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1
Füchsel, Sascha. "Trockene Desagglomeration von Nanopartikelflocken in einer Gegenstrahlmühle mit kombinierter Onlineüberwachung." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-112090.
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Mit Untersuchungen auf dem Gebiet der trockenen Desagglomeration konnte nachgewiesen werden, dass mit Strahlmühlen unter bestimmten technischen Voraussetzungen Materialagglomerate aus der Produktklasse Nanopartikelfocken auf Partikelgrößen kleiner 1 µm bei maximal möglicher Beladung stabil desagglomerierbar sind. Dabei zeigt sich vor allem, dass mit sinkender spezifischer Oberfläche des Ausgangsmaterials eine höhere Dispersität bei vergleichbarem Input an Desagglomerationsenergie möglich ist. Voraussetzung hierfür ist die speziell auf die Desagglomerationsaufgabe angepasste Versuchsanlage. Mit der zur Bestimmung der Dispersität entwickelten Online-Messstrecke sind Partikelgrößen von 10 nm bis hin zu ca. 42 µm in einem Körnungsband erfassbar. Mit den gegebenen Möglichkeiten der Prozessanalyse zu wesentlichen Einflussparametern wird eine Überwachung der Prozessstabilität ermöglicht. Die Variation der Transportstrecke bei den verschiedenen Produktaerosolen mit maximaler Dispersität zeigt, dass technisch sinnvolle und kurze Wege bis 1 m die Einleitung stabiler Aerosole hoher Dispersität bis in den Bereich der Materialaggregate bei 100 nm bis 200 nm in einen Folgeprozess (z.B. Coating) ermöglichen.
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Gallavardin, Stéphane. "Analysis concepts of aerosols by on-line aerosol mass spectrometry." [S.l.] : [s.n.], 2006. http://mediatum2.ub.tum.de/doc/603768/document.pdf.
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Alfarra, Mohammedrami. "Insights into atmospheric organic aerosols using an aerosol mass spectrometer." Thesis, University of Manchester, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577471.
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Natali, Luciene. "Utilização dos produtos obtidos por sensoriamento remoto na caracterização da qualidade do ar na Região Metropolitana de São Paulo." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-07122008-151154/.
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O objetivo desse trabalho foi estudar a relação entre profundidade óptica de aerossóis (AOD), obtida por sensoriamento remoto, e a concentração de material particulado (MP10 e MP2,5) medida próximo à superfície sobre a Região Metropolitana de São Paulo (RMSP). A profundidade óptica foi derivada a partir de medidas de radiâncias fornecidas pelos sensores MODIS. Estes sensores estão posicionados a bordo dos satélites EOS-TERRA e EOS-AQUA, operados pela NASA. As concentrações de MP10 e MP2,5 foram obtidas nas estações da rede operacional da CETESB. Foram feitos alguns estudos de caso considerando diferentes situações atmosféricas, aos quais se aplicou a metodologia proposta por Castanho (2005) que busca reduzir as incertezas na determinação da profundidade óptica derivada do MODIS e identificar qual o modelo de aerossol é mais adequado para aplicação em estudos de qualidade do ar. Os valores de AOD calculados para as diferentes situações foram comparados com aqueles obtidos pela AERONET e com as concentrações anteriormente citadas, buscando uma validação dos mesmos. Valores médios de AOD foram calculados para áreas de 10 km x 10 km ao redor das estações de monitoramento do MP. Testes foram realizados para verificar os efeitos de sazonalidade, da quantidade de água na coluna atmosférica, da resposta da AOD por faixas de concentração de MP10, da geometria do sensor, da presença de nuvens e da presença de aerossol acima da Camada de Mistura (CM). Os resultados foram apresentados por estações com o objetivo de se visualizar diferentes condições sobre a região estudada. Alguns dos fatores relevantes observados durante a comparação entre a concentração de MP10 e a AOD foram: a influência do período do ano e da quantidade de água na coluna atmosférica. A geometria do sensor foi fator determinante para melhora das correlações, quando limitado o ângulo de espalhamento em 140°. Situações em que há ausência de nuvens, identificadas através de imagens do MODIS no visível, também apresentaram melhores resultados. Outro fator de extrema importância foi a estrutura vertical da CM. Através de medidas obtidas de um LIDAR foi verificado que a presença de aerossóis acima da CM, a qual é determinada principalmente pelas condições atmosféricas, é determinante para as correlações entre AOD e o MP.<br>The main purpose of this work was to study the relationship between the Aerosol Optical Depth (AOD), obtained by remote sensing, and the particulate material concentration (PM10 and PM2.5), near to the surface over the Metropolitan Area of Sao Paulo (MASP). The Aerosol Optical Depth was retrieved based on reflectance measurements provided by MODIS sensors. These sensors are carried aboard EOS-TERRA and EOS-AQUA satellites, which are operated by NASA. The PM10 and PM2.5 concentrations were obtained in the CETESB operational network. Case studies were performed, considering several atmospheric conditions, applying the methodology proposed by CASTANHO (2005), designed both to reduce the uncertainty in the determination of the MODIS derived Optical Depth and to identify which aerosol model is more appropriated for air quality studies. Some derived results were compared with AERONET data and with the previously mentioned concentrations as a cross-check test. Mean AOD values were calculated using 10 km x 10 km area ground around PM monitoring stations. Tests were performed to estimate the effects of seasonality, atmospheric column water content, AOD response to PM10 concentration, sensor geometry, clouds and aerosol concentration above the Mixing Layer (ML). To stress the different conditions of the studied region, the results were presented considering each station. Some of the relevant observed factors in the PM10 concentration and AOD comparison were the year period influence and the atmospheric column water content. The sensor geometry was an important factor to the improvement of the obtained correlations when the scattering angle was bounded to 140°. Cloudless situations, identified by MODIS true color images, also improved the results. Another important factor was the Mixing Layer vertical structure. Using LIDAR measurements it was verified that the presence of aerosols above the ML, which is determined mainly by atmospheric conditions, is crucial for the correlations between AOD and PM.
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Odum, Jay Russell Seinfeld John H. Seinfeld John H. "Secondary organic aerosol formation and gas/aerosol partitioning /." Diss., Pasadena, Calif. : California Institute of Technology, 1998. http://resolver.caltech.edu/CaltechETD:etd-01252008-155400.
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Duong, Hanh To. "Studies of Organic Aerosol and Aerosol-Cloud Interactions." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/311585.
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Atmospheric aerosols can influence society and the environment in many ways including altering the planet's energy budget, the hydrologic cycle, and public health. However, the Fourth Assessment Report of the Intergovernmental Panel on Climate Change indicates that the anthropogenic radiative forcing associated with aerosol effects on clouds has the highest uncertainty in the future climate predictions. This thesis focuses on the nature of the organic fraction of ambient particles and how particles interact with clouds using a combination of tools including aircraft and ground measurements, models, and satellite data. Fine aerosol particles typically contain between 20 - 90% organic matter by mass and a major component of this fraction includes water soluble organic carbon (WSOC). Consequently, water-soluble organic species can strongly influence aerosol water-uptake and optical properties. However, the chemical composition of this fraction is not well-understood. PILS-TOC was used to characterize WSOC in ambient aerosol in Los Angeles, California. The spatial distribution of WSOC was found to be influenced by (i) a wide range of aerosol sources within this urban metropolitan area, (ii) transport of pollutants by the characteristic daytime sea breeze trajectory, (iii) topography, and (iv) secondary production during transport. Meteorology is linked with the strength of many of these various processes. Many methods and instruments have been used to study aerosol-cloud interactions. Each observational platform is characterized by different temporal/spatial resolutions and operational principles, and thus there are disagreements between different studies for the magnitude of mathematical constructs used to represent the strength of aerosol-cloud interactions. This work points to the sensitivity of the magnitude of aerosol-cloud interactions to cloud lifetime and spatial resolution of measurements and model simulations. Failure to account for above-cloud aerosol layers and wet scavenging are also shown to cause biases in the magnitude of aerosol-cloud interaction metrics. Air mass source origin and meteorology are also shown to be important factors that influence aerosol-cloud interactions. The results from this work contribute towards a better understanding of atmospheric aerosols and are meant to improve parameterizations that can be embedded in models that treat aerosol affects on clouds, precipitation, air quality, and public health.
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Palaniswaamy, Geethpriya. "DSMC multicomponent aerosol dynamics sampling algorithms and aerosol processes /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4737.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Dec. 12, 2007). Vita. Includes bibliographical references.
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Li, Xihao. "Characterization of Perphenazine and Scopolamine Aerosols Generated Using the Capillary Aerosol Generator." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/901.
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The characterization of perphenazine and scopolamine aerosols generated using the capillary aerosol generator (CAG) was reported. Variables including steady state power, the formulation vehicle, the drug concentration and the formulation flow rate were studied for their effects on the chemical stability and particle size of these drug aerosols.Stability-indicating HPLC and LC-MS assays were developed and validated for perphenazine and scopolamine, respectively. The chemical stability of each compound was investigated under a variety of stress conditions and the structure of degradation products was proposed.Perphenazine aerosols were generated from propylene glycol (PG) formulations with concentrations of 9, 48 and 90mM at formulation flow rates of 2.5 and 5.0µL/s at a series of steady state powers. At higher aerosolization powers, the low concentration formulation (9mM) degraded with dehalogenation being the major pathway. The size of perphenazine aerosols was between 0.4 to 0.6µm. Changing the solute concentration produced only small changes (~0.2µm) in perphenazine aerosol particle size. The formulation flow rate did not significantly affect the aerosol size.Scopolamine degraded significantly when aerosolized in PG formulations. It was possible to generate chemically stable scopolamine aerosols from ethanol formulations. Significant amounts of degradation products were formed only at or above 4.6W at 5.0µL/s. Hydrolysis and dehydration appeared to be the major degradation pathways at higher powers and low formulation flow rate. The MMAD of scopolamine aerosols was between 0.5 and 2.0µm from 8, 20 and 40mM formulations at 5.0 and 10.0µL/s. The size of scopolamine aerosols increased as a function of increasing the solute concentration. Increasing the formulation flow rate increased the linear velocity of the spray, thus the Reynolds number was increased and smaller particles were generated.
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Adikesavalu, Ravichandran. "Preliminary modeling of in-duct desulfurization using condensation aerosols." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177616476.
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DeCarlo, Peter F. "Improving submicron aerosol measurements with real-time aerosol mass spectrometry." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3284467.
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Ridley, David A. "Aerosol Radiative Properties Analysed using Global Models of Aerosol Microphysics." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494262.
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Pringle, Kirsty Jane. "Aerosol - cloud interactions in a global model of aerosol microphysics." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431991.
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Wang, Shuo. "Retrieval of Aerosol Chemical Composition based on aerosol optical properties." Thesis, Littoral, 2020. https://tel.archives-ouvertes.fr/tel-03178823.
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La composition chimique des aérosols permet de mieux comprendre leurs interactions avec le changement climatique et la santé humaine. La composition chimique des aérosols est étroitement liée aux propriétés optiques. Actuellement, les propriétés optiques des aérosols sont mesurées, intégrées ou non sur la colonne atmosphérique, à une échelle globale. Le développement d'algorithmes permettant de déterminer, à une résolution spatiale et temporelle élevée, la composition chimique des aérosols à partir de leurs propriétés optiques est essentiel. Ce travail de thèse vise à tester et à améliorer les méthodes actuelles de classification et d'estimation de la composition chimique des aérosols. (1) Méthodes basées sur le coefficient d'Ǻngström (AE) : ces méthodes s'appuient sur la dépendance spectrale du coefficient de diffusion (SAE) et d'absorption (AAE). En effet, de nombreuses recherches distinguent les différents types d'aérosols en fonction de leur SAE et AAE. Afin de déterminer des valeurs seuils des SAE et AAE pour différents aérosols absorbants, la dépendance spectrale du SAE et AAR en fonction de la taille des particules, l'épaisseur relative d'une éventuelle couche surfacique et les longueurs d'ondes choisies pour le calcul. Les résultats montrent que SAE et AAE dépendent fortement des longueurs d'onde utilisées et sont également fortement affectés par la taille de l'aérosol. Les différents types de particules peuvent exister dans l'atmosphère dans les mêmes classes de taille et dans ce cas, SAE et AAE ne peuvent pas être utilisés pour distinguer efficacement ces différents composants.(2) Méthodes basées sur k : le but de ces méthodes est d'estimer la concentration massique des différents composants de l'aérosol à partir de la paie imaginaire de l'indice de réfraction (CRI, m=n + k i). A partir des indices de réfraction et de la variation spectrale de l'albédo à diffusion unique (dSSA), reportés par le réseau AERONET, la variation de la composition chimique des aérosols intégrée sur la colonne a été estimée puis comparée à la distribution saisonnière des émissions d'aérosols couplée au transport régional pendant différentes saisons. Cette comparaison montre des résultats très encourageants même si les compositions chimiques sont sensiblement différentes (intégrées sur la colonne et estimée en surface). La validation de cette méthode nécessite donc de disposer de jeux de mesures de la composition chimique plus comparables.(3) Méthode de k-p : afin de faciliter la distinction entre les poussières minérales (MD) et le carbone organique (OC), une nouvelle méthode basée sur la partie imaginaire du CRI (k) et de la densité des aérosols (p) a été développée. L'application de cet algorithme sur des données (propriétés optiques et physiques) recueillies lors d'une campagne d'observation à Shouxian permet d'obtenir la variation de la composition chimique des aérosols en temps réel. La composition chimique de l'aérosol estimé par cette méthode est cohérente avec les résultats des mesures in-situ. La concentration massique des MD est la moins bien estimée par cet algorithme (R²=0.43) probablement dur à une plus grande incertitude dans la mesure<br>Aerosol chemical composition is an essential factor to better understand aerosol interactions with climate change, atmospheric environment and human health. Aerosol optical property is closely associated to chemical composition. Nowadays, vertical and global aerosol optical properties are measured. Development of aerosol chemical composition retrieval algorithm based on optical properties is essential to derive aerosol chemical composition with high spatial and temporal resolution. This thesis aims to test and improve the present methods for aerosol chemical composition classification and retrieval. (1) Ǻngström Exponent (AE) methods : these methods are based on Scattering (SAE) ans Absorption (AAE) AE to derive absorption coefficients by different aerosols or distinguish aerosol types, but many studies used different SAE and AAE values or thresholds. To understand these discrepancies, SAE and AAE dependencies to particle size, relative coating thickness and wavelength pairs were studied for different absorbing aerosols. The results reveal that SAE and AAE depend on wavelength pairs used for calculations and are also greatly influenced by aerosol size, thus knowledge of aerosol size information could reduce the uncertainty of calculating absorption coefficients by different aerosols using AAE. As aerosol particles could exist within the same size bin, SAE and AAE cannot be used to distinguish different compositions effectively by setting thresholds.(2)k-based methods : these methods aim to retrieve the mass concentrations of different aerosol compounds based on the imaginary part of Complex Refractive Index (CRI, m=n + k i). For the application and examination of the k-based methods, columnar aerosol chemical compositions were retrieved based on CRI and spectral variation of Single Scattering Albedo (dSSA) using long-term AERONET measurements. Dependence of retrieved columnar aerosol chemical compositions on regional transported was investigated in different seasons. This result is comparable to seasonal aerosol emission distribution and transport process. But the reliable aerosol chemical composition at the same level is still needed to verify algorithm. (3) k-p method : to tackle the difficulty to distinguish Organic Carbon (OC), from Mineral Dust (MD), a new method based on CRI imaginary part (k) and aerosol density (p) was developed. This algorithm was used to obtain the real-time aerosol chemical composition varation during an observation campaign in Shouxian. The retrieved aerosol chemical compositions were consistent with in-situ measurements.The weaker agreement (R²=0.43) of MD compared to the other species is due to the larger uncertainties from retrievals and measurements
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Wurl, Daniela. "Optimal Estimation Retrieval of Aerosol Microphysical Properties in the Lower Stratosphere from SAGE II Satellite Observations." Thesis, University of Canterbury. Physics and Astronomy, 2007. http://hdl.handle.net/10092/1533.
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A new retrieval algorithm has been developed based on the Optimal Estimation (OE) approach, which retrieves lognormal aerosol size distribution parameters from multiwavelength aerosol extinction data, as measured by the Stratospheric Aerosol and Gas Experiment (SAGE) II in the lower stratosphere. Retrieving these aerosol properties becomes increasingly more difficult under aerosol background conditions, when tiny particles (« 0.1 µm) prevail, to which the experiment is nearly or entirely insensitive. A successful retrieval algorithm must then be able (a) to fill the 'blind spot' with suitable information about the practically invisible particles, and (b) to identify 'the best' of many possible solutions. The OE approach differs from other previously used aerosol retrieval techniques by taking a statistical approach to the multiple solution problem, in which the entire range of possible solutions are considered (including the smallest particles) and characterized by probability density functions. The three main parts of this thesis are (1) the development of the new OE retrieval algorithm, (2) the validation of this algorithm on the basis of synthetic extinction data, and (3) application of the new algorithm to SAGE II measurements of stratospheric background aerosol. The validation results indicate that the new method is able to retrieve the particle size of typical background aerosols reasonably well, and that the retrieved uncertainties are a good estimate of the true errors. The derived surface area densities (A), and volume densities (V ) tend to be closer to the correct solutions than the directly retrieved number density (N), median radius (R), and lognormal distribution width (S). Aerosol properties as retrieved from SAGE II measurements (recorded in 1999) are observed to be close to correlative in situ data. In many cases the OE and in situ data agree within the (OE and/or the in situ ) uncertainties. The retrieved error estimates are of the order of 69% (σN), 33% (σR), 14% (σS), 23% (σA), 12% (σV), and 13% (σReff ). The OE number densities are generally larger, and the OE median particle sizes are generally smaller than those N and R retrieved by Bingen et al. (2004a), who suggest that their results underestimate (N) or overestimate (R) correlative in situ data due to the 'small particle problem'. The OE surface area estimates are generally closer to correlative in situ profiles (courtesy of T. Deshler, University of Wyoming), and larger than Principal Component Analysis (PCA) retrieval solutions of A (courtesy of L. W. Thomason, NASA LaRC) that have been observed to underestimate correlative in situ data by 40-50%. These observations suggest that the new OE retrieval algorithm is a successful approach to the aerosol retrieval problem, which is able to add to the current knowledge by improving current estimates of aerosol properties in the lower stratosphere under low aerosol loading conditions.
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Bones, David Lawrence. "Liquid Aerosol Photochemistry." Thesis, University of Canterbury. Chemistry, 2008. http://hdl.handle.net/10092/1500.
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Aerosols of nitrate solutions were irradiated in the presence of radical scavengers in an attempt to measure the yield of hydroxyl radical in both the aqueous phase and the gas phase. Carbon monoxide, benzoic acid, benzene and cyclohexane were used as scavengers to trap hydroxyl radical. The products from the reaction of these scavengers with hydroxyl radical were analysed with High Performance Liquid Chromatography and mass spectrometry. The radiant flux in the chamber was measured via ferrioxalate actinometry, both with bulk liquid and aerosol droplets. Many quantitative results were obtained but several anomalies were found. This suggests that Mie theory is not capable of predicting rates of photochemical reactions within droplets.
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Lohmann, Ulrike, Leon Rotstayn, Trude Storelvmo, et al. "Total aerosol effect." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186027.
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Uncertainties in aerosol radiative forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of precipitation
formation. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to
define properly. Here we argue that fast feedbacks should be included because they act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations
(RFP), that takes these fast feedbacks and interactions into account. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models.
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Quaas, Johannes, Yi Ming, Surabi Menon, et al. "Aerosol indirect effects." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186329.
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Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs)
is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (tau a) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. cloud droplet number concentration (N d) compares relatively well to the satellite data at least over the ocean. The relationship between (tau a) and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and tau a as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld–tau a relationship, our results indicate that none can be identified as a unique explanation. Relationships similar
to the ones found in satellite data between tau a and cloud top
temperature or outgoing long-wave radiation (OLR) are simulated
by only a few GCMs. The GCMs that simulate a negative OLR - tau a relationship show a strong positive correlation between tau a and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of tau a, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good
predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5Wm−2. In an alternative approach, the radiative flux perturbation due to anthropogenic
aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clearand cloudy-sky forcings with estimates of anthropogenic tau a
and satellite-retrieved Nd–tau a regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5Wm−2, with a total estimate of −1.2±0.4Wm−2.
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Quaas, Johannes, Yi Ming, Surabi Menon, et al. "Aerosol indirect effects." Atmospheric chemistry and physics (2009) 9, S. 8697-8717, 2009. https://ul.qucosa.de/id/qucosa%3A13849.
Full textAbstract:
Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs)
is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (tau a) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. cloud droplet number concentration (N d) compares relatively well to the satellite data at least over the ocean. The relationship between (tau a) and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and tau a as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld–tau a relationship, our results indicate that none can be identified as a unique explanation. Relationships similar
to the ones found in satellite data between tau a and cloud top
temperature or outgoing long-wave radiation (OLR) are simulated
by only a few GCMs. The GCMs that simulate a negative OLR - tau a relationship show a strong positive correlation between tau a and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of tau a, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good
predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5Wm−2. In an alternative approach, the radiative flux perturbation due to anthropogenic
aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clearand cloudy-sky forcings with estimates of anthropogenic tau a
and satellite-retrieved Nd–tau a regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5Wm−2, with a total estimate of −1.2±0.4Wm−2.
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Grythe, Henrik. "Quantification of sources and removal mechanisms of atmospheric aerosol particles." Doctoral thesis, Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-138903.
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The focus of this work has been to quantify important processes for climatically relevant aerosols, and to improve our understanding of, and ability to accurately model, aerosols in the atmosphere on a large scale. This thesis contains five papers focused on different parts of the life cycle of atmospheric aerosol particles. Two papers describe the physical process of emission of primary marine aerosols. The large uncertainties in these processes are demonstrated by examining the diversity of existing parameterizations for emissions. Building from laboratory experiments to validation of model results with observations, new parameterizations are suggested. These take into account also effects of water temperature on primary marine aerosol production. In the third paper the main focus was to develop a new aerosol wet removal scheme in the Lagrangian transport and dispersion model FLEXPART. Removal timescales and atmospheric concentrations are found to be close to observation based estimates. The final two papers focus on atmospheric black carbon aerosols at high latitudes. As an example of increased human activities in the Arctic, local emissions from cruise ships visiting the research base in Ny Ålesund had demonstrable effects on the level of pollutants measured there. In contrast, inland Antarctic air was shown to be clean compared to the Arctic, due to the extremely long transport time from any major aerosol sources. The work done in this thesis has addressed critical uncertainties regarding the aerosol lifecycle, by better constraining aerosol emissions and atmospheric lifetimes. The development of the new wet removal scheme has improved FLEXPART model accuracy, which will be beneficial in future applications of the model.<br><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>
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Deaconu, Lucia-Timea. "Study on multi-layer "aerosol" situations and of "aerosol-cloud" interactions." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10165.
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Le premier objectif de cette étude est d’analyser la cohérence entre les restitutions d’aérosols au-dessus des nuages (AAC) réalisées à partir de mesures spatiales passive et active. Nous avons considéré la méthode basée sur les mesures polarisées de POLDER, la méthode développée pour le lidar spatial CALIOP et la méthode basée sur le rapport de dépolarisation CALIOP (DRM), pour laquelle nous proposons une version calibrée. Nos analyses régionale et pluriannuelle globale mettent en évidence un bon accord statistique entre les restitutions DRM et POLDER AOT (R2=0,68 - échelle globale), qui donne confiance dans notre capacité à mesurer les propriétés de l'AAC. Des différences se produisent lors du contact entre les couches d'aérosols et de nuages. La méthode opérationnelle de CALIOP sous-estime l’AOT, comparé aux deux autres méthodes. Le second objectif est d'étudier l'impact des aérosols sur les propriétés des nuages et leur forçage radiatif, sur l'océan Atlantique Sud. Nous avons considéré une synergie entre les restitutions CALIOP et POLDER avec des paramètres météorologiques colocalisés. Nous réalisons des calculs de transfert radiatif dans les domaines visible et infrarouge, et analysons l'effet de la charge en aérosol sur les propriétés des nuages et la météorologie. Nous avons trouvé que les aérosols et le contenu en vapeur d’eau pourraient impacter la convection des nuages. Nos résultats montrent que sous de fortes charges de AAC, les nuages deviennent optiquement plus épais, avec une augmentation du contenu en eau liquide de 20 g.m-2 et des altitudes plus basses du sommet du nuage (~200 m); indiquant un potentiel effet semi-direct des aérosols au-dessus des nuages<br>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
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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.
Full textAbstract:
Le premier objectif de cette étude est d’analyser la cohérence entre les restitutions d’aérosols au-dessus des nuages (AAC) réalisées à partir de mesures spatiales passive et active. Nous avons considéré la méthode basée sur les mesures polarisées de POLDER, la méthode développée pour le lidar spatial CALIOP et la méthode basée sur le rapport de dépolarisation CALIOP (DRM), pour laquelle nous proposons une version calibrée. Nos analyses régionale et pluriannuelle globale mettent en évidence un bon accord statistique entre les restitutions DRM et POLDER AOT (R2=0,68 - échelle globale), qui donne confiance dans notre capacité à mesurer les propriétés de l'AAC. Des différences se produisent lors du contact entre les couches d'aérosols et de nuages. La méthode opérationnelle de CALIOP sous-estime l’AOT, comparé aux deux autres méthodes. Le second objectif est d'étudier l'impact des aérosols sur les propriétés des nuages et leur forçage radiatif, sur l'océan Atlantique Sud. Nous avons considéré une synergie entre les restitutions CALIOP et POLDER avec des paramètres météorologiques colocalisés. Nous réalisons des calculs de transfert radiatif dans les domaines visible et infrarouge, et analysons l'effet de la charge en aérosol sur les propriétés des nuages et la météorologie. Nous avons trouvé que les aérosols et le contenu en vapeur d’eau pourraient impacter la convection des nuages. Nos résultats montrent que sous de fortes charges de AAC, les nuages deviennent optiquement plus épais, avec une augmentation du contenu en eau liquide de 20 g.m-2 et des altitudes plus basses du sommet du nuage (~200 m); indiquant un potentiel effet semi-direct des aérosols au-dessus des nuages<br>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
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Posselt, Julia Rebekka. "Influence of giant sea salt aerosols on global precipitation and aerosol indirect effect /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17467.
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Dreyfus, Matthew A. "Laboratory and field measurements of organic aerosols with the photoionization aerosol mass spectrometer." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 166 p, 2008. http://proquest.umi.com/pqdweb?did=1654492141&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Lízal, František. "Experimentální výzkum transportu a depozice aerosolů v dýchacím traktu člověka." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-234006.
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Human health is significantly influenced by inhaled aerosols. Insight to the aerosol transport and deposition mechanisms is a prerequisite for both, toxicological protection against harmful particles and efficient application of inhaled therapeutic aerosols. The purpose of this doctoral thesis was to gain new knowledge of this topic on the basis of in vitro measurements. Phase-Doppler Anemometry was chosen for aerosol transport measurement, for it allows simultaneous measurement of particle size and velocity. Results were processed by means of statistical methods and frequency analysis. Deposition of spherical aerosol particles was measured by Positron Emission Tomography, while deposition of fibrous aerosol was measured by Phase-Contrast Microscopy combined with automated image analysis. All experiments were performed on physical models created on the basis of the real lung geometry. New knowledge of flow characteristics, transition from laminar to turbulent flow, effect of breathing pattern or particle size on aerosol transport and deposition in human lungs are outcomes of this work. Significant effect of the oral cavity was ascertained due to comparison of aerosol deposition in realistic and semi-realistic model with cylindrical smooth walls. Acquired data not merely extended our knowledge of aerosol behavior in lungs but it can also be used for validation of numerical simulations.
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Bulgin, Claire Elizabeth. "Improved understanding of aerosol processes using satellite observations of aerosol optical properties." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4906.
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Atmospheric aerosols are the largest remaining uncertainty in the Earth’s radiative budget and it is important that we improve our knowledge of aerosol processes if we are to understand current radiative forcing and accurately project changes in future climate. Aerosols affect the radiation balance directly through the absorption and scattering of incoming solar radiation and indirectly through the modification of cloud microphysical properties. Understanding aerosol forcing remains challenging due to the short atmospheric residence time of aerosols resulting in large spatial and temporal heterogeneity in aerosol loading and chemical composition. Satellite retrievals are becoming increasingly important to improving our knowledge of aerosol forcing. They provide regular global data at finer spatial and temporal resolution than available through sparse groundbased point measurements or localised aircraft campaigns, but cannot unambiguously determine aerosol speciation, relying heavily on a priori assumptions. In this thesis I use data from two satellite instruments: the Along Track Scanning Radiometer 2 (ATSR-2) and the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) interpreted using the Oxford-RAL Aerosol and Cloud (ORAC) retrieval scheme in three pieces of interrelated work. First I use satellite observations of aerosol optical depth a and cloud particle effective radius re from the ATSR-2 instrument in 1997 to investigate the Twomey indirect effect (IE, -δ ln re /δ ln τa) in regions of continental outflow. I generally find a negative correlation between τa and re with the strongest inverse relationships downwind of Africa. North America and eastern Asian continental outflow exhibits a strong seasonal dependence, as expected. Global values for IE range from 0.10 to 0.16, consistent with theoretical predictions. Downwind of Africa, I find that the IE is unphysically high but robust (r = −0.85) during JJA associated with high aerosol loading, and attribute this tentatively to the Twomey hypothesis accounting only for a limited number of physical properties of aerosols. Second, I test the response of the Oxford-RAL Aerosol and Cloud (ORAC) retrieval algorithm for MSG SEVIRI to changes in the aerosol properties used in the dust aerosol model, using data from the Dust Outflow and Deposition to the Ocean (DODO) flight campaign in August 2006. I find that using the observed DODO free tropospheric aerosol size distribution and refractive index compared with the dust aerosol properties from the Optical Properties of Aerosol and Cloud (OPAC) package, increases simulated top of the atmosphere radiance at 0.55 μm assuming a fixed aerosol optical depth of 0.5, by 10–15%, reaching a maximum difference at low solar zenith angles. This difference is sensitive to changes in AOD, increasing by ~2–4% between AOD of 0.4–0.6. I test the sensitivity of the retrieval to the vertical distribution of the aerosol and find that this is unimportant in determining simulated radiance at 0.55 μm. I also test the ability of the ORAC retrieval when used to produce the GlobAerosol dataset to correctly identify continental aerosol outflow from the African continent and I find that it poorly constrains aerosol speciation. I develop spatially and temporally resolved prior distributions of aerosols to inform the retrieval which incorporates five aerosol models: desert dust, maritime, biomass burning, urban and continental. I use a Saharan Dust Index and the GEOS-Chem chemistry transport model to describe dust and biomass burning aerosol outflow, and compare AOD using my speciation against the GlobAerosol retrieval during January and July 2006. I find AOD discrepancies of 0.2–1 over regions of biomass burning outflow, where AOD from my aerosol speciation and the GlobAerosol speciation can differ by as much as 50 - 70 %. Finally I use satellite observations of aerosol optical depth and cloud fraction from the MSG SEVIRI instrument to investigate the semi-direct effect of Saharan dust aerosol on marine stratocumulus cloud cover over the Atlantic during July 2006. I first use these data to study the spatial autocorrelation of aerosol optical depth and find that it is correlated over a lag of 0.1◦ (approximately 10 km at low latitudes), beyond which it rapidly decorrelates. I find a 15 % higher cloud fraction in regions with high dust loading (AOD > 0.5), compared with scenes with a lower dust loading (AOD < 0.5), which for high dust scenes increases with local static stability. I attribute this tentatively to aerosol solar shielding enhancing longwave cloud top radiative cooling which drives marine stratocumulus convection.
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Schmidt, Anja. "Modelling tropospheric volcanic aerosol : from aerosol microphysical processes to Earth system impacts." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540764.
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Silva, Bianca Lobo. "Estudo do efeito das partículas de aerossol emitidas por queimadas sobre a radiação solar incidente em superfície a partir de medições efetuadas na Reserva Biológica do Jaru." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-14082013-132802/.
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Durante a estação seca, é comum se observar um grande número de queimadas ocorrendo no Brasil. A fumaça proveniente da queima intensa é facilmente vista em imagens de satélite, principalmente na região de Cerrado e na Bacia Amazônica, e é responsável pela injeção de uma grande quantidade de partículas na atmosfera. Essas partículas de aerossol irão interagir diretamente com a radiação solar incidente, pelos processos de absorção e espalhamento, o que afetará a irradiância solar global incidente em superfície, a fração entre componente direto e difuso e a distribuição espectral. A modelagem precisa dessa interação ainda requer investigação científica. Nesse contexto, os resultados apresentados neste trabalho buscaram avaliar o desempenho de modelos ópticos para o aerossol de queimadas propostos por Rosário (2011) para a região da Reserva Biológica do Jaru (ou Rebio Jaru), Rondônia, durante a estação seca de 2007. Os modelos ópticos foram separados em intervalos de albedo simples, resultando em três grupos ou regimes: um mais absorvedor, um moderadamente absorvedor e um mais espalhador. Os dados simulados utilizando o código de transferência radiativa SBDART foram comparados com medidas feitas in situ na Rebio Jaru. Os dados foram obtidos entre os dias 24 de agosto e 31 de outubro de 2007. Foram analisados dados medidos por um Multifilter Rotating Shadowband Radiometer (MFRSR - canais de 670, 870 e 1036 nm e da irradiância solar total), por um sensor PAR (irradiância fotossinteticamente ativa) e dados de um pirânometro (irradiância solar total). A irradiância fotossinteticamente ativa compreende o intervalo entre 400 e 700 nm e corresponde à energia solar utilizada na fotossíntese realizada pelas plantas. Ela foi utilizada para avaliar o desempenho dos modelos propostos por Rosário (2011). Para esse intervalo espectral, o modelo óptico mais espalhador é o que melhor representou o período analisado. Estudos de caso foram feitos para avaliar o comportamento dos demais dados para dias com valores distintos da profundidade óptica do aerossol em 550nm. Os resultados obtidos pela análise das medidas feitas pelo MFRSR divergiram com relação ao do sensor PAR e do Piranômetro. As divergências observadas podem estar associadas à degradação instrumental. Sugere-se que sejam realizados estudos mais detalhados levando em consideração o conteúdo integrado de vapor dágua, entre outras variáveis meteorológicas, com a finalidade de definir um método eficiente para determinar o melhor modelo óptico para o aerossol de queimadas e para diferentes regiões da Bacia Amazônica, como efetuado por Rosário (2011) na região de Alta Floresta.<br>During the dry season biomass burning activities are frequent in Brazil. The smoke from these intense fires can easily be seen with satellite imaging, mostly in the centermost region of Brazil and the Amazon, and it is responsible for the input of large amounts of particles to the atmosphere. These aerosol particles interact directly with the incoming solar radiation, through absorption and scattering processes, which will affect the incoming global solar irradiation reaching the surface, the fraction between the direct and diffuse components and the spectral distribution. The accurate modeling of these interactions requires further scientific investigation. In this context, the present work evaluated the performance of biomass burning aerosol optical models proposed by Rosario (2011) for the southern Amazon, in the Jaru Biological Reserve, Rondônia, during the dry season of 2007. The proposed models were classified according to single scattering albedo intervals, and three distinct groups or regimes were identified: one for more absorbing particles, one for moderately absorbing particles and one for more scattering particles. Simulated data using the Radiative Transfer code SBDART were compared with in situ measurements performed at Rebio Jaru. The data were collected between August 24th and October 31st 2007. Data measured by a Multifilter Shadowband Rotating Radiometer (MFRSR - channels 670, 870 and 1036 nm and the total solar irradiance) from a PAR sensor (photosynthetically active radiation) and from a pyranometer (total solar irradiance) were included in the analysis. Photosynthetically active irradiance spectral interval spans between 400 and 700 nm, and corresponds to the solar energy used on the vegetation photosynthesis. This spectral region was chosen to evaluate the performance of the optical models. For this spectral interval, the more scattering optical model better represented the measured values. Case studies were conducted to evaluate the performance of the radiative transfer code and the optical models on days with distinct values of the aerosol optical depth at 550nm. The results showed that simulations for MFRSR channels diverged from the PAR sensor and the pyranometer. These divergences could be associated to instrumental degradation. It is suggested that further studies be conducted taking into account water vapor content variability, and other meteorological variables, in order to define an efficient method to determine the best optical model for the smoke aerosol and for different regions in the Amazon Basin, as performed by Rosario (2011) for Alta Floresta.
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Harrison, Richard Giles. "Aerosol charging and radioactivity." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321184.
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Grandey, Benjamin Stephen. "Investigating aerosol-cloud interactions." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:8b48c02b-3d43-4b04-ae55-d9885960103d.
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Microphysical and dynamical interactions between aerosols and clouds are associated with some of the largest uncertainties in projections of future climate. Many possible aerosol effects on clouds have been suggested, but large uncertainties remain. In order to improve model projections of future climate, it is essential that we improve our quantitative understanding of anthropogenic aerosol effects. Several studies investigating interactions between satellite-observed aerosol and cloud properties have been published in recent years. However, the observed relationships are not necessarily due to aerosol effects on clouds. They may be due to cloud and precipitation effects on aerosol, meteorological covariation, observational data errors or methodological errors. An analysis of methodological errors arising through climatological spatial gradients is performed. For region sizes larger than 4°×4°, commonly used in the literature, spurious spatial variations in retrieved cloud and aerosol properties are found to introduce widespread significant errors to calculations of aerosol-cloud relationships. Small scale analysis prior to error-weighted aggregation to larger region sizes is recommended. Appropriate ways of quantifying relationships between aerosol optical depth (τ) and cloud properties are considered, and results are presented for three satellite datasets. There is much disagreement in observed relationships between τ and liquid cloud droplet number concentration and between τ and liquid cloud droplet effective radius, particularly over land. However, all three satellite datasets are in agreement about strong positive relationships between τ and cloud top height and between τ and cloud fraction (f_c). Using reanalysis τ data, which are less affected by retrieval artifacts, it is suggested that a large part of the observed f_c-τ signal may be due to cloud contamination of τ. General circulation model simulations further demonstrate that positive f_c-τ relationships may primarily arise due to covariation with relative humidity, and that negative f_c-τ relationships may arise due to scavenging of aerosol by precipitation. A new method of investigating the contribution of meteorological covariation to the observed relationships is introduced. Extratropical cyclone storm-centric composites of retrieved aerosol and cloud properties are investigated. A storm-centric description of the synoptics is found to be capable of explaining spurious f_c-τ relationships, although the spurious relationships explained are considerably smaller than observed relationships.
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Cameron, Lee R. J. "Aerosol explosion hazard quantification." Thesis, Cardiff University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311674.
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Quaas, Johannes. "The aerosol indirect effect." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-189795.
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Global climate change is considered to be one of the most serious concerns of humankind (United Nations, 1992; United Nations, 2002). Anthropogenic greenhouse gases and aerosols impact considerably the energy balance of the Earth system, possibly provoking adverse effects on social, ecological, and economical equilibria. This is one of the main reasons why the understanding of the Earth’s climate system is of major
importance. If better predictions of the response of the climate system to anthropogenic perturbations were available, political decisions against negative impacts could be taken, and social adaptations to changed climate conditions would be possible.
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Gryspeerdt, Edward. "Aerosol-cloud-precipitation interactions." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:3d1210b0-2ada-403c-8fdf-2bef1724fcd8.
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Aerosols are thought to have a large effect on the climate, especially through their interactions with clouds. The magnitude and in some cases the sign of aerosol effects on cloud and precipitation are highly uncertain. Part of the uncertainty comes from the multiple competing effects that aerosols have been proposed to have on cloud properties. In addition, covariation of clouds and aerosol properties with changing meteorological conditions has the ability to generate spurious correlations between cloud and aerosol properties. This work presents a new way to investigate aerosol-cloud-precipitation interactions while accounting for the influence of meteorology on cloud and aerosol. The clouds are separated into cloud regimes, which have similar retrieved cloud properties, to investigate the regime dependence of aerosol-cloud-precipitation interactions. The strong aerosol optical depth (AOD)- cloud fraction (CF) correlation is shown to have the ability to generate spurious correlations. The AOD-CF correlation is accounted for by investigating the frequency of transitions between cloud regimes in different aerosol environments. This time-dependent analysis is also extended to investigate the development of precipitation from each of the regimes as a function of their aerosol environment. A modification of the regime transition frequencies consistent with an increase in stratocumulus persistence over ocean is found with increasing AI (aerosol index). Increases in transitions into the deep convective regime and in the precipitation rate consistent with an aerosol invigoration effect are also found over land. Comparisons to model output suggest that a large fraction of the observed effect on the stratocumulus persistence may be due to aerosol indirect effects. The model is not able to reproduce the observed effects on convective cloud, most likely due to the lack of parametrised effects of aerosol on convection. The magnitude of these effects is considerably smaller than correlations found by previous studies, emphasising the importance of meteorological covariation on observed aerosol-cloud-precipitation interactions.
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Huang, David Da-Teh. "Aerosol coagulation and nucleation." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06222005-162441.
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Sodeman, David Alan. "Characterization of ambient, automobile, and diesel aerosols utilizing aerosol time of flight mass spectrometry /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3144344.
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Mills, Jessica Breyan. "Evaluation of the DiSCmini personal aerosol monitor for submicrometer sodium chloride and metal aerosols." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/2584.
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This work evaluated the robust, lightweight DiSCmini (DM) aerosol monitor for its ability to measure the concentration and mean diameter of submicrometer aerosols. Tests were conducted with monodispersed and polydispersed aerosols composed of two particle types (sodium chloride, NaCl, and spark generated metal particles, which simulate particles found in welding fume) at three different steady-state concentration ranges (Low, <103; Medium, 103-104; and High, >104 particles/cm3). Particle number concentration, lung deposited surface area (LDSA) concentration, and mean size measured with the DM were compared to those measured with reference instruments, a scanning mobility particle sizer (SMPS) and a handheld condensation particle counter (CPC). Particle number concentrations measured with the DM were within 16% of those measured by the CPC for polydispersed aerosols. Poorer agreement was observed for monodispersed aerosols (±35% for most tests and +101% for 300-nm NaCl). LDSA concentrations measured by the DM were 96% to 155% of those estimated with the SMPS. The geometric mean diameters measured with the DM were within 30% of those measured with the SMPS for monodispersed aerosols and within 25% for polydispersed aerosols (except for the case when the aerosol contained a substantial number of particles larger than 300 nm). The accuracy of the DM is reasonable for particles smaller than 300 nm but caution should be exercised when particles larger than 300 nm are present.
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Junior, Theotonio Mendes Pauliquevis. "\"Os efeitos de aerossóis emitidos por queimadas na formação de gotas de nuvens e na composição da precipitação na Amazônia\"." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-27082007-101307/.
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Este trabalho teve como objetivo investigar a relação entre produtos de atividades antropogênicas na Amazônia e sua influência no efeito indireto dos aerossóis no clima. Para isso, foi feita uma caracterização físico-química detalhada dos aerossóis naturais e de queimadas na Amazônia e procurou-se compreender como estes diferentes tipos de aerossóis se comportam como Núcleos de Condensação de Nuvens. Foi estudado também a influência dos aerossóis de queimadas na composição química da precipitação e no transporte de nutrientes. Visando atingir estes objetivos, foram feitas medidas em regiões distintas da Amazônia com relação ao impacto por atividades antropogênicas, principalmente queimadas. Foi possível observar em várias circunstâncias uma relação entre a composição do material particulado e da precipitação, o que nos permitiu concluir que as emissões antropogênicas influenciam significativamente a composição da precipitação. Foram identificadas as principais componentes que afetam a composição do material particulado em suspensão na Amazônia, e concluimos que o material particulado originado de emissões biogênicas é predominante em regiões preservadas, com pequena contribuição também de poeira de solo e transporte de aerossóis marinhos. Em regiões sob influência de atividades antropogênicas, observou-se que a composição dos aerossóis e da precipitação é afetada mesmo na estação úmida. No estudo das propriedades físicas e químicas das partículas de aerossol que são relevantes para o seu papel como Núcleos de Condensação de Nuvens, concluiu-se que a distribuição de tamanho é mais importante do que a composição química das partículas, devido ao fato das emissões de novas partículas por queimadas ocorrer predominantemente acima do diâmetro seco de ativação. A composição química só foi importante em valores de supersaturação baixos (< 0.2%), o que significa que esse efeito pode ser importante para nuvens estratiformes, onde o valor máximo de supersaturação é baixo, devido a baixa velocidade de ascensão das parcelas. A exportação de nutrientes devido ao transporte em larga escala de aerossóis de emissões de queimadas se mostrou particularmente crítica com relação às quantidades de fósforo que estão sendo perdidas irreversivelmente pela floresta amazônica, que foi cerca de 7 vezes maior do que a quantidade reposta por deposição úmida. Essa perda de fósforo pode ser crítica para o ecossistema em longo prazo.<br>The main objective of this study was to investigate the relationship between anthropogenic emissions in the Amazon basin and the indirect aerosol effect on climate. A detailed study of physical and chemical properties of natural and biomass burning aerosols was conducted, in order to understand how these completely different aerosols behave as Cloud Condensation Nuclei (CCN). It was also investigated the influence of biomass burning aerosols in chemical composition of precipitation, and transport of nutrients. The measurements were carried out in completely different regions respect to the impact of anthropogenic activities, especially biomass burning emissions. The analysis of aerosols and rainwater chemistry showed that anthropogenic emissions have a significant influence in the composition of precipitation. Factor analysis was applied to perform source identification, and the conclusion is that at remote and free of anthropogenic emission areas, the most important contribution was from biogenic emissions, with a small contribution of soil dust and marine aerosols advection. It was quite different at regions under influence of anthropogenic activities, where measurements showed a clear anthropogenic influence even during wet season both in aerosols and precipitation chemistry. In the study of hygroscopic properties of aerosol particles, the main conclusion was that size distribution of particles is the most important parameter to determine the ability of aerosols to act as CCN, because most of biomass burning emission are particles bigger than the activation diameter. Chemical composition was an important factor only if supersaturation is below 0.2%, because in this supersaturation range the activation diameter is extremely sensible to small changes in supersaturation. Transport of nutrients due to largescale transport of biomass burning aerosols was specially critical concerning phosphorus exportation, estimated as 7 times the apportionment through wet deposition. Continuous exportation of phosphorus can be a long term limitation to the forest ecosystem, if biomass burning activity maintain its present levels.
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Popovici, Ioana Elisabeta. "Aerosol spatial and temporal variability as seen by Mobile Aerosol Monitoring System (MAMS)." Thesis, Lille, 2018. http://www.theses.fr/2018LIL1R070.
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Les aérosols sont une composante variable de l'atmosphère, ayant un rôle important et complexe sur la qualité de l'air et le climat. La plupart des observations d'aérosols au sol sont limitées à des emplacements fixes, ce qui réduit la connaissance sur leur variabilité spatiale. Afin de compléter cette information, un système mobile d’observation des aérosols (MAMS - Mobile Aerosol Monitoring System) a été mis au point pour explorer la variabilité verticale et spatiale des propriétés optiques et microphysiques des aérosols. MAMS est un « laboratoire » conçu sur un véhicule, se distinguant des autres plateformes transportables par sa capacité à effectuer des mesures au cours du mouvement. Equipé d'instruments de télédétection et in situ, MAMS a exploré la variabilité des aérosols au travers de campagnes mobiles sur routes dans diverses situations. Ce travail présente les études de variabilité et des événements remarquables observés en France et en Chine. L’une des variables aérosols recherchée est leur concentration massique et leur distribution verticale. Ce défi est relevé dans ce travail. Le système mobile offre une grande flexibilité, et un bon rapport coût-efficacité, car il permet de réagir rapidement en cas d’événements aérosols soudains, tels que des épisodes de pollution, poussières, incendies ou éruptions volcaniques, démontrant son utilité pour les réseaux d’observation recherche et opérationnels. Les applications de la plateforme d'exploration mobile pour les activités de validation des missions spatiales d’observation de la Terre et de l’atmosphère, pour l’évaluation des modèles et les campagnes d’intercomparaison d’instruments sont présentées. Des nouvelles perspectives, tant au niveau instrumental que méthodologique, sont introduites, laissant la place à des améliorations dans les observations mobiles des aérosols<br>Aerosols are a variable component of the atmosphere, having an important and complex role on air quality and climate. Most of the ground-based aerosol observations are limited to fixed locations, narrowing the knowledge on their spatial variability. In order to overcome this issue, a compact Mobile Aerosol Monitoring System (MAMS) has been developed to explore the vertical and spatial variability of aerosol optical and microphysical properties. MAMS is a vehicle-based laboratory, distinguished by other transportable platforms through its ability to perform measurements during the movement. Equipped with remote sensing and in situ instruments, MAMS explored the aerosol variability through mobile on-road campaigns in various situations. This work presents variability studies and remarkable events observed both in France and in China. One of the researched aerosol variables is their mass concentration and vertical distribution. This challenge is taken up in this work. The mobile system presents a great flexibility and is cost-effective, being able to respond quickly in case of sudden aerosol events such as pollution episodes, dust, fire or volcano outbreaks, proving to be a useful platform for aerosol observation and operational networks. Applications of the mobile exploratory platform for validation activities of space missions observing the Earth and the atmosphere, for models’ evaluation and for instrument intercomparison campaigns are presented. New perspectives, both on instrumental and methodology levels are introduced, leaving place for improvements in the mobile aerosol observations
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Popovici, Ioana Elisabeta. "Aerosol spatial and temporal variability as seen by Mobile Aerosol Monitoring System (MAMS)." Electronic Thesis or Diss., Université de Lille (2018-2021), 2018. http://www.theses.fr/2018LILUR070.
Full textAbstract:
Les aérosols sont une composante variable de l'atmosphère, ayant un rôle important et complexe sur la qualité de l'air et le climat. La plupart des observations d'aérosols au sol sont limitées à des emplacements fixes, ce qui réduit la connaissance sur leur variabilité spatiale. Afin de compléter cette information, un système mobile d’observation des aérosols (MAMS - Mobile Aerosol Monitoring System) a été mis au point pour explorer la variabilité verticale et spatiale des propriétés optiques et microphysiques des aérosols. MAMS est un « laboratoire » conçu sur un véhicule, se distinguant des autres plateformes transportables par sa capacité à effectuer des mesures au cours du mouvement. Equipé d'instruments de télédétection et in situ, MAMS a exploré la variabilité des aérosols au travers de campagnes mobiles sur routes dans diverses situations. Ce travail présente les études de variabilité et des événements remarquables observés en France et en Chine. L’une des variables aérosols recherchée est leur concentration massique et leur distribution verticale. Ce défi est relevé dans ce travail. Le système mobile offre une grande flexibilité, et un bon rapport coût-efficacité, car il permet de réagir rapidement en cas d’événements aérosols soudains, tels que des épisodes de pollution, poussières, incendies ou éruptions volcaniques, démontrant son utilité pour les réseaux d’observation recherche et opérationnels. Les applications de la plateforme d'exploration mobile pour les activités de validation des missions spatiales d’observation de la Terre et de l’atmosphère, pour l’évaluation des modèles et les campagnes d’intercomparaison d’instruments sont présentées. Des nouvelles perspectives, tant au niveau instrumental que méthodologique, sont introduites, laissant la place à des améliorations dans les observations mobiles des aérosols<br>Aerosols are a variable component of the atmosphere, having an important and complex role on air quality and climate. Most of the ground-based aerosol observations are limited to fixed locations, narrowing the knowledge on their spatial variability. In order to overcome this issue, a compact Mobile Aerosol Monitoring System (MAMS) has been developed to explore the vertical and spatial variability of aerosol optical and microphysical properties. MAMS is a vehicle-based laboratory, distinguished by other transportable platforms through its ability to perform measurements during the movement. Equipped with remote sensing and in situ instruments, MAMS explored the aerosol variability through mobile on-road campaigns in various situations. This work presents variability studies and remarkable events observed both in France and in China. One of the researched aerosol variables is their mass concentration and vertical distribution. This challenge is taken up in this work. The mobile system presents a great flexibility and is cost-effective, being able to respond quickly in case of sudden aerosol events such as pollution episodes, dust, fire or volcano outbreaks, proving to be a useful platform for aerosol observation and operational networks. Applications of the mobile exploratory platform for validation activities of space missions observing the Earth and the atmosphere, for models’ evaluation and for instrument intercomparison campaigns are presented. New perspectives, both on instrumental and methodology levels are introduced, leaving place for improvements in the mobile aerosol observations
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Silva, Mariana Palagano Ramalho. ""Modelagem numérica dos processos de remoção úmida de poluentes atmosféricos: estudo de caso para a região amazônica (Rondônia)"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-08082006-104152/.
Full textAbstract:
Os processos de remoção de espécies químicas da atmosfera têm sido estudados atualmente utilizando modelos numéricos, na tentativa de compreender melhor, os processos de transferências de gases e material particulado (sejam elas naturais ou antropogênicas) intra-reservatórios na atmosfera e seus efeitos na dinâmica do tempo e clima. Neste estudo, foi utilizado o modelo RAMS para simular a estrutura vertical das nuvens que se desenvolvem na região amazônica, em conjunto ao modelo de remoção B. V. 2, para os processos de remoção úmida que ocorrem tanto dentro quanto abaixo da nuvem, além das condições atmosféricas locais da região da Bacia Amazônica para, assim, simular a transferência das espécies químicas da atmosfera para a hidrosfera dentro do escopo do projeto LBA. Dentro deste projeto, foram realizadas campanhas intensivas de medições, como a LBA/DRY-TO-WET e LBA/SMOCC (setembro a novembro de 2002) na região de Rondônia. No período das campanhas, foram realizadas medições das concentrações dos gases amônia, ácido nítrico e dióxido de enxofre, além das espécies inorgânicas solúveis em água, como amônio, nitrato e sulfato, entre outros. Estas concentrações de gases e partículas, bem como os parâmetros meteorológicos obtidos durante as campanhas, realizadas durante o período de transição entre as estações seca e chuvosa na região, foram utilizados como dados de entrada para ambos os modelos, onde foram escolhidos alguns eventos específicos. Com intuito de melhor representar o espectro de gotículas de nuvens no modelo de remoção, foram utilizadas a função de distribuição de Levine & Schwartz, 1982 e funções gama ajustadas aos dados observados em distribuição de gotículas de nuvem obtidas em vôos efetuados durante o experimento. Conseqüentemente, este trabalho visou à simulação da concentração na água de chuva de três espécies químicas (SO42-, NO3- e NH4+) removidas da atmosfera pelo evento de precipitação, comparando-as às composições químicas da água de chuva observadas experimentalmente, em dois eventos selecionados (9 e 10 de outubro de 2002). Simulações atmosféricas com o RAMS apresentaram resultados bastante satisfatórios conseguindo representar aspectos microfísicos das nuvens que se desenvolvem na região amazônica com bastante fidelidade. Os resultados da modelagem dos processos de remoção mostraram uma boa concordância com os observados, principalmente para o sulfato (que em alguns casos a quantidade encontrada na água de chuva pela simulação foi 97% da observada) em ambos os eventos, quando a altura da nuvem foi considerada mais realista para região (16 km). Além disso, observou-se que o espectro de gotículas de nuvem utilizado foi um parâmetro importante nos resultados. Os resultados mostraram ainda, uma predominância dos processos que ocorrem dentro da nuvem, sendo estes responsáveis por cerca de 80% a 97% da concentração da espécie química encontrada na água de chuva, corroborando a literatura. Com isso, ficou evidente a complexidade das interações e transferências entre os reservatórios atmosfera / hidrosfera através dos processos de remoção de poluentes, ressaltando assim, a importância dos estudos sobre este assunto.<br>The scavenging processes of chemical species have been studied using numerical modeling in order to understand the gases and particulate matter intra-reservoir transferences (natural or anthropogenic) which affect weather and climate. In this study RAMS model was used in turn to simulate cloud vertical structure formed over Amazonian area working together to B.V.2 scavenging model. The last model was used to simulate the in- and below-cloud scavenging processes, besides the local atmospheric conditions within the LBA Project. In this Project, there were evaluated many measurements of LBA/DRY-TO-WET and LBA/SMOCC (September to November) Campaigns at Rondonia State. During the Campaigns, ammonia, nitric acid and sulfur dioxide gases were evaluated and their respective particulate matter, ammonium, nitrate and sulfate, among others, as well as rainwater chemistry. These concentrations and meteorological parameters were also obtained, during the transition from dry to wet season, and used as input data to the both modeling, where some events were chosen. With the intention of modeling improvement, cloud droplet spectra were used from Levine & Schwartz, 1982 and gamma functions, according to each case and based on the droplet distribution obtained from flight collected data during the field Campaign. Consequently, this work simulated the rainwater concentrations of three chemical species (SO42-, NO3- e NH4+) scavenged from atmosphere by the precipitation event and compared to the observed data of two selected events (9 and 10 October 2002). RAMS atmospheric simulations presented satisfactory results which showed detailed cloud microphysics processes of Amazonian region. The modeling results show good agreement of observed data, mainly to sulfate, reaching 97% of the observed sulfate for both events, when the cloud height was considered more realistic for the region (16 km). Besides, the cloud droplet spectra were an important parameter to the modeling. The results also showed that the in-cloud process is responsible by 80% to 97% of the chemical species found in rainwater. Additionally, it was clear that the complexity of the interaction and intra-reservoir transferences through the scavenging processes and their importance.
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Boer, Gregory Jon. "Investigation of high spectral resolution signatures and radiative forcing of tropospheric aerosol in the thermal infrared." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34001.
Full textAbstract:
An investigation of the high spectral resolution signatures and radiative forcing of tropospheric aerosol in the thermal infrared was conducted. To do so and to support advanced modeling of optical properties, a high spectral resolution library of atmospheric aerosol optical constants was developed. This library includes new optical constants of sulfate-nitrate-ammonium aqueous solutions and the collection of a broad range of existing optical constants for aerosol components, particularly mineral optical constants. The mineral optical constants were used to model and study infrared dust optical signatures as a function of composition, size, shape and mixing state. In particular, spherical and non-spherical optical models of dust particles were examined and compared to high spectral resolution laboratory extinction measurements. Then the performance of some of the most common effective medium approximations for internal mixtures was examined by modeling the optical constants of the newly determined sulfate-nitrate-ammonium mixtures. The optical signature analysis was applied to airborne and satellite high spectral resolution thermal infrared radiance data impacted by Saharan dust events. A new technique to retrieve dust microphysical properties from the dust spectral signature was developed and compared to a standard technique. The microphysics retrieved from this new technique and from a standard technique were then used to investigate the effects of dust on radiative forcing and cooling rates in the thermal IR.
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Hennigan, Christopher James. "Properties of secondary organic aerosol in the ambient atmosphere sources, formation, and partitioning /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26598.
Full textAbstract:
Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Weber, Rodney; Committee Co-Chair: Bergin, Michael; Committee Member: Mulholland, James; Committee Member: Nenes, Athanasios; Committee Member: Russell, Armistead. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Zuluaga-Arias, Manuel D. "Spatio-temporal variability of aerosols in the tropics relationship with atmospheric and oceanic environments." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41202.
Full textAbstract:
Earth's radiation budget is directly influenced by aerosols through the absorption of solar radiation and subsequent heating of the atmosphere. Aerosols modulate the hydrological cycle indirectly by modifying cloud properties, precipitation and ocean heat storage. In addition, polluting aerosols impose health risks in local, regional and global scales.
In spite of recent advances in the study of aerosols variability, uncertainty in their spatial and temporal distributions still presents a challenge in the understanding of climate variability. For example, aerosol loading varies not only from year to year but also on higher frequency intraseasonal time scales producing strong variability on local and regional scales. An assessment of the impact of aerosol variability requires long period measurements of aerosols at both regional and global scales.
The present dissertation compiles a large database of remotely sensed aerosol loading in order to analyze its spatio-temporal variability, and how this load interacts with different variables that characterize the dynamic and thermodynamic states of the environment. Aerosol Index (AI) and Aerosol Optical Depth (AOD) were used as measures of the atmospheric aerosol load. In addition, atmospheric and oceanic satellite observations, and reanalysis datasets is used in the analysis to investigate aerosol-environment interactions. A diagnostic study is conducted to produce global and regional aerosol satellite climatologies, and to analyze and compare the validity of aerosol retrievals. We find similarities and differences between the aerosol distributions over various regions of the globe when comparing the different satellite retrievals. A nonparametric approach is also used to examine the spatial distribution of the recent trends in aerosol concentration. A significant positive trend was found over the Middle East, Arabian Sea and South Asian regions strongly influenced by increases in dust events.
Spectral and composite analyses of surface temperature, atmospheric wind, geopotential height, outgoing longwave radiation, water vapor and precipitation together with the climatology of aerosols provide insight on how the variables interact. Different modes of variability, especially in intraseasonal time scales appear as strong modulators of the aerosol distribution. In particular, we investigate how two modes of variability related to the westward propagating synoptic African Easterly Waves of the Tropical Atlantic Ocean affect the horizontal and vertical structure of the environment. The statistical significance of these two modes is tested with the use of two different spectral techniques. The pattern of propagation of aerosol load shows good correspondence with the progression of the atmospheric and oceanic synoptic conditions suitable for dust mobilization over the Atlantic Ocean. We present extensions to previous studies related with dust variability over the Atlantic region by evaluating the performance of the long period satellite aerosol retrievals in determining modes of aerosol variability. Results of the covariability between aerosols-environment motivate the use of statistical regression models to test the significance of the forecasting skill of daily AOD time series. The regression models are calibrated using atmospheric variables as predictors from the reanalysis variables. The results show poor forecasting skill with significant error growing after the 3rd day of the prediction. It is hypothesized that the simplicity of linear models results in an inability to provide a useful forecast.
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Metzger, Axel. "Chamber studies of secondary organic aerosol formation : from gas phase degradation to aerosol yields /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17853.
Full text
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Jeong, Myeong Jae. "Analyses of multiple global and regional aerosol products investigation of aerosol effects and artifacts /." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3171.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2005.<br>Thesis research directed by: Meteorology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Rothenberg, Daniel (Daniel Alexander). "Fundamental aerosol-cloud interactions and their influence on the aerosol indirect effect on climate." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108963.
Full textAbstract:
Thesis: Ph. D. in Atmospheric Science, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 173-189).<br>The influence of anthropogenic aerosol emissions on the optical properties of clouds and the radiative forcing arising from these interactions, known as the aerosol indirect effect on climate, constitutes a fundamental uncertainty in our understanding of 2 0 th century climate change. In this dissertation, we investigate the role of a keystone physical process, droplet activation, in contributing to this uncertainty. The first half of the ensuing work focuses on the parameterization of this process in global model, assessing both existing schemes and developing a novel one. The second half then quantifies the influence of activation by using a suite of aerosol-climate models which include a complete description of the physics which give rise to the indirect effect. Parameterizations of droplet activation perform well for idealized single-mode aerosol populations, but show systematic biases in high-pollution, weak-updraft regimes. These are exacerbated when the aerosol in question is a complex mixture. We show that estimates of droplet nucleation are highly sensitive to changes in the accumulation mode size and number concentration; this mode is itself sensitive to anthropogenic aerosol emissions, which potentially further biases modeled cloud droplet number. Using a model emulation technique, we develop a framework for building efficient metamodels of activation, which greatly reduce the mean error in droplet number predicted across regimes. The biases in these parameterizations raise questions the influence of activation on the indirect effect. Using different schemes, we calculate a spread of 1 W m- 2 in the indirect effect, which we show is equal to the spread computed from an independent suite of global models with different aerosol and physics modules. The estimated indirect effect scales more strongly with the baseline cloud droplet number concentration simulated by each model than by its change from pre-industrial to present day, indicating a strong saturation effect. While present-day estimates of aerosol-cloud interactions derived from satellite-based instruments are inadequate at constraining the pre-industrial cloud droplet burden, we show that process-based measurements could overcome this problem.<br>by Daniel Alexander Rothenberg.<br>Ph. D. in Atmospheric Science
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Kwon, Deokhyeon. "Optical and physicochemical properties of secondary organic aerosol and aerosol generated from humic substances." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6455.
Full textAbstract:
A great deal of attention has been paid to brown carbon aerosol in the troposphere because it can both scatter and absorb solar radiation, thus affecting the Earth’s climate. However, knowledge of the optical and chemical properties of brown carbon aerosol is still limited. In this thesis, we have investigated different aspects of the optical and physicochemical properties of various brown carbon aerosol samples of potential atmospheric importance.
First, reactions involving the di-carbonyl species methylglyoxal (MG) have been previously suggested as an important pathway for the production of secondary organic aerosol (SOA) in the atmosphere. Reaction in an aqueous inorganic salt solution, such as ammonium sulfate (AS), leads to the formation of light-absorbing brown carbon (BrC) product. In this thesis work, we employed a variety of experimental approaches to investigate the optical and physicochemical properties of BrC aerosol generated from this AS-MG reaction (BrC (AS/MG)). Optical properties of the dried BrC (AS/MG) aerosol particles were studied by Fourier transform infrared (FTIR) extinction spectroscopy in the mid-infrared region, cavity ring-down spectroscopy (CRDS) at 403 nm in the visible, and by measuring the light scattering phase function and polarization profiles at two different visible wavelengths, 532 and 402 nm. In addition, we used UV−vis spectroscopy to measure the mass absorption coefficient (MAC) of the solution-phase reaction products. The different optical properties were measured as a function of reaction time for a period of up to 22 days. The UV-vis absorption spectra showed a clear increase in measured MAC in the visible and near UV as the solution aged. However, analysis of the light scattering data showed no significant differences between AS and BrC aerosol in the derived refractive indices at either 532 or 402 nm, even for the longest reaction times. The FTIR extinction spectra was modeled in a Mie theory simulation to derive the complex refractive index in the mid-IR range (7000-800 cm−1); the results showed no significant changes in either the real or the imaginary parts of the refractive indices for BrC (AS/MG) aerosol particles when compared to unreacted AS aerosol. From the CRDS extinction data, the optical constants for BrC (AS/MG) particles at 403 nm were also determined through a Mie theory based analysis. The retrieved real index of refraction at 403 nm is n = 1.551 ± 0.005, with an imaginary index value of k = 0.000 ± 0.002; these values do not appear to change significantly with aging time over the course of 22 days and are not markedly different from the AS aerosol values. The small imaginary index value suggests that BrC (AS/MG) aerosol formed from this pathway may not significantly contribute to warming. In addition, CRDS measurements of the BrC (AS/MG) aerosol extinction at 403 nm as a function of particle size show a significant deviation from Mie theory simulations for particles with diameters of ≳500 nm, probably as a result of non-spherical particle shape effects. We also employed atomic force microscopy (AFM)-based IR spectroscopy to investigate the morphology and chemical composition of single SOA particles. AFM analysis of the particle morphology shows that a significant fraction of BrC (AS/MG) particles with diameters of ≳500 nm are non-spherical in shape, consistent with our observed breakdown in the applicability of Mie theory for larger particles. In addition to these measurements, we have characterized additional physicochemical properties of the BrC (AS/MG) aerosol particles including hygroscopic growth using a tandem-differential mobility analyzer. Compared to AS, BrC aerosol particles are found to have lower deliquescence relative humidity (DRH), efflorescence relative humidity (ERH), and hygroscopic growth at the same relative humidity values.
Second, we investigated the optical properties of the water soluble products of limonene BrC generated from ozonolysis of d-limonene with further aging by AS. Optical constants for the dried limonene BrC aerosol product were measured at 403 nm by CRDS over the course of 9 days of aging. While the fresh limonene BrC aerosol showed a significant non-zero absorption index, the aged samples showed absorption index values consistent with zero. This result was somewhat unexpected because UV-vis absorption spectra of the bulk reaction solution showed a continued increase in absorption as the solution aged. One possible explanation for this result is that there could be an increase in the fraction of volatile chromophores as the solution ages, that are then removed in the aerosol drying process.
Third, we investigated optical properties and chemical compositions of several humic substance (HS) reference samples including humic acid (HA) and fulvic acid (FA) standards by CRDS, UV-vis spectroscopy, elemental analysis, and 13C NMR spectroscopy. Measurements of the optical properties of HS is important in atmospheric science, because it is thought that HS samples have similar optical properties to organic materials, such as HUmic-Like Substances (HULIS), that exist in clouds, fogs, rainwater, and atmospheric aerosol. The humic acid aerosol samples generally showed higher absorption index values than the fulvic acid aerosol samples. We also found a correlation between the absorption index and chemical composition, with the value for k generally increasing with both increasing carbon-to-oxygen atomic ratio and sample aromaticity. In addition, we compared our measured optical constants for the HS aerosol samples with results from previous studies of field collected HULIS. The absorption index values for the fulvic acid aerosol samples give a better match than the humic acid samples when compared to the results from the field collected samples.
Overall, these studies provide new details of the optical and physicochemical properties of a class of brown carbon organic aerosol which may have important implications for atmospheric chemistry and climate.
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Mårtensson, Monica. "Submicrometre aerosol emissions from sea spray and road traffic." Doctoral thesis, Stockholm University, Department of Meteorology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7006.
Full textAbstract:
<p>The uncertainty of the climate and health effects of aerosols is still large, one important reason being lack of knowledge of the primary emissions. This thesis combines laboratory and field experiments, and process modelling in an effort to better quantify the submicrometre aerosol emissions and to understand some of the processes in the atmosphere.</p><p>A parameterisation was derived for the source flux of sea salt particles (particles m<sup>-2 </sup>s<sup>-1</sup>) in the size range 0.02-2.8 µm dry diameter (D<sub>p</sub>), it is the first parameterisation to almost cover two full decades of the submicrometre sea salt aerosol production, and to include the effect of water temperature. This sea salt parameterisation was validated for temperate water in the 0.1-1.1 μm D<sub>p</sub> range using in situ size resolved emissions of marine aerosol particles, which were measured with the eddy covariance (EC) method. For periods sampled air was heated to 300ºC in order to evaporate semi-volatile organics and isolate the sea salt fraction. Comparisons with the total aerosol emissions suggest that in these emissions organic carbon and sea salt are internally mixed in the same particles. Finally an aerosol dynamics model was modified for marine conditions. In the model parameterised emissions of sea salt was included together with aerosol dynamics, chemistry and clouds representative for the marine boundary layer. The sea salt emissions are together with secondary sulphate, and cloud processing able to reproduce a typical marine aerosol size distribution and cloud condensation nuclei population.</p><p>Measurements with the EC method of the road traffic related aerosol source number flux for D<sub>p</sub>>0.011 µm show that the major part of the aerosol fluxes is due to road traffic emissions. Both an emission factor for the whole fleet mix in Stockholm (1.4x10<sup>14</sup> vehicle<sup>-1</sup> km<sup>-1</sup>) and separate emission factors for light- and heavy-duty vehicles (HDV) were deduced. The result shows that during weekdays 70-80% of the emissions come from HDV.</p>
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BARCELAR, Jacqueline de Melo. "Efeitos da obesidade na distribuição e deposição pulmonar de aerossol e eficácia do heliox em mulheres obesas com e sem asma estável através da cintilografia pulmonar." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18516.
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Previous issue date: 2016-03-04<br>Introdução: A obesidade é um fator de risco para asma, cujo tratamento principal consiste no
uso dos aerossóis inalados. Entretanto, não existem dados na literatura a cerca do padrão de
deposição de aerossol em indivíduos obesos não asmáticos e asmáticos. Além disso, existe
uma lacuna no conhecimento do uso do heliox nesta população, pois este gás diminui a
resistência ao fluxo aéreo e aumenta a ventilação. Objetivo: 1-Analisar a distribuição e
deposição pulmonar e extrapulmonar de radioaerossol em mulheres adultas saudáveis com
peso normal e obesas e 2-Analisar a distribuição e deposição pulmonar de radioaerossol, após
inalação de radiofármaco carreado por oxigênio e heliox, em mulheres obesas não asmáticas e
asmáticas, através de cintilografia pulmonar. Método: O estudo foi realizado em duas partes.
A primeira um corte transversal com 29 mulheres: 15 obesas (IMC ≥30 kg/m2) e 14 com IMC
=18,5–24,9 kg/m2. A segunda parte foi um ensaio clínico randomizado e crossover com
mulheres obesas (IMC ≥30 kg/m2), 10 não asmáticas e 10 asmáticas estáveis. Todas as
participantes inalaram 99mTc-DTPA tecnésio, com atividade de 37MBq (Megabequereis),
associado a 0,9% de solução salina. Na primeira parte foi utilizado um nebulizador de
membrana (NM) (Adágio, Dance Biopharm, San Francisco, CA) ativado pela respiração
(volume solução=0,2mL). Na segunda parte foi utilizado o mesmo radiofármaco associado a
0.9% de solução salina e broncodilatadores, (volume solução= 1,5mL), utilizando NM
(Aerogen® Solo, Aerogen Ltd, Galway, Irlanda) associado ao gás oxigênio ou heliox. Após a
inalação, foram adquiridas as imagens cintilográficas de tórax posterior e anterior, face e
equipamentos, com tempo 300 segundos para cada imagem. Para analisar as imagens foram
criadas regiões de interesse (ROI) para regiões pulmonares e extra pulmonar. Resultados: No
primeiro estudo, verificou-se maior deposição do radioaerossol nas vias aéreas superiores no
grupo de obesas comparado com as de peso normal (9,54±3,68% versus 4,94±1,92%,
p=0,002). Na comparação entre os grupos, os gradientes horizontal e vertical apresentaram
padrão de distribuição semelhante, apesar de maior deposição pulmonar ter ocorrido em
mulheres com peso normal (61,65 ± 7,37% versus 46,48 ± 8,94%, p<0,001). No segundo
estudo, ao respirar oxigênio, o grupo de asmáticas apresentou 5% maior deposição pulmonar
em comparação as não-asmáticas (p =0,016), e maior deposição do radioaerossol nas áreas
centrais no pulmão direito (0,90±0,23 versus 0,71±1,13; p<0,05). Não foram observadas
diferenças significativas na deposição pulmonar de radioaerossol entre os grupos com o uso
do heliox, porém foi encontrada redução significativa do radioaerossol no nível de orofaringe
nas não asmáticas (p=0,009) e aumento no filtro expiratório (p=0,023). Conclusão: Mulheres
obesas demonstraram reduzida deposição pulmonar de radioaerossol e maior deposição na
região da orofaringe quando comparadas com as mulheres com peso normal. Na segunda
parte do estudo, as mulheres asmáticas apresentaram maior deposição pulmonar total e na
região central de radioaerossol comparada com as mulheres obesas não asmáticas. Utilizando
heliox, não foi observado aumento da deposição pulmonar de radioaerossol nas mulheres
obesas não asmáticas e asmáticas. Entretanto, o heliox diminuiu a deposição de radioaerossol
na orofaringe das mulheres obesas não asmáticas.<br>Introduction: Obesity is a risk factor for asthma the treatment is mainly with the use of
inhaled aerosols. However, there is no data in the literature about the aerosol deposition
pattern in obese subjects with and without asthma. Furthermore, there is a lack in knowledge
regarding the use of heliox in this population, since the gas reduces the airflow resistance and
increased ventilation. Objective: 1- Analyze radioaerosol distribution and deposition in
pulmonary and extrapulmonary in healthy adult women with normal weight and obese, 2-
Assess distribution and pulmonary and extrapulmonary deposition of radioaerosol, after
radiolabel inhalation carried by oxygen and heliox in non-asthmatic and asthmatic obese
women with stable asthma using pulmonary scintigraphy. Method: The study was conducted
in two stages. The first was a cross-section with 28 women: 15 obese (BMI ≥30kg/m2) and 14
with BMI =18.5-24.9kg/m2. The second part was a randomized crossover trial, with obese
women (BMI ≥ 30 kg/m2), 10 non-asthmatic and 10 asthmatic stable asthma. All subjects
inhaled technetium 99m Tc-DTPA with 37 MBq (Megabecquerels) activity associated with
0.9% saline. In the first part was used a nebulizer membrane (NM) (Adage, Dance Biopharm,
San Francisco, CA) activated by breath (solution volume = 0.2 mL). In the second part was
used the same radiopharmaceutical associated with 0.9% saline and bronchodilators (solution
volume =1.5mL) using NM (Aerogen® Solo, Aerogen Ltd, Galway, Ireland) associated with
the gas oxygen or heliox. After inhalation were acquired the scintigraphic images of posterior
and anterior chest, face and equipment, with time 300 seconds for each image. To analyze the
images were created regions of interest (ROI) for pulmonary and extra pulmonary regions.
Results: In the first study, a higher deposition radioaerossol upper airways in obese group
compared with those of normal weight (9.54±3.68% versus 4.94±1.92%, p=0.002).
Comparing the groups, the horizontal and vertical gradients showed similar distribution
pattern, although greater lung deposition occurred in women with normal weight
(61.65±7.37% versus 46.48±8.94%, P<0.001). In the second study, breathing oxygen, the
asthmatic group had 5% higher lung deposition compared to non-asthmatics (p=0.016), and
increased deposition of radioaerossol in the central areas in the right lung (0.90±0.23 versus
0.71±1.13; p<0.05). Significant differences in lung deposition of radioaerosol between groups
with use of heliox, but found significant reduction of radioaerosol in the level of the
oropharynx without asthma (p=0.009) and increase in expiratory filter were observed
(p=0.023). In the second part of the study, asthmatic women showed higher total lung
deposition and central radioaerossol compared with obese women without asthma. Using heliox was not observed increased lung deposition radioaerossol in obese women without
asthma and asthma. However, heliox decreased deposition radioaerossol oropharyngeal obese
women without asthma
49
Rodrigues, Patricia Ferrini. "Avaliação da higroscopicidade de aerossóis urbanos pela técnica LIDAR Raman." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-02022015-134326/.
Full textAbstract:
A cobertura de nuvens e os aerossóis são os dois principais fatores que modulam a energia solar que atinge a superfície e é absorvida pela atmosfera. Esses dois fatores, portanto, têm um papel essencial no clima do planeta. Há atualmente um interesse nos efeitos radiativos dos aerossóis, particularmente por causa da atividade antrópica, que aumenta sua concentração na atmosfera, e por sua íntima relação com a formação de nuvens. Partículas que podem ser ativadas e ganhar água para se tornarem nevoeiro ou gotas de nuvens, na presença de supersaturação de vapor de água, são chamadas de Núcleo de Condensação de Nuvens. O estudo das partículas que aumentam de tamanho com o ganho de água conforme aumenta a umidade relativa (higroscopicidade) torna-se então de fundamental importância no entendimento da contribuição dos aerossóis na regulação do clima do planeta. O LIDAR é um instrumento promissor no estudo da higroscopicidade dos aerossóis atmosféricos, porque pode operar em ambiente não perturbado e em condições muito próximas da saturação. O LIDAR Raman apresenta a vantagem de poder obter o perfil de vapor de água e retroespalhamento de aerossóis no mesmo volume atmosférico e sem nenhuma suposição a priori a respeito da razão LIDAR Este trabalho objetiva avaliar o crescimento higroscópico do material particulado urbano em São Paulo, Brasil, e em Washington, D.C, Estados Unidos durante a campanha NASA-Discover-AQ com o uso da técnica LIDAR Raman, obtendo o fator de crescimento por higroscopicidade. Apesar da metodologia que se baseia na determinação de uma atmosfera bem misturada com o uso de radiossondagem já ter sido utilizada na literatura, este trabalho acrescenta importantes informações, já que não se tem notícias de outros estudos extensos com múltiplos casos feitos com o LIDAR Raman para avaliação de higroscopicidade nos Estados Unidos, bem como é a primeira vez que este estudo é feito em São Paulo, como resultado de três anos de aquisição de dados. Os resultados mostram que é possível identificar o crescimento higroscópico dos aerossóis em ambas os ambientes de estudo, cuja detecção depende de condições atmosféricas que estão raramente presentes, tornando o estudo da higroscopicidade com o LIDAR um desafio que exige uma extensa coleta de dados. Mostram ainda que a determinação da origem e o estudo conjugado das propriedades químicas da população de aerossóis são informações que auxiliariam no entendimento do comportamento higroscópico, aprofundamentos estes que podem ser derivados deste trabalho.<br>The cloud cover and aerosols are two main factors that modulate the solar energy that reaches the surface and is absorbed by the atmosphere. These two factors therefore have a key role in global climate. There is currently an interest in the radiative effects of aerosols, particularly because of human activity, increasing its concentration in the atmosphere, and its close relationship with cloud formation Particles that can be activated and gain water to form fog or cloud droplets in the presence of water vapor supersaturation, are called Cloud Condensation Nucleus. The study of particles that increase in size because of the uptake of water under increasing relative humidity conditions (hygroscopicity) then becomes of fundamental importance in understanding the contribution of aerosols in regulating the global climate. The LIDAR is a promising tool in the study of hygroscopic properties of atmospheric aerosols, because it can operate in undisturbed environment and much close to saturation conditions. The Raman LIDAR has the advantage of being able to obtain the profile of water vapor and aerosol backscatter at the same atmospheric volume and no a priori assumption of the LIDAR ratio. This study aims to evaluate the hygroscopic growth of urban particulate matter in Sao Paulo, Brazil, and Washington, DC, United States during the NASA-Discover-AQ campaign using the technique Raman LIDAR, getting the growth factor by hygroscopicity . Although the methodology - which is based on determination of a well-mixed atmosphere using radiosonde - have already been described in the literature, this work adds important information, since they do not have other news with multiple cases extensive studies made with the LIDAR Raman hygroscopicity for evaluation in the United States, and is the first time that this study is done in São Paulo, as a result of three years of data acquisition. The results show that it is possible to identify the hygroscopic growth of aerosol in both environments, whose detection depends on atmospheric conditions that are rarely present, making the study of hygroscopic properties with LIDAR a challenge that requires extensive data collection. Also, show that the determination of origin and the combined study of chemical properties of the population of aerosols would assist in the understanding of hygroscopic behavior.
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Wagner, Swen. "Ermittlung von Parametern zur Beschreibung von atmosphärisch relevanten Phasenübergängen." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=96803280X.
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