Developing Models Of Aerosol Representation To Investigate Composition Evolution Optical Properties And Ccn Spectra Using Measurements Of Size Resolved Hygroscopicity

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Developing Models of Aerosol Representation to Investigate Composition, Evolution, Optical Properties, and CCN Spectra Using Measurements of Size-resolved Hygroscopicity

Author : Roberto Gasparini
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (89 download)

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Book Synopsis Developing Models of Aerosol Representation to Investigate Composition, Evolution, Optical Properties, and CCN Spectra Using Measurements of Size-resolved Hygroscopicity by : Roberto Gasparini

Download or read book Developing Models of Aerosol Representation to Investigate Composition, Evolution, Optical Properties, and CCN Spectra Using Measurements of Size-resolved Hygroscopicity written by Roberto Gasparini and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) was used to measure size distributions, hygroscopicity, and volatility during the May 2003 Aerosol Intensive Operational Period at the Central Facility of the Atmospheric Radiation Measurement Southern Great Plains site. Hygroscopic growth factor distributions for particles at eight dry diameters ranging from 0.012 [mu]m to 0.600 [mu]m were measured. These measurements, along with backtrajectory clustering, were used to infer aerosol composition and evolution. The hygroscopic growth of the smallest and largest particles analyzed was typically less than that of particles with dry diameters of about 0.100 [mu]m. Condensation of secondary organic aerosol on nucleation mode particles may be responsible for the minimal growth observed at the smallest sizes. Growth factor distributions of the largest particles typically contained a non-hygroscopic mode believed to be composed of dust. A model was developed to characterize the hygroscopic properties of particles within a size distribution mode through analysis of the fixed-size hygroscopic growth measurements. This model was used to examine three cases in which the sampled aerosol evolved over a period of hours or days. Additionally, size and hygroscopicity information were combined to model the aerosol as a population of multi-component particles. With this model, the aerosol hygroscopic growth factor f(RH), relating the submicron scattering at high RH to that at low RH, is predicted. The f(RH) values predicted when the hygroscopic fraction of the aerosol is assumed to be metastable agree better with measurements than do those predicted under the assumption of crystalline aerosol. Agreement decreases at RH greater than 65%. This multi-component aerosol model is used to derive cloud condensation nuclei (CCN) spectra for comparison with spectra measured directly with two Desert Research Institute (DRI) CCN spectrometers. Among the 1490 pairs of DMA/TDMA-predicted and DRI-measured CCN concentrations at various critical supersaturations from 0.02-1.05%, the sample number-weighted mean R2 value is 0.74. CCN concentrations are slightly overpredicted at both the lowest (0.02-0.04%) and highest (0.80-1.05%) supersaturations measured. Overall, this multi-component aerosol model based on size distributions and size-resolved hygroscopicity yields reasonable predictions of the humidity-dependent optical properties and CCN spectra of the aerosol.

Dissertation Abstracts International

Author :
Publisher :
ISBN 13 :
Total Pages : 846 pages
Book Rating : 4.F/5 ( download)

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Book Synopsis Dissertation Abstracts International by :

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 846 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Investigation of the Optical and Cloud Forming Properties of Pollution, Biomass Burning, and Mineral Dust Aerosols

Author : Yong Seob Lee
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (811 download)

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Book Synopsis Investigation of the Optical and Cloud Forming Properties of Pollution, Biomass Burning, and Mineral Dust Aerosols by : Yong Seob Lee

Download or read book Investigation of the Optical and Cloud Forming Properties of Pollution, Biomass Burning, and Mineral Dust Aerosols written by Yong Seob Lee and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the use of measured aerosol size distributions and size-resolved hygroscopic growth to examine the physical and chemical properties of several particle classes. The primary objective of this work was to investigate the optical and cloud forming properties of a range of ambient aerosol types measured in a number of different locations. The tool used for most of these analyses is a differential mobility analyzer / tandem differential mobility analyzer (DMA / TDMA) system developed in our research group. To collect the data described in two of the chapters of this dissertation, an aircraft-based version of the DMA / TDMA was deployed to Japan and California. The data described in two other chapters were conveniently collected during a period when the aerosol of interest came to us. The unique aspect of this analysis is the use of these data to isolate the size distributions of distinct aerosol types in order to quantify their optical and cloud forming properties. I used collected data during the Asian Aerosol Characterization Experiment (ACE-Asia) to examine the composition and homogeneity of a complex aerosol generated in the deserts and urban regions of China and other Asian countries. An aircraft-based TDMA was used for the first time during this campaign to examine the size-resolved hygroscopic properties of the aerosol. The Asian Dust Above Monterey (ADAM-2003) study was designed both to evaluate the degree to which models can predict the long-range transport of Asian dust, and to examine the physical and optical properties of that aged dust upon reaching the California coast. Aerosol size distributions and hygroscopic growth were measured in College Station, Texas to investigate the cloud nucleating and optical properties of a biomass burning aerosol generated from fires on the Yucatan Peninsula. Measured aerosol size distributions and size-resolved hygroscopicity and volatility were used to infer critical supersaturation distributions of the distinct particle types that were observed during this period. The predicted cloud condensation nuclei concentrations were used in a cloud model to determine the impact of the different aerosol types on the expected cloud droplet concentration. RH-dependent aerosol extinction coefficients were also calculated.

Models for the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on Their Optical Properties

Author : Eric P. Shettle
Publisher :
ISBN 13 :
Total Pages : 100 pages
Book Rating : 4.3/5 (91 download)

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Book Synopsis Models for the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on Their Optical Properties by : Eric P. Shettle

Download or read book Models for the Aerosols of the Lower Atmosphere and the Effects of Humidity Variations on Their Optical Properties written by Eric P. Shettle and published by . This book was released on 1979 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosol models have been developed for the lower atmosphere. These models are representative of conditions found in rural, urban, and maritime air masses. The changes in the aerosol properties with variations in the relative humidity are discussed. To describe the aerosol optical properties in the extreme of 100 percent relative humidity, several fog models are presented. For each model the coefficients for extinction, scattering, and absorption, the angular scattering distribution, and other optical parameters have been computed for wavelengths between 0.2 and 40 microns. These aerosol models are presented together with a review of their experimental basis. The optical properties of these models are discussed and some comparisons of the model with experimental measurements are presented.

Size Dependent Morphology of Organic Aerosol

Author : Muhammad Altaf
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (992 download)

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Book Synopsis Size Dependent Morphology of Organic Aerosol by : Muhammad Altaf

Download or read book Size Dependent Morphology of Organic Aerosol written by Muhammad Altaf and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Earths atmosphere is composed of a wide variety of gas phase species and particulate matter that have a large impact on our climate. Though our understanding of the climate system has improved significantly over the past few decades, the impact of aerosol particles remains uncertain. Aerosol particles can affect climate through the absorption and scattering of radiation (aerosol direct effect) and by serving as cloud condensation nuclei (aerosol indirect effect). It is known that aerosol particles cause a net cooling effect on the planet, but the magnitude of cooling is unclear and remains under investigation. A large part of this uncertainty is due to an incomplete understanding of the complex physical and chemical properties of aerosol particles such as composition, morphology, and phase state.In this dissertation, we focus on investigating the role of particle size and composition in determining morphology. We have discovered that for some organic aerosol systems, particle morphology depends on size, where small particles are homogeneous and large particles are phase separated. To explore the origins of this size dependent behavior, we have worked with a model organic aerosol system, poly(ethylene glycol)-400 mixed with ammonium sulfate. We have used cryogenic-transmission electron microscopy to probe the effect of phase separation mechanism on particle morphology by varying the organic aerosol composition. Our results suggest that a size dependent morphology occurs due to an activated process, where the presence or absence of an activation barrier to phase separation controls the resulting morphology.We have also explored the kinetics and thermodynamics of the phase separation process that results in a size dependent morphology by varying the experimental drying rates. Drying rates that span over four orders of magnitude were investigated. We have observed that at the fastest drying rates, the size of the transition region where both phase separated and homogeneous morphologies exist is on the order of ~100 nm. At the slowest drying rates, the transition region shifts to smaller diameters and the width narrows to ~3 nm. Our results suggest that a size dependent morphology persists to the slowest drying rates. Thus, we conclude that an underlying thermodynamic effect results in this size dependent behavior, rather than solely a kinetic phenomenon.To determine the atmospheric implications of a size dependent morphology, we have used a cloud condensation nuclei counter to probe the effect of a homogeneous vs. a phase separated morphology on cloud condensation nuclei (CCN) activity. We have found that the activation diameters differ for particles which have the same composition, but varying morphology. Since aerosol optical properties are a sensitive measure of particle structure, we have studied the morphology-resolved optical properties of organic aerosol using cavity ring-down spectroscopy. Our spectroscopy data indicate that the optical properties of core-shell and partially engulfed particles are approximately equal, but different than the prediction for homogeneous particles. By accurately parametrizing aerosol particle morphology, optical properties, and CCN activity we will be able to better predict heterogeneous chemistry in the atmosphere, in addition to the aerosol direct and aerosol indirect effects which play a critical role in constraining climate forcing.

Atmospheric Aerosols: Their Optical Properties and Effects

Author :
Publisher :
ISBN 13 :
Total Pages : 348 pages
Book Rating : 4.:/5 (317 download)

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Book Synopsis Atmospheric Aerosols: Their Optical Properties and Effects by :

Download or read book Atmospheric Aerosols: Their Optical Properties and Effects written by and published by . This book was released on 1976 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Opportunities to Improve Representation of Clouds and Aerosols in Climate Models with Classified Observing Systems

Author : National Academies of Sciences, Engineering, and Medicine
Publisher : National Academies Press
ISBN 13 : 0309443458
Total Pages : 53 pages
Book Rating : 4.3/5 (94 download)

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Book Synopsis Opportunities to Improve Representation of Clouds and Aerosols in Climate Models with Classified Observing Systems by : National Academies of Sciences, Engineering, and Medicine

Download or read book Opportunities to Improve Representation of Clouds and Aerosols in Climate Models with Classified Observing Systems written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2016-08-31 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most significant and uncertain aspects of climate change projections is the impact of aerosols on the climate system. Aerosols influence the climate indirectly by interacting with nearby clouds leading to small changes in cloud cover, thickness, and altitude, which significantly affect Earth's radiative balance. Advancements have been made in recent years on understanding the complex processes and atmospheric interactions involved when aerosols interact with surrounding clouds, but further progress has been hindered by limited observations. The National Academies of Sciences, Engineering, and Medicine organized a workshop to discuss the usefulness of the classified observing systems in advancing understanding of cloud and aerosol interactions. Because these systems were not developed with weather and climate modeling as a primary mission objective, many participants said it is necessary for scientists to find creative ways to utilize the data. The data from these systems have the potential to be useful in advancing understanding of cloud and aerosol interactions. This publication summarizes the presentations and discussions from the workshop.

Aerosol Characteristics and Visibility

Author : Alan P. Waggoner
Publisher :
ISBN 13 :
Total Pages : 56 pages
Book Rating : 4.:/5 (31 download)

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Book Synopsis Aerosol Characteristics and Visibility by : Alan P. Waggoner

Download or read book Aerosol Characteristics and Visibility written by Alan P. Waggoner and published by . This book was released on 1977 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Using Measurements of CCN Activity to Characterize the Mixing State, Chemical Composition, and Droplet Growth Kinetics of Atmospheric Aerosols to Constrain the Aerosol Indirect Effect

Download Using Measurements of CCN Activity to Characterize the Mixing State, Chemical Composition, and Droplet Growth Kinetics of Atmospheric Aerosols to Constrain the Aerosol Indirect Effect PDF Online Free

Author : Richard Herbert Moore
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (844 download)

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Book Synopsis Using Measurements of CCN Activity to Characterize the Mixing State, Chemical Composition, and Droplet Growth Kinetics of Atmospheric Aerosols to Constrain the Aerosol Indirect Effect by : Richard Herbert Moore

Download or read book Using Measurements of CCN Activity to Characterize the Mixing State, Chemical Composition, and Droplet Growth Kinetics of Atmospheric Aerosols to Constrain the Aerosol Indirect Effect written by Richard Herbert Moore and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric aerosols are known to exert a significant influence on the Earth's climate system; however, the magnitude of this influence is highly uncertain because of the complex interaction between aerosols and water vapor to form clouds. Toward reducing this uncertainty, this dissertation outlines a series of laboratory and in-situ field measurements, instrument technique development, and model simulations designed to characterize the ability of aerosols to act as cloud condensation nuclei (CCN) and form cloud droplets. Specifically, we empirically quantify the mixing state and thermodynamic properties of organic aerosols (e.g., hygroscopicity and droplet condensational uptake coefficient) measured in polluted and non-polluted environments including Alaska, California, and Georgia. It is shown that organic aerosols comprise a substantial portion of the aerosol mass and are often water soluble. CCN measurements are compared to predictions from theory in order to determine the error associated with simplified composition and mixing state assumptions employed by current large-scale models, and these errors are used to constrain the uncertainty of global and regional cloud droplet number and albedo using a recently-developed cloud droplet parameterization adjoint coupled with the GMI chemical transport model. These sensitivities are important because they describe the main determinants of climate forcing. We also present two novel techniques for fast measurements of CCN concentrations with high size, supersaturation, and temporal resolution that substantially improve the state of the art by several orders of magnitude. Ultimately, this work represents a step toward better understanding how atmospheric aerosols influence cloud properties and Earth's climate.

Clouds in the Perturbed Climate System

Author : Jost Heintzenberg
Publisher : Strungmann Forum Reports
ISBN 13 : 9780262012874
Total Pages : 0 pages
Book Rating : 4.0/5 (128 download)

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Book Synopsis Clouds in the Perturbed Climate System by : Jost Heintzenberg

Download or read book Clouds in the Perturbed Climate System written by Jost Heintzenberg and published by Strungmann Forum Reports. This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: More than half the globe is covered by visible clouds.

Chemistry of Atmospheric Aerosol Particles and Their Resulting Warm Cloud-nucleation Properties

Author : Meagan Julia Kerry Moore
Publisher :
ISBN 13 : 9781124543123
Total Pages : 281 pages
Book Rating : 4.5/5 (431 download)

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Book Synopsis Chemistry of Atmospheric Aerosol Particles and Their Resulting Warm Cloud-nucleation Properties by : Meagan Julia Kerry Moore

Download or read book Chemistry of Atmospheric Aerosol Particles and Their Resulting Warm Cloud-nucleation Properties written by Meagan Julia Kerry Moore and published by . This book was released on 2011 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric aerosol particles are a major component of the troposphere and affect regional and global atmospheric chemistry and climate. The size and chemistry of these particles influences the warm and cold cloud nucleation ability and optical properties of the aerosol particles. This dissertation investigates the atmospheric chemistry of aerosol particles and their role in warm cloud nucleation through a combination of laboratory experiments and field measurements. The effect of organics on the cloud condensation nuclei (CCN) activity of sea spray aerosols is described in Chapter 2. Sea spray aerosol produced by bubbling solutions composed of simplistic mixtures of NaCl and oleic acid or SDS had a significant effect on CCN activity, even in very small amounts; while artificial seawater solutions containing microorganisms, the common cyanobacteria (Synechococcus) and DMS-producing green algae (Ostreococcus), produced particles containing ~34 times more carbon than the particles produced from pure ASW, with no significant change observed in the overall CCN activity. During the fall of 2007 and 2008, over 300,000 acres burned in San Diego County wildfires. The resulting particle chemistry and estimated hygroscopicity during these wildfire events are explored in Chapter 3. The contribution of wildfire emissions were much larger and played a more significant role in affecting cloud condensation nuclei and total particle concentrations in 2007 than in 2008. The overall particle hygroscopicity during the biomass burning dominated periods was very similar; however in 2008, the particle hygroscopicity was dominated by local sources rather than biomass burning, due to the much smaller particle size mode. Owens Lake is one of the largest sources of PM2.5 in the Western Hemisphere, producing highly soluble dust plumes, and therefore there is great potential for those particles to impact cloud formation and possibly precipitation in the region. Chapter 4 explores particle chemistry and estimated hygroscopicity at Owens Lake. No significant change in particle hygroscopicity or CCN activity occurred concurrently with the change in mixing of particle classes during two different dust events at Owens Lake; indicating that the large dust particles were most likely completely CCN active and the smaller particles are likely dictating the hygroscopicity, as most of the dust particles are large enough and would activate to become CCN regardless of their hygroscopicity. The Cloud Indirect Forcing Experiment (CIFEX) took place to study the influence of aerosols on cloud properties at Trinidad Head, a coastal site in northern California representing clean marine air with periodic long-range transport. Chapters 5 & 6 explore particle chemistry, mixing state, optical properties and estimated hygroscopicity during CIFEX. Our measurements demonstrate how changes in hygroscopicity and optical properties evolve over time in the atmosphere as a function of particle chemistry and the mixing state of the aerosol. Two distinct oxalate events with enrichment of oxalate on different particle types and sizes suggest two separate sources of oxalate.

Quantifying Compositional Impacts of Ambient Aerosol on Cloud Formation

Author : Sara Lance
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (43 download)

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Book Synopsis Quantifying Compositional Impacts of Ambient Aerosol on Cloud Formation by : Sara Lance

Download or read book Quantifying Compositional Impacts of Ambient Aerosol on Cloud Formation written by Sara Lance and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been historically assumed that most of the uncertainty associated with the aerosol indirect effect on climate can be attributed to the unpredictability of updrafts. We assess the sensitivity of cloud droplet number density to realistic variations in aerosol chemical properties and to variable updraft velocities using a 1-dimensional cloud parcel model. The results suggest that aerosol chemical variability may be as important to the aerosol indirect effect as the effect of unresolved cloud dynamics, especially in polluted environments. We next used a continuous flow streamwise thermal gradient Cloud Condesnation Nuclei counter (CCNc) to study the water-uptake properties of the ambient aerosol, by exposing an aerosol sample to a controlled water vapor supersaturation and counting the resulting number of droplets. The heat transfer properties and droplet growth within the CCNc were first modeled and experimentally characterized. We describe results from the MIRAGE field campaign at a ground-based site during March, 2006. Size-resolved CCN activation spectra and hygroscopic growth factor distributions of the ambient aerosol in Mexico City were obtained, and an analytical technique was developed to quantify a probability distribution of solute volume fractions for the CCN, as well as the aerosol mixing-state. The CCN were shown to be much less CCN active than ammonium sulfate, with water uptake properties more consistent with low molecular weight organic compounds. We also describe results from the GoMACCS field study, an airborne field campaign in Houston, Texas during August-September, 2006. GoMACCS tested our ability to predict CCN for highly polluted conditions with limited chemical information. Assuming the particles were composed purely of ammonium sulfate, CCN closure was obtained with a 10% overprediction bias on average for CCN concentrations ranging from less than 100 cm-3 to over 10,000 cm-3, but with on average 50% variability. Assuming measured concentrations of organics to be internally mixed and insoluble tended to reduce the overprediction bias for less polluted conditions, but led to underprediction bias in the most polluted conditions. Comparing the two campaigns, it is clear that the chemistry of the particles plays an important role in our ability to predict CCN concentrations.

Fine Particles

Author : Benjamin Y.H. Liu
Publisher : Elsevier
ISBN 13 : 0323142214
Total Pages : 852 pages
Book Rating : 4.3/5 (231 download)

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Book Synopsis Fine Particles by : Benjamin Y.H. Liu

Download or read book Fine Particles written by Benjamin Y.H. Liu and published by Elsevier. This book was released on 2012-12-02 with total page 852 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fine Particles: Aerosol Generation, Measurement, Sampling, and Analysis is a collection of technical papers presented at the Symposium on Fine Particles held in Minneapolis, Minnesota, on May 28-30, 1975. The symposium aims to explore the developments in instrumentation and experimental techniques for aerosol studies. This book is organized into four parts encompassing 34 chapters that focus on fine particles below about 3.5 μm in diameter. Part I presents the research and development in Europe and Japan on fine particles and aerosols, as well as the aerosol standards development work at the Particle Technology Laboratory, University of Minnesota. This part also includes calibration studies on condensation nuclei counters and the diffusion battery. Significant chapters in Part II are devoted to the common techniques for generation of aerosols of various sizes, from fine particles to monodisperse aerosols. This part further looks into the equipment limitations and problems in producing fine particle aerosols for life testing air cleaning systems and for weather modification experimentation. Part III describes the techniques and equipment used for size-selective aerosol sampling in terms of the design principles applied, the correspondence between design and performance of specific samplers, their applicability to field conditions, and their ability to satisfy sampler acceptance criteria. Part IV deals first with the methods for determination of aerosol properties, including their optical, electrical, and spectral properties. Other chapters examine the principles, mode of operation, and application of processes and instruments for aerosol studies.

Morphology Dependent Optical Properties of Mixed Organic/Inorganic Aerosol Particles

Author : Kristin Di Monte
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (133 download)

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Book Synopsis Morphology Dependent Optical Properties of Mixed Organic/Inorganic Aerosol Particles by : Kristin Di Monte

Download or read book Morphology Dependent Optical Properties of Mixed Organic/Inorganic Aerosol Particles written by Kristin Di Monte and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Light extinction by atmospheric aerosol particles and their interactions with water are heavily dependent on their chemical composition, morphology, and mixing state. Both properties are crucial for determining the impact aerosol particles have on our climate. Since light extinction directly impacts visibility as well as climate, measurements of the extinction at varying relative humidities (RH) are needed in order to improve climate models. In this work we have measured the relative humidity dependence of aerosol light extinction and water uptake at 643 nm for particles of varying ammonium sulfate/organic compositions. Internal as well as external mixtures of levoglucosan, sucrose, and adipic acid with ammonium sulfate are investigated using cavity ring-down spectroscopy (CRDS). Optical growth factor (fRH) and hygroscopicity parameters ([kappa]) are reported for each aerosol system.

Laboratory Experiments and Instrument Intercomparison Studies of Carbonaceous Aerosol Particles

Author :
Publisher :
ISBN 13 :
Total Pages : 13 pages
Book Rating : 4.:/5 (946 download)

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Book Synopsis Laboratory Experiments and Instrument Intercomparison Studies of Carbonaceous Aerosol Particles by :

Download or read book Laboratory Experiments and Instrument Intercomparison Studies of Carbonaceous Aerosol Particles written by and published by . This book was released on 2015 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosols containing black carbon (and some specific types of organic particulate matter) directly absorb incoming light, heating the atmosphere. In addition, all aerosol particles backscatter solar light, leading to a net-cooling effect. Indirect effects involve hydrophilic aerosols, which serve as cloud condensation nuclei (CCN) that affect cloud cover and cloud stability, impacting both atmospheric radiation balance and precipitation patterns. At night, all clouds produce local warming, but overall clouds exert a net-cooling effect on the Earth. The effect of aerosol radiative forcing on climate may be as large as that of the greenhouse gases, but predominantly opposite in sign and much more uncertain. The uncertainties in the representation of aerosol interactions in climate models makes it problematic to use model projections to guide energy policy. The objective of our program is to reduce the uncertainties in the aerosol radiative forcing in the two areas highlighted in the ASR Science and Program Plan. That is, (1) addressing the direct effect by correlating particle chemistry and morphology with particle optical properties (i.e. absorption, scattering, extinction), and (2) addressing the indirect effect by correlating particle hygroscopicity and CCN activity with particle size, chemistry, and morphology. In this connection we are systematically studying particle formation, oxidation, and the effects of particle coating. The work is specifically focused on carbonaceous particles where the uncertainties in the climate relevant properties are the highest. The ongoing work consists of laboratory experiments and related instrument inter-comparison studies both coordinated with field and modeling studies, with the aim of providing reliable data to represent aerosol processes in climate models. The work is performed in the aerosol laboratory at Boston College. At the center of our laboratory setup are two main sources for the production of aerosol particles: (a) two well-characterized source of soot particles and (b) a flow reactor for controlled OH and/or O3 oxidation of relevant gas phase species to produce well-characterized SOA particles. After formation, the aerosol particles are subjected to physical and chemical processes that simulate aerosol growth and aging. A suite of instruments in our laboratory is used to characterize the physical and chemical properties of aerosol particles before and after processing. The Time of Flight Aerosol Mass Spectrometer (ToF-AMS) together with a Scanning Mobility Particle Sizer (SMPS) measures particle mass, volume, density, composition (including black carbon content), dynamic shape factor, and fractal dimension. The-ToF-AMS was developed at ARI with Boston College participation. About 120 AMS instruments are now in service (including 5 built for DOE laboratories) performing field and laboratory studies world-wide. Other major instruments include a thermal denuder, two Differential Mobility Analyzers (DMA), a Cloud Condensation Nuclei Counter (CCN), a Thermal desorption Aerosol GC/MS (TAG) and the new Soot Particle Aerosol Mass Spectrometer (SP-AMS). Optical instrumentation required for the studies have been brought to our laboratory as part of ongoing and planned collaborative projects with colleagues from DOE, NOAA and university laboratories. Optical instruments that will be utilized include a Photoacoustic Spectrometer (PAS), a Cavity Ring Down Aerosol Extinction Spectrometer (CRD-AES), a Photo Thermal Interferometer (PTI), a new 7-wavelength Aethalometer and a Cavity Attenuated Phase Shift Extinction Monitor (CAPS). These instruments are providing aerosol absorption, extinction and scattering coefficients at a range of atmospherically relevant wavelengths. During the past two years our work has continued along the lines of our original proposal. We report on 12 completed and/or continuing projects conducted during the period 08/14 to 0814/2015. These projects are described in ...

Modeling the Spectral Optical Properties of Ammonium Sulfate and Biomass Burning Aerosols

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (684 download)

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Book Synopsis Modeling the Spectral Optical Properties of Ammonium Sulfate and Biomass Burning Aerosols by :

Download or read book Modeling the Spectral Optical Properties of Ammonium Sulfate and Biomass Burning Aerosols written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The importance of including the global and regional radiative effects of aerosols in climate models has increasingly been realized. Accurate modeling of solar radiative forcing due to aerosols from anthropogenic sulfate and biomass burning emissions requires adequate spectral resolution and treatment of spatial and temporal variability. The variation of aerosol spectral optical properties with local relative humidity and dry aerosol composition must be considered. Because the cost of directly including Mie calculations within a climate model is prohibitive, parameterizations from offline calculations must be used. Starting from a log-normal size distribution of dry ammonium sulfate, we developed optical properties for tropospheric sulfate aerosol at 15 relative humidities up to 99 percent. The resulting aerosol size distributions were then used to calculate bulk optical properties at wavelengths between 0.175[micro]m and 4[micro]m. Finally, functional fits of optical properties were made for each of 12 wavelength bands as a function of relative humidity. Significant variations in optical properties occurred across the total solar spectrum. Relative increases in specific extinction and asymmetry factor with increasing relative humidity became larger at longer wavelengths. Significant variation in single-scattering albedo was found only in the longest near-IR band. This is also the band with the lowest albedo. A similar treatment was done for aerosols from biomass burning. In this case, size distributions were taken as having two carbonaceous size modes and a larger dust mode. The two carbonaceous modes were considered to be humidity dependent. Equilibrium size distributions and compositions were calculated for 15 relative humidities and five black carbon fractions. Mie calculations and Chandrasekhar averages of optical properties were done for each of the resulting 75 cases. Finally, fits were made for each of 12 spectral bands as functions of relative humidity and black carbon fraction.

Mixed-Phase Clouds

Author : Constantin Andronache
Publisher : Elsevier
ISBN 13 : 012810550X
Total Pages : 302 pages
Book Rating : 4.1/5 (281 download)

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Book Synopsis Mixed-Phase Clouds by : Constantin Andronache

Download or read book Mixed-Phase Clouds written by Constantin Andronache and published by Elsevier. This book was released on 2017-09-28 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. - Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate - Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry - Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling