Auswahl der wissenschaftlichen Literatur zum Thema „Poussières minérales – Propriétés optiques“
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Dissertationen zum Thema "Poussières minérales – Propriétés optiques":
Lafon, Sandra. „Les oxydes de fer dans l'aérosol désertique en relation avec ses propriétés optiques : caractérisation physico-chimique de poussières minérales générées en soufflerie“. Paris 12, 2004. https://athena.u-pec.fr/primo-explore/search?query=any,exact,990002151550204611&vid=upec.
Direct radiative impacts of desert aerosols emitted bv wind erosion on arid and semi arid zones are a major source of uncertainties of climate models. In this work, aerosols have been generated in wind-tuimel from soils of source region (Niger. Tunisia and Chine). These samples have been characterized with original methods, regarding properties controlling scattering and absorption properties of solar and telluric radiation: size distribution. Particle rnorphologv, mineralogical and chemical compositions, content and status of iron oxides. These data allow evaluation of dust optical properties and assessment of a relationship between iron oxides and absorption in the visible spectrum. In the near future, this should make it possible to include a parameterization ofoptical properties in dust emission models
Herreras, Giralda Marcos. „Développement d’un algorithme de restitution des propriétés des aérosols atmosphériques en utilisant la synergie du spectre solaire et infrarouge thermique“. Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR013.
Knowledge and monitoring of atmospheric aerosol chemical composition is highly important for the understanding and evaluation of Earth's climate, environmental processes and air quality. The aerosol composition drives the efficiency of interactions with clouds, direct interaction of radiation with the Particulate Matter, impact on marine ecosystem after the aerosol deposition, etc.. Mineral dust represents the second, after the marine aerosol, largest fraction of the global atmospheric aerosol emissions. The net radiative effect of the atmospheric dust depends on its mineralogical composition. The vast variety of soil mineralogy determines the variability of airborne dust composition, but direct link between them is not evident. Mineralogical composition of volcanic ash is even less predictable, while has an importance for aviation safety. Finally, the fraction of aerosol hygroscopic species is determinant for aerosol cloud interactions. The objective of this thesis is to establish a framework for the combined and consistent retrieval of atmospheric aerosol optical properties and aerosol components using synergy of solar and Thermal Infrared (TIR) measurements. The implementation is done as part of the GRASP algorithm (Dubovik et al., 2021). Synergy between both parts of the spectra is expected to provide an enhanced sensitivity to aerosol microphysical properties as well as a finer characterization of the mineral dust components, e.g. Quartz and clays fractions separation. The presented development is an extension the of previously developed GRASP/Components approach (Li et al., 2019). An important update has been done on the incorporation of Planck emission into the Successive Orders of Scattering radiative transfer scheme that is employed in the GRASP algorithm. In addition, line-by-line and K-Distribution methodologies to integrate gas absorption lines and a methodology to deal with the highly varying aerosol refractive index in TIR was implemented in order to fulfill the objectives. Synthetic tests were performed to evaluate the accuracy of (i) the designed methodology for the measurements simulation of a thermal infrared radiometer and (ii) the updated aerosol components parameterization. Furthermore, a synthetic study was conducted to evaluate the influence of a priori assumed information. An enhancement of the sensitivity to the coarse mode particles, a finer characterization of the dust components, the retrieval of the Aerosol Mean Height (AMH) from passive measurements and finally the retrieval of total column water vapor concentration was illustrated as possible based on the Solar-TIR measurements synergy. Namely, the new combined solar-TIR GRASP/Components retrieval algorithm was applied to the AERONET (AErosol RObotic Network) (Holben et al., 1998) sun photometer and the CLIMAT Thermal Infrared radiometer (Legrand et al., 1999; Brogniez et al., 2003) combined measurements conducted by LOA in Senegal. The observations conducted between November 2020 to April 2021 at the Dakar Belair site were selected for the application of the Solar-TIR GRASP/Components retrieval. A high degree of agreement was found between the derived values and the corresponding standard AERONET retrievals. Moreover, it was found that the total column water vapor and AMH can be retrieved simultaneously with the aerosol characteristics. The retrievals showed good correlation with the independently derived AERONET precipitable water and a qualitative agreement with lidar aerosol profiles observations. The future steps of this work include a further validation of the retrieved aerosol components. The perspective is in the algorithm application to combined 3MI and IASI-NG sensors that will fly onboard of MetOp-SG A space mission or similar
Hubert, Patrice. „Spectres d’extinction de particules minérales et restitution des indices complexes de réfraction dans l’infrarouge et l’UV-visible“. Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10139/document.
Due to their ability to absorb and scatter radiations, aerosols play an important role in the Earth’s radiative budget. However, quantitative estimations of their effects on climate are quite uncertain due to their large spatial and temporal variability in terms of concentration and physical properties. Measurements from remote sensing instruments are efficient tools to observe and investigate aerosol distributions from regional to global scales. Nevertheless, to fully exploit instrument capabilities, precise optical properties – dependent on chemical or mineralogical properties – are needed. These properties are linked by the Complex Refractive Index (CRI), which represents one of the main sources of uncertainty for studying aerosols from remote sensing instruments.The objective of this study is to propose and exploit a new methodology, aiming to determine precise CRI of particles. For this purpose, a new robust and versatile approach has been developed and implemented. Moreover, to determine capabilities of this approach, validation of each step in the procedure for CRI determination has been realized. The complete approach has been also applied for suspended particles of amorphous and crystalline SiO2, which are the major fraction of volcanic and mineral dust aerosols. Lastly, first results from collected samples from measurement campaigns are also presented. These results highlight the potential of the proposed approach to determine CRI, in order to improve the aerosol measurement exploitations by remote sensing instruments
Unga, Florin. „Investigation of atmospheric aerosol mixing state effect on measured and retrieved optical characteristics : an approach integrating individual particle analysis, remote sensing and numerical simulations“. Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10023/document.
Tropospheric aerosols play an important role in atmospheric chemistry, Earth’s radiative budget and climate. After their generation, aerosol can suffer ageing processes and altering their physicochemical properties. An accurate accounting for these processes requires observations of the aerosol properties on different temporal and spatial scales. The current thesis work is dedicated to: (i) study of physicochemical properties and mixing state of individual particles by means of analytical scanning and transmission electron microscopy for aerosols collected during episodes of elevated aerosol loading; (ii) analysis of the effect of microphysical properties on optical characteristics as measured and retrieved by remote sensing; and (iii) investigation of possible parameterization of aerosol composition and structure in remote sensing algorithms. The work presents observations conducted in northern France and western Africa (Senegal) as part of Labex CaPPA project and SHADOW field campaigns. It includes simultaneous analyses of collected individual particles composition and structure, remote sensing and in situ observations of urban/industrial, Saharan dust and biomass burning particles near the surface and on different altitudes. A series of numerical simulation devoted to an analysis of sensitivity of remote sensing observations to aerosol mixing state is conducted. Insights on possible parameterization of aerosol core-shell structure in retrieval algorithms are finally presented
Klaver, Anne. „Estimation des propriétés optiques des poussières désertiques d'origines saharienne et sahélienne, à proximité de leurs zones sources d'émission, à partir de leurs propriétés physico-chimiques“. Paris 7, 2012. http://www.theses.fr/2012PA077179.
By absorption and scattering of the solar and terrestrial radiations, mineral dust has a direct radiative effect. At the global scale, this direct radiative effet is currently estimated between -0. 56 and + 0. 1 W m⁻², which doesn't allow to say if the mineral dust cools or warms the Earth/Atmosphere System. The estimation of this effect still remains uncertain because of the limited knowledge concerning the optical properties of mineral dust (scattering and absorption) which are linked with their physico-chemical properties. My work is incorporated within the issues of the reduction of these uncertainties. It involved the study of the physico-chemical (mineralogical composition, size and shape) and optical (scattering, absorption and extinction coefficients, single scattering albedo and asymmetry parameter) properties of thé minéral dust coming from western Africa, observed in the framework of the African Monsoon Multidisciplinary Analysis (AMMA) program at Banizoumbou (Niger) station in winter and summer 2006. With an optical model, these observations have been used in order to perform closure studies of the optical properties. I tried to determine if it is possible to estimate the optical properties of the mineral dust based on the knowledge of their physico-chemical properties. I showed a good representation of the scattering and absorption coefficients by calculation (calculation/measurement discrepancy < 13 %). However, efforts have to be performed concerning the estimation of the absorption coefficient and single scattering albedo (calculation/measurement discrepancy up to 291 %)
Boucher, Virginie. „Élaboration de polymères nanocomposites transparents : relations structure/propriétés“. Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10161/document.
This study deals with the preparation of transparent polycarbonate nanocomposites for industrial applications such as optical lenses or automotive glazing. Incorporating nanoparticles to polycarbonate matrix aimed to improve some of its properties such as stiffness, dimensional stability, or scratch resistance, while maintaining intrinsic properties such as its transparency. Polycarbonate nanocomposites transparency depends on one hand on mineral partic/es diameter and refractive index, and on the other hand on the good dispersion of particles in polymer matrix. Therefore, different types of mineral fillers were selected and incorporated in polycarbonate matrix. The evaluation of mechanical and optical properties of these nanocomposites permitted not only to refine particles selection, but also to highlight polycarbonate degradation during compounding with nanofillers. ln order to optimize materials performances, a thorough study of degradation mechanisms was carried out, and the nanocomposites preparation process was modified so as to Iimit polycarbonate degradation in presence of mineral fillers. Lastly, in a more general framework, the reinforcement mechanisms involved in nanocomposite materials were investigated, and showed the existence of correlations between materials structure and properties, and the effect of mineral fi/lers on polycarbonate molecular dynamics
Deschutter, Lise. „Propriétés optiques des poussières désertiques de Gobi et de ses composés purs : spectres d'extinction expérimentaux et détermination des indices complexes de réfraction“. Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR018.
Spectrometers are powerful instruments, especially when used from satellites to detect atmospheric aerosols at a global scale and with high spectral resolution. However, to fully exploit their capabilities and be able to link the optical properties, chemical composition and mass concentration of aerosols, it is essential to have access to the complex refractive indices (CRI) of these particles. The CRI of a natural aerosol source can be retrieved from measurements performed directly from the natural sample or by applying some effective medium approximation using the CRI of the pure compounds present in the particles. But in that case, it is necessary to know the mass fraction of each chemical species and also their CRI. In the literature, CRI databases of numerous compounds exist. But several limitations are encountered because the measurements are carried out over limited wavelength ranges and by reflectance on bulk materials or pressed pellets that do not represent aerosols.This thesis is dedicated to the study of the optical properties of particles collected in the Gobi Desert. The objective is to determine the CRI of the natural sample of Gobi and its main compounds (illite, calcite and quartz). The particles in powder form are resuspended and driven through a continuous flow to an infrared and a UV-visible spectrometers to record extinction spectra and then to particle sizers. The recorded extinction spectra are associated with an inversion algorithm combining different theories as Rayleigh, Continuous Distribution of Ellipsoid (CDE) and Mie. Through the single-subtractive relation of Kramers-Kronig and an optimal estimation method, the optical constants n and k are retrieved and can be implemented in the CRI databases.Finally, comparisons between the Gobi CRI retrieved by our methodology and those calculated by the mixing theories will be presented