraft campaign: pathway of an observed hydration patch
2018
The source and pathway of the hydration patch in the TTL (tropical tropopause layer) that was measured during the Stratospheric and upper tropospheric processes for better climate predictions (StratoClim) field campaign during the Asian summer monsoon in 2017 and its connection to convective overshoots are investigated. During flight no. 7, two remarkable layers are measured in the TTL, namely (1) the moist layer (ML) with a water vapour content of 4.8–5.7 ppmv in altitudes of 18–19 km in the lower stratosphere and (2) the ice layer (IL) with ice content up to 1.9 eq. ppmv (equivalent parts per million by volume) in altitudes of 17–18 km in the upper tropo…
Précipitations à Madagascar, Mayotte, la Réunion et les Îles Éparses durant la saison des pluies (1971-1999) : rôle et contribution des talwegs tropi…
2014
7 pages; International audience; Cette étude, sur la base d’un jeu de données pluviométriques original, recherche les mécanismes à l’origine de lavariabilité spatiotemporelle des précipitations journalières observées sur Madagascar, Mayotte, La Réunion et les îlesÉparses. L’étude se concentre sur le début et le coeur de l’été austral de 1971 à 1999. Un focus sur la contribution desTalwegs Tropicaux-Tempérés (TTT) est réalisé. Dans une première partie, une classification sur les séries de précipitationsde vingt-neuf stations a mis en évidence six types de jours et de mécanismes associés. La classe sèche est associée à desanomalies cycloniques, deux des cinq classes dont associées à des TTT, …
Shallow water rogue waves in nonlinear optical fibers
2013
The dynamics of extreme waves, often known as freak or rogue waves (RW), is presently a subject of intensive research. In oceanography, RW are mostly known as a sudden deep-water event which is responsible for ship wreakages and can be modeled by the 1D Nonlinear Schrodinger Equation (NLSE). In this framework, an ideal testbed is provided by optical pulse propagation in nonlinear optical fibers: extreme solitary wave emissions during supercontinuum generation or the first experimental observation of the Peregrine solitons have indeed been carried out exploiting the modulation instability occuring in fibers with anomalous dispersion.
Environmental effects on the natural vibrations of nanoplatelets: a high pressure study.
2017
International audience; Resonant acoustic modes from ultrathin CdS colloidal nanoplatelets (NPLs) are probed under high pressure using low frequency Raman spectroscopy. In particular we focus on the characterization of the recently evidenced mass load effect that is responsible for a significant downshift of the NPL breathing frequency due to the inert mass of organic ligands. We show that a key parameter in the observation of the mass effect is whether the surrounding medium is able to support THz acoustic wave propagation, at a frequency close to that of the inorganic vibrating core. At low pressures, surface organic molecules show a single particle-like behavior and a strong mass effect …
EXO-PLANETARY HIGH-TEMPERATURE HYDROCARBONS BY EMISSION AND ABSORPTION SPECTROSCOPY (e-PYTHEAS PROJECT)
2019
International audience; e-PYTHEAS is a multidisciplinary project which combines theoretical and experimental work with exoplanet modelling applications. It sits on the frontier between molecular physics, theoretical chemistry and astrophysics. It aims at enhancing our understanding of the radiative properties of hot gaseous media to allow for improved analysis and interpretation of the large mass of data available on the thousands of exoplanets and exoplanetary systems known to date. Our approach is to use theoretical research validated by laboratory experiments and to then inject it into models of the atmospheres of the giant gaseous planets in the solar system and other planetary systems.…
Influence du paysage et des abondances de bioagresseurs sur l’utilisation de produits phytosanitaires en grandes cultures
2022
Dans cette étude, nous avons cherché à identifier les déterminants des abondances de bioagresseurs à l’échelle nationale, en mobilisant les données EPIPHYT, collectées dans le cadre du BSV, Bulletin de Santé du Végétal. Les niveaux d’occurrence de trois types de bioagresseurs (les limaces, les pucerons des céréales, et les ravageurs du colza) ont été analysées pour l’année 2018 afin d’identifier le poids relatif du climat et du paysage dans leurs niveaux d’occurrence, au grain spatial de la Petite Région Agricole (PRA). Les données de paysage ont été générées par agrégation de plusieurs bases de données d’occupation du sols (BD TOPO, RPG, OSO). L’approche statistique utilisée est une analys…
Impacts de l'occupation du sol sur les ressources en eau du complexe Mono-Couffo (Afrique de l'Ouest)
2009
International audience; En Afrique de l'ouest en général et au Bénin comme au Togo en particulier, les cours d'eau sont des pôles particulièrement attractifs pour la population du fait de la diversité des activités socio-économiques qu'ils permettent. Mais, les variations pluviométriques et la pression humaine de ces dernières années, sur le complexe Mono-Couffo ont eu une influence négative sur les ressources en eau et les écosystèmes en particulier. Les données utilisées sont : la pluviométrie, les débits (Athiémé et Lanta), la superficie des unités d'occupation du sol, la turbidité, le taux de dépôts solides (TDS) et la production halieutique. Ces données ont permis d'analyser d'une part…