Im Rahmen dieser Dissertation wurden die mikrophysikalischen Eigenschaften von Aerosolpartikeln im Passatklima und deren Einfluss auf Passatwolken untersucht. Die Arbeit basiert auf Messungen mit der hubschrauber-getragenen Messplattform ACTOS. Es wurden zwei Intensivmesskampagnen im November 2010 und April 2011 durchgeführt, welche 31 Forschungsflüge in der Nähe der östlichsten Karibik-Insel Barbados umfassen. Die gemessenen Partikel-Anzahl-Größenverteilungen weisen meist eine bimodale Verteilung auf, welche typisch für marines Aerosol ist. Im Vergleich zu kontinentalen Verhältnissen ist die Totalanzahlkonzentration der Aerosolpartikel von 100-1000 cm-3 gering. Eine statistische Analyse einzelner Wolken lässt auf typische Anzahlkonzentrationen von aktivierten Partikeln bis zu 400 cm-3 und minimale Aktivierungsdurchmesser in der Größenordnung von 40 nm bis 180 nm mit entsprechenden maximalen kritischen Übersättigungen zwischen 0.1 und 0.9% schließen. Zusätzlich wurden wesentliche Einflussfaktoren auf die Anzahlkonzentration aktivierter Partikel identifiziert: 1) Vertikalwind an der Wolkenunterkante und 2) Anzahlkonzentration der verfügbaren Aerosolpartikel, die als Wolkenkondensationskeime dienen können. Mit Hilfe von Beobachtungsdaten und einer umfassenden Sensitivitätsstudie unter Verwendung eines Luftpaketmodells mit spektraler Wolkenmikrophysik wurde die Sensitivität der Wolkentropfenkonzentration gegenüber Änderungen in den physikalischen Eigenschaften und der Hygroskopizität von Aerosolpartikeln untersucht. Die beobachteten Ergebnisse in Form von sogenannten \"aerosol-cloud interaction metrics\" (ACI, Maß für den Einfluss von Änderungen einer bestimmten Aerosoleigenschaft auf eine bestimmte Wolkeneigenschaft) zeigen eine sehr hohe Sensitivität der Tropfenanzahlkonzentration gegenüber Änderungen in der Partikelanzahlkonzentration (in der Nähe des physikalisch sinnvollen Maximums von eins). Diese abgeleiteten ACI-Metriken eignen sich als Basis für Abschätzungen des indirekten Strahlungsantriebes auf der Grundlage von Beobachtungen. Zusätzliche Modellrechnungen umfassen die gemessenen Partikeleigenschaften während der gesamten Kampagnen. Die Ergebnisse unterstreichen besonders die Bedeutung der physikalischen Partikeleigenschaften. Die Suszeptibilität der Tropfenanzahlkonzentration gegenüber Änderungen in der Partikelanzahlkonzentration (Wertebereich: 0-1) ist am größten (> 0.9) für den Fall eines stark ausgeprägten Akkumulations-Mode und nimmt ab, je stärker der Aitken-Mode ausgeprägt ist (> 0.6). Im Gegensatz dazu ist die Sensitivität der Tropfenanzahlkonzentration gegenüber Änderungen in der Hygroskopizität der Partikel generell geringer (< 0.4). Die hier präsentierten Ergebnisse stellen eine umfangreiche Charakterisierung der Aerosol- und Wolkeneigenschaften im Passatklima dar und können helfen, die vorhergesagte Sensitivität der Wolkeneigenschaften in Klimamodellen gegenüber Änderungen der Aerosoleigenschaften zu evaluieren und deren Unsicherheiten zu reduzieren. / Within the scope of this dissertation, microphysical properties of aerosol particles in the trade wind regime and their influence on microphysical properties of trade wind cumulus clouds have been investigated. The study is based on measurements performed with the helicopter-borne measurement platform ACTOS. Two intensive measurement periods were carried out in November 2010 and April 2011, including 31 research flights close to the easternmost Caribbean island - Barbados. Aerosol particle number size distributions show a bimodal structure, which is typical for marine aerosol particles. The total particle concentrations of approximately 100-1000 cm-3 are compared to continental conditions relatively low. A statistical analysis of individual clouds reveals typical number concentrations of activated particles up to 400 cm-3 and minimum activation diameters between 40 and 180 nm with corresponding critical supersaturations between 0.1 and 1%. Additionally, major factors affecting the number concentration of activated particles are identifed: 1) vertical wind velocity at cloud base and, 2) number concentration of available aerosol particles as potential cloud condensation nuclei. With the help of observational data and a comprehensive sensitivity study using a spectral cloud microphysical parcel model, the sensitivity of the cloud droplet number concentration towards changes in the microphysical aerosol particle properties and their hygroscopicity has been investigated. Observational results in terms of so-called aerosol-cloud interactions metrics (describes a measure of the influence of changes in one specific aerosol property on one specific cloud property) show a very high sensitivity (close to the physical meaningful maximum of unity) of the number concentration of activated particles towards changes in the particle number concentration. These aerosol-cloud interaction metrics can be used as basis for observationally-based radiative forcing estimates. Additional model calculations cover the entire range of the observed aerosol properties during both campaigns. The results underline particularly the importance of the physical aerosol properties. The calculated susceptibility (valuation: 0-1) of the droplet number concentration towards changes in the particle number concentration is highest (> 0.9) for accumulation mode dominated particle number size distributions and decreases for Aitken mode dominated size distributions (> 0.6). In contrast, for the modeled parameter space, the sensitivity towards changes in the particle hygroscopicity is generally below 0.4. The findings presented in this study represent a comprehensive characterization of aerosol and cloud microphysical properties in the trade wind regime. These findings may help to evaluate the predicted sensitivity of cloud microphysical properties by climate models towards changes in particle microphysical properties and reduce the uncertainties in climate sensitivity estimates.

Defence Research and Development Canada - Atlantic is currently under a project arrangement with Sweden and Holland to investigate new or emerging fire suppression technologies in naval applications. One possible outcome of this project arrangement could be the identification of a safe and effective Halon 1301 replacement suppression agent within the respective navies. The subject area Canada has agreed to investigate is aerosol fire extinguishing agent technologies. Although aerosols have been shown to be effective in suppressing demonstration fires, to date there has been little systematic scientific research into fire suppression using aerosol particulates. Therefore, there is a need for more in depth investigation of some of the commercial aerosol products available on the market to determine their fire suppression efficacy in naval applications, as well as any potential negative impacts that the aerosol may have on personnel, equipment and the environment. Aerosol suppression systems range from small handheld grenade extinguishers to large fitted and remotely activated aerosol dispersal units. The fire research and testing presented in this thesis looks specifically at the efficacy and safe use of two variants of the small handheld aerosol extinguishers, while also assessing aerosol agent suppression technologies overall. The Royal Canadian Navy (RCN) currently uses a two tiered response to fire, consisting of first response by a Rapid Response Team (RRT), followed by full response by an Attack Team (AT). A Rapid Attack Team (RAT) has been introduced as an intermediate response team. To enhance efficiency of the RRTs or RATs, handheld aerosol units, in this evaluation the Dry Sprinkler Powder Aerosol (DSPA) and StatX fire knock down aerosol extinguishers, could potentially be stored throughout the ship or transported by the teams to a fire scene and used to control, suppress or even extinguish a fire prior to the AT arriving on the scene, particularly in the case of smaller enclosure fires. To fully evaluate their potential for use in this capacity, it is important to carefully study the suppression efficacy of these units under conditions similar to those in which they would be deployed, as well as to better understand their impact on a fire environment in terms of important parameters such as compartment temperature reduction, visibility, oxygen concentration, aerosol particulate dwell time, and toxicity. In terms of operational issues related to deployment of these pyrotechnic tools onboard RCN vessels, it is critical to assess the requirements for extinguisher safe storage and to gain an understanding of the incendiary potential of the units, as well as post suppression overhaul, smoke/agent clearing and compartment gas free certification. The thesis includes a description of the experimental design, measurement techniques, and key results and conclusions for each of the 26 full-scale simulated marine enclosure live fire tests that were conducted. In general, handheld aerosol extinguishers have proven to be effective for fire control and even suppression under certain circumstances. They can improve the fire safety of RCN vessels when used correctly. Experimental data measured that relate to the consequences of accidental discharge and incendiary potential can also be used to ensure naval applications are safe and effective.

This thesis characterizes properties of ambient secondary organic aerosol (SOA), an important and abundant component of particulate matter. The findings presented in this thesis are significant because they represent the results from ambient measurements, which are relatively scarce, and because they report on properties of SOA that, until now, were highly uncertain. The analyses utilized the fraction of particulate organic carbon that was soluble in water (WSOCp) to approximate SOA concentrations in two largely different urban environments, Mexico City and Atlanta. In Mexico City, measurements of atmospheric gases and fine particle chemistry were made at a site ~ 30 km down wind of the city center. Using box model analyses and a comparison to ammonium nitrate aerosol, a species whose thermodynamic properties are generally understood, the morning formation and mid-day evaporation of SOA are investigated. In Atlanta, simultaneous measurements of WSOCp and water-soluble organic carbon in the gas phase (WSOCg) were carried out for an entire summer to investigate the sources and partitioning of WSOC. The results suggest that both WSOCp and WSOCg were secondary and biogenic, except possibly in several strong biomass burning events. The gas/particle partitioning of WSOC in Atlanta was investigated through the parameter, Fp, which represented the fraction of WSOC in the particle phase. Factors that appear to influence WSOC partitioning in Atlanta include ambient relative humidity and the WSOCp mass concentration. There was also a relationship between the NOx concentration and Fp, though this was not likely related to the partitioning process. Temperature did not appear to impact Fp, though this may have been due to positive relationships WSOCp and WSOCg each exhibited with temperature. Neither the total Organic Carbon aerosol mass concentration nor the ozone concentration impacted WSOC partitioning.

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.

The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on aerosol-cloud interactions. Vertical wind velocities near cloud base, and cloud condensation nuclei (CCN) spectra, are the two most important input parameters for aerosol-cloud parcel models in determining cloud microphysical and optical properties. Therefore, the present study focuses on the instrumental development for vertical wind measurements to improve aerosol-cloud closure studies. Enhancements in Remotely Piloted Aircraft Systems (RPAS) have demonstrated their potential as tools in atmospheric research to study the boundary layer dynamics, aerosols and clouds. However, as a relatively new tool for atmospheric research, RPA require instrumental development and validation to address current observational needs. A 5-hole probe is implemented on a remotely piloted aircraft (RPA) platform, with an inertial navigation system (INS) to obtain atmospheric wind vectors. The 5- hole probe is first calibrated in a wind tunnel (at Météo-France, Toulouse, France), and an error analysis is conducted on the vertical wind measurement. Atmospheric wind vectors obtained from RPA flights are compared with wind vectors determined from sonic anemometers located at different levels on a 60 m meteorological mast (Centre de Recherches Atmosphériques, Lannemezan, France). Good agreements between vertical wind velocity probability density functions are obtained. The power spectral density of the three wind components follow the -5/3 line for the established regime of turbulence (Kolmogorov law). Turbulent kinetic energy (TKE) values calculated from the RPA are somewhat higher than TKE compared to the sonic anemometer; however, the results agree with those reported in other experiments that compare RPA platforms and sonic anemometers (Lampert et al. (2016), Båserud et al. (2016)). As the RPA equipped with a 5-hole probe (defined as the ``wind-RPA'') is developed for aerosol-cloud observations, updraft velocities near cloud base are compared with cloud radar data during a BACCHUS field campaign (Mace Head Research Station, Ireland). Three case studies illustrate the similarity of in-cloud updrafts measured between the wind-RPA and the cloud radar. A good agreement between vertical velocities of both instruments over a range of different meteorological conditions is found. Updraft velocity measurements from the wind-RPA are implemented in the aerosol-cloud parcel model to conduct a closure study for stratocumulus case with convection sampled during a BACCHUS field campaign in Cyprus. Aerosol size distributions and CCN were measured at a ground-site, which served as input to the aerosol-cloud parcel model along with the updraft velocities at cloud base measured by the RPA. In addition, the RPA conducted a vertical profile through the cloud layer and measured the shortwave transmission of solar irradiance during the ascent. The aerosol-cloud parcel model also shows that entrainment has a greater impact on cloud optical properties than variability in updraft velocity and aerosol particle concentration. Results of the case study for the Cyprus field experiment are consistent with results for similar closure studies conducted during the Mace Head field campaign (Sanchez et al., 2017), and reinforce the significance of including entrainment processes in cloud models to reduce uncertainties in aerosol-cloud interactions.

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. / 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.

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. / 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.

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. / 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.

Long and short-term exposure to particulate matter (PM) are linked to adverse heath endpoints. Evidence indicates that PM composition such as metals and organic carbon (OC) might drive the health effects. As airborne pollutants show significant intracity spatiotemporal variation, mobile sampling and distributed monitors are utilized to capture the variation pattern. The measurements are then fed to develop models to better characterize the relationship between exposure and health outcomes. Two sampling campaigns were conducted. One was sole mobile sampling in 2013 summer and winter in Pittsburgh, PA. Thirty-six sites were chosen based on three stratification variables: traffic density, proximity to point sources, and elevation. The other one was hybrid sampling network, incorporating a mobile sampling platform, 15 distributed monitors, and a supersite. We designed two case studies (transect and downtown), selected 14 neighborhoods (~1 km2), and conducted sampling in 2016 summer/fall and winter. Spatial variation of PM2.5 mass and composition was studied in the 2013 campaign. X-ray fluorescence (XRF) was used to analyze concentrations of 26 elements: Na, Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Zr, Cd, Sb, and Pb. Trace elements had a broad range of concentrations from 0 to 300 ng/m3. Comparison of data from mobile sampling with stationary monitors showed reasonable agreement. We developed Land use regression (LUR) models to describe spatial variation of PM2.5, Si, S, Cl, K, Ca, Ti, Cr, Fe, Cu, and Zn. Independent variables included traffic influence, land-use type, and facility emissions. Models had an average R2 of 0.57 (SD = 0.16). Traffic related variables explained the most variability with an average R2 contribution of 0.20 (SD = 0.20). Overall, these results demonstrated significant intra-urban spatial variability of fine particle composition. Spatial variation of OC was based on the 2013 campaign as well. We collected organic carbon (OC) on quartz filters, quantified different OC components with thermaloptical analysis, and grouped them based on volatility in decreasing order (OC1, OC2, OC3, OC4, and pyrolyzed carbon (PC)). We compared our ambient OC concentrations (both gas and particle phase) to similar measurements from vehicle dynamometer tests, cooking emissions, biomass burning emissions, and a highway traffic tunnel. OC2 and OC3 loading on ambient filters showed a strong correlation with primary emissions while OC4 and PC were more spatially homogenous. While we tested our hypothesis of OC2 and OC3 as markers of fresh source exposure for Pittsburgh, the relationship seemed to hold at a national level. Land use regression (LUR) models were developed for the OC fractions, and models had an average R2 of 0.64 (SD = 0.09). We demonstrate that OC2 and OC3 can be useful markers for fresh emissions, OC4 is a secondary OC indicator, and PC represents both biomass burning and secondary aerosol. People with higher OC exposure are likely inhaling more fresh OC2 and OC3, since secondary OC4 and PC varies much less drastically in space or with local primary sources. With the 2016 hybrid sampling campaign, we addressed the intracity exposure patterns, as they could be more complex than intercity ones because of local traffic, restaurants, land use, and point sources. This network studied a wide range of pollutants (CO2, CO, NO2, PM1 mass and composition, and particle number PN). Mobile measurements and distributed monitors show good agreement. PN hotspots are strongly associated with restaurants and highway traffic. PN at sites with large local source impacts tends to have larger diurnal variation than daily variation, while CO in downtown center shows the opposite trend. PN exhibits the largest spatial and temporal variations. Spatial variation is generally larger than temporal variation among all five pollutants (CO2, NO2, CO, PN, and PM1). These findings provide quantitative comparison between spatial and temporal variation in different scales, and support the theoretical validity of developing long-term exposure models from short-term mobile measurement. A combined sampling network with mobile and distributed monitor could prove more valuable in studying intracity air pollution. In the 2016 hybrid sampling campaign, we also studied spatial variability of air pollution in the vicinity of monitors. Monitoring network is essential for protecting public health, though evaluation is needed to assess spatial representativeness of monitors in different environments. Mobile sampling was conducted repeatedly around 15 distributed monitors. Substantial short-range spatial variability was observed. Spatial variation was consistently larger than temporal variation for NO2 and CO at different sites. Ultrafine particles were highly dynamic both in space and time. PM1 was less spatially and temporally variable. Urban locations had more frequent episodic source plume events compared with background sites. Using a single monitor measurement to represent surrounding ~1 km2 areas could introduce an average daily exposure misclassification of 46 ppb (SD = 26) for CO (30% of regional background), 3 ppb (SD = 2) for NO2 (43% of background), 4007 #/cm3 (SD = 1909) for ultrafine particle number (64% of background), and 1.2 μg/m3 (SD = 1.0) for PM1 (13% of background). Exposure differences showed fair correlation with traditional land use covariates such as traffic and restaurant density, and the magnitude of misclassification could be even bigger for urban neighborhoods.

Airborne aerosols are crucial atmospheric constituents that are involved in global climate change and human life qualities. Understanding the nature and magnitude of aerosol-cloud-precipitation interactions is critical in model predictions for atmospheric radiation budget and the water cycle. The interactions depend on a variety of factors including aerosol physicochemical complexity, cloud types, meteorological and thermodynamic regimes and data processing techniques. This PhD work is an effort to quantify the relationships among aerosol, clouds, and precipitation on both global and regional scales by using satellite retrievals and aircraft measurements. The first study examines spatial distributions of conversion rate of cloud water to rainwater in warm maritime clouds over the globe by using NASA A-Train satellite data. This study compares the time scale of the onset of precipitation with different aerosol categories defined by values of aerosol optical depth, fine mode fraction, and Ångstrom Exponent. The results indicate that conversion time scales are actually quite sensitive to lower tropospheric static stability (LTSS) and cloud liquid water path (LWP), in addition to aerosol type. Analysis shows that tropical Pacific Ocean is dominated by the highest average conversion rate while subtropical warm cloud regions (far northeastern Pacific Ocean, far southeastern Pacific Ocean, Western Africa coastal area) exhibit the opposite result. Conversion times are mostly shorter for lower LTSS regimes. When LTSS condition is fixed, higher conversion rates coincide with higher LWP and lower aerosol index categories. After a general global view of physical property quantifications, the rest of the presented PhD studies is focused on regional airborne observations, especially bulk cloud water chemistry and aerosol aqueous-phase reactions during the summertime off the California coast. Local air mass origins are categorized into three distinct types (ocean, ships, and land) with their influences on cloud water composition examined and implications of wet deposition discussed. Chemical analysis of cloud water samples indicates a wide pH range between 2.92 and 7.58, with an average as 4.46. The highest pH values were observed north of San Francisco, coincident with the strongest land mass influence (e.g. Si, B, and Cs). Conversely, the lowest pH values were observed south of San Francisco where there is heavy ship traffic, resulting in the highest concentrations of sulfate, nitrate, V, Fe, Al, P, Cd, Ti, Sb, P, and Mn. The acidic cloud environment with influences from various air mass types can affect the California coastal aquatic ecosystem since it can promote the conversion of micronutrients to more soluble forms. Beyond characterization of how regional air mass sources affect cloud water composition, aircraft cloud water collection provides precious information on tracking cloud processing with specific species such as oxalic acid, which is the most abundant dicarboxylic acid in tropospheric aerosols. Particular attention is given to explore relationship between detected metals with oxalate aqueous-phase production mechanisms. A number of case flights show that oxalate concentrations drop by nearly an order of magnitude relative to samples in the same vicinity with similar environmental and cloud physical conditions. Such a unique feature was consistent with an inverse relationship between oxalate and Fe. In order to examine the hypothesis that oxalate decreasing is potentially related to existing of Fe, chemistry box model simulations were conducted. The prediction results show that the loss of oxalate due to the photolysis of iron oxalato complexes is likely a significant oxalate sink in the study region due to the ubiquity of oxalate precursors, clouds, and metal emissions from ships, the ocean, and continental sources.