Physical Sciences and Mathematics Commons^™

Requirements, Design And Prototype Of A Virtual User Interface For The Afit Virtual Spaceplane, John M. Lewis

Theses and Dissertations

The United States Air Force is evaluating the feasibility of designing a military spaceplane capable of accomplishing military objectives from a low earth orbit and atmospheric flight regimes. Current efforts are involved in determining the scientific, operational, and budgetary constraints associated with this concept. This thesis looks at the exploration of new interface techniques associated with the design of a virtual spaceplane and is a subset of the overall virtual spaceplane effort which will assist researchers in determining the feasibility of a military spaceplane. Interface techniques are integrated into a virtual user interface that is designed to accommodate expected operations …

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 …

A Validation Of The Parameterized Real-Time Ionospheric Specification Model (Prism) Version 1.7b, Shawn D. Filby

Theses and Dissertations

The most current version of the Parameterized Real-time Ionospheric Specification Model (PRISM), version 1.7b, was validated using Digital Ionospheric Sounding System (DISS) measurements of F2 layer critical frequency (foF2) and F2 peak electron density height (hmF2) as the "ground truth." PRISM was executed, first, with no real-time input parameter and, second, with Global Positioning System (GPS) Total Electron Content (TEC) measurements as the sole real-time parameter. Hourly values of hmF2 and foF2 over 123 days in 1994-1996 (solar minimum conditions) and covering three seasons (equinox, summer solstice, and winter solstice) were compared for Wallops Island, Virginia, and Point Arguello, California, …

Systematics Of The Freshwater Amphipod Genus Crangonyx (Crangonyctidae) In North America, Jun Zhang

Biological Sciences Theses & Dissertations

The systematics of the amphipod genus Crangonyx of North America (north of Mexico) is revised, based on available collections (ca. 2240) and literature dealing with the genus. A grand total of 42 North America species of Crangonyx are recognized in the present study, 24 of them new to science. All species are described or redescribed and figured, utilizing external morphological features. Keys to both species groups and individual species are given. Phylogenetic trees are built using computer programs (PAUP, Hennig86, MacClade) based on 26 characters. Wagner parsimony produced 18 parsimonious trees and Fitch parsimony produced 45 trees. The consensus tree …

Developmental Taxonomy And Distribution Of Paralarval Squid From The Florida Current, Carrie Leeonne Adams

Theses and Dissertations

Distribution patterns of paralarval squid across the continental shelf of Florida were examined based on five years of collections. Squid occurrence patterns were described in relation to coastal, intermediate, and Florida Current (Gulf Stream) water masses by comparing horizontal and vertical distribution patterns of squid species to physical-chemical distribution patterns Twenty-six squid taxa were collected in this study. Representative taxonomic descriptions and illustrations of all taxa were produced to serve as an identification aid for the paralarval squid from the Florida shelf. Patterns of species composition among stations were analyzed with cluster analysis based on four sampling approaches. Species distribution …

Coastal Circulations Driven By River Outflow, Shuliang Zhang

HCNSO Student Theses and Dissertations

Variable-density, 1^1/2- and 2^1/2- layer models are used to examine the behavior of plumes resulting from a fresher outflow of transport M_r and salinity S_r into a pre-existing oceanic layer of initial thickness H₁ and salinity S₁. It is found that the plumes exhibit a variety of features depending on conditions of the outflow, the situation of the ambient ocean, and external forcing. Perhaps the most interesting feature is that the plume can flow along the upstream (to the left of the river mouth, looking seaward in the northern hemisphere) coast …

Ecology Of The Early Life History Of The Caribbean Spiny Lobster, Panulirus Argus: Recruitment, Predation, And Habitat Requirements, Charles A. Acosta

Biological Sciences Theses & Dissertations

Recruitment variability of the early life history stages of marine benthic organisms can have profound consequences on population dynamics. I studied factors affecting recruitment success of postlarvae and early juveniles of the Caribbean spiny lobster. I examined patterns in postlarval supply, investigated wind forcing as a potential transport mechanism for recruiting postlarvae, and quantified predation on postlarvae in south Florida, USA. In an eight-year time series, spiny lobster postlarval supply occurred year-round between the new and first quarter lunar phases. The major annual peak occurred around March corresponding to spawning activity ten months earlier, and a smaller non-seasonal peak occurred …

Microzooplankton Dynamics In Lower Chesapeake Bay And Its Major Tributaries, Gyung Soo Park

Biological Sciences Theses & Dissertations

This study identified the temporal and spatial variability of microzooplankton density and biomass at 14 stations located within Chesapeake Bay and four rivers. Microzooplankton are defined as those heterotrophic organisms which range from 20 to 200 $\mu$m in size, and in this study were mainly composed of copepod nauplii, rotifers, and ciliates. Ciliates were the most abundant microzooplankton, comprising more than 90% of the total density, with copepod nauplii representing approximately 50% of the total microzooplankton biomass (carbon content). Rotifers contributed less than 5% for both density and biomass of the total microzooplankton.

Maximum ciliate abundance occurred from spring to …

Influence Of Physics On The Distribution Of Ichthyoplankton Across The Chesapeake Bay Plume, Christian S. Reiss

OES Theses and Dissertations

Most marine fish have retained pelagic larval stages that are spawned away from juvenile habitats. Physical and biological processes on a number of scales may affect larval survival. Mesoscale features like estuarine or riverine plumes and fronts are thought to affect larval survival by transporting larvae to juvenile habitats or by retaining larvae in favorable developmental habitats. It is likely that these features are major contributors in the regulation of shelf-spawned estuarine-dependent taxa.

This study examined how physical oceanographic features affected the spatial distribution of ichthyoplankton across the Chesapeake Bay Plume. Larval surveys were conducted across the shelf and within …

An Examination Of The Hanson Contrail Forecast Algorithm Under Low Relative Humidity Conditions, Robert P. Asbury Iii

Theses and Dissertations

Accurate forecasts of contrail occurrence are essential to military aircrews. Although classical forecast methods have been reasonably successful predicting contrails, there is need for improvement at low ambient relative humidity. This thesis examines the performance of the Hanson method, which was developed to provide better contrail forecasts under drier atmospheric conditions. As a secondary objective, the forecast methods of Schumann and Hanson are compared to the algorithm currently in use by the Air Force Global Weather Central. Data used to validate the algorithms were collected at Wright-Patterson AFB, OH and Edwards AFB, CA. Theoretical contrail forecasts were made for each …

A Validation Study Of The Ssm/I Temperature Algorithm And Comparison With The Cal/Val Land Surface Temperatures, Ronald L. Comoglio

Theses and Dissertations

The USAF operational cloud model, the Real-Time Nephanalysis (RTNEPH), requires infrared and visual scene scans as well as input from the Special Sensor Microwave Imager (SSM/I), featured on the Defense Meteorological Satellite Program (DMSP) polar orbiters. Additionally, SSM/I provides input to the Air Force Global Weather Center (AFGWC) surface temperature model (SFCTMP). The global surface temperatures are required for identifying which pixel of a scene is cloud and which is ground and as a first guess input to initialize NWP models. The SSM/I provides brightness temperatures sampled at four discrete: frequencies and dual polarizations to produce surface temperatures. Two algorithms …

An Atmospheric Sensitivity And Validation Study Of The Variable Terrain Radio Parabolic Equation Model (Vtrpe), Matthew K. Doggett

Theses and Dissertations

The Variable Terrain Radio Parabolic Equation (VTRPE) computer model is a powerful and flexible program that provides calculations of the radar propagation conditions of the atmosphere. It is limited however, by the accuracy and resolution of the input data. This study quantifies the sensitivity of the VTRPE model to the accuracy and resolution of the atmospheric parameters that go into it. Also, two case studies are examined to test the utility of VTRPE in operational use. The sensitivity to measurements of pressure, temperature, and humidity was found to be dependent on the meteorological environment. In standard and subrefractive environments, average …

Optimization Of The Velocity Azimuth Display (Vad) Algorithm's Adaptable Parameters In The Wsr-88d System, Donald R. Farris

Theses and Dissertations

Meteorologists have encountered problems with the Velocity Azimuth Display (VAD) algorithm in the Weather Surveillance Radar - 1988 Doppler (WSR-88D) System. Under certain meteorological conditions, forecasters have observed differences between the radar's wind profiles and wind profiles from rawinsonde upper-air soundings, or wind profilers. One of the main causes of this problem is inversions in the atmosphere which cause the radar beam to subrefract or superefract, causing the VAD winds to be inaccurately reported at a particular height. This thesis used the WSR-88D Algorithm Testing and Display System (WATADS) to compare VAD winds from recorded Level 2 NEXRAD data at …

Adaption Of The Air Weather Service Fog Model To Forecast Radiation Fog Events In The Southeast United States, Andrew C. Goodnite

Theses and Dissertations

This research examined the performance of the Air Weather Service (AWS) Fog Model and the potential for using it in the Southeast United States for predicting fog. This task was accomplished in four separate steps. First, a correlation study was performed by comparing different weather elements in observations that met radiational cooling conditions to the observed visibility. This correlation study showed that the 22 UTC dewpoint depression was correlated (0.60) with early morning fog and no other weather elements that are commonly observed had significant correlation with early morning fog. Second, a verification study was conducted on the Saint Louis …

Quantification Of Weather Effects On Imaging Laser Radar, Clifton D. Stargardt

Theses and Dissertations

The Air Force is investigating the use of imaging laser radar systems as autonomous guidance systems on future precision guided munitions. The Air Force's Wright Laboratory is currently testing a 1.06 micron wavelength laser radar (ladar) at Eglin Air Force Base. Since laser radiation can be susceptible to propagation problems through weather, quantitative understanding of these effects is important to the development of this weapon system. Ladar image degradation, in the form of target dropouts and false returns, was evaluated in various weather conditions. Statistical analysis of the images presented expected degrees of degradation according to visibility and rain fall …

Development And Implementation Of An Isentropic Potential Vorticity Algorithm For Use At Air Force Global Weather Center, Jay B. Desjardins Jr.

Theses and Dissertations

This thesis presents and validates methods for calculating isentropic potential vorticity (IPV) and applies these methods in software programs planned for implementation at the Air Force Global Weather Center (AFGWC). The IPV programs will provide Air Force Weather forecasters additional tools to diagnose atmospheric kinematics and understand atmospheric dynamics. A FORTRAN program is recommended using mandatory-level isobaric data projected to be available on AFGWC computer systems, specifically, from the Navy Operational Global Atmosphere Prediction System and Medium Range Forecast models. Program development and analysis consists of three main steps: (1) data retrieval; (2) IPV calculations; and, (3) interpolation to an …

Moisture Sensitivity Of Contrail Forecast Algorithms, Allen C. Rabayda

Theses and Dissertations

This thesis looked at using new relative humidity (RH) climatologies to improve the Air Force Global Weather Center's (AFGWC) contrail forecasts. To study the effect of the new RH climatolgies, the currently used empirical relative humidity (RH) profile is replaced with a more accurate climatological one, the Stratospheric And Gaseous Experiment II (SAGE II). The study begins by examining accuracy and bias of forecast contrail bases generated by the empirical and SAGE II RH profiles on 42 days. Both sets of forecast bases are shown to be statistically similar with a series of hypothesis tests. Additional RH profiles, from 0% …

Validation Of The Air Force Global Weather Center Relocatable Window Model Total Cloud Forecast, Edward C. Harris

Theses and Dissertations

Air Force Global Weather Center's (AFGWC) Relocatable Window Model (RWM) total cloud forecasts were validated using data for selected days in May, June, and July, 1996. Forecasts were generated twice daily (00 UTC and 12 UTC) to determine the RWM's ability to accurately forecast total cloud cover during the late spring and early summer. The RWM forecasts were post-processed using the Slingo cloud forecast algorithm and compared against AFGWC's operational real time nephanalysis (RTNEPH) cloud analysis model. As a minimal-skill baseline comparison to the RWM's total cloud forecast, the RTNEPH initial analysis hour was persisted and evaluated against the same …

Automatic Digital Processing For Calibration Data Of Open Skies Treaty Sensors, Donna D. Keating

Theses and Dissertations

The Open Skies Treaty provides guidelines allowing participants to fly in air space over other participants' countries to monitor strategic military placement and development. The treaty restricts the ground size of the smallest detail recorded by these aerial imaging systems to any size larger than 30 cm. This restriction is enforced by placing a lower limit on the altitude at which a participating aircraft can fly and it is computed as the value of Hmin. Current techniques rely on human photographic interpreters to select the value of Hmin for every calibration pass and is very resource intensive. The Open Skies …

Response Modes Of The Lower Chesapeake Bay Wave Field, Katherine L. Farnsworth

Dissertations, Theses, and Masters Projects

An extensive wave monitoring program was conducted in the lower Chesapeake Bay from fall 1989 through spring 1995. From October 23, 1992 - April 20, 1993 the Virginia Institute of Marine Science deployed an aluminum tetrapod containing wave and current sensing and recording equipment in the Thimble Shoal region of the lower Chesapeake Bay. Measurements were made in half hour bursts every three hours to document the area’s dynamic wave characteristics. It was shown previously by Boon et al. (1990 - 1996) that a bimodal frequency distribution of waves in the Thimble Shoal region existed, which was not seen in …

Spatial, Geostatistical, And Fractal Measures Of Seafloor Microtopography Across The Eel River Shelf, Off Northern California, George Randall. Cutter

Dissertations, Theses, and Masters Projects

No abstract provided.

New Data On Ichthyoplankton Of The Southwestern Pacific, Andrei V. Suntsov

Dissertations, Theses, and Masters Projects

No abstract provided.

Correspondence Between Environmental Gradients And The Assemblage Structure Of Littoral Fishes In The Tidal Portion Of Three Virginia Coastal Plain Rivers, Clifford Michael Wagner

Dissertations, Theses, and Masters Projects

No abstract provided.

On The Circulation Of The Northern North Sea And The Patagonian Shelf, Pablo D. Glorioso

Dissertations, Theses, and Masters Projects

The Northern North Sea and the Patagonian Shelf have similar characteristics, and their circulation is determined by strong tidal regimes, significant wind-driven flow, and by density gradients to a lesser degree. The influence of oceanic currents is notable in the Patagonian Shelf, where the Falkland Current flows along the shelf edge, but less important in the North Sea. While the North Sea is perhaps the most studied body of water in the world, the circulation of the Patagonian Shelf have remained fairly unknown. This study presents evidence of near-inertial oscillations in the Northern North Sea, not reported previously, derived from …

Distribution Of Freshwater Amphipoda In The Lake Matoaka/College Woods Area, Williamsburg, Virginia, Susan Alexandra Mahon

Dissertations, Theses, and Masters Projects

No abstract provided.

Climatologically Forced Coherence Between Diverse Juvenile Populations In The Virginia Tributaries To The Chesapeake Bay, Thomas C. Mosca Iii

Dissertations, Theses, and Masters Projects

Long term trends in juvenile recruitment of oyster, bluecrab, and 24 species of finfish in a large temperate estuary (lower Chesapeake Bay, USA) are coherent across the three major tributaries (the Virginia rivers James, York, and Rappahannock). The driving force for these long term trends is geographically large in scale. Anomalous winters in the mid 1970's, with the warmest years on record followed immediately by the coldest, caused a severe perturbation in population dynamics. The extreme conditions caused the system to shift, with recruitment patterns following temperatures by a one year lag. Following this anomalous episode, smoothed mean winter water …

Winter/Spring Steady-State Water Balances For A Palustrine Forested Wetland Located In Southeastern Virginia, Daniel Otis Redgate

Dissertations, Theses, and Masters Projects

No abstract provided.

Effects Of Spot (Leisostomus Xanthurus) Induced Bioturbation And Suspension On The Transport And Fate Of Sediments And A Particle-Associated Organic Contaminant, Michele A. Horvath

Dissertations, Theses, and Masters Projects

No abstract provided.

Distribution Of Free Marine Viruses Of Lower Chesapeake Bay And Their Effects On Life-History Parameters Of The Estuarine Copepod Acartia Tonsa Dana, Lisa A. Drake

OES Theses and Dissertations

Naturally occurring viruses are very abundant in fresh, estuarine, and marine waters, with densities on the order of 10⁵-10⁸ viruses ml^-1. Research has focused on virus effects on bacteria, cyanobacteria, and phytoplankton, as well as mechanisms of virus production and decay. However, little is known about the distribution of viruses in benthic environments or virus effects on organisms in higher trophic levels.

To determine the distribution of virus-like particles (VLPs) and bacteria in the lower Chesapeake Bay, vertical profiles of VLPs and bacteria were determined through the water column and 15-25 cm into the sediment …

Modeling Plankton Community Structure Under Environmental Forcing On The Southeastern United States Continental Shelf, Andrew Glenn Edward Haskell

OES Theses and Dissertations

A system of coupled ordinary differential equations was developed to investigate the time-dependent behavior of phytoplankton, copepod, and doliolid populations associated with upwelling features on the outer southeastern U.S. continental shelf. Model equations describe the interactions of nitrate, ammonium, two phytoplankton size fractions, five copepod developmental stages, doliolids, and a detrital pool. Model dynamics are based primarily upon data obtained from field and laboratory experiments made for southeastern U.S. continental shelf plankton populations. Numerous simulations were performed to investigate the effects of environmental variability on the temporal distribution of the structure of resident plankton populations. Variations on a reference simulation, …