Browsing by Subject "Dust"
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Item Climatology of blowing dust and triggering mechanisms across West Texas(Texas Tech University, 1995-08) Bernier, Scott A.Wigner (1984) stated that blowing dust climatologies for stations other than Lubbock need to be compiled to better understand this phenomenon across the South Plains. It is with this statement in mind that this thesis has been written. The main objective of this thesis is to present detailed blowing dust climatologies for Amarillo, Midland, Reese Air Force Base, and Lubbock (updated). Intercomparisons of the four stations are provided. Lubbock and Reese Air Force Base are compared to attempt to determine which station better represents the Lubbock area. A possible explanation for the change in blowing dust patterns over the forty-one year (forty-two for Reese and Lubbock) period is presented.Item Optical Properties of Saharan Dust and Asian Dust: Application to Radiative Transfer Simulations(2012-07-16) Fang, GuangyangBecause the bulk optical properties of dust are largely dependent on their chemical composition, published reports from numerous dust field studies enabled us to compile observation data sets to derive the effective complex refractive indices of Saharan and Asian dust. We considered the individual mineral components as aggregates and used the Bruggeman approximation to derive the effective refractive indices. Using the results, we calculated the single-scattering properties, including phase matrix, single-scattering albedo and asymmetry factor, with a combination of the T-matrix method and an improved geometric optics method (IGOM). The single-scattering properties were averaged by the measured particle size distribution to provide bulk optical properties for radiative transfer simulations. Using a Rapid Radiative Transfer Model (RRTM), the radiative forcing of mineral dust was computed at both the top of the atmosphere and the surface. By analyzing samples from various in-situ measurements, we assumed the Saharan and Asian dust to have average volume compositions and average aspect ratios. The effective refractive indices for Saharan and Asian dust were derived based on the assumed composition models. Bulk optical properties were integrated using the modified log-normal particle size distributions. The aspect ratio assumed in this study is 1.6 for both Saharan and Asian dust. The longwave radiative (IR) forcings at the top of the atmosphere (TOA) and at the surface were found to be positive and sensitive to wavelength. The shortwave (solar) radiative forcing at TOA, was also positive, but may possibly have been due to the strong absorption components considered in the composition models.Item Plasma simulation with a dielectric object in the presence of an ion flow(Texas Tech University, 1999-05) Zhang, WuRecent dusty plasma experiments have investigated the crystallization of dust grains near the edge of a plasma sheath. Some theories were proposed to explain the crystallization mechanisms. The purpose of this simulation work is to study the electrostatics of a dielectric object immersed in a plasma sheath where the ion flow velocity is greater than the ion acoustic velocity, utilizing the object-oriented particle-incell code called XOOPIC developed at UC-Berkeley. This simulation is designed to investigate the polarization in a charging process and the electrostatic traps downstream of an object caused by an ion flow in a plasma discharge. Both the polarization and electrostatic traps in the wake field are considered important factors in the formation of plasma crystals. In this thesis, the simulation model based on the XOOPIC code is established, and the simulation results on wake potentials and polarization are obtained and analyzed. This simulation work was completed on the Sun workstation in the Department of Electrical Engineering at TTU.Item The Development of Measurement Techniques to Identify and Characterize Dusts and Ice Nuclei in the Atmosphere(2014-01-15) Glen, AndrewMineral dusts and ice crystals directly influence the Earth's radiative budget through radiative scattering and absorption. The interaction of spherical particles on the radiative budget are well known, however mineral dusts and ice crystals are generally non-spherical leading to large uncertainties in the radiative impacts of these particles. In addition, atmospheric dust has the ability to act as an Ice Nuclei (IN) aiding in the formation of ice crystals in the atmosphere through four well known nucleation mechanisms. The work presented here discusses new instrumentation and methods to measure and identify both the optical scattering properties and ice nucleation properties of atmospherically relevant dusts. The Texas A&M University Continuous Flow Diffusion Chamber (CFDC) was constructed and characterized in the laboratory using a known effective IN, silver iodide. This instrument was then deployed in the Arctic as part of the Indirect Semi-Direct Aerosol Campaign (ISDAC) where it measured the concentration of potential IN under atmospheric conditions. The results of which, showed the Arctic has higher particle concentrations during the spring compared to data collected in the fall during other field projects. In addition, extreme nucleation events were observed with average IN concentrations as high as 100 L^(-1). The optical scattering properties of atmospherically relevant dusts were measured using a prototype instrument, the Cloud Aerosol Spectrometer with Polarization (CASPOL) under laboratory conditions. The data collected using this instrument allowed the classification of 13 atmospherically relevant dusts into 3 distinct groups based on the optical scattering properties. This instrument was then upgraded by the manufacturer and used to measure the optical scattering properties of both atmospherically relevant dusts and ice crystals generated using the CFDC with the previously examined dusts as potential IN. The results show the dusts can still be categorized into 3 distinct groups and can be differentiated from generated ice crystals. These results provide methodologies for differentiating atmospheric dust from ice crystals in the atmosphere using remote sensing instrumentation.