Atmospheric Science Papers (Blue Books)
Permanent URI for this collection
Much of this digital collection of Blue Books comes from CSU's Department of Atmospheric Science. Included are student theses and dissertations and project reports dating from 1959 to 2007. The works focus on different areas of atmospheric science research such as climate change, severe weather, climatology, solar radiation, remote sensing, wind forecasting, and air quality.
Browse
Browsing Atmospheric Science Papers (Blue Books) by Subject "Aerosols"
Now showing 1 - 14 of 14
Results Per Page
Sort Options
Item Open Access A characterization of mixed silver iodide-silver chloride ice nuclei(Colorado State University. Libraries, 1982) DeMott, Paul J., author; Grant, Lewis O., author; Department of Atmospheric Science, Colorado State University, publisherIntroduces a new approach and methodology to study the ice nucleation properties of aerosols used for weather modification.Item Open Access Aeolian transport and vegetative capture of particulates(Colorado State University. Libraries, 1979) Glendening, John W., author; Department of Atmospheric Science, Colorado State University, publisherItem Open Access Chemical heterogeneity among cloud drop populations and its influence on aerosol processing in winter clouds(Colorado State University. Libraries, 1998-12) Xu, Gang, author; Collett, Jeffrey L., Jr., authorDrop-size resolved measurements of winter cloud composition in the Rocky mountains of northern Colorado revealed significant variations of cloud drop pH, ion (SO/, N03-, NH/, Ca2+) concentrations, and concentrations of trace metal catalysts (Fe and Mn) with drop size. The observed chemical heterogeneity across the cloud drop size spectrum was used to evaluate its influence on rates of in-cloud sulfate production and scavenging of major inorganic aerosol components by precipitation. The findings indicates that the size-dependent chemical composition of clouds tends to enhance aqueous sulfate production rates and to reduce the efficiency with which accumulation mode aerosol species are scavenged by precipitation. Simultaneous measurements of snow chemical composition and the degree of cloud drop capture by snow crystals (riming) revealed a significant positive correlation between snow composition and the extent of ice crystal riming in two of four cases studied. In the remaining cases it was found that the variations of snow composition were significantly correlated with air mass changes. Measurements of the size spectra of cloud drops attached on the surface of snow crystals showed that 10-17 µm and >17 µm cloud drop size fractions contributed significantly to accreted drop mass; little accreted mass was associated with drops smaller than 10 µm diameter.Item Open Access How does acidification of drops due to aqueous phase acid production limit aerosol formation in fog drops?(Colorado State University. Libraries, 1998-12) Collett, Jeffrey L., Jr., author; Hoag, Katherine J., author; Pandis, Spyros N., authorItem Open Access Influence of drop size-dependent fog chemistry on aerosol production and deposition in San Joaquin Valley fogs(Colorado State University. Libraries, 1998-10) Collett, Jeffrey L., Jr., author; Hoag, Katherine J., author; Pandis, Spyros N., authorItem Open Access Numerical and experimental performance evaluation of two multi-stage cloud collectors(Colorado State University. Libraries, 1999-01) Straub, Derek J., author; Collett, Jeffrey L., Jr., authorAn evaluation of the collection characteristics of two new multi-stage cascade inertial impactors designed for size-resolved cloud drop collection has been performed. The FROSTY supercooled cloud collector is intended for the collection of supercooled cloud drops in a winter environment in three independent size fractions with stage 50% cut diameters of 15 μm, 10 μm, and 4 μm . The CSU 5-Stage cloud collector is designed for sampling warm clouds in five distinct fractions on five stages that have desired 50% cut diameters of 30, 25, 15 , 10, and 4 μm. Two approaches were selected for the evaluation of the FROSTY and CSU 5-Stage cloud collectors. Numerical simulations provided a visualization of the air flow patterns and drop trajectories through the collectors while experimental laboratory calibrations provided a quantitative analysis of true collection performance. For each of these methods, 50% cut diameters, efficiency curves, and wall losses for each stage of the FROSTY and CSU 5-Stage collectors were derived. The experimental calibration work indicated that distinct fractions of cloudwater are collected in each stage of the FROSTY and CSU 5-Stage collectors. At laboratory conditions, the experimentally determined 50% cut diameters for the three stages of the FROSTY supercooled cloud collector were 19, 11.5, and 5 μm. Drop losses to the interstage wall surfaces in the FROSTY collector peaked at approximately 35% for 16 μm drops and were lower for larger and smaller drop sizes. For operation at design conditions of 3000 m elevation and -4° C, the 50% cut diameters are expected to decrease to 17, 10.5, and 4.5 μm. The experimentally determined 50% cut diameters, measured at laboratory conditions, for the CSU 5-Stage cloud collector were 25.5, 29, 17.5, 10.5, and 4.5 μm for stages 1 through 5, respectively. Wall losses tended to be higher than those for the FROSTY cloud collector across the drop size range under consideration. Losses peaked at nearly 45% for drops between 10 and 18 μm in diameter and decreased to about 20% at the largest and smallest drop sizes. 50% cut diameters are expected to remain essentially unchanged for CSU 5-Stage collector operation at sea level design conditions. Numerical modeling of the air flow patterns as well as drop trajectories through the FROSTY and CSU 5-Stage cloud collectors was performed with the commercially available Computational Fluid Dynamics (CFO) software package FLUENT, from Fluent, Inc. FLUENT offered two alternatives for the calculation of drop trajectories. Trajectory simulations based on the average continuous phase (air) velocity field as well as trajectory simulations which included the effects of statistically derived turbulent velocity fluctuations on drop motion were performed. Drop collection patterns based on these types of trajectory calculations were used to generate collection efficiency curves. Comparisons were made between the numerically predicted collection efficiency curves and efficiency curves established through experimental calibration. These comparisons indicated that the inclusion of turbulent fluctuation effects on drop motion provided better agreement with experimental observations than trajectories based only on average flow field velocities. However, the use of velocity fluctuations defined by default parameters also produced unrealistic losses to wall surfaces for small drop sizes. The parameters controlling turb lent velocity fluctuation effects on drop motion were examined in an effort to provide better agreement between the numerical and experimental results. Despite this shortcoming, numerically derived 50% cut diameters and overall collection efficiency curve shapes, for drop trajectories including turbulent velocity fluctuations, agreed reasonably well with experimental observations in most cases.Item Open Access Processing of aerosol particles and soluble trace gases by chemically heterogeneous radiation fogs(Colorado State University. Libraries, 2004-07) Chang, Hui, authorPersistent radiation fogs often form in California' s San Joaquin Valley (SJV) during periods of winter air stagnation. During winter 2000/2001 an extensive fog study was conducted in the San Joaquin Valley (SJV) in California, within the framework of the California Regional PM10/PM2.5 Air Quality Study (CRPAQS). The purpose of the study was to gain more information about the role of fogs in aerosol processing in the San Joaquin Valley. In addition to the CRPAQS fog study, samples from an additional radiation fog field campaign in January 2004 in Fresno, California were also analyzed as part of this project. The dominant contributors to SJV fog composition include ammonium, nitrate, sulfate, nitrite, acetate, formate, formaldehyde, glyoxal, and methyl glyoxal. Significant differences were observed between the composition of small and large SJV fog drops. Small drops contain higher concentrations of ammonium, nitrate, sulfate, and organic carbon, but lower concentrations of nitrite. The pH values measured in large and small fog drops were similar in this study, in contrast to previous measurements in the SJV. SJV fogs typically have high pH values, above 6, due to large atmospheric concentrations of water soluble ammonia. The high drop pH promotes rapid formation of aqueous aldehyde-S(IV) complexes and rapid oxidation of dissolved sulfur dioxide by ozone. Model simulations indicate that formation of the S(IV)-formaldehyde adduct hydroxymethanesulfonate is the dominant fate of dissolved sulfur dioxide in both large and small fog drops. S(IV) oxidation is limited due to finite rates of reactant mass transport into the drops and competition for available sulfite and bisulfite by formaldehyde. Fogs play an important role as cleansers of the polluted winter SJV atmosphere. Scavenging of atmospheric fine particles and soluble trace gases by fog drops, followed by drop deposition to the ground, removes large amounts of nitrate, sulfate, ammonium, and organic carbon from the atmosphere. Deposition fluxes of fog water were observed to vary with fog liquid water content and drop effective diameter. Deposition velocities for nitrate, ammonium, sulfate, and organic carbon were observed to be of the order of 1 cm/s, much larger than expected in the absence of fog. Deposition velocities for nitrate, sulfate, ammonium, and organic carbon in fog were observed to be slightly lower than the deposition velocity of fog water itself. This pattern results from enrichment of these species in smaller fog drops that settle more slowly and the dominance of sedimentation as a drop deposition mechanism in environments with low wind speeds and low surface roughness. The deposition velocity of nitrite was typically higher than for fog water, due to its enrichment in larger, faster settling droplets. Overall, the observed deposition fluxes of these major inorganic aerosol species are significant and can offset or exceed aqueous phase production of new aerosol mass. Typical reductions in boundary layer concentrations of organic carbon, nitrate, sulfate, and ammonium due to fog deposition were estimated to be of the order of 1 μg/m3·hr. Numerous reports have appeared in the recent literature indicating the likelihood of fog/cloud processing of carbonaceous aerosol particles. Fog composition measurements also indicate the important role fogs play as processors of carbonaceous species. This study reveals the presence of numerous organic species in SJV fog, including formaldehyde, low molecular weight carboxylic acids such as acetate and formate, dicarboxylic acids, carbonyls and dicarbonyls including glyoxal and methyl glyoxal. Together these compounds make up the majority of low molecular weight (< 500 Daltons) carbon in the fog water. Significant amounts of higher molecular weight organic matter were also identified in the fogs using ultrafiltration. Identification of the nature and properties of this higher molecular weight material should be a focus in future fog studies. In order to provide some additional insight into the types of organic molecules present in the fog water, we followed an approach previously outlined by Decesari et al. (2000) using anion exchange chromatography on a DEAE cellulose column. Chromatograms obtained using this approach have been claimed to indicate the composition of the sample as divided into neutral/basic, mono- and di-carboxylic acid, and polycarboxylic acid fractions. Results from this approach have been widely used in recent studies to derive new models for the organic composition of aerosols and fogs. Chromatograms obtained for the California fog samples are similar in appearance to those reported elsewhere in the literature. However, tests of this method using individual compound standards reveal a tendency for the method to misclassify important families of organic compounds (e.g., phenolic compounds and dicarbonyls) as carboxylic acids. Caution is certainly warranted, therefore, in interpretation of sample chromatograms obtained with this method.Item Open Access Quantifying ice nucleation by silver iodide aerosols(Colorado State University. Libraries, 1990-05) Demott, Paul Judson, authorLaboratory studies of artificial ice nucleating aerosols used for weather modification by cloud seeding have generally been inadequate for describing their complex action in the varied temperature, pressure humidity, and cloud conditions that can be encountered in the atmosphere. This study provides a quantitative framework for predicting ice formation by aerosol particles based on experiments which specifically target currently accepted mechanisms by which ice can form. A physical system for reproducing realistic atmospheric cloud conditions, the Colorado State University dynamic (controlled expansion) cloud chamber, is described. Physical simulations of adiabatic cloud formation and growth are demonstrated. Methodologies were also formulated to use the cloud chamber and other available instrumentation to isolate the action of ice nucleating aerosols by accepted primary ice nucleation modes. These methods were applied to the study of two chemically different silver iodide (AgI) - type aerosols, generated in the exact form in which they have been used for seeding natural clouds . The results were formulated as a function of basic thermodynamic quantities and particle size. An available one dimensional numerical cloud model with microphysical detail was adapted for the equivalent simulation of experiments performed in the cloud chamber. The model was utilized as a diagnostic tool to estimate water supersaturation in association with experiments and it was used for comparison of the predictions of new ice nucleus formulations with observations from generalized seeding simulations conducted in the cloud chamber. The nucleant and mode-specific formulations represent vast improvements compared to available formulations for "pure" AgI. The general implications of these new results were tested by using the model to simulate a few common seeding situations in the atmosphere, and the transferability of results was evaluated by modeling two actual seeding experiment s conducted in summertime cumuli . Within the limitations of the cloud model used, agreement with the atmospheric results was very good. The results of this study should be most useful for designing standard and better methods for the quantitative, study of ice nucleation by artificially generated and natural aerosols, and for evaluating cloud seeding methodologies and potential seeding effects using more complex microphysical - dynamic cloud models.Item Open Access Radiative characteristics of soil derived aerosols(Colorado State University. Libraries, 1987-07) Ackerman, Steven A., author; Cox, Stephen K., authorA multiple scattering model is employed to study the impact of a dust layer on the radiative fluxes at the top of the atmosphere, at the bottom of the atmosphere and within the atmosphere. The sensitivity of the radiative fluxes to various changes in the optical properties of the dust is assessed. Model calculations of the radiative fluxes , with environmental conditions as input, are compared to the aircraft measured fluxes. A parameterization of the extinction coefficient, the single scattering albedo and the asymmetry parameter for a dust layer in the SW spectral region is presented which accounts for the physical and chemical changes of a dust layer as it is mobilized and transported. It is demonstrated that the parameterization scheme is applicable to other aerosols, including water clouds. A scaling parameter is presented which can be used to describe the optical properties of an aerosol layer with a large effective size parameter. The parameterization of the LW radiative properties of the dust layer follows the classic emissivity approach. The effective emissivity is derived for a non-isothermal layer. The radiative parameterizations are incorporated into a radiative-convective equilibrium climate model to assess the impact of the dust microphysical properties on the steady state temperature.Item Open Access Radiative effects of boundary layer aerosols: detectability of hazes by GOES-8 and estimation of their direct effect(Colorado State University. Libraries, 1996) Knapp, Kenneth R., author; Department of Atmospheric Science, Colorado State University, publisherItem Open Access Studies of stratocumulus cloud, drizzle and aerosol interaction(Colorado State University. Libraries, 1996-04) Chen, Aidong, authorA stratocumulus-capped marine mixed layer model has been developed. It focuses on a new parameterization of drizzle which is regulated by a predicted CCN number con- centration. When the CCN number concentration increases, the drizzle rate decreases, so that the boundary-layer cloud remains thick. When the CCN number concentration decreases, the drizzle rate increases and as a result, the boundary-layer cloud becomes thinner. The boundary layer's macroscopic structure is thus sensitive to the CCN number concentration. Aerosol particles in this model are divided into two modes. One represents the small nucleation mode particles, and the other represents the CCN mode particles. Both number and mass balances are considered in this report. Two steady states are obtained, similar to the results of Baker and Charlson (1990). The lower steady state CCN number concentration corresponds to the typical marine time boundary layer. The higher steady state CCN number concentration is regarded as the continental air mass case. A difference between the results from this model and those reported by Baker and Charlson (1990) is that a smoother transition between these two states is found. This result supports some observations that suggest there is no sharp transition between the drizzling and non-drizzling steady states of CCN number concentration in the marine boundary layer. The model is tested using ASTEX observational data. The model results are in good agreement with the observations.Item Open Access Study of the theoretical behavior of ammonium sulfate aerosols in the vicinity of cloud base(Colorado State University. Libraries, 1993-08-25) Stevens, Bjorn, authorThe theoretical behavior of hygroscopic aerosols in an environment typical of cloud base and sub-cloud regions is reviewed. Particular attention is paid to an evaluation of the appropriateness of a variety of assumptions typically made in the treatment of aerosol to cloud drop transitions. It is found that the ideal assumptions associated with the solute modification to surface vapor pressure involves significant errors for the small CCN. While small hygroscopic aerosols are well characterized by their equilibrium size, the slow response times of larger aerosols make them poor candidates for description by equilibrium theory. Non equilibrium effects are quantified as a function of size. The activation process is also considered for a variety of specified supersaturation fields. In general, the activation of hygroscopic aerosols is not instantaneous, the lag time associated with activation is particularly important for the larger aerosols. The implications of these findings on numerical cloud models is discussed.Item Open Access The effects of long-range transport of air pollutants on Arctic cloud-active aerosol(Colorado State University. Libraries, 1983) Borys, Randolph Dean, author; Grant, Lewis O., author; Department of Atmospheric Science, Colorado State University, publisherItem Open Access The relationship between marine aerosol particles and the satellite-detected radiance(Colorado State University. Libraries, 1984) Durkee, Philip A. (Philip Andrew), author; Department of Atmospheric Science, Colorado State University, publisher