The response of cloud processes to an aerosol perturbation is one of the largest uncertainties in the anthropogenic forcing of the climate. It occurs at a variety of timescales, from the near-instantaneous Twomey effect to the longer timescales required for cloud adjustments. Understanding the temporal evolution of cloud properties following an aerosol perturbation is necessary to interpret the results of so-called “natural experiments” from a known aerosol source such as a ship or industrial site. This work uses reanalysis wind fields and ship emission information matched to observations of ship tracks to measure the timescales of cloud responses to aerosol in instantaneous (or“snapshot”) images taken by polar-orbiting satellites. As in previous studies, the local meteorological environment is shown to have a strong impact on the occurrence and properties of ship tracks, but there is a strong time dependence in their properties. The largest droplet number concentration (Nd) responses are found within 3 h of emission, while cloud adjustments continue to evolve over periods of 10 h or more. Cloud fraction is increased within the early life of ship tracks, with the formation of ship tracks in otherwise clear skies indicating that around 5 %–10%of clear-sky cases in this region may be aerosol-limited. The liquid water path (LWP) enhancement and the Nd– LWP sensitivity are also time dependent and strong functions of the background cloud and meteorological state. The nearinstant response of the LWP within ship tracks may be evidence of a bias in estimates of the LWP response to aerosol derived from natural experiments. These results highlight the importance of temporal development and the background cloud field for quantifying the aerosol impact on clouds, even in situations where the aerosol perturbation is clear.

The Diagnostic Instrumentation and Analysis Laboratory (DIAL) at Mississippi State University was awarded a project to study the feasibility of measuring particulate matter downstream of a high efficiency particulate air (HEPA) filter by testing commercially available equipment used to monitor the downstream side of a HEPA filter. In order to perform the work required for this project, a test stand to accommodate a 12? x 12? x 11.5? HEPA filter with a rated flow of 250 standard cubic feet per minute (scfm) was constructed. The test stand required an aerosol generator capable of producing a mass loading rate of 30 mg/m3 of dry aerosol at the face of the HEPA filter. It was determined that there was not a commercially available aerosol generator that quite fit the needs of the project. Therefore, it was necessary to develop an aerosol generator with the capabilities required for the project.

While research on the environmental impacts of engineered nanoparticles (ENPs) is growing, the potential for them to be chemically transformed in the atmosphere has been largely ignored. The overall objective of this work was to assess the atmospheric transformation of carbonaceous nanoparticles (CNPs). The research focuses on C₆₀ fullerene because it is an important member of the carbonaceous nanoparticle (CNP) family and is used in a wide variety of applications. The first specific objective was to review the potential of atmospheric transformations to alter the environmental impacts of CNPs. We described atmospheric processes that were likely to physically or chemically alter aerosolized CNPs and demonstrated their relevance to CNP behavior and toxicity in the aqueous and terrestrial environment. In order to investigate the transformations of CNP aerosols under controlled conditions, we developed an aerosolization technique that produces nano-scale aerosols without using solvents, which can alter the surface chemistry of the aerosols. We demonstrated the technique with carbonaceous (C₆₀) and metal oxide (TiO₂, CeO₂) nanoparticle powders. All resulting aerosols exhibited unimodal size distributions and mode particle diameters below 100 nm. We used the new aerosolization technique to investigate the reaction between aerosolized C₆₀ and atmospherically realistic levels of ozone (O₃) in terms of reaction products, reaction rate, and oxidative stress potential. We identified C₆₀O, C₆₀O2, and C₆₀O3 as products of the C₆₀-O3 reaction. We demonstrated that the oxidative stress potential of C₆₀ may be enhanced by exposure to O3. We found the pseudo-first order reaction rate to be 9 x 10⁻⁶ to 2 x 10⁻⁵ s⁻¹, which is several orders of magnitude lower than the rate for several PAH species under comparable conditions. This research has demonstrated that a thorough understanding of atmospheric chemistry of ENPs is critical for accurate prediction of their environmental impacts. It has also enabled future research in that vein by developing a novel technique to produce nanoscale aerosols from nanoparticle powders. Results of this research will help guide the formulation of appropriate environmental policy concerning the regulation of ENPs. / Ph. D.

Die entsprechend der Quellstärke größte Fraktion des atmosphärischen Aerosols ist der natürliche Grobstaub (Seesalz, Mineralstaub und primär biologische Partikel). Nahezu alle natürlichen Grobstaubpartikel in trockener Phase weisen mehr oder weniger starke Abweichungen von der sphärischen Form auf. Der Einfluss der Asphärizität auf die aerodynamischen und optischen Eigenschaften kann durch sogenannte Formfaktoren unter Verwendung einer Referenzgröße berücksichtigt werden. Für wissenschaftliche Fragestellungen, die sowohl auf aerodynamischen wie auch optischen Aspekten beruhen, bedarf es einer vollständigen Betrachtung des Einflusses der Partikelmorphologie, um ein physikalisch plausibles Ergebnis zu erhalten. Gegenstand dieser Arbeit ist die Analyse der Relationen zwischen aerodynamischen und optischen Eigenschaften. Ziel ist die approximative Darstellung der optischen Formfaktoren durch den aerodynamischen Formfaktor als Maßzahl der Asphärizität. Hierfür wurden sowohl geometrische Formparameter als auch aerodynamische und optische Formfaktoren für ein Ensemble von regelmäßigen und unregelmäßigen Partikeln simuliert. Der Approximation der optischen Formfaktoren durch den aerodynamischen Formfaktor werden theoretische Überlegungen und Ergebnisse numerischer Simulationen vorangestellt. Die optischen Formfaktoren sind dabei primär eine Funktion des Größenparameters (Partikelgröße und Wellenlänge) und des aerodynamischen Formfaktors. In Laborexperimenten wurden beide Abhängigkeiten unter Verwendung von Proben mit Partikeln unterschiedlicher Asphärizität validiert. Die resultierende Approximation ermöglicht eine einfache und konsistente Beschreibung des Einflusses der Partikelmorphologie auf die aerodynamischen und optischen Eigenschaften. Dies ist eine unabdingbare Voraussetzung für eine genauere Analyse von Partikeleigenschaften, die aus aerodynamisch und optisch basierten In-situ-Messungen abgeleitet werden.

In diesem Beitrag werden Ansätze beschrieben, wie man aus flugzeuggetragenen Messungen von Eigenschaften atmosphärischer Extingenten die für Strahlungstransportrechnungen notwendigen Größen und Parameter rekonstruieren kann. Angewendet wird das Programm zur ersten Auswertung für bezüglich der Strahlung verschiedene atmosphärische Situationen. Die Daten hierzu wurden auf der ersten Messkampagne des Projektes INSPECTRO gesammelt. Es zeigt sich für den Fall einer Atmosphäre mit stratiformer Bewölkung eine gute Übereinstimmung mit den Messungen. Eine genaue Berechnung der Extinktion durchWolken mittels Tropfenspektren bringt derzeit keine Vorteile gegenüber einer einfachen Parametrisierung. Für den Fall eines durchbrochenen Wolkenfeldes ergeben sich lokal große Unterschiede zwischen Simulation und Messung. Dennoch läßt sich zeigen, daß die gemessenen und berechneten Felder des aktinischen Flusses einander sehr ähnliche statistische Eigenschaften haben. / In this article some methods to reconstruct an artificial three-dimensional atmosphere from flight measurement data are described. The artificial atmosphere shall accurately represent the scattering properties of the real atmosphere, that are necessary to perform radiative transfer simulations. The method is applied to conduct a preliminary analysis of several atmospheric situations corresponding to different sets of radiative properties. The analyzed measurement data was collected during the first measurement campaign within the INSPECTRO project. In the case of an atmosphere containing a stratiform cloud layer, the measurements and simulation results are in very good agreement. A more accurate calculation of the extinction of radiation within the clouds by way of accounting for measured droplet spectra does momentarily not lead to an improvement in comparison with the simple parameterization method. In the case of a broken cloud field the significant local discrepancies between the measurement data and simulation results are to be noted. Nevertheless it can be shown that the statistical properties of the measured and calculated actinic flux fields resemble each other very closely.

(EN) This Diploma Thesis is concerned with statistical analysis of coarse aerosol at the area of the capital city Prague with focus on its time and space variability. The data covers time period from year 2005 up to year 2010 included. The concentrations of coarse aerosol were originally calculated from recorded values of PM10 a PM2,5. The assessment used in this thesis is based on concentrations of coarse aerosol recorded on four pollutant stations which are localized in the capital city. Three out of four those air pollution monitoring stations are characterized as traffic stations kind of purse, where we can assume the traffic's impact over the coarse aerosol concentration. The last station is distinguished to be background to report the data of region less loaded by pollution. The analysis is executed within particular parameters supposing that main source of coarse aerosol is traffic in urban environment. For time period examination variability the year, season, week and day running was carried out. The spatial variability was researched by the air pollution monitoring stations localization. To determine a rate of dependency among particular parameters the correlation analysis according to Spearman was used within the calculation of correlation coefficients. Beside the analysis this thesis...

This paper describes approaches to retrieve important aerosol results from the strong lidar return signals that are received by the space-borne CALIPSO lidar system after reflecting off-ocean surfaces. Relations, from which the theoretically expected values of area under ocean surface returns can be computed, are presented. A detailed description of the lidar system response to the ocean surface returns and the processes of sampling and averaging of lidar return signals are provided. An effective technique that reconstructs the lidar response to surface returnsstarting from down-linked samplesand calculates the area under it, has been developed and described. The calculated area values are validated after comparing them to their theoretically predicted counterpart values. Methods to retrieve aerosol optical depths (AODs) from these calculated areas are described and retrieval results are presented, including retrieval comparison with independent AOD measurements made by an airborne High Spectral Resolution Lidar (HSRL) that yielded quite good agreement. Techniques and results are also presented on using the spectral ratios of the surface response areas to determine spectral ratios of aerosol round-trip transmission and AOD spectral difference, without need of a specific/accurate ocean-surface reflectance model.

Durch Messungen von spektraler optischer Dicke, Sonnenaureole und Himmelshelligkeit in Kombination mit den Programmen CIRATRA und BILANZ werden die optischen Eigenschaften von Sahara-Wüstenaerosol und dessen klimatische Wirkung unter Berücksichtigung der Nichtsphärizität der Aerosolpartikel untersucht. / By combining measurements of spectral optical thickness, solar aureole and sky brightness with the programs CIRATRA and BILANZ the optical porperties of Saharan desert aerosol and its climatic effects are investigated, including a consideration of the Nonsphericity of the aerosol particles.

<p>Predmet istraživanja ove doktorske disertacije<br />je bio formiranje i proučavanje osobina i<br />pona&scaron;anja organskih aerosola nastalih<br />atomiziranjem stabilnih emulzija dominantno<br />pod dejstvom centrifugalne sile. Kori&scaron;ćene su<br />vodene emulzije komercijalnih sredstava za<br />hlađenje i podmazivanje (SHP), koja se koriste<br />pri obradi metalnih odlivaka. Cilj istraživanja je<br />bio ispitati i objasniti uticaj koncentracije SHP<br />emulzije, brzine strujanja vazduha, prirode kako<br />ulja, tako i osobina emulzija, kao &scaron;to su gustina,<br />viskoznost, povr&scaron;inski napon, kao i udaljenost<br />od mesta atomiziranja na masenu koncentraciju,<br />broj i veličinu kapi aerosola u kontrolisanim<br />laboratorijskim uslovima.<br />Uslovi eksperimenta isključili su uticaj toplote<br />nastale kao posledica trenja alata i delova koji<br />se obrađuju. Pored toga isključeno je prisustvo<br />čvrstih mikronskih čestica koje potiču od delova<br />koji se obrađuju, kao i prisutvo plivajućeg<br />hidrauličnog ulja i mikroorganizama koji uvek<br />prate realan industrijski fluid.<br />Eksperimentalni program je realizovan na tri<br />komercijalna SHP sredstva različitog porekla.<br />Proučavani su aerosoli formirani atomiziranjem<br />emulzije tri različite koncentracije uljne faze: 1,<br />6 i 10 %. Pri jednakim eksperimentalnim<br />uslovima ispitivan je i aerosol formiran, od<br />vode kori&scaron;ćene za pripremu emulzija. Određene<br />su osobine ulja i emulzija koje su od značaja za<br />atomiziranje tečnosti. Proučavan je i uticaj<br />brzine ventilacionog vazduha na osobine<br />aerosola. Eksperimenti su realizovani pri<br />brzinama vazduha od 1, 3, 6, 8 m/s.<br />Uzorkovanje aerosola je realizovano u komori,<br />na ulazu u ventilacini vod i duž ventilacione<br />cevi dužine 8m na pet mernih tačaka koje se<br />nalaze na 0,5, 1, 2, 4, 6, 8 m u odnosu na<br />komoru.<br />Značajan doprinos ove doktorske disertacije je<br />postavljanje teorije da atomiziranjem emulzije<br />kao heterogene tečnosti, nastaje heterogen<br />aerosol, pri čemu mogu nastati kapi različite<br />prirode, između ostalog i kapi čistog ulja. Na taj<br />način je obja&scaron;njen fenomen da porastom<br />koncentracije emulzije raste veličina kapi<br />nastalog aerosola. Aerosoli nastali od<br />koncentrovanijih emulzija pokazuju uređenije<br />strujanje kroz ventilacionu cev, &scaron;to je od<br />značaja za uspe&scaron;nije projektovanje ventilacionih<br />sistema i filtara za njihovu separaciju u cilju<br />za&scaron;tite zdravlja radnika i za&scaron;tite okoline.</p> / <p> This PhD Thesis presents an experimental<br /> study of organic aerosols formed from stable<br /> water emulsions, predominantly by centrifugal<br /> force under laboratory conditions. Emulsions of<br /> metalworking fluids (MWF) were used in the<br /> experiments. The aim of this investigation was<br /> to explain the influence of MWF emulsion<br /> concentration, oil and emulsion properties<br /> (density, viscosity, and surface tension), air<br /> velocity, as well as distance from atomization<br /> generator on aerosol behavior and properties as<br /> size distribution, mass and number<br /> concentration. The experimental conditions<br /> excluded the influence of the heat arising from<br /> the friction between the tool and the<br /> workpieces. In this way the mechanism of<br /> aerosol formation by the<br /> evaporation/condensation is minimized.<br /> Besides, the presence of solid micrometer sized<br /> particulates originated from the work piece is<br /> excluded, as well as the presence of tramp oil<br /> and microorganisms, always accompanying a<br /> real industrial fluid.<br /> Three different commercial MWFs were<br /> investigated at three different oil-in-water<br /> emulsion concentrations, 1, 6, and 10 %<br /> respectively. Water aerosol was investigated<br /> under same experimental conditions. Properties<br /> of MWF oils and emulsion, which are important<br /> for liquid atomization, were determined.<br /> Influence of ventilation air velocity on aerosol<br /> properties was investigated as well.<br /> Experiments were realized under four different<br /> air velocities: 1, 3, 6, and 8 m/s. Samples were<br /> taken at three different points: at the camber, at<br /> the entrance of ventilation pipe, and at five<br /> sampling points along the pipe. Ventilation pipe<br /> was 8 m long, and sampling point were at 0.5, 1,<br /> 2, 4, 6, 8 m from the aerosol camber.<br /> The main contribution of this dissertation is<br /> the new theory that atomization of emulsion as a<br /> heterogeneous fluid leads to the formation of<br /> heterogeneous aerosol, containing droplets of a<br /> different nature, including droplets of pure oil.<br /> This theory explains the phenomenon that the<br /> aerosol droplet sizes increase with the increase<br /> of the emulsion concentration. Obtained results<br /> show that aerosols formed from the emulsions<br /> of higher concentration (6 and 10 %) have less<br /> chaotic flow through the ventilation pipe. This<br /> observation is important for better design of<br /> ventilation systems and filters for mist<br /> separation in order to protect human health and<br /> the environment.&nbsp;</p>

In this thesis the occurrence and the properties of atmospheric particles within Europe are studied by means of the regional transport model COSMO-MUSCAT (Consortium for Small-scale Modeling - MultiScale Atmospheric Transport Model). The model is used to perform calculations for a summer (19-26 July 2006) and a winter (16-26 February 2007) period. Individual extinction coefficients are computed taking into account hygroscopic growth and mass extinction efficiencies of specific chemical compounds. The model study focuses on vertical backscatter profiles, aerosol optical depths, particle surface concentrations and radiative effects. Different descriptions of the vertical distribution of chemical compounds at the lateral model boundaries are tested. The results show that for the tested model setup the influence of the aerosol distribution at the model boundaries on European aerosol is limited. Information from lidar profiles may improve the description at the lateral model boundaries. This may be more important for smaller model domains. Space-based lidar (light detection and ranging) observations (CALIOP - Cloud-Aerosol Lidar with Orthogonal Polarization) observations are compared to the simulated backscatter profiles caused by the simulated anthropogenic aerosol. The model reproduces the shape and magnitude of the vertical backscatter profiles well for both time periods. Better agreements are found for night-time observations compared to day-time data. Satisfying agreements between the model results and experimental observations of ground-based vertical backscatter profiles, aerosol optical depths and particle surface concentrations are also found for the two time periods in Europe. Discrepancies between measurement and simulation highlight the difficulties to describe horizontal and vertical aerosol properties properly. The direct and semi-direct radiative effects of the absorbing aerosol are studied for both summer and winter period. For both periods, an increase of the solar heating rate due to the aerosol forcing is determined. This heating leads to an average decrease of the total cloud cover of 1.0% (summer) and of 0.7% (winter). This semi-direct radiative effect causes a positive forcing at the surface and at the top-of-atmosphere in the European domain.