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Дисертації з теми "Aérosols – Propriétés microphysiques":
Perry, Guillaume. "Télédétection des propriétés optiques et microphysiques des aérosols avec le radiomètre POLDER : préparation de la mission satellitaire." Lille 1, 1996. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1996/50376-1996-107.pdf.
Lafrique, Pierre. "Lidar multispectral pour la caractérisation des aérosols." Thesis, Toulouse, ISAE, 2015. http://www.theses.fr/2015ESAE0033/document.
The purpose of this thesis is to show the contribution of a multispectral Iidar for the characterisation of aerosols, in particular hen wavelengths in near infrared are added. Indeed, compared with a mono-wavelength Iidar, the information contained in multispectral profiles allow to retrieve the microphysical properties of aerosols (particule size distribution and composition). To this end, we adapted a multispectral Iidar signal simulator to our study in order to develop and test two methods which objective is to obtain the microphysical properties of aerosol along the line-of-sight from synthetic lidar signals. The first method, based on the inversion of lidar signals, enables to find the length distribution of aerosols and therefore to educe their concentration and their modal radius. This method requires a priori information about the aerosols. An error budget was made by introducing uncertainties on the a priori parameters. It shows that the results obtained regarding the concentration and modal radius are accurate (respectively 16% and 17% uncertainty). The advantage of this method is that it does not require absolute calibration of the instrument. The principle of the second method is to minimize the difference between the studied and the simulated signals. Even if the accuracy on the size distribution is lower (35% and 40% on the concentration and modal radius) and the calibration constant of the instrument has to be known, this method has the advantage to find the concentration of the aerosols in 74% of the cases. Finally, the first method was validated on real data, coming from a collaboration with the RSLab (Barcelona), by comparing ur results with those obtained by this team (7% difference on the modal radius)
Mazoyer, Marie. "Impact du processus d'activation sur les propriétés microphysiques des brouillards et sur leur cycle de vie." Thesis, Toulouse, INPT, 2016. http://www.theses.fr/2016INPT0025/document.
Fogs are complex meteorological systems dealing with fine scale processes. Their lifecycles are closely related to the interactions between radiation, fog dynamics, turbulence and fog microphysics that make their forecasting difficult. Fogs are formed by the activation of aerosols particles into water droplets. To date, understanding the impact of the aerosols properties on the fog life cycle remains still challenging. This thesis aims at investigating the impact of activation processes on fog microphysics and lifecycles. In the framework of the PréViBoss project, in-situ measurements of fog properties were performed during winters 2010 to 2013 at the SIRTA site in the south of Paris. A detailed characterization of aerosols and fog microphysics, including number size spectrum of both particles under dry and wet conditions and droplets, was performed in order to investigate the aerosols efficiency to act as cloud condensation nuclei (CCN). A large number of case studies are presented, which include 23 case studies on fog formation from the activation of aerosols and 48 fog events on the temporal evolution of fog microphysics. An original method has been used to investigate the link between supersaturation values and concentrations of CCN with aerosols properties (distribution, concentration and hygroscopicity). We show that supersaturation values determine the droplets concentration, independently of the concentration of aerosols. The evolution of fog microphysics of the 48 cases follows 4 phases with distinct behaviours, driven by condensation/evaporation and deactivation/ activation processes. The fog droplets concentration is determined during the first phase, then it fluctuate around this value during fog life cycle. Large eddy simulation of fog cases observed during PréViBoss are performed with the Meso-NH model to evaluate the impact of microphysics on fog lifetime. It allows to explore the close interactions between aerosols and physical processes. A two moments scheme is used for microphysic and two schemes for supersaturation have been evaluated, the first one estimate the maximal supersaturation and the second one considers a pseudoprognostic evolution of supersaturation following Thouron et al. (2012). Much lower supersaturation values were obtained with the second scheme. Addtional processes, such as condensation or mixing that were not included in previous scheme, are modeled. While CCN concentrations obtained with this new scheme are lower, they remain higher than the observations. We postulate that this behaviour could be due to the representation of dynamics. Sensibilitiy tests for different aerosols concentrations reveal a weak impact on fog life cycle. Only for extreme cases where the aerosol concentrations are low, the fog dissipation is delayed. This study shows that the fog life cycle is mainly driven by thermodynamics, dynamics and surface conditions through their impact on boundary layer stability. Moreover, surface heterogeneities greatly modify fog life cycle trough turbulent motions and should be considered for future experimental studies
Mallet, Marc. "Etude des propriétés microphysiques et optiques de l'aérosol en zone periurbaine durant ESCOMPTE : estimation de l'impact radiatif direct." Toulon, 2003. http://www.theses.fr/2003TOUL0001.
Anthropogenic aerosols are now well recognized to modify the climate through three well known processes. Directly, by scattering the solar radiation back to space, and (or) by absorbing the solar radiation. Indirectly, by changing the clouds properties when aerosol act as cloud condensation nuclei. Semi-directly, by evaporating the clouds when high concentration of absorbing aerosols are present in the atmosphere. The main aim of this work is to investigate the direct radiative forcing of the main anthropogenic aerosol species in peri urban zone for a strong pollution event, during the ESCOMPTE experiment. We used a methodology based on in situ, photometric and satellite measurements in order to first determine the aerosol optical properties of the main aerosol species (BC, POM, AS, N), and then to determine the aerosol direct radiative forcing at a local scale. Optical properties of the total aerosol layer (including all aerosol species) show that 90 % of the Iight extinction is due to anthropogenic aerosols and 10 % to natural ones. Ammonium sulphate (AS) is the major contributor with 45 % of the extinction. Optical computations show the predominant rote of the black carbon and the particulate organic matter which contribute to 21 and 20 %. The mean observed single scattering albedo equals to 0. 85, indicating a strong absorption of the solar radiation, and in the same time, the mean asymmetry parameter equals to 0. 59. Comparison with AERONET retrievals is coherent (0. 87 / 0. 64). The layer of anthropogenic aerosols reduce the daily surface illumination (- 32 Wm 2) by reflection to space (-7 Wm-2) and by absorption of the solar radiation (25 Wm 2). The resulting energy available in the atmospheric column warms the lower troposphere with a mean radiative temperature of +1. 68 0Kdaÿ-'. Our study shows an huge contribution in surface of the BC (almost 50% of the total daily forcing) for this peri urban zone, whereas the AS leads to about 10%. The aerosol optical properties and the associated direct radiative effect are investigated in a internat mixing state as well. Whereas the asymmetry parameter remains constant, wo is shown to be very sensitive and could be reduced by 15 %, increasing the absorption processes. Compare to the extemal mixture, the surface illumination is reduced by 25 % (-42 Wm 2). This is due, in a large part, to an increasing of 50 % of the energy absorbed by the aerosol layer ( 38 Wm 2)
Elias, Thierry. "Restitution des propriétés optiques et microphysiques des aérosols à partir d'observation sol des luminances totale et polarisée dans le visible et le proche infrarouge." Lille 1, 2000. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2000/50376-2000-89.pdf.
Ces deux parametres definissent un modele d'aerosols qui permet de calculer la matrice de phase des aerosols, en supposant les particules spheriques. Un code de transfert radiatif integre le modele d'aerosols et l'albedo de diffusion simple pour evaluer la distribution angulaire du champ de luminance dans l'atmosphere. La methodologie est appliquee a des mesures acquises a lille le 10 mars 1997 par un prototype de polarimetre developpe au laboratoire d'optique atmospherique, quand les aerosols etaient abondants. Le modele d'aerosols restitue est caracteristique de particules originaires de zone urbaine. Parmi les perspectives qui se presentent, la contribution des aerosols au rayonnement ascendant peut etre evalue afin de valider et approfondir les informations issues du traitement des donnees acquises par polder (polarization and directionality of the earth's reflectance), embarque sur le satellite adeos (advanced earth observing system)
Korgo, Bruno. "Caractérisation optique et microphysique des aérosols atmosphériques en zone urbaine ouest africaine : application aux calculs du forçage radiatif à Ouagadougou." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22509/document.
In this thesis, we analyze the main characteristics of atmospheric aerosols on an urban site in West Africa: Ouagadougou. This analysis is followed by an assessment of the radiative forcing produced by this population of aerosols at the top of the atmosphere, in the atmospheric layer and at the Earth's surface. A climatological study of the optical properties (optical thickness, Angstrom exponent, single scattering albedo, asymmetry factor) and microphysical properties (particle size distribution, complex refractive index) was performed on basis of data obtained from photometric measurement and inversions of AERONET network. The analysis of these data allowed us to define the different variabilities of the properties studied at various time scales. These properties have highlighted the combined effects of human activity, the cycle production of mineral dust from the Sahara region, the seasonal succession and the climate dynamics known in this region of the earth. The composition of the aerosol plume was also deduced from the analysis of optical data, and the conclusions were found to be in good agreement with chemical analysis carried out at LSCE on samples obtained by sampling on filters at Ouagadougou. The radiation balance was assessed using the GAME model. This simulation showed a strong relationship of the radiative forcing with the succesion of wet and dry seasons, with extreme values in August (wet) and Mars (dry with maximum dust emissions). The results showed a cooling at the surface that can reach -41 W / m 2 in March, a warming of the atmosphere, ranging from 15 to 35 W / m 2 about and a cooling at the top of the atmosphere between -2 and -6 W / m 2 . The representation of the radiative forcing calculated as a function of the single scattering albedo showed a linear trend with a correlation coefficient reflecting relatively good reliability of our results (about 88%). The consistency of simulated values was also shown by a comparison with the results obtained in the West African region by other researchers using different techniques. Similarly, the representation of the radiative efficiency simulated as a function of the inverted AERONET one showed a very good agreement
Guyot, Gwennolé. "Caractérisation des propriétés microphysiques des nuages et de l'interaction aérosol-nuage en Arctique à partir de mesures in-situ au sol pendant la campagne CLIMSLIP-NyA, Svalbard." Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22699/document.
The arctic region is especially sensitive to climate change. At high latitudes, arctic clouds have an important effect on the surface radiative budget. The first part of this work consists in a ground based cloud instrumentation intercomparison in the PUY station in May 2013. The measurements showed a good correlation between the effective diameters and the droplet size distributions obtained by the instruments, but with a systematical bias on the concentrations. These biases have been relied to the assessment of the sampling volume and we thus proposed a methodology to standardize the data according to an ensemble of particles probe. Moreover, the FSSP and the FM have been the subject of experiments to assess the influence of the deflection angle according to exterior wind and the wind speed. The second part of this work is about the measurement campaign at the Mount-Zeppelin station, Ny-Alesund, Svalbard, from March to May 2012 in the frame of the CLIMSLIP project. A comparison has been performed between a « polluted » case, with air masses coming from East Asia and Europe, and a « clean » case, where the aerosol sources are predominantly local and do not exceed the northern Europe. The results showed that the polluted case possessed higher concentrations in BC, aerosols and drops, an accumulation mode more important, weaker droplet diameters and higher activation fraction. Finally, the first and second aerosol indirect effects have been quantified
Chang, Yuyang. "Développement d'un nouvelle technique de mesure du profil atmosphérique en aérosols à l'aide d'un lidar Raman-dépolarisation-fluorescence." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDSMRE/2023/2023ULILR060.pdf.
Vertical information on aerosol optical and microphysical properties is of significant importance to study aerosol evolution, transport, as well as their impacts on human health, local environment and global climate. This thesis developed an algorithm, the Basic algOrithm for REtrieval of Aerosol with Lidar (BOREAL), for retrieving heigh-resolved aerosol microphysical properties from combinations of extinction, backscattering and depolarization lidar measurements. Based on maximum likelihood estimation, the retrieval algorithm uses a nonlinear iteration approach to search for the best fit to both measurements and constraints. The retrieved aerosol microphysical properties include particle size distribution, volume concentration, effective radius, complex refractive index (CRI) and single scattering albedo (SSA).The performance of BOREAL, retrieval accuracy and measurement sensitivity are assessed through simulated data. In general, retrieval accuracy is higher for fine-mode particles than coarse-mode particles. The simulations demonstrate the importance of exploiting a priori constraint to improve the retrieval accuracy of CRI and SSA. Apart from spherical particles, performance of retrieving non-spherical particles is also evaluated by integrating three different particle scattering models, i.e., the Sphere, Spheroid and Irregular-Hexahedral (IH) models, into BOREAL. The results show incorporating depolarization measurements into inversion is essential to better constrain and stabilize the retrieval. Besides, approximating non-spherical particles to spheres will evidently degrade retrieval quality in cases of lidar measurements. In addition, BOREAL is applied to real lidar observations of different aerosol types, including biomass burning, dust and continental polluted aerosols at the ATOLL observatory. Results are analyzed and compared with retrievals from AERONET and previous studies, which demonstrates the robustness of BOREAL for real data application and aerosol characterization.Overall, this work contributes to Labex CaPPA and ACTRIS efforts to better quantify aerosol microphysical properties using lidar measurements
Deaconu, Lucia-Timea. "Study on multi-layer "aerosol" situations and of "aerosol-cloud" interactions." Electronic Thesis or Diss., Lille 1, 2017. http://www.theses.fr/2017LIL10165.
One of the main objectives of this study is to analyze the consistency between the aerosol above clouds (AAC) retrievals from passive and active satellite measurements. We consider the method based on the passive polarization measurements provided by the POLDER instrument, the operational method developed for the space borne lidar CALIOP, and the CALIOP-based depolarization ratio method (DRM), for which we also propose a calibrated version. We perform a regional analysis and a global multi-annual analysis to provide robust statistics results. Our findings show good agreement between DRM and POLDER AOT retrievals (R2=0.68 at global scale). This result gives confidence in our ability to measure the properties of AAC. Differences occur when the aerosol and cloud layers are in contact. CALIOP operational method is largely underestimating the above cloud AOT, compared to the other two methods.The second objective is to study the impact of aerosols on the cloud properties and their radiative forcing, over the South Atlantic Ocean. We perform a synergy between CALIOP vertical profiles and POLDER retrievals, with collocated meteorological parameters. We performed radiative transfer calculations in the short- and longwave domains, and analyzed the effect of aerosol loading on the cloud properties and meteorology. We found that aerosols and water vapor effects could impact the cloud convection. Our results show that under large loads of AACs, clouds become optically thicker, with an increase in liquid water path of 20 g.m-2 and their cloud top altitudes are lower by 200 m, which may indicate a potential semi-direct effect of aerosols above clouds
Deaconu, Lucia-Timea. "Study on multi-layer "aerosol" situations and of "aerosol-cloud" interactions." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10165.
One of the main objectives of this study is to analyze the consistency between the aerosol above clouds (AAC) retrievals from passive and active satellite measurements. We consider the method based on the passive polarization measurements provided by the POLDER instrument, the operational method developed for the space borne lidar CALIOP, and the CALIOP-based depolarization ratio method (DRM), for which we also propose a calibrated version. We perform a regional analysis and a global multi-annual analysis to provide robust statistics results. Our findings show good agreement between DRM and POLDER AOT retrievals (R2=0.68 at global scale). This result gives confidence in our ability to measure the properties of AAC. Differences occur when the aerosol and cloud layers are in contact. CALIOP operational method is largely underestimating the above cloud AOT, compared to the other two methods.The second objective is to study the impact of aerosols on the cloud properties and their radiative forcing, over the South Atlantic Ocean. We perform a synergy between CALIOP vertical profiles and POLDER retrievals, with collocated meteorological parameters. We performed radiative transfer calculations in the short- and longwave domains, and analyzed the effect of aerosol loading on the cloud properties and meteorology. We found that aerosols and water vapor effects could impact the cloud convection. Our results show that under large loads of AACs, clouds become optically thicker, with an increase in liquid water path of 20 g.m-2 and their cloud top altitudes are lower by 200 m, which may indicate a potential semi-direct effect of aerosols above clouds