FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Os processos microfÃsicos, em particular, representam, hoje em dia, uma das incertezas mais cruciais no entendimento da convecÃÃo tropical. A questÃo reside no fato de, em Ãltima instÃncia, ser ao nÃvel dos processos microfÃsicos que à liberada grande parte da energia necessÃria para os movimentos atmosfÃricos nos trÃpicos. DaÃ, uma correta representaÃÃo dos processos fÃsicos envolvendo nuvens e sua interaÃÃo com a circulaÃÃo atmosfÃrica em escalas maiores à condiÃÃo essencial para que modelos de circulaÃÃo geral, por exemplo, possam oferecer bons resultados em previsÃo climÃtica e simulaÃÃes de mudanÃas climÃticas globais. Neste trabalho à feito um estudo (revisÃo) da teoria dos aerossÃis atmosfÃricos e uma caracterizaÃÃo da regiÃo AmazÃnica, uma descriÃÃo completa dos experimentos de campo EMfiN!/LBA/SMOCC, bem como, um estudo da relaÃÃo entre os nÃcleos de condensaÃÃo e a microestrutura de nuvens atà a interaÃÃo destas com a estrutura termodinÃmica do ambiente de grande escala, possÃveis modificaÃÃes climÃticas provocadas por fatores antropogÃnicos (queimadas) e tambÃm estudos utilizando modelos numÃricos: um modelo de parcela, um modelo bidimensional axi-simÃtrico e um modelo de ensemble de nuvens, todos foram iniciados com base em dados obtidos dos experimentos acima citados. Os resultados experimentais e numÃricos sugerem que a poluiÃÃo inibe a formaÃÃo e o desenvolvimento da precipitaÃÃo na fase lÃquida (chuva quente), e altera os fluxos de radiaÃÃo, com conseqÃÃncias significativas no clima, pelo menos em escala regional. / The microphysics processes, represent nowadays, one of the most crucial uncertainties in the understanding of the tropical convection. This is due to the fact that great part of the energy necessary for the tropical atmospheric movements is released by the microphysics processes. Then a correct representation of the microphysics processes in general circulation models involving clouds and his interaction with the atmospheric circulation in larger scales is an essential condition for the obtention of good results in climatic forecast and simulations of global climatic changes. This work consist of a study (revision) of the theory atmospheric aerosols and a characterization of the Amazonian area, a complete description of the field experiments EMfiN!/LBA/SMOCC, as well, a study of the relationship between the condensation nuclei and the cloud microstructure, up to interaction of the clouds with the thermodynamic structure of the atmosphere of larger scale, possible climatic modifications provoked by anthropogenic factors (forest fire) and also studies using numerical models: one of parcels, one bin-microphysics cloud model and another of ensemble of clouds, all were initiated with data from the above mentioned experiments. The experimental and numerical results suggest that the pollution inhibits the formation and the development of the precipitation in the liquid phase (warm rain), and it alters the radiation flow, with significant consequences in the climatic, at least in regional scale.

O sistema climático terrestre é regido pela interação entre o fluxo de radiação solar e diversos elementos presentes na atmosfera e na superfície. Entre esses elementos destacamos o papel que as nuvens desempenham nesse processo devido a sua elevada cobertura terrestre, que chega a média de três quartos de todo o globo. Do total de radiação solar que atinge a atmosfera, as nuvens são responsáveis pela reflexão direta de cerca de 23% da radiação incidente de volta ao espaço evitando, assim, o aquecimento da superfície. Por outro lado, parte da radiação térmica emitida pelo solo é absorvida e reemitida pelas nuvens podendo ocasionar em um aumento de temperatura próximo à superfície dependendo da sua altitude. Todo esse processo está intimamente relacionado a quantidade de nuvens, sua espessura óptica e o comprimento de onda da radiação, podendo a resposta do sistema variar conforme muda-se alguma dessas condições. Outro elemento que influencia tanto nas características das nuvens quanto no balanço radiativo terrestre é o aerossol atmosférico. Sua presença na atmosfera pode tanto aumentar a temperatura em solo quanto diminuí-la, dependendo do tipo de aerossol, sua quantidade, distribuição espacial e da radiação com a qual está interagindo. Ele também participa na formação das nuvens ao atuar como núcleo condensador de nuvens em atmosfera supersaturada, facilitando a aglutinação de vapor de água em torno de si. A presença de elevadas quantidades de aerossóis para uma determinada taxa de umidade do ar, dificulta a formação e o desenvolvimento vertical da nuvem, podendo até mesmo acarretar sua evaporação. Como a variabilidade dos aerossóis na atmosfera, em geral, é muito alta e devido a sua interação com a radiação variar com o comprimento de onda, a determinação precisa do seu efeito no balanço radiativo terrestre é prejudicada. Esses processos citados evidenciam a enorme complexidade no entendimento das relações envolvendo esses dois elementos presentes na atmosfera terrestre. Para diminuir essa lacuna, sobrevoamos uma região próxima a Porto Velho (RO) entre os dias 21 e 28 de setembro de 2012 munidos de um aparato experimental a fim de analisar o perfil vertical das nuvens. Esse aparato continha uma câmera sensível a comprimentos de onda visíveis (aproximadamente de 440nm a 700nm), uma câmera térmica, sensível a comprimentos de onda entre 8 e 14m, e outra sensível a comprimentos de onda no infravermelho próximo, entre 900nm e 2500nm. Esse conjunto de instrumentos permitiu obter medidas da radiação emergente da lateral de nuvens convectivas na região estudada. / none

Nuvens desempenham papel fundamental no balanço radiativo terrestre, e o conhecimento de suas propriedades micro e macrofísicas é importante para o estudo do clima global. O desenvolvimento de nuvens esta ligado à dinâmica da atmosfera, fluxos de energia térmica e radiativa à superfície, e também depende crucialmente do tamanho de seus hidrometeoros. Uma ferramenta importante para o estudo de hidrometeoros em nuvens de grande escala e o sensoriamento remoto por satélite, que representa uma alternativa para se estudar propriedades de nuvens em grandes escalas espaciais. No entanto, atualmente não há estudos para subsidiar análises de propriedades microfísicas de nuvens a partir de plataformas geoestacionárias. Neste trabalho foram comparados dois códigos de transferência radiativa amplamente utilizados pela comunidade científica, SBDART e libRadtran, em simulações considerando variações de propriedades atmosféricas, de superfície, macro e microfísicas de nuvens. Em seguida estudou-se a transferência radiativa em nuvens de água e gelo determinando o impacto simulado de diversas geometrias de iluminação e observação nas radiâncias medidas por sensoriamento remoto. Finalmente, foram desenvolvidas tabelas de referência para a determinação de tamanho de hidrometeoros em nuvens, para fases líquida e solida, a partir de radiâncias medidas por um sensor em satélite geoestacionário. As comparações entre SBDART e libRadtran mostram resultados sistematicamente subestimados pelo libRadtran. Em um céu sem nuvens a diferença entre as refletâncias calculadas em ambos os modelos é inferior a 4% quando consideradas variações em albedo de superfície e coluna de ozônio. Em um céu com nuvens a diferença entre os resultados dos modelos para comprimento de onda de 630 nm e intervalo visível (590 a 660 nm) pode chegar ate 18% para variações de profundidade óptica entre 0 e 20. Para profundidade óptica maior que 20 essas diferenças variam entre 4 e 9%, além de refletâncias constantes para o intervalo entre 3850 e 4000 nm e para comprimento de onda de 3900 nm. A divergência de resultados obtidos pelos dois modelos é atribuída a diferenças estruturais entre os códigos, uma vez que atualmente apenas o libRadtran apresenta atualizações periódicas pela comunidade científica. Assim, este modelo foi utilizado para a construção da tabela de referência simulando medidas de radiâncias em plataforma geoestacionária. A tabela construída compreende 86 valores de raios efetivos de hidrometeoros, variando entre 2 e 59m, com fases termodinâmicas de água e gelo, 16 valores de geometria de observação solar, 3 valores de âgulos de observação, 2 valores de azimute relativo, e condições fixas de profundidade óptica de nuvem de 50, conteúdo integrado de ozônio de 255 DU e 60mm de vapor d água. Essas condições foram escolhidas como representativas para a região Amazônica. Em um teste de aplicação direta da tabela de referência a medidas de radiância realizadas com satélite geoestacionário foram obtidos raios efetivos entre 2 e 30m para gotículas de água e até 24m para cristais de gelo. Os resultados obtidos neste trabalho poderão ser aplicados futuramente a medidas obtidas por plataformas geoestacionárias em estudos de tamanhos de hidrometeoros, tornando possível a análise de sua evolução temporal. / Clouds play a fundamental role in the terrestrial radiative balance, and knowledge of its micro and macrophysical properties is important for the study of global climate. Cloud development is linked to the dynamics of the atmosphere, thermal and radiative energy flows to the surface, and also depends crucially on the size of its hydrometeors. An important tool for the study of large-scale cloud hydrometeors is satellite remote sensing, which represents an alternative to study cloud properties at large spatial scales. However, there are currently no studies to support analyzes of microphysical properties of clouds from geostationary platforms. In this work, two radiative transfer codes widely used by the scientific community, SBDART and libRadtran, were compared in simulations considering variations of atmospheric, surface, macro and microphysical properties of clouds. Next, radiative transference was studied in water and ice clouds, determining the simulated impact of various lighting and observation geometries on radiances measured by remote sensing. Finally, look-up tables were developed for the determination of the size of hydrometeors in clouds, for liquid and solid phases, from radiances measured by a geostationary satellite sensor. The comparisons between SBDART and libRadtran show results systematically underestimated by the libRadtran. In a cloudless sky the difference between the reflectances calculated in both models is less than 4% when considering variations in surface albedo and ozone. In a clouded sky the difference between the model results for wavelengths of 630 nm and the visible range (590 to 660 nm) can reach up to 18% for optical depth variations between 0 and 20. For optical depths greater than 20, these differences range from 4 to 9%, in addition to constant reflections for the range of 3850 to 4000 nm and for a wavelength of 3900 nm. The divergence of results obtained by the two models is attributed to structural differences between the codes, since currently only the libRadtran presents periodic updates by the scientific community. Thus, this model was used for the construction of the reference table simulating measurements of radiances in geostationary platform. The constructed table comprises 86 values of effective radii of hydrometeors, ranging from 2 to 59m, with thermodynamic phases of water and ice, 14 values of geometry of solar observation, 3 values of angles of observation, 2 relative azimuth values, and fixed cloud optical depth conditions of 50, integrated ozone content of 255 DU and 60mm of water vapor. These conditions were chosen as representative for the Amazon region. In a test of direct application of the look-up table to measurements of radiance obtained with geostationary satelite we obtained effective radius up to between 2 and 30 for water droplets and up to 24 for ice crystals. The results obtained in this work can be applied in the future to measurements obtained by geostationary platforms in studies of sizes of hydrometeors, making possible the analysis of their temporal evolution.

This thesis presents the development of a software model that simulates a payload instrument onboard the MATS satellite. The goal of this model is to provide an understanding of how the instrument impacts the measured data. This model is important for error analysis and may help in correcting the measured data for systematic flaws in the instrument. The software will consist of 5 main modules as follows: Scene Generator, Optics Module,Stray Light Module, Charge-Coupled Device Module and Electronics Module. This thesis forms a basic foundation for the software by designing the CCD module and a part of the Optics module, and concludes the effects of both on the output of the system. It takes into account important mission defined procedures that ultimately aim to improve image quality, resolve vertical structures in different bandwidths and analyze noise effects on the measured data.

Mars is the fourth planet of the Solar System starting from the Sun. Compared to Earth, Mars has an atmosphere that is significantly thinner and undergoes also a seasonal cycle that is more marked. A Martian year lasts about two terrestrial years. One of the particularity of the Martian atmosphere is the continuous presence of an airborne dust layer.SPICAM is an instrument on board the Mars-Express satellite orbiting around Mars since the end of 2003. This instrument is divided in two modules: SPICAM/IR, a infrared spectrometer (1.0 - 1.7 µm) and SPICAM/UV, a spectrometer working in the ultraviolet range (106 - 317 nm). In this work, we have analysed the SPICAM/UV measurements that have been recorded in nadir viewing and in the spectral interval between 220 and 290 nm.The analysis of this spectral domain allows to study different species and constituents of the Martian atmosphere such as ozone, dust and ice clouds. In the frame of this work, we have developed a method capable of inverting the SPICAM spectra obtained in nadir viewing in order to simultaneously retrieve the integrated quantities of these different species i.e. the ozone total column, and the integrated optical depths of dust and ice clouds. The method is based on a radiative transfer code that allows to take into account the scattering of light by the different molecules and aerosols of the Martian atmosphere. The surface reflectivity is also considered and is retrieved in the cases where no ice clouds are present in the observed scenes, ice clouds reducing the sensitivity in the surface albedo. Therefore, a cloud detection algorithm has been developed and its results were compared with results obtained with other methods and instruments for validation.Our method has been used to invert the data measured by SPICAM/UV over more than four Martian years which allowed to obtain climatologies of the different studied species: the spatial and seasonal distributions of the ozone column, the optical depths of dust and ice clouds and also the surface albedo are presented in this work. These distributions are discussed and compared to those obtained in previous works obtained with other instruments.This work is also a preparation for the future measurement analysis of the NOMAD/UVIS, an instrument that will be on board the ExoMars Trace Gas Orbiter which is planned to be launched in the beginning of 2016. The algorithm developed in this thesis has also been used to assess performances of NOMAD/UVIS such as the detection limits of particular gases (O3, SO2 et NH3) and the values of the signal-to-noise ratio. / Mars est la quatrième planète du Système Solaire en partant du Soleil. Comparée à la Terre, Mars se caractérise par une atmosphère significativement plus ténue, et possède également un cycle annuel des saisons plus marqué. Une année martienne dure environ deux années terrestres. Une des particularités de l'atmosphère de Mars réside en la présence persistante d'une couche de poussière en suspension.SPICAM est un instrument embarqué à bord du satellite Mars-Express qui orbite autour de Mars depuis fin 2003. Il comprend deux modules: SPICAM/IR, un spectromètre infrarouge (1.0 - 1.7 µm) et SPICAM/UV, un spectromètre opérant dans le domaine ultraviolet (106 - 317 nm). Dans le cadre de ce travail, nous avons analysé les mesures de SPICAM/UV obtenues en visée nadir dans l'intervalle spectral s'étendant de 220 à 290 nm.L'analyse de ce domaine spectral permet d'étudier différentes espèces ou constituants de l'atmosphère martienne telles que l'ozone, les poussières ainsi que les nuages de glace. Dans le cadre de ce travail, nous avons développé une méthode capable d'inverser les spectres SPICAM/UV en visée nadir afin de restituer simultanément les quantités intégrées de ces différentes espèces, à savoir la colonne totale d'ozone ainsi que l'opacité intégrée des poussières et des nuages. Cette méthode est basée sur un code de transfert radiatif, permettant de tenir compte de la diffusion de la lumière par les particules en suspension dans l'atmosphère martienne. La réflectivité de la surface martienne est également étudiée et restituée pour les cas où aucun nuage n'est présent dans les scènes observées, les nuages réduisant la sensibilité en l'albédo de surface. Pour ce faire, un algorithme de détection des nuages a été développé et ses résultats ont été comparés avec les résultats obtenus par d'autres méthodes et instruments afin de le valider.Notre méthode d'inversion a été utilisée pour analyser les données recueillies par SPICAM/UV pendant plus de 4 années martiennes, permettant d'obtenir une climatologie des différentes espèces étudiées: des distributions spatiales et saisonnières de la colonne d'ozone, de l'opacité des poussières et nuages de glace ainsi que de l'albédo de surface sont présentées dans ce travail. Ces distributions sont discutées et comparées à celles obtenues dans des travaux antérieurs à l'aide d'autres instruments.Ce travail constitue également une préparation en vue de l'analyse des données de l'instrument NOMAD/UVIS, supervisé par l'IASB-BIRA, et qui sera lancé à bord de la sonde ExoMars Trace Gas Orbiter en direction de Mars au début de l'année 2016. L'algorithme développé dans ce travail a notamment été utilisé pour l'estimation de performances de NOMAD/UVIS telles que les limites de détection de certains gaz (O3, SO2 et NH3) ou encore les valeurs du rapport de signal-sur-bruit. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Le modèle de climat global martien (GCM) du Laboratoire de Météorologie Dynamique est appliqué à l'étude du cycle de l'eau de la planète rouge. Les observations disponibles sont comparées aux simulations pour comprendre les phénomènes physiques influençant le cycle, en se focalisant sur les nuages et la vapeur d'eau. De nouvelles inversions de données de vapeur d'eau sont présentées, pour compléter notre connaissance du cycle et de sa variabilité interannuelle. De telles intercomparaisons ont des limites qu'il faut mettre en évidence pour mieux les surmonter. Les observations contraignent l'épaisseur et l'étendue des nuages ainsi que leur chronologie saisonnière. Pour améliorer la représentation du cycle de l'eau, la piste de la simulation à haute résolution est explorée, avec des simulations de un degré en résolution horizontale. Des phénomènes nouveaux émergent, comme des tempêtes en spirale. Des changements visibles affectent le cycle de l'eau, avec des transitions ondulatoires, des instabilités renforcées, une modification du dépôt de givre et une meilleure représentation du cycle de condensation et sublimation. La circulation est intensifiée, tout comme la variabilité du cycle, et l'on découvre une atmosphère plus humide, nuageuse et changeante. Suite aux découvertes de la haute résolution, on cherche à mieux représenter la couverture nuageuse dans le modèle à résolution standard. La nouvelle paramétrisation de la couverture nuageuse partielle sous maille est décrite et ses conséquences sur le cycle de l'eau analysées. Elle est prometteuse pour améliorer le réalisme du modèle mais semble déstabiliser le cycle. / The global climate model (GCM) of the Laboratoire de Météorologie Dynamique is used to study the Martian water cycle. Available observations are compared to simulations to unravel the physical phenomena affecting the cycle, with a focus on clouds and water vapor. New inversions of water vapor observations are described and analyzed, to further our understanding of the cycle and of its interannual variability. Such comparisons are limited by bias that have to be studied. Observations constrain the timing, thickness and cover of the clouds. To improve the water cycle simulation and understanding, new high-resolution simulations with an horizontal resolution of one degree are shown. New phenomena appear, like spiral storms. The water cycle undergoes visible changes, with wave transitions, strengthened instabilities, shifts in frost deposition and a better simulation of the condensation and sublimation seasonal processes. The circulation is strengthened, as is variability. The atmosphere is wetter, more cloudy and more variable. Following the details discovered in the high-resolution simulations, we try to improve the representation of cloud cover in the standard resolution simulations. The subsequent new subgrid-scale parametrization of partial cloudiness is described, and its consequences on the water cycle are analyzed. Results are promising as the model agrees more with observations in some ways, but the parametrization causes further instability.

Today, there are only a limited number of surveys of the sky at 1 to 20 GHz. These frequencies lie below the all-sky surveys of WMAP and Planck, but are critical in constraining the spectral slope of Galactic synchrotron emission. Knowledge of the large-scale spectral morphology of Galactic synchrotron emission is critical in the understanding of the interstellar medium and the weak signal from the polarised cosmic microwave background. Recently, ground based observations from S-PASS, C-BASS and the QUIJOTE Multifrequency Instrument (MFI) have been populating these missing frequencies. This thesis presents the first QUIJOTE MFI maps of the Northern sky in total intensity at 11, 13, 17 and 19 GHz, and the first single-dish mapping observations of Lynds dark cloud, LDN1622 at 5 and 13.7GHz. The observations from both instruments are used to probe the nature of spinning dust emission on degree and arcminute scales within the Galaxy. A full data reduction and calibration pipeline for QUIJOTE MFI time-ordered-data is described. The absolute flux density scale uncertainty of the MFI data is between 2 and 3 per cent. The pipeline characterises key properties of the MFI, such as the RFI sources, beams, bandpasses, 1/f noise and more. A key part of the pipeline was the development of an MPI ready Destriping map-maker and a maximum-likelihood map-maker. The map-making code can be applied to a range of different single-dish instruments and is used to reduce both the QUIJOTE MFI wide-survey maps of the Northern sky, and the GBT arcminute resolution raster observations of LDN 1622. A detailed discussion is given on the simulations used to test the integrity of the map-making implementation. Parametric model fitting to the SEDs of four spinning dust emission regions is performed. The MFI wide-survey maps are used in conjunction with existing multifrequency 1degree survey data. The addition of MFI maps is used to confirm the previously tentative spinning dust emission source LDN 1582/84. The mean peak frequency of spinning dust emission over the four spinning dust sources is found to be ⟨νsp⟩ = 27.2 +/- 0.7 GHz, and the mean ratio of the peak spinning dust brightness over the dust optical depth is ⟨Asp/τ250⟩ = 1.24 +/- 0.18 × 104 Jy/τ250. Spectral index maps are derived from the MFI wide-survey data in combination with 408 MHz and WMAP 23 GHz data. These maps are used to further quantify the ubiquity of spinning dust emission throughout the Galaxy. The results show that the median flux density spectral index within the inner Galactic disk for |b| < 2° is 0.24 +/- 0.07. This implies that at 23 GHz, spinning dust emission contributes 25 +/- 5 per cent of the total integrated emission within the inner disk of the Galaxy.

Afin de mieux comprendre les processus et les interactions entre l'atmosphère, la glace de mer et l'océan en arctique, un financement EQUIPEX a permis de développer et déployer le projet IAOOS (Ice-Atmosphere-Ocean-Observing-System) de réseau de bouées multi-instrumentées. Pour la partie atmosphère un LiDAR rétrodiffusion innovant a été développé pour répondre aux contraintes du projet et de l'environnement arctique. Un modèle analytique du rapport signal sur bruit en air clair a permis de préciser les paramètres clés de la conception. Des simulations numériques ont ensuite permis d'affiner les performances du système. Un prototype évolutif a été réalisé dans le planning serré de cet EQUIPEX, avant la mise en œuvre d'une première bouée complète au Pôle Nord en avril 2014, qui a fonctionné jusqu'en décembre 2014. Un second déploiement de deux bouées a ensuite été réalisé à l'occasion de la campagne N-ICE de janvier à juin 2015, dont l'une était équipée d'une version polarisée du LiDAR. Les deux campagnes ont permis d'obtenir des premières statistiques de la distribution des aérosols et des nuages en arctique central avec un système LiDAR autonome. Les premiers résultats montrent la présence de couches d'aérosols assez fréquentes au printemps dans la moyenne troposphère et des nuages bas très fréquents. Les mesures LiDAR ont été utilisées pour effectuer une estimation des flux infrarouge et visible descendants. Les résultats des deux premiers déploiements et les comparaisons avec des analyses et des sorties du modèle WRF fournissent des premiers éléments sur l'apport que pourra présenter ce réseau de bouées multi-instrumentées en région centrale arctique. / To improve our knowledge of the processes and interactions which occur in Arctic between atmosphere, sea ice and ocean, an EQUIPEX funding was granted to the IAOOS project. This improvement will be reached by deploying a network of multi-instrumented buoys. For the atmospheric analyses an innovative backscattering LiDAR meeting with constraints of the project and arctic environment has been developed. An analytical model of signal to noise ratio in clear sky led to the instrumental key parameters, and numerical simulations helped in improving the system performances. An evolutive prototype has been realized within the tight planning of this EQUIPEX. The first whole equiped buoy was deployed close to the north pole in April 2014 and worked until the beginning of December 2014. A second deployment of two buoys, including a polarized version, was then realized within the N-ICE campaign from January to June 2015. These first campaigns gave first statistics of aerosols and clouds distribution in the central arctic region with an autonomous LiDAR. First results show frequent aerosols layers in mid-troposphere during spring, as well as a high occurence of very low clouds. LiDAR measurements were also used to estimate downwelling longwave and shortwave at surface. Results obtained from these first deployments and comparisons with analysis and outputs from the WRF model show a first overview of what can be expected from this network of multi-instrumented buoys in the central arctic region.

La région arctique est particulièrement sensible au changement climatique. Aux latitudes polaires, les nuages arctiques ont un effet important sur le bilan radiatif à la surface. La première partie de ce travail est constitué de l’intercomparaison instrumentale au sol à la station PUY en Mai 2013. Les mesures ont montré une bonne corrélation entre les diamètres effectifs et les distributions en taille des gouttelettes d’eau obtenus par les instruments, mais avec des biais systématiques sur les concentrations. Ces biais ont été reliés à l’estimation du volume d’échantillonnage et nous avons donc proposé une méthode consistant à normaliser les données par rapport à un instrument qui réalise des mesures intégrées. D’autre part, le FSSP et le FM ont fait l’objet d’expériences visant à évaluer l’influence de l’angle de déviation par rapport au vent extérieur et de la vitesse du vent. La seconde partie de ce travail a pour objet la campagne de mesure qui s’est déroulée à la station du Mont-Zeppelin, Ny-Alesund, Svalbard, de Mars à Mai 2012 dans le cadre du projet CLIMSLIP. Une comparaison a été effectuée entre un cas « pollué », avec des masses d’air provenant d’Asie de l’Est et d’Europe, et un cas « propre », dont les sources d’aérosols sont majoritairement locales et ne dépassent pas l’Europe du Nord. Les résultats ont montré que le cas pollué possède des concentrations en BC, aérosols et gouttes plus élevées, un mode accumulation plus important, un diamètre de gouttes plus faible et une fraction d’activation plus élevée. Enfin, le premier et le second effet indirect des aérosols ont pu être quantifiés. / 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.

The Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg2 (distributed over similar to 2400 square degrees at similar to 20% filling factor) to similar to 24th. mag in ugriz. The primary goals of SMASH are to identify low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds, and to derive spatially resolved star formation histories. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, the PHOTRED automated point-spread-function photometry pipeline, and custom calibration software. The astrometric precision is similar to 15 mas and the accuracy is similar to 2 mas with respect to the Gaia reference frame. The photometric precision is similar to 0.5%-0.7% in griz and similar to 1% in u with a calibration accuracy of similar to 1.3% in all bands. The median 5s point source depths in ugriz are 23.9, 24.8, 24.5, 24.2, and 23.5 mag. The SMASH data have already been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and extended stellar populations around the LMC out to R. similar to. 18.4 kpc. SMASH DR1 contains measurements of similar to 100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access and exploration tools.