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Articles 1 - 15 of 15
Full-Text Articles in Atmospheric Sciences
Spectra Of Atmospheric And Astronomical Molecules, W. D. Cameron
Spectra Of Atmospheric And Astronomical Molecules, W. D. Cameron
Physics Theses & Dissertations
Spectroscopy techniques are focused on spectra of molecules of interest to the Earth’s atmosphere and/or astronomy and astrophysics. Laboratory spectroscopy as well as remote satellite sensing are applied. Using the Fourier transform spectrometer aboard the Atmospheric Chemistry Experiment (ACE) satellite to measure the absorption spectra of the Earth’s atmosphere through solar occultation limb observation demonstrates that volcanic eruption plumes can be located and tracked through their SO2 content. The presence of those plumes is corroborated by overlaying infrared atmospheric aerosol extinction observed by the 1 μm imager on the same satellite. Tracking atmospheric aerosol movement with the ACE …
Investigating Ice Nucleation At Negative Pressures Using Molecular Dynamics: A First Order Approximation Of The Dependence Of Ice Nucleation Rate On Pressure, Elise Rosky
Dissertations, Master's Theses and Master's Reports
Atmospheric scientists and climate modelers are faced with uncertainty around the process of ice production in clouds. While significant progress has been made in predicting homogeneous and heterogeneous ice nucleation rates as a function of temperature, recent experiments have shown that ice nucleation rates can be enhanced without decreasing temperature, through various mechanical agitations. One hypothesis for these findings is that mechanisms of stretching water and thereby inducing negative pressure in the liquid could lead to an increase in freezing rate. To better understand the viability of this concept, the effect of negative pressure on ice nucleation rates needs to …
Physics-Constrained Hyperspectral Data Exploitation Across Diverse Atmospheric Scenarios, Nicholas M. Westing
Physics-Constrained Hyperspectral Data Exploitation Across Diverse Atmospheric Scenarios, Nicholas M. Westing
Theses and Dissertations
Hyperspectral target detection promises new operational advantages, with increasing instrument spectral resolution and robust material discrimination. Resolving surface materials requires a fast and accurate accounting of atmospheric effects to increase detection accuracy while minimizing false alarms. This dissertation investigates deep learning methods constrained by the processes governing radiative transfer to efficiently perform atmospheric compensation on data collected by long-wave infrared (LWIR) hyperspectral sensors. These compensation methods depend on generative modeling techniques and permutation invariant neural network architectures to predict LWIR spectral radiometric quantities. The compensation algorithms developed in this work were examined from the perspective of target detection performance using …
Measurement Of Solar Spectral Irradiance And Surface Ozone At Carrollton, Georgia, Usa, During The Great American Eclipse On 21 August 2017, Kirthi Tennakone, L Ajith Desilva, Charles A. Zander*, Shea Rose, Austin B. Kerlin
Measurement Of Solar Spectral Irradiance And Surface Ozone At Carrollton, Georgia, Usa, During The Great American Eclipse On 21 August 2017, Kirthi Tennakone, L Ajith Desilva, Charles A. Zander*, Shea Rose, Austin B. Kerlin
Georgia Journal of Science
Measurements conducted at the University of West Georgia, Carrollton, Georgia, during the time of the solar eclipse of 21st August 2017 demonstrated that the integrated spectral irradiance in defined wavelength ranges in the ultraviolet and visible calculated as a fraction of the total irradiance reached a minimum at maximum obscuration of the Sun, whereas in an infrared range it was maximum. The method of analysis adopted supports the view that the changes in spectral irradiance during highly obscured partial phases is a consequence of limb darkening. In a surface ozone measurement, a minimum in ozone concentration occurred 30 +_ …
Analysis Of The Red And Green Optical Absorption Spectrum Of Gas Phase Ammonia, Nikolai F. Zobov, Phillip A. Coles, Roman I. Ovsyannikov, Aleksandra A. Kyuberis, Robert J. Hargreaves, Peter F. Bernath, Jonathan Tennyson, Sergei N. Yurchenko, Oleg L. Polyansky
Analysis Of The Red And Green Optical Absorption Spectrum Of Gas Phase Ammonia, Nikolai F. Zobov, Phillip A. Coles, Roman I. Ovsyannikov, Aleksandra A. Kyuberis, Robert J. Hargreaves, Peter F. Bernath, Jonathan Tennyson, Sergei N. Yurchenko, Oleg L. Polyansky
Chemistry & Biochemistry Faculty Publications
Room temperature NH3 absorption spectra recorded at the Kitt Peak National Solar Observatory in 1980 are analyzed. The spectra cover two regions in the visible: 15,200 - 15,700 cm-1 and 17,950 - 18,250 cm-1. These high overtone rotation-vibration spectra are analyzed using both combination differences and variational line lists. Two variational line lists were computed using the TROVE nuclear motion program: one is based on an ab initio potential energy surface (PES) while the other used a semi-empirical PES. Ab initio dipole moment surfaces are used in both cases. 95 energy levels with J = 1 …
Comparison Of Various Mean Field Formulations For Retrieving Refractive Indices Of Aerosol Particles Containing Inclusions, Kristin S. Dooley, Jessica Deyoung
Comparison Of Various Mean Field Formulations For Retrieving Refractive Indices Of Aerosol Particles Containing Inclusions, Kristin S. Dooley, Jessica Deyoung
Journal of the Arkansas Academy of Science
Application of effective medium approximation (EMA) methods to two-component systems are presented. Systems studied are composed of water, sulfate, soot, and dust as these are commonly encountered atmospheric aerosol components. Atmospheric models often employ EMAs to include internally mixed aerosols without the computational burden of exact theory. In the current work, several types of mixing rules (Maxwell-Garnet, Bruggeman, and coherent potential approximation) have been applied to various two-component internally mixed particles at 550 nm using volume fractions of the minor component below 0.1. As expected, results show that the formulations tested produce very similar effective refractive indices indicating that electric …
Early Rayleigh-Scatter Lidar Temperature Measurements From The Lower Thermosphere, Leda Sox, Vincent B. Wickwar
Early Rayleigh-Scatter Lidar Temperature Measurements From The Lower Thermosphere, Leda Sox, Vincent B. Wickwar
Leda Sox
Rayleigh-scatter lidar observations were made on many clear nights at the Atmospheric Lidar Observatory (ALO) at Utah State University (USU) from 1993 to 2004 in the altitude range 45–90 km. An upgraded facility, 66 times more sensitive, has been brought on line. It has resulted in temperature measurements with maximum altitudes that extend into new territory—the lower thermosphere. All-night temperature averages have been recorded up to an altitude of 114 km. Temperatures from each month, starting in June 2014, are presented and discussed. They are compared to each other, to the ALO-USU climatology from the original lidar, and to temperatures …
Effects Of Major Sudden Stratospheric Warmings Identified In Midlatitude Mesospheric Rayleigh-Scatter Lidar Temperatures, Leda Sox, Vincent B. Wickwar, Chad Fish, Josh Herron
Effects Of Major Sudden Stratospheric Warmings Identified In Midlatitude Mesospheric Rayleigh-Scatter Lidar Temperatures, Leda Sox, Vincent B. Wickwar, Chad Fish, Josh Herron
Physics Student Research
Mesospheric temperature anomalies associated with Sudden Stratospheric Warmings (SSWs) have been observed extensively in the polar regions. However, observations of these anomalies at midlatitudes are sparse. The very dense 11-year data set, collected between 1993–2004, with the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory (ALO; 41.7°N, 111.8°W) at the Center for Atmospheric and Space Sciences (CASS) on the campus of Utah State University (USU), has been carefully examined for such anomalies. The temperatures derived from these data extend over the mesosphere, from 45 to 90 km. During this period extensive data were acquired during seven major SSW events. In this …
Passive Ranging Using Infra-Red Atmospheric Attenuation, Douglas J. Macdonald
Passive Ranging Using Infra-Red Atmospheric Attenuation, Douglas J. Macdonald
Theses and Dissertations
Methods of estimating range to an emissive target based on the depth of an atmospheric absorption band are demonstrated. The present work uses measurements of the CO2 absorption band centered at 2.0 µm where signal-to-background ratios are maximum for many applications. Model results, based on high-resolution transmission molecular absorption (HITRAN) database cross sections, are used to predict range accuracy at ranges of up to 50 km and are compared with short range (<5km) experimental results. The spectra of 23 high explosive events were used to validate the model. Using the assumption of a blackbody spectrum, extracted ranges consistently underestimated the true range by approximately 13%. By incorporating the stoichiometry of the fireball from previous research and using particulate contribution as a parameter, the error for the range estimates could be reduced to 3%.
Demonstration And Verification Of A Broad Spectrum Anomalous Dispersion Effects Tool For Index Of Refraction And Optical Turbulence Calculations, J. Jean Cohen
Theses and Dissertations
An atmospheric optical turbulence strength model with a broad wavelength range of 355nm (ultraviolet) to 8.6m (radio frequencies) has been created at AFIT and implemented into the High Energy Laser End-to-End Operational Simulation tool (HELEEOS). This modeling and simulation tool is a first principles atmospheric propagation and characterization model. Within HELEEOS lies the High-Resolution Transmission Molecular Absorption (HITRAN) database, containing 1,734,469 spectral lines for 37 different molecules as of version 12.0 (2004). HITRAN affords HELEEOS incredible accuracy for electromagnetic (EM) propagation prediction. A full understanding of optical turbulence is needed to successfully predict EM radiation propagation, particularly within the application …
Radiometric Analysis Of Daytime Satellite Detection, Katherine B. Lilevjen
Radiometric Analysis Of Daytime Satellite Detection, Katherine B. Lilevjen
Theses and Dissertations
A radiometric model for daylight satellite detection is developed and used to evaluate the effects of various parameters on signal-to-noise ratio (SNR). Detection of reflected sunlight from a low-earth orbit, diffuse, planar satellite by a single-pixel infrared photovoltaic detector is considered. Noise considered includes photon noise from the background and signal, as well as thermal noise. Parameters considered include atmospheric conditions, optical parameters, and detector parameters. The Phillips Laboratory Expert-assisted User System, an atmospheric modeling tool that employs the MODTRAN and FASCODE transmission codes, is used to model wavelength-dependent atmospheric transmission and background radiance. The SNR is found to increase …
Measurement Of Proton Transfer Reaction Rates In A Microwave Cavity Discharge Flowing Afterglow, George M. Brooke Iv
Measurement Of Proton Transfer Reaction Rates In A Microwave Cavity Discharge Flowing Afterglow, George M. Brooke Iv
Physics Theses & Dissertations
The reaction rate coefficients between the hydronium ion and the molecules ethene (C2H4), propene (C3H6), 1-butene (C4H8) and hydrogen sulfide (H2S) were measured at 296 K. The measured reaction rates were compared to collision rates calculated using average dipole orientation (ADO) theory. Reaction efficiency depends primarily upon the proton affinity of the molecules. All the measurements were obtained using the newly developed microwave cavity discharge flowing afterglow (MCD-FA) apparatus. This device uses an Asmussen-type microwave cavity discharge ion source that is …
Atmospheric Temperature Profiles By Ground-Based Infrared Spectrometer Measurements, Jon M. Saul
Atmospheric Temperature Profiles By Ground-Based Infrared Spectrometer Measurements, Jon M. Saul
Theses and Dissertations
A method to recover atmospheric temperature profiles using a ground-based Fourier Transform Infrared spectrometer was investigated. The method used a difference form of the radiative transfer equation, a Bomem MR series Fourier Transform Infrared Spectrometer to collect atmospheric radiance values, and the Phillips Laboratory Expert- assisted User Software (PLEXUS) atmospheric radiance model, to recover an atmospheric temperature profile. The method researched uses radiance values from both the spectrometer measurements and the atmospheric model, along with kernel functions calculated by the atmospheric model as input to a difference form of the radiation transfer equation. From this the change in brightness temperatures …
Tunable Mid-Ir Optical Parametric Oscillator Using Periodically Poled Rubidum Titanyl Arsenate, Frank J. Glavic
Tunable Mid-Ir Optical Parametric Oscillator Using Periodically Poled Rubidum Titanyl Arsenate, Frank J. Glavic
Theses and Dissertations
Tunable sources of coherent radiation are needed for a variety of military and commercial applications, including infrared countermeasures and atmospheric remote sensing. This research investigates a tunable mid-infrared coherent source using periodically-poled rubidium titanyl arsenate (PPRTA) as a quasi-phase matched (QPM) optical parametric oscillator (OPO). The advantages of PPRTA over periodically poled lithium niobate (PPLN) are presented. Quasi-phase matching and periodic poling theory are discussed, along with some important historical results and current developments. Experimental setups for determining threshold, conversion efficiency, pump depletion, and beam quality are presented along with experimental results. The research effort is focused on characterizing PPRTA …
A Comparison Of Methods For Estimating Rms Error: A `Brute Force" Approach Versus A Mathematically-Elegant Approach, As Applied To The Calculation Of A Specific Retrieval Error For A Limb-Scanning Microwave Radiometer-Spectrometer, Larry L. Johnson
Theses and Dissertations
The Millimeter-wave Atmospheric Sounder (MAS) is a high resolution limb- scanning microwave radiometer-spectrometer which has been flown aboard the Space Shuttle. The instrument was designed to sense the microwave emission from several upper atmospheric constituents, including water vapor and ozone. The resonant frequencies of water vapor and ozone are extremely close (183 and 184 GHz, respectively), so that the high-frequency wing of the water vapor spectrum overlaps the low frequency wing of the ozone spectrum. Consequently, the measured ozone spectrum incorporates a slight water vapor contribution; therefore, the retrieved ozone profile is dependent on the true water vapor profile. The …