Oceanography and Atmospheric Sciences and Meteorology Commons^™

Infrasound Propagation In Terrestrial Planetary Atmospheres, Lynsey B. Schroeder

Doctoral Dissertations and Master's Theses

Acoustic waves in the infrasonic frequency range, that is below 10 Hertz, have been observed to propagate to high altitudes in Earth's atmosphere. These waves have many sources, both natural and artificial, such as seismic events, convective storm systems, and nuclear explosions. Here, we seek to better understand the characteristics of atmospheric infrasound- below 0.1 Hz in particular- so as to improve the ability to detect their presence and sources. It is well-known that ambient attributes of an atmosphere, such as temperature, density, and composition, directly affect the propagation and growth of waves, and therefore it is likely that these …

Observation And Modeling Of Gravity Wave Propagation Through Reflection And Critical Layers Above Andes Lidar Observatory At Cerro Pachón, Chile, Bing Cao, Christopher J. Heale, Yafang Guo, Alan Z. Liu, Jonathan B. Snively

Publications

A complex gravity wave event was observed from 04:30 to 08:10 UTC on 16 January 2015 by a narrow-band sodium lidar and an all-sky airglow imager located at Andes Lidar Observatory (ALO) in Cerro Pachón (30.25∘S, 70.73∘W), Chile. The gravity wave packet had a period of 18–35 min and a horizontal wavelength of about 40–50 km. Strong enhancements of the vertical wind perturbation, exceeding10 m s−1, were found at ∼90 km and ∼103 km, consistent with nearly evanescent wave behavior near a reflection layer. A reduction in vertical wavelength was found as the phase speed approached the background wind speed …

Breakdown Of Itcz-Like Pv Patterns, Ajay Raghavendra, Thomas A. Guinn

Beyond: Undergraduate Research Journal

The Inter-Tropical Convergence Zone (ITCZ) is a zonal belt of intense convection, responsible for the genesis of over 80% of all tropical cyclones. This region of intense diabatic heating and shear results in a maximum of Ertel's potential vorticity (PV) meeting Rayleigh's necessary condition for barotropic instability. A fundamental issue is understanding the necessary precursor events leading to the breakdown of the ITCZ and subsequent formation of tropical cyclones. Our research examines the non-linear PV dynamics of the breakdown of both finite-length and infinite-length vorticity strips of varying widths and shapes, simulating the ITCZ found near the tropical eastern Pacific …

On Safety Assessment Of Novel Approach To Robust Uav Flight Control In Gusty Environments, Vladimir Golubev, Petr Kazarin, William Mackunis, Sherry Borener, Derek Hufty

Publications

In a follow-up to our previous study, the current work examines the gust-induced “cone of uncertainty” in a small unmanned aerial vehicle’s (UAV) flight trajectory addressed in the context of safety assessments of UAV operations. Such analysis is a critical facet of the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), particularly in terminal airspace. The paper describes a predictive, robust feedback-loop flight control model that is applicable to various classes of UAVs and unsteady flight-path scenarios. The control design presented in this paper extends previous research results by demonstrating asymptotic (zero steady-state error) altitude regulation …

Tsunami Warning System, Amay Vijay Desai

Doctoral Dissertations and Master's Theses

The effects of a tsunami on a coastline can be devastating. In an attempt to mitigate the damages caused by tsunamis, and to provide coastal communities with evacuation alerts, it is essential to have early warning systems installed offshore. Tsunami early warning systems can detect the formation of tsunami waves long before they reach shore, providing coastal communities with information about the strength of an incoming tsunami.

Since providing accurate information about oceanic wave patterns is absolutely necessary to forecast the magnitude of a tsunami as it forms, the focus of this research is to develop a novel approach which …

The Influence Of Model Resolution On The Simulated Sensitivity Of North Atlantic Tropical Cyclone Maximum Intensity To Sea Surface Temperature, Sarah Strazzo, James Elsner, Timothy Larow, Hiroyuki Murakami, Michael Wehner, Ming Zhao

Publications

No abstract provided.

Predicting General Aviation Pilots’ Weather-Related Performance Through A Scenario-Based Written Assessment, Jessica Cruit

Doctoral Dissertations and Master's Theses

Weather-related accidents continue to challenge the general aviation community and with the development of advanced weather technology, GA pilots need additional education and training on how to effectively use these weather products to ensure flight safety. Currently, the literature on aviation weather suggests that there is a gap in both training and assessment strategy for GA pilots. Furthermore, several studies suggest that there needs to be more assessment of weather-related scenario/application questions for the private pilot’s written knowledge exam in order to assess a deeper level of knowledge for weather-related material. The purpose of this study is to design a …

Energy Transfer From Wind To Wave Groups: Theory And Experiment, Andrei Ludu, Shahrdad G. Sajjadi

Publications

Three major unresolved problems that remain in oceanography are studied in depth, namely (a) unsteady waves, where waves are allowed to grow or decay in time and space; (b) sharp-crested waves (also known as fully nonlinear Stoke waves), which are note characteristic in oceans; and (c) group of waves, which can often become sharp crested as they propagate downstream, as demonstrated here experimentally in a wave tank. The ultimate aim of such investigation is to improve the parameterization of the energy input from wind to waves. In this paper, we (i) present results on the simplest approximation to wave groups …

Forecast Verification Of The Current Icing Potential (Cip) To Predict Lightning Hazards At U.S. Spaceports, Robert Edward Haley

Doctoral Dissertations and Master's Theses

Government spaceports employ extensive lightning detection networks that may not be available at commercial spaceports. Therefore, the Federal Aviation Administration identified the need for diagnosing the threat of triggered lightning without in-situ measurements. Anecdotal observations of the Aviation Weather Center’s Current Icing Potential (CIP) diagnostic model indicated a potentially high correlation between lightning activity and icing potential. A forecast verification study and supporting representative case studies were conducted to quantify the CIP’s ability to diagnose existing lightning hazards. The study showed that high positive statistical correlations between the CIP and lightning activity do exist, but so do negative correlations. During …

Measuring The Seeds Of Ion Outflow: Auroral Sounding Rocket Observations Of Low-Altitude Ion Heating And Circulation, P. A. Fernandes, K. A. Lynch, M. Zettergren, D. L. Hampton, T. A. Bekkeng, Et Al.

Publications

We present an analysis of in situ measurements from the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) nightside auroral sounding rocket with comparisons to a multifluid ionospheric model. MICA made observations at altitudes below 325 km of the thermal ion kinetic particle distributions that are the origins of ion outflow. Late flight, in the vicinity of an auroral arc, we observe frictional processes controlling the ion temperature. Upflow of these cold ions is attributed to either the ambipolar field resulting from the heated electrons or possibly to ion-neutral collisions. We measure convection away from the arc (poleward) and downflows of …

Evidence Of Dispersion And Refraction Of A Spectrally Broad Gravity Wave Packet In The Mesopause Region Observed By The Na Lidar And Mesospheric Temperature Mapper Above Logan, Utah, T. Yuan, C. J. Heale, J. B. Snively, X. Cai, P.- D. Pautet, C. Fish, Y. Zhao, M. J. Taylor, W. R. Pendleton Jr., V. Wickwar, N. J. Mitchell

Publications

"Gravity wave packets excited by a source of finite duration and size possess a broad frequency and wave number spectrum and thus span a range of temporal and spatial scales. Observing at a single location relatively close to the source, the wave components with higher frequency and larger vertical wavelength dominate at earlier times and at higher altitudes, while the lower frequency components, with shorter vertical wavelength, dominate during the latter part of the propagation. Utilizing observations fromthe Na lidar at Utah State University and the nearby Mesospheric Temperature Mapper at Bear Lake Observatory (41.9°N, 111.4°W), we investigate a unique …

New Metric For Defining The Time Of Extratropical Transition Of Tropical Cyclones, Ajay Raghavendra, Shawn M. Milrad

Publications

Almost half of all tropical cyclones (TCs) in the Atlantic basin undergo extratropical transition (ET). During an ET event, wind fields often expand dramatically, resulting in more widely-felt impacts. Moreover, the heaviest precipitation typically shifts to the left-of-center (LOC), which can result in inland flash flooding hundreds of kilometers from the cyclone center. While several objective metrics to track and predict ET have been developed, they rely at least partially on internal tropical cyclone structure, for which numerical models show less skill. Further, these metrics fail to account for static stability, which plays a vital role in determining precipitation amounts. …

The Tornado That Struck Embry-Riddle Aeronautical University On Christmas Day, 2006: Lessons Learned From A Near-Miss, John M. Lanicci

Journal of Aviation/Aerospace Education & Research

An F2 tornado that touched down in Daytona Beach on Christmas Day afternoon caused over $50 million of damage to the Embry-Riddle Aeronautical University campus and nearby neighborhoods. The tornado was part of a severe-weather outbreak over Florida, Georgia, and South Carolina that began during the overnight hours of 25 December 2006. Examination of surface and upper-level meteorological charts and vertical soundings on the morning of 25 December showed stability and wind-shear conditions favorable for tornadic thunderstorms over this region. The evolution of the squall line that moved through east-central Florida, and the parent thunderstorm that produced the tornado was …

First Measurement Of Horizontal Wind And Temperature In The Lower Thermosphere (105–140 Km) With A Na Lidar At Andes Lidar Observatory, Alan Liu, Yafang Guo, Fabia A. Vargas, Gary Swenson,

Publications

We report the first measurement of nighttime atmospheric temperature and horizontal wind profiles in the lower thermosphere up to 140 km with the Na lidar at Andes Lidar Observatory in Cerro Pachón, Chile (30.25°S, 70.74°W), when enhanced thermospheric Na was observed. Temperature and horizontal wind were derived up to 140 km using various resolutions, with the lowest resolution of about 2.7 hr and 15 km above 130 km. Thus, the measurements span 60 km in vertical, more than double the traditional 25 km. On the night of 17 April 2015, the horizontal wind magnitude in the thermosphere exceeds 150 ms−1, …

Evidence Of The Excitation Of A Ring-Like Gravity Wave In The Mesosphere Over The Andes Lidar Observatory, Fabio Vargas, Gary Swenson,, Alan Liu, Dominique Pautet

Publications

On 23 March 2012, our all-sky imager recorded a concentric, ring-like gravity wave pattern. The wave arose within the area covered by images of both OH and O(1S) nightglow emissions taken at the Andes Lidar Observatory (ALO), Chile (30.3°S, 70.7°W). We have estimated the observed and intrinsic parameters of the event and located the wave source within the lower mesosphere altitude range using a reverse ray tracing method. By the analysis of GOES and LIS satellite images, we have not found evidence of neither convective nor lightning activity nearby ALO, indicating that the source of the ring-like wave …

Turbulence And Overturning Gravity Wave Effects Deduced From Mesospheric Na Density Between 100-105 Km At Andes Lidar Observatory, Chile, Alan Z. Liu, Channing P. Philbrick, Gary R. Swenson, Fabio A. Vargas

Publications

Atmospheric turbulence activity in the mesosphere and lower thermosphere (MLT) region is determined from narrowband Na lidar measurements obtained over 27 nights between 85-105 km altitude at the Andes Lidar Observatory (ALO) in Cerro Pachón, Chile (30.3ºS, 70.7ºW). Photocount perturbations in the applicable spectral subrange are used as a tracer of turbulence activity. Mean altitude profiles reveal a log-scale linear increase in turbulence perturbation amplitude above 95 km. The observed trend is compared against global mean constituent transport profiles derived from SABER and SCIAMACHY satellite borne measurements.

Intermittency Of Gravity Wave Momentum Flux In The Mesopause Region Observed With An All-Sky Airglow Imager, Bing Cao, Alan Z. Liu

Publications

The intermittency of gravity wave momentum flux (MF) near the OH airglow layer (∼87 km) in the mesopause region is investigated for the first time using observation of all-sky airglow imager over Maui, Hawaii (20.7∘N, 156.3∘W), and Cerro Pachón, Chile (30.3∘S, 70.7∘W). At both sites, the probability density function (pdf) of gravity wave MF shows two distinct distributions depending on the magnitude of the MF. For MF smaller (larger) than ∼16 m2 s−2 (0.091 mPa), the pdf follows a lognormal (power law) distribution. The intermittency represented by the Bernoulli proxy and the percentile ratio shows that gravity waves have higher …

Chemical Transport Of Neutral Atmospheric Constituents By Waves And Turbulence: Theory And Observations, Chester S. Gardner, Alan Liu

Publications

Vertical chemical transport occurs when the density fluctuations of a species, caused by perturbations of its chemistry, are strongly correlated with the vertical wind fluctuations. Chemical transport can exceed dynamical and eddy transport of chemically active species. Theoretical expressions are derived for the chemical fluxes and transport velocities and used to characterize the vertical transport of mesospheric O3 and meteoric Na and Fe between 85 and 100 km. Chemical transport is dependent on the intrinsic frequency spectrum of the temperature fluctuations and on the chemical cutoff periods of the species. For O3 only high-frequency fluctuations contribute to chemical transport because …

Southern Hemisphere Summer Mesopause Responses To El Niño–Southern Oscillation, Tao Li, Natalia Calvo, Jia Yue, James Russell Iii, Alan Liu

Publications

In the Southern Hemisphere (SH) polar region, satellite observations reveal a significant uppermesosphere cooling and a lower-thermosphere warming during warm ENSO events in December. An opposite pattern is observed in the tropical mesopause region. The observed upper-mesosphere cooling agrees with a climate model simulation. Analysis of the simulation suggests that enhanced planetary wave (PW) dissipation in the Northern Hemisphere (NH) high-latitude stratosphere during El Niño strengthens the Brewer–Dobson circulation and cools the equatorial stratosphere. This increases the magnitude of the SH stratosphere meridional temperature gradient and thus causes the anomalous stratospheric easterly zonal wind and early breakdown of the SH …

Dynamics Of Density Cavities Generated By Frictional Heating: Formation, Distortion, And Instability, M. D. Zettergren, J. L. Semeter, H. Dahlgren

Publications

A simulation study of the generation and evolution of mesoscale density cavities in the polar ionosphere is conducted using a time-dependent, nonlinear, quasi-electrostatic model. The model demonstrates that density cavities, generated by frictional heating, can form in as little as 90 s due to strong electric fields of ∼120 mV/m, which are sometimes observed near auroral zone and polar cap arcs. Asymmetric density cavity features and strong plasma density gradients perpendicular to the geomagnetic field are naturally generated as a consequence of the strong convection and finite extent of the auroral feature. The walls of the auroral density cavities are …

Enhancing Quality Assurance Using Virtual Design Engineering: Case Study Of Space Shuttle Challenger, Kouroush Jenab, Scot Paterson

International Journal of Aviation, Aeronautics, and Aerospace

Virtual Design Engineering is an emerging method of increasing quality of systems. Including Virtual Design as a part of the traditional established Failure Mode, Effects, and Criticality Analysis process greatly enhances hazard and risk analysis while reducing overall costs. In this study these enhancements are explored and expanded upon to discover how overall system quality could be increased and all stakeholders could more accurately understand the hazards involved. Stakeholder misunderstanding or misapplication of hazards is of great importance to complex systems. An illustrative example of how these factors could have changed the outcome of a real-world engineering failure is provided.

Examining Unmanned Aerial System Threats & Defenses: A Conceptual Analysis, Ryan J. Wallace, Jon M. Loffi

International Journal of Aviation, Aeronautics, and Aerospace

The integration of unmanned aerial systems (UAS) into the already complex global aviation system presents new and unique hazards. While many studies have addressed the potential safety concerns of UAS integration, little research has been dedicated to the potential security implications. This study sought to identify potential uses and adaptations of civil UAS systems as weapons of terrorism or crime and potential UAS defenses. Researchers examined 68 academic studies, unclassified government reports, and news articles using Conceptual Analysis to systematically capture and categorize various threats. Using the collected data, researchers developed a UAS threat model for categorically evaluating potential threats. …

Ionospheric Response To Infrasonic-Acoustic Waves Generated By Natural Hazard Events, M. D. Zettergren, J. B. Snively

Publications

"Recent measurements of GPS-derived total electron content (TEC) reveal acoustic wave periods of ∼1–4 min in the F region ionosphere following natural hazard events, such as earthquakes, severe weather, and volcanoes. Here we simulate the ionospheric responses to infrasonic-acoustic waves, generated by vertical accelerations at the Earth’s surface or within the lower atmosphere, using a compressible atmospheric dynamics model to perturb a multifluid ionospheric model. Response dependencies on wave source geometry and spectrum are investigated at middle, low, and equatorial latitudes. Results suggest constraints on wave amplitudes that are consistent with observations and that provide insight on the geographical variability …

Self-Accleration And Instability Of Gravity Wave Packets: 1. Effects Of Temporal Localization, David C. Fritts, Brian Laughman, Thomas S. Lund, Jonathan B. Snively

Publications

"An anelastic numerical model is used to explore the dynamics accompanying the attainment of large amplitudes by gravity waves (GWs) that are localized in altitude and time. GW momentum transport induces mean flow variations accompanying a GW packet that grows exponentially with altitude, is localized in altitude, and induces significant GW phase speed, and phase, variations across the GW packet. These variations arise because the GW occupies the region undergoing accelerations, with the induced phase speed variations referred to as “self-acceleration.” Results presented here reveal that self-acceleration of a GW packet localized in time and altitude ultimately leads to stalling …

Aviation Bird Hazard In Nexrad Dual Polarization Weather Radar Confirmed By Visual Observations, Bradley M. Muller, Frederick R. Mosher, Christopher G. Herbster, Anthony T. Brickhouse

International Journal of Aviation, Aeronautics, and Aerospace

Birds represent a significant hazard to flying aircraft as illustrated by the “Miracle on the Hudson” encounter in 2009 between U.S. Airways Flight 1549 and a flock of Canada Geese, forcing the flight to ditch in the river. Birds are common in the skies over Florida during the spring migration season, and often appear in the National Weather Service’s (NWS) NEXRAD weather radar imagery as an easily recognizable signature known as a “roost ring.” This paper presents a NEXRAD roost ring case in central Florida in a rare instance where the signatures were confirmed by visual observations of the birds. …

Global Optimized Isothermal And Nonlinear Models Of Earth’S Standard Atmosphere, Nihad E. Daidzic, Ph.D.,

International Journal of Aviation, Aeronautics, and Aerospace

Both, a global isothermal temperature model and a nonlinear quadratic temperature model of the ISA was developed and presented here. Constrained optimization techniques in conjunction with the least-square-root approximations were used to design best-fit isothermal models for ISA pressure and density changes up to 47 geopotential km for NLPAM, and 86 orthometric km for ISOAM respectively. The mass of the dry atmosphere and the relevant fractional-mass scale heights have been computed utilizing the very accurate eight-point Gauss-Legendre numerical quadrature for both ISOAM and NLPAM. Both, the ISOAM and the NLPAM represent viable alternatives to ISA in many practical applications and …

The Life Cycle Of Instability Features Measured From The Andes Lidar Observatory Over Cerro Pachon On 24 March 2012, J. H. Hecht, K. Wan, Lynette Gelinas, David Fritts, R. L. Walterscheid, R. J. Rudy, Alan Liu, Steven J. Franke, Fabio Vargas, P. -D. Pautet, Michael Taylor, Gary Swenson,

Publications

The Aerospace Corporation's Nightglow Imager (ANI) observes nighttime OH emission (near 1.6 µm) every 2 s over an approximate 73¬∞ field of view. ANI had previously been used to study instability features seen over Maui. Here we describe observations of instabilities seen from 5 to 8 UT on 24 March 2012 over Cerro Pachon, Chile, and compare them with previous results from Maui, with theory, and with Direct Numerical Simulations (DNS). The atmosphere had reduced stability because of the large negative temperature gradients measured by a Na lidar. Thus, regions of dynamical and convective instabilities are expected to form, depending …

Bio-Fuel Alternatives In South African Airways (Saa) Operations - Is It An Effective Response To Vulnerability Over Carbon Taxes And Penalty?, Daniel Kwasi Adjekum

International Journal of Aviation, Aeronautics, and Aerospace

The paper did a comparative analysis of the carbon emission and European Union Emission Trading Surcharges (EU ETS) of South African Airways (SAA) current fleet that used aviation jet A1 fuel and the same fleet if it had used a 25% bio-fuel ‘drop in’ for the European routes within the first quarter of the 2014 flying year (FY 14). Operational data in terms of the flight scheduled, aircraft type, total time enroute, route stage length, passenger estimates were obtained through SAA’s flight operations website. An independent t–test was conducted to compare means of the emissions. The mean carbon dioxide …

Design And Validation Of Hardware-In-The-Loop Testbed For Proximity Operations Payloads, Kristia K. Harris

Doctoral Dissertations and Master's Theses

The research presented here is a new testbed design for CubeSat and payload testing and development. This research demonstrates a low-cost, hardware-in-the-loop testing apparatus for use with university CubeSat programs for testing throughout the different levels of the development process. The average university CubeSat program undergoes very little hardware-in-the-loop testing. Most of the focus is the targeted towards performance testing and environmental testing which occur after completion the development process. This research shows that, for minimal schedule and cost impact, testing can occur early in the development process. The testbed presented here demonstrates suitable accuracy to be used for advanced …

A Meteorological Analysis Of The 2013 Alberta Flood: Antecendent Large-Scale Flow Pattern And Synoptic-Dynamic Characteristics, Shawn M. Milrad, John R. Gyakum, Eyad H. Atallah

Publications

The 19–21 June 2013 Alberta flood was the costliest (CAD $6 billion) natural disaster in Canadian history. The flood was caused by a combination of above-normal spring snowmelt in the Canadian Rockies, large antecedent precipitation, and an extreme rainfall event on 19–21 June that produced rainfall totals of 76 mm in Calgary and 91 mm in the foothills. As is typical of flash floods along the Front Range of the Rocky Mountains, rapidly rising streamflow proceeded to move downhill (eastward) into Calgary.

A meteorological analysis traces an antecedent Rossby wave train across the North Pacific Ocean, starting with intense baroclinic …