Atmospheric Sciences Commons^™

Comparison Of Ray Tracing Through Ionospheric Models, Shayne C. Aune

Theses and Dissertations

A comparison of ray tracing predictions for transionospheric electromagnetic wave refraction and group delays through ionospheric models is presented. Impacted applications include over-the-horizon RADAR, high frequency communications, direction finding, and satellite communications. The ionospheric models used are version 2.1 of Utah State University's Global Assimilation of Ionospheric Measurements (USU GAIM) model and the 2001 version of the International Reference Ionosphere (IRI) model. In order to provide ray tracing results applicable to satellite communications for satellites at geosynchronous orbit (GEO), a third ionospheric model is used to extend the sub-2000-km USU GAIM and IRI ionospheric specifications to 36540 km in altitude. …

Coupled Oceanic-Atmospheric Variability And U.S. Streamflow, Glenn A. Tootle, Thomas C. Piechota, Ashok Singh

Civil and Environmental Engineering and Construction Faculty Research

A study of the influence of interdecadal, decadal, and interannual oceanic-atmospheric influences on streamflow in the United States is presented. Unimpaired streamflow was identified for 639 stations in the United States for the period 1951–2002. The phases (cold/negative or warm/positive) of Pacific Ocean (El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) and Atlantic Ocean (Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO)) oceanic-atmospheric influences were identified for the year prior to the streamflow year (i.e., long lead time). Statistical significance testing of streamflow, based on the interdecadal, decadal, and interannual oceanic-atmospheric phase (warm/positive or cold/negative), was performed by …

A Recommendation For An Enhanced Fujita Scale (Ef-Scale)

United States Department of Commerce: Staff Publications

Background

National Weather Service (NWS) personnel who are responsible for rating tornadoes have expressed frustrations in applying the Fujita Scale in a consistent and accurate manner. Weak links in a structural system or a slow-moving storm sometimes lead to an overrating of a tornado event. Several technical articles suggest that wind speeds associated with some descriptions of damage are too high. For example, a 260 mph wind speed is not required to completely destroy a well constructed house and blow away the debris. The damage occurs at significantly lower wind speeds. Minor et al. (1977) and Phan and Simiu (2003) …

Comparative Study On The Use Of Coherent Radar-Derived Electric Fields Vs. Statistical Electric Fields For The Initialization Of A High-Latitude Ionospheric Model, Christopher M. Hogue

Theses and Dissertations

The structure and time development of the magnetosphere-ionosphere system have significant impacts on the Air Force and its mission. Specifically, an accurate knowledge of ionospheric plasma densities is important for the operation of many Air Force systems. This research analyzes plasma density structure development through comparing two distinct electric field models. The two models compared here are a commonly used statistical model created by Heppner and Maynard 1987, and a more recently developed model using real-time coherent radar measurements from the SuperDARN radar network. Ionospheric simulations were run using Utah State University s Time-Dependent Ionospheric Model (TDIM) with the two …

Estimating Equatorial F-Region Daytime Vertical E X B Drift Velocities From Ground-Based Magnetometer Measurements In The Philippine Longitude Sector, Shauna M. Kinkela

Theses and Dissertations

Ionospheric disturbances can severely impact Department of Defense (DoD) systems, such as radar. satellite. and navigation technologies. Forecasting disturbances and describing the Earth's ionosphere, in turn, relies upon innovative computer-based models that gather input parameters from ground and space-borne observations and empirical models for ionospheric drivers. Equatorial E x B drift velocities are significant input parameters that go into many ionospheric models, because they help describe vertical plasma motions near the magnetic equator. Previous work by Anderson, et al 2002 has demonstrated the ability to derive Peruvian longitude sector, daytime vertical E x B drifts from ground-based magnetometer data. The …

Atmospheric Simulation Using A Liquid Crystal Wavefront Controlling Device, Matthew R. Brooks

Theses and Dissertations

Test and evaluation of laser warning devices is important due to the increased use of laser devices in aerial applications. In this thesis, an atmospheric aberrating system is developed to enable in-lab testing of laser warning devices. This system employs laser light at 632.8nm from a Helium-Neon source and a spatial light modulator (SLM) to cause phase changes using a birefringent liquid crystal material. Before the system can be used, the SLM phase response must be quantified to ensure proper manipulation of index of refraction. Additionally, diffraction from the SLM and real-world system scaling are addressed. Once completed, the atmospheric …

Atmospheric Water Vapor Lidar Measurements Using Analog And Photon Counting Techniques, Anuj Maheshkumar Shah

Electrical & Computer Engineering Theses & Dissertations

Atmospheric water vapor measurements are essential for the understanding of Earth's weather and radiation budget, along with the water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a commanding method used for water vapor measurements from aircraft, spaceborne, and ground-based platforms. The new unmanned aerial vehicle (UAV) water vapor DIAL system provides great feasibility due to the weight and size limitations. The system has significantly less weight, power consumption, and noise presence, thus making it great for UAV applications.

This thesis discusses a UAV water vapor DIAL system that was designed, developed, and evaluated. The research effort was …

Atmospheric Turbulence Conditions Leading To Focused And Folded Sonic Boom Wave Fronts, Andrew A. Piacsek

All Faculty Scholarship for the College of the Sciences

The propagation and subsequent distortion of sonic booms with rippled wave fronts are investigated theoretically using a nonlinear time-domain finite-difference scheme. This work seeks to validate the rippled wave front approach as a method for explaining the significant effects of turbulence on sonic booms [A. S. Pierce and D. J. Maglieri, J. Acoust. Soc. Am. 51, 702–721 (1971)]. A very simple description of turbulence is employed in which velocity perturbations within a shallow layer of the atmosphere form strings of vortices characterized by their size and speed. Passage of a steady-state plane shock front through such a vortex layer …

Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch

Electrical & Computer Engineering Theses & Dissertations

A lidar system was developed for making combined range-resolved measurements of wind speed and direction, water vapor concentration, and carbon dioxide concentration in the atmosphere. This lidar combines the coherent Doppler technique for wind detection and the differential absorption lidar (DIAL) technique to provide a multifunctional capability. DIAL and coherent lidars have traditionally been thought of and implemented as separate instruments, but the research reported here has shown a demonstration of combining the coherent and DIAL techniques into a single instrument using solid-state lasers. The lasers used are of Ho:Tm:YLF, which operates at a wavelength of 2 μm. This wavelength …

Mitigation Of Water Vapor Interference For Infrared Polarization-Modulated Gas Filter Correlation Radiometry, David K. Lockwood

Electrical & Computer Engineering Theses & Dissertations

Gas filter correlation radiometry (GFCR) is a high-resolution, high-specificity technique for sensing gaseous species. A variation of absorption spectroscopy, GFCR has a long-proven record on orbital platforms for quantitative measurements of atmospheric constituents, as well as common usage in ground-based sensing applications. PMGFCR (Polarization-modulated GFCR) is a recent refinement of the technique with several advantages over the traditional method, including reducing the number of photodetectors required, increased sensitivity, and elimination of moving parts.

To date, no infrared remote sensors have successfully measured nitric oxide (NO) in vehicle exhaust due to spectral overlap by strong water vapor (H₂O_{v …}

Simulating Wet Deposition Of Radiocesium From The Chernobyl Accident, Aaron M. Kinser

Theses and Dissertations

In response to the Chernobyl nuclear power plant accident of 1986, a cesium-137 deposition dataset was assembled. Most of the airborne Chernobyl cesium was wet deposited, either via interception by falling raindrops or via absorption into cloud droplets destined to become raindrops. The Hybrid Single-Particle Lagrangian rated Transport (HYSPLIT) model, developed at Air Resources Laboratory, is used to simulate the transport and deposition of Chernobyl cesium-137. A cloud base parameterization modification is tested and appears to slightly improve the accuracy of one HYSPLIT simulation of daily Chernobyl cesium-137 deposition over the course of the accident at isolated European sites, and …

Assessment Of The Effects Of Entrainment And Wind Shear On Nuclear Cloud Rise Modeling, Daniel E. Zalewski

Theses and Dissertations

The Missile Defense Agency (MDA) plans to construct, during a two-week period, an X-Band Radar (XBR) on Shemya, AK. Wind speeds must not, at any time during the construction, exceed a 25 knot limit set by the MDA for lifting the massive dome panels into place. The goal of this research was to explore the possibilities of long-range forecasts to determine the feasibility of predicting any upcoming two-week windows of opportunity, well in advance, that will ensure the successful completion of constructing the XBR on Shemya. In order to reach this goal, the following objectives were achieved; (1) a climatological …

Application Of Tree-Structured Regression For Regional Precipitation Prediction Using General Circulation Model Output, Xiangshang Li, David J. Sailor

Mechanical and Materials Engineering Faculty Publications and Presentations

This study presents a tree-structured regression (TSR) method to relate daily precipitation with a variety of free-atmosphere variables. Historical data were used to identify distinct weather patterns associated with differing types of precipitation events. Models were developed using 67% of the data for training and the remaining data for model validation. Seasonal models were built for each of 2 US sites: San Francisco, California, and San Antonio, Texas. The average correlation between observed and simulated daily precipitation data series is 0.75 for the training set and 0.68 for the validation set. Relative humidity was found to be the dominant variable …

Advanced Atmospheric Water Vapor Dial Detection System, Tamer Refaat

Electrical & Computer Engineering Theses & Dissertations

Measurement of atmospheric water vapor is very important for understanding the Earth's climate and water cycle. The remote sensing Differential Absorption Lidar (DIAL) technique is a powerful method to perform such measurement from aircraft and space. This thesis describes a new advanced detection system, which incorporates major improvements regarding sensitivity and size. These improvements include a low noise advanced avalanche photodiode detector, a custom analog circuit, a 14-bit digitizer, a microcontroller for on board averaging and finally a fast computer interface.

This thesis describes the design and validation of this new water vapor DIAL detection system which was integrated onto …

Inversion And Analysis Of Remotely Sensed Atmospheric Water Vapor Measurements At 940nm, Jack Cutler Larsen

Mechanical & Aerospace Engineering Theses & Dissertations

The understanding and acceptance of remotely sensed atmospheric data depends strongly on the steps taken to characterize experiment error and validate observations through comparisons to other independent measurements. A formal error analysis of the Stratospheric Aerosol and Gas Experiment II (SAGE II) water vapor operational inversion algorithm is performed and compared to previous results. Random measurement errors were characterized by segmented least-squares profile fitting of the slant path absorption which found the error to be uncorrelated in the stratosphere with estimated variances significantly smaller than expected from 18-30 km. Estimates of null space error were developed from radiosonde hygrometers in …

Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain

Theses and Dissertations

A new atmospheric turbulence screen generator is developed for use in performance calculations of adaptive optics systems valid over a wide range of atmospheric turbulence parameters. The screen generator accounts for diffraction effects caused by weak turbulence and incorporates the phase, amplitude, and cross statistics of the perturbed optical field. The wavefront's phase and amplitude perturbations are taken from the correlation functions developed by Lee and Harp and the cross correlation of the phase and amplitude derived in this thesis. The screen generator uses a modal representation to perform a Fourier series expansion of the wavefront phase and amplitude over …

Analysis Of Multimode Low-Probability-Of-Intercept (Lpi) Communications With Atmospheric Effects, Ala Ghordlo

Theses and Dissertations

This research expanded Low Probability of Intercept (LPI) communications analysis in two areas. First, multimode communication was included to account for ground to ground and air to ground links in addition to the standard air to air links traditionally used in LPI analysis. The propagation equations for the three modes of interest were derived and included in LPI analytic models in the form of a mode quality factor to account for multimode LPI scenarios. This new quality factor was used in studying several communication and interception link combinations. Variations due to differences between the communication and interception modes were presented …

Performance Analysis Of A Hartman Wavefront Sensor Used For Sensing Atmospheric Turbulence Statistics, Toby D. Reeves

Theses and Dissertations

Atmospheric turbulence parameters, such as Fried's coherence diameter, the outer scale of turbulence, and the turbulence power law, are related to the wavefront slope structure function (SSF). The SSF is defined as the second moment of the wavefront slope difference as a function of both time and position. Knowledge of the SSF allows turbulence parameters to be estimated. Hartmann wavefront sensor (H-WFS) slope measurements composed of both signal and noise, allow the SSF to be estimated by computing a mean square difference of H-WFS slope measurements. The quality of the SSF estimate is quantified by the signal-to-noise ratio (SNR) of …

Investigation Of Radio Wave Propagation In The Martian Ionosphere Utilizing Hf Sounding Techniques, Robert J. Yowell

Theses and Dissertations

This thesis presents a preliminary design of an ionospheric sounder to be carried aboard one or more of NASA's Mars Surveyor landers. Past Russian and American probes have indicated the existence of an ionosphere, but none of these missions remotely sensed this atmospheric layer from the surface. The rationale for utilizing a surface-based Martian ionospheric sounder is discussed. Based on NASA's choice of launch vehicle and power source, a low-weight, low-powered Chirp sounder using a horizontally-polarized dipole antenna is recommended for the sounder experiment. The sounder experiment should be conducted for at least one Martian year, in order to investigate …

Application Of Autoregressive Moving Average Linear Prediction Filters To The Characterization Of Solar Wind-Magnetosphere Coupling, Carter N. Borst

Theses and Dissertations

Linear prediction filtering techniques have been used in studying the coupling processes between the solar wind and magnetosphere. The magnetosphere is a complex, dynamic system with at least two independent coupling methods for energy input, driven and unloading. Linear models were built and tested on the Bargatze data set, consisting of over 70 days of geomagnetic indices and solar wind data ordered in 34 intervals of increasing geomagnetic activity. Linear filtering techniques employing single-and multiple-input, autoregressive models predicted values of the magnetic index AL from solar wind data. The impulse response curves of the AL-coupling function groups showed amplitude peaks …

The Role Of Frame Selection And Bispectrum Phase Reconstruction For Speckle Imaging Through Atmospheric Turbulence, Elizabeth A. Harpold

Theses and Dissertations

Frame selection using quality sharpness metrics have been shown in previous AFIT theses, to be effective in improving the final product of images obtained using adaptive optics. This thesis extends this idea to noncompensated speckle image data. Speckle image reconstruction is simulated with and without frame selection. Speckle images require the processing of hundreds of data frames. Frame selection is a method of reducing the amount of data required to reconstruct the image. A collection of short exposure image data frames of a single object are sorted based on sharpness metrics. Only the highest quality frames are retained and processed …

Analysis And Interpretation Of Ion Data Associated With Neutral Gas Releases In The Earth's Ionosphere, Timothy M. Shadid

Theses and Dissertations

Barium and strontium release experiments were conducted throughout 1991 from the Combined Release and Radiation Effects Satellite (CRRES) to study both natural and man-made disturbances in the earth's ionosphere. A mass spectrometer on the spacecraft counted the Ba and Sr ions as the cloud expanded. In this study, data from the G-1 (in sunlight) and G-11b (in darkness) releases were modeled to understand the source of the ion signals. The model reproduced the Ba⁺ sun data well assuming photoionization (τ = 28 s) was the primary ionization mechanism. However, it was not able to account for the remaining ion …

The Effect Of Meteorological Data Averaging Times On Plume Concentrations From Explosive Ordnance Disposal Open Burning Operations, Ida L. Widmann

Theses and Dissertations

Explosive Ordnance Disposal (EOD) Open Burning (OB) operations are performed to treat and dispose of unserviceable munitions in the Department of Defense (DOD) inventory. Air pollution modeling of OB operations is an Environmental Protection Agency requirement for permit issuance at OB sites. Specific OB regulation is still in its infancy; therefore, establishment of OB modeling techniques is still in the early stages. This thesis effort sought to develop a computer model, based upon the Gaussian Puff Equation. The model varies from standard plume modeling practices by not making the assumption that the wind direction, wind speed and turbulence are uniform …

A Guide To Floodplain Cattle Fencing, Department Of Agriculture, Western Australia, Main Roads, Western Australia

Animal production and livestock published reports

A seminar and workshop was held at Fitzroy Crossing in October 1993 to address the consequences of flooding to landholders and communities.

Damage to flood plain fencing was identified as one of the major concerns to landholders.

An outcome from the workshop was the decision to draw on local knowledge and collate information on options for fence and floodgate designs.

This information was to be made available to land holders and other interested parties - hence this publication.

Shock Wave Interaction With L-Shaped Structures, Richard C. Miller

Theses and Dissertations

This study investigated the interaction of shock waves with L-shaped structures using the CTH hydrodynamics code developed by Sandia National Laboratories. Computer models of shock waves traveling through air were developed using techniques similar to shock tube experiments. Models of L-shaped buildings were used to determine overpressures achieved by the reflecting shock versus angle of incidence of the shock front. An L-shaped building model rotated 45 degrees to the planar shock front produced the highest reflected overpressure of 9.73 atmospheres in the corner joining the two wings, a value 9.5 times the incident overpressure of 1.02 atmospheres. The same L-shaped …

Analytical Modeling And Simulation For Investigation Of A Digital Gas Filter Correlation Radiometer, Catherine P. Mcgowan

Electrical & Computer Engineering Theses & Dissertations

This thesis investigates a digital gas filter correlation radiometer called the Tropospheric Radiometer for Atmospheric Chemistry and Environmental Research (TRACER), which will be used to remotely measure carbon monoxide at three levels in the troposphere. The nadir-viewing radiometer measures the differential absorption of radiation through the atmosphere at 4.67@m and 2.33pm wavelengths. This thesis develops an analytical model of the TRACER measurement process to evaluate the effect of varying certain system parameters on the measurement. The independent sampling criterion and the response of linear systems to random signals are explained. A parametric simulation model is also developed to evaluate the …

Modifications To Mcnp, Version 3b: Incorporating A Variable Density Atmosphere. Addendum, David L. Monti, Kirk A. Mathews

AFIT Documents

MCNP version 3B was modified to incorporate a continuously variable density atmosphere. This was accomplished by representing the variation of air density as a function of altitude with a series of continuous piecewise exponential curves up to a maximum altitude of 1000 km. User-written subroutines and functions were written which incorporated these piecewise functions. These subroutines and functions were subsequently incorporated into a production version of MCNP. Several MCNP subroutines and files were modified in support of these modifications. This report discusses detailed information regarding the theoretical development of the variable density model, the user written subroutines and functions, the …

Monte Carlo Simulation Of Atmospheric Neutron Transport At High Altitudes Using Mcnp, Donald R. Culp, David L. Monti, James R. Shoemaker, David Wesley, Kirk A. Mathews

AFIT Documents

Neutron transport calculations were performed using the Monte Carol code, MCNP. The transport problem considered has a point source at high altitude (40 km). Since atmospheric density decreases with altitude, two-dimensional effects (cylindrical coordinates) can be important. Results were compared to those obtained with the SMAUG-II computer code, which performs mass-integral scaling of approximate fits to one-dimensional spherical discrete ordinates solutions. These comparisons show the importance of two-dimensional computations. The report discusses practical issues of applying MCNP to this problem, without code modifications and includes example input files for MCNP and for SMAUG-II. Computational modelling of neutron transport in the …

To The U.S. Department Of Transportation: Comments Of The Environmental Defense Fund On The Secretary Of Transportation’S National Transportation Policy, Robert E. Yuhnke

Air Quality Protection in the West (November 27-28)

20 pages.

Motor Vehicle Air Pollution Control: The Remaining Issues, Michael P. Walsh

Air Quality Protection in the West (November 27-28)

26 pages (includes illustrations).

Contains references.