Morphological Effects on the Radiative Properties of Soot Aerosols in Different Internally Mixing States with Sulfate PDF Download
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Languages : en
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Author: Alexander Kokhanovsky
Publisher: Springer
ISBN: 3030034453
Category : Science
Languages : en
Pages : 221
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This book presents a survey of modern theoretical techniques in studies of radiative transfer and light scattering phenomena in turbid media. It offers a comprehensive analysis of polarized radiative transfer, and also discusses advances in planetary spectroscopy as far as aerosol layer height determination is of interest. Further, it describes approximate methods of the radiative transfer equation solution for a special case of strongly scattering media. A separate chapter focuses on optical properties of Black Carbon aggregates.
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Languages : en
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Abstract : Soot particles form during incomplete combustion of carbonaceous materials. These particles strongly absorb light and directly affect Earth's climate by warming our atmosphere. When freshly emitted, soot particles have a fractal-like morphology consisting of aggregates of carbon spherules. During atmospheric processing, soot aggregates interact with other materials present in our atmosphere (i.e., other aerosol or condensable vapors) and these interactions can result in the formation of coated, mixed or compacted soot particles with different morphologies. Any process that alters the morphology (shape, size and internal structure) and mixing state of soot also affects its optical properties, which in turn affect the soot radiative forcing in the atmosphere. The complex morphology and internal mixing state of soot makes it difficult to estimate the soot's radiative properties. A detailed investigation of soot at the single particle level using electron microscopy, thus, becomes essential to provide accurate information for climate models, which generally assumes simple spherical morphologies. Tar balls are another type of carbonaceous aerosol, in the brown carbon family, commonly formed during smoldering combustion of biomass materials. Like soot, tar balls can also form aggregates. Tar balls aggregates have different optical properties from those of individual tar balls. During my doctorate studies, I made extensive use of electron microscopy and image analysis tools to investigate the morphology and mixing state of soot and tar balls collected during different laboratory and field studies. In one of my research projects, I explored the morphology of cloud processed soot. For this, I investigated the morphology of soot particles collected from the Po Valley in Italy where fog often forms, especially in winter. Our investigation showed that soot particles became compacted after fog processing. The compaction of soot was further corroborated by a laboratory study, in which cloud processing was carried out within the Michigan Technological University cloud chamber. In another research project, I studied the effects of thermodenuding on the morphology of soot. I investigated the morphology of five sets of soot samples of different sizes before xiii and after themodenuding. Our investigation showed no significant change in the morphology of soot by thermodenuding, a result that is important for those who attempt to measure the optical properties of internally mixed coated particles. In a third study, I used T-Matrix and Lorenz-Mie models to calculate the optical properties and then estimate the radiative forcing of tar ball aggregates and individual tar balls. In fact, in a recent publication, we reported a significant fraction of tar ball aggregates from different locations on Earth. My numerical calculations showed that the optical properties of tar ball aggregates are different from those of individual tar balls and are not always well approximated by Lorentz-Mie calculations. These findings highlight the necessity to account for the aggregation of tar balls in global models. My doctorate research provides detailed information on the morphology and mixing state of soot and tar ball aggregates. This information can be used to improve global climate models and reduce uncertainties in the radiative forcing of these aerosol particles.
Author: Swarup China
Publisher: MDPI
ISBN: 3038971332
Category : Science
Languages : en
Pages : 215
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This book is a printed edition of the Special Issue "Morphology and Internal Mixing of Atmospheric Particles" that was published in Atmosphere
Author: Craig F. Bohren
Publisher: John Wiley & Sons
ISBN: 3527618163
Category : Science
Languages : en
Pages : 544
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Book Description
Absorption and Scattering of Light by Small Particles Treating absorption and scattering in equal measure, this self-contained, interdisciplinary study examines and illustrates how small particles absorb and scatter light. The authors emphasize that any discussion of the optical behavior of small particles is inseparable from a full understanding of the optical behavior of the parent material-bulk matter. To divorce one concept from the other is to render any study on scattering theory seriously incomplete. Special features and important topics covered in this book include: * Classical theories of optical properties based on idealized models * Measurements for three representative materials: magnesium oxide, aluminum, and water * An extensive discussion of electromagnetic theory * Numerous exact and approximate solutions to various scattering problems * Examples and applications from physics, astrophysics, atmospheric physics, and biophysics * Some 500 references emphasizing work done since Kerker's 1969 work on scattering theory * Computer programs for calculating scattering by spheres, coated spheres, and infinite cylinders
Author: Huaxin Xue
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Languages : en
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Soot aerosols are well known to be atmospheric constituents, but the hydrophobic nature of fresh soot likely prohibits them from encouraging cloud development. Soot aged through contact with oxygenated organic compounds may become hydrophilic enough to promote water uptake. In this study, the tandem differential mobility analyzer (TDMA) and differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) were employed to measure the changes in morphology and hygroscopicity of soot aerosol particles upon coating with succinic and glutaric acids. The effective densities, fractal dimensions and dynamic shape factors of fresh and coated soot aerosol particles have been determined. Significant size-dependent increases of soot particle mobility diameter, mass, and effective density ([rho]eff) were observed upon coating of aggregates with succinic acid. These properties were restored back to their initial states once the acid was removed by heating, suggesting no restructuring of the soot core had occurred. Coating of soot with glutaric acid, on the other hand, leads to a strong size shrinking with a diameter growth factor ~0.60, even after the acid has been removed by heating suggesting the strong restructuring of the soot agglomerate. The additional 90% RH cycle can evidently enhance the restructuring process. The extinction and scattering properties at 532 nm of soot particles internally mixed with dicarboxylic acids were investigated experimentally using a cavity ring-down spectrometer and an integrating nephelometer, respectively, and the absorption is derived as the difference between extinction and scattering. It was found that the organic coatings significantly affect the optical and microphysical properties of the soot aggregates. The size-dependent amplification factors of light scattering were as much as 3.8 and 1.7 with glutaric and succinic acids coatings, respectively. Additional measurements with soot particles that are first coated with glutaric acid and then heated to remove the coating show that both scattering and absorption are enhanced by irreversible restructuring of soot aggregates to more compact globules. These results reveal the microphysical state of soot aerosol with incomplete restructuring in the atmosphere, and advance the treatment of atmospheric aged soot aerosol in the Mie theory shell-and-core model.
Author: Dan Zhang
Publisher:
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Category :
Languages : en
Pages :
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Soot particles released from fossil fuel combustion and biomass burning have a large impact on the regional/global climate by altering the atmospheric radiativeproperties and by serving as cloud condensation nuclei (CCN). However, the exact forcing is affected by the mixing of soot with other aerosol constituents, such as sulfuric acid. In this work, experimental studies have been carried out focusing on three integral parts: (1) heterogeneous uptake of sulfuric acid on soot; (2) hygroscopic growth of H2SO4-coated soot aerosols; (3) effect of H2SO4 coating on scattering and extinction properties of soot particles. A low-pressure laminar-flow reactor, coupled to ion drift chemical ionization mass spectrometry (ID-CIMS) detection, is used to study uptake coefficients of H2SO4 on combustion soot. The results suggest that uptake of H2SO4 takes place efficiently on soot particles, representing an important route to convert hydrophobic soot to hydrophilic aerosols. A tandem differential mobility analyzing (TDMA) system is employed to determine the hygroscopicity of freshly generated soot in the presence of H2SO4 coating. It is found that fresh soot particles are highly hydrophobic, while coating of H2SO4 significantly facilitates water uptake on soot even at sub-saturation relative humidities. The results indicate that aged soot particles in the atmosphere can potentially be an efficient source of CCN. Scattering and extinction coefficient measurements of the soot-H2SO4 mixed particles are conducted using a three wave length Nephelometer and a multi-path extinction cell. Coating of H2SO4 is found to increase the single scattering albedo (SSA) of soot particles which has impact on the aerosol direct radiative effect. Other laboratory techniques such as transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FTIR) are utilized to examine the morphology and chemical composition of the soot-H2SO4 particles. This work provides critical information concerning the heterogeneous interaction of soot and sulfuric acid, and how their mixing affects the hygroscopic and optical properties of soot. The results will improve our ability to model and assess the soot direct and indirect forcing and hence enhance our understanding of the impact of anthropogenic activities on the climate.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309133505
Category : Science
Languages : en
Pages : 222
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Book Description
Changes in climate are driven by natural and human-induced perturbations of the Earth's energy balance. These climate drivers or "forcings" include variations in greenhouse gases, aerosols, land use, and the amount of energy Earth receives from the Sun. Although climate throughout Earth's history has varied from "snowball" conditions with global ice cover to "hothouse" conditions when glaciers all but disappeared, the climate over the past 10,000 years has been remarkably stable and favorable to human civilization. Increasing evidence points to a large human impact on global climate over the past century. The report reviews current knowledge of climate forcings and recommends critical research needed to improve understanding. Whereas emphasis to date has been on how these climate forcings affect global mean temperature, the report finds that regional variation and climate impacts other than temperature deserve increased attention.
Author: Claudio Tomasi
Publisher: John Wiley & Sons
ISBN: 3527336451
Category : Science
Languages : en
Pages : 706
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Book Description
Ein Blick auf die morphologischen, physikalischen und chemischen Eigenschaften von Aerosolen aus den unterschiedlichsten natürlichen und anthropogenen Quellen trägt zum besseren Verständnis der Rolle bei, die Aerosolpartikel bei der Streuung und Absorption kurz- und langwelliger Strahlung spielen. Dieses Fachbuch bietet Informationen, die sonst schwer zu finden sind, und vermittelt ausführlich die Kenntnisse, die erforderlich sind, um die mikrophysikalischen, chemischen und Strahlungsparameter zu charakterisieren, die bei der Wechselwirkung von Sonnen- und Erdstrahlen so überaus wichtig sind. Besonderes Augenmerk liegt auf den indirekten Auswirkungen von Aerosolen auf das Klima im Rahmen des komplexen Systems aus Aerosolen, Wolken und der Atmosphäre. Auch geht es vorrangig um die Wirkungen natürlicher und anthropogener Aerosole auf die Luftqualität und die Umwelt, auf die menschliche Gesundheit und unser kulturelles Erbe. Mit einem durchgängig lösungsorientierten Ansatz werden nicht nur die Probleme und Gefahren dieser Aerosole behandelt, sondern auch praktikable Lösungswege aufgezeigt.
Author: Aihua Zhu
Publisher:
ISBN: 9781124187099
Category :
Languages : en
Pages : 446
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Book Description
By integrating experimental data, radiative transfer theory, and numerical modelling, this dissertation aims to improve our understanding of the radiative and the climate impacts of the major absorbing aerosols: mineral dust, black carbon (BC) and brown carbon. The research presented here combines existing surface, satellite and aircraft measurements and develops self-consistent models for aerosol mixing state, global and regional radiative forcing of absorbing aerosols and their climate effects. The first part of this dissertation presents the climatology and radiative impacts of dust plumes over the Pacific, the Indian and the Atlantic Oceans using multiple satellite datasets in conjunction with MACR (Monte Carlo Aerosol-Cloud-Radiation) model. A core-shell internally mixed aerosol model has been developed using the microphysical, chemical, and radiative observations as constraints. It is shown that internal mixing enhances the aerosol absorption and contributes to over 20% increase of radiative forcing. The aerosol mixing model is validated by comparing model simulated spectrally-resolved irradiance with observations. The results show that aerosol induced forcing is mainly confined in the visible band and the largest forcing occurs in the blue channel. distribution of the spectral radiative forcing is obtained. The aerosol forcing is used to drive a general circulation model (GCM) with prescribed sea surface temperature to investigate the impact of absorbing aerosols on regional climate. One of the main model findings is that heating of the atmosphere by absorbing aerosols can contribute to significant reductions in low level clouds, which in turn amplifies the warming. The simulated cloudiness reduction is particularly strong over the Arctic and China and the simulated warming over the Arctic exceeds 1.5°C. The findings of cloud reduction over China and the warming over the Arctic are consistent with observations. The above effects are relatively weak or negligible when absorbing aerosols are treated as externally mixed which is used as the assumption by most GCM studies thus far. This study reveals the fundamental importance of accounting for the observed chemical and physical properties of absorbing aerosols.
