Physical Sciences and Mathematics Commons^™

Precipitation Variability And Predictability Over The Arabian Peninsula, Central Southwest Asia, And Southern Africa, Matthew Francis Horan

Doctoral Dissertations

The Northern Hemisphere winter is the main rainy season for the Arabian Peninsula (AP), Central Southwest Asia (CSWA), and Southern Africa (SF), where precipitation predictability is limited or understudied. This dissertation research focuses on improving our understanding of these regions' wet-season precipitation characteristics and predictability.

First, I have identified the AP's key moisture sources through a Lagrangian back-trajectory algorithm. Mid-latitude land and water bodies, such as the Mediterranean and Caspian Seas, are the primary moisture sources in the northern region. Areas further south rely on moisture transport from the Western Indian Ocean and the African continent. A significant drying trend …

Climatological Analysis Of Tropical Cyclone Occurrence Dates And Landfall Characteristics In The North Atlantic And Eastern North Pacific, Nicholas Sava Grondin

Doctoral Dissertations

Tropical cyclones (TCs) are significant hazards to coastal and inland regions across the globe, especially in North America. North America is affected by TCs from two basins, the North Atlantic (NATL) and eastern North Pacific (ENP), with the former being the predominate focus of past research. In this dissertation, I present three studies that directly compare TCs in the NATL and ENP by using the same methods for each basin in studying occurrence dates and intraseasonal variability, effects of environmental parameters on occurrence dates and seasonal forecasting, and the behavior of TCs during the final 36 hours before landfall in …

Machine Learning For Earth Systems Modeling, Analysis And Predictability, Linsey Passarella

Doctoral Dissertations

Artificial intelligence (AI) and machine learning (ML) methods and applications have been continuously explored in many areas of scientific research. While these methods have lead to many advances in climate science, there remains room for growth especially in Earth System Modeling, analysis and predictability. Due to their high computational expense and large volumes of complex data they produce, earth system models (ESMs) provide an abundance of potential for enhancing both our understanding of the climate system as well as improving performance of ESMs themselves using ML techniques. Here I demonstrate 3 specific areas of development using ML: statistical downscaling, predictability …

Nashville-Basin Tornadoes: Using Storm Types To Elucidate The Local Climatology And Forecasting Challenges, Morgan Steckler, Kelsey Ellis

Pursuit - The Journal of Undergraduate Research at The University of Tennessee

Early 3 March 2020 was a devastating night for many middle Tennessee residents. A strong EF-3 tornado tore through Nashville at 65 mph, and another EF-4 killed 18 in Baxter and Cookeville alone. Residents of the Southeastern United States are particularly vulnerable to tornadoes. This study aims to better understand local forecasting challenges by looking at the types of storms that produce tornadoes. Storm types, also known as convective modes, divide tornado-producing storms into categories by length, shape, multiplicity, and intensity. Distinguishing storms by these modes allows for a broader understanding of their occurrences and impacts. This study specifically evaluates …

Hazardous Weather And Human Response In The Southeastern United States, Daniel Burow

Doctoral Dissertations

Effectively mitigating the human costs of future hazardous weather events requires examining meteorological threats, their long-term patterns, and human response to these events. The southeastern United States is a region that has both a high climatological risk and a high societal vulnerability to many different meteorological hazards. In this dissertation, I study hazardous weather and human response in the Southeast through three different lenses: identifying uniquely simultaneous hazards posed by tropical cyclones, assessing precipitation and synoptic weather patterns on hazardous weather days, and examining patterns in intended response to tornado watches. I find that simultaneous and collocated tornado and flash …

Conservation Agriculture As A Climate Change Mitigation Strategy In Zimbabwe, Deb O'Dell, Neal Eash, Bruce B. Hicks, Joel Oetting, Thomas J. Sauer, Dayton M. Lambert, Tarirai Muoni, Joanne Logan, James A. Zahn, John J. Goddard

Biosystems Engineering and Soil Science Publications and Other Works

There is a need to quantify agriculture’s potential to sequester carbon (C) to inform global approaches aimed at mitigating climate change effects. Many factors including climate, crop, soil management practices, and soil type can influence the contribution of agriculture to the global carbon cycle. The objective of this study was to investigate the C sequestration potential of conservation agriculture (CA) (defined by minimal soil disturbance, maintaining permanent soil cover, and crop rotations). This study used micrometeorological methods to measure carbon dioxide (CO₂) flux from several alternative CA practices in Harare, central Zimbabwe. Micrometeorological methods can detect differences in …

Analysis Of Hurricane Track Forecast Accuracy During The 2018 Season, Jonathan D. Unger

Pursuit - The Journal of Undergraduate Research at The University of Tennessee

Hurricane track forecasting has become more accurate in recent years due to technological advances in modeling methods. However, due to the complex nature of the relationship between oceanic and atmospheric variables and hurricane tracks, noteworthy errors in track prediction, especially for predictions several days into the future, still remain. In this study, two different methods of forecasting hurricane tracks are compared. Using the four United States landfalling hurricanes of the 2018 season as a sample, the official forecast tracks published by the National Hurricane Center (NHC) and hypothetical tracks based purely on climatology were mapped simultaneously with the preliminary best …

Analysis Of Hurricane Track Forecast Accuracy During The 2018 Season, Jonathan Unger

Chancellor’s Honors Program Projects

No abstract provided.

Movement Of Lifetime Maximum Intensity Locations During The North Atlantic Hurricane Season, Morgan Steckler

EURēCA: Exhibition of Undergraduate Research and Creative Achievement

Where a storm reaches its lifetime maximum intensity (LMI) can be a powerful indicator of tropical cyclone intensification patterns. Any changes in this location may demonstrate how hurricanes are affected by climate change. Studies on the annual and decadal trends in LMI location have shown that the latitude where storms are reaching their LMI is shifting, but at different rates and in different directions depending on the ocean basin. In the North Atlantic, for example, LMI location seems to be moving slightly closer to the equator, especially for those storms with the greatest intensities. LMI location patterns have yet to …

Spatial Analysis Of Tornado Warning System Understanding And Relationship With Tornado Occurrence, Chesnea A. Skeen

Pursuit - The Journal of Undergraduate Research at The University of Tennessee

Tornadoes present a significant threat to life and property. The National Weather Service watch and warning system warns the public of tornadoes. If these warnings are not heeded by the public, the potential fatalities and destruction of property cannot be minimized. Thus, to prevent further loss of life and property, it is necessary to understand how the public understands the watch and warning system, as well as how they react. This paper aims to understand the correlation between understanding of watches and warnings and the occurrence of tornadoes, as well as how understanding varies spatially. Survey data were collected from …

Determining Sources Of Nitrate In The Semi-Arid Rio Grande Using Nitrogen And Oxygen Isotopes, Diego Alberto Sanchez Hernandez

Masters Theses

The Rio Grande, a semi-arid river in the American Southwest, is a major source of surface water for agriculture and drinking supplies in New Mexico and Texas. In addition to increasing salinity, considerable increases of NO₃^- [nitrate] have been observed in the semi-arid portion of the Rio Grande. It is possible that elevated water salinity inhibits denitrification on irrigated fields and, thus, fails to mediate excess nutrient load from anthropogenic activities. Therefore, two major goals of this project were to 1) characterize and quantify major NO₃^- sources, and 2) assess whether elevated water salinity affects microbial …

Convective Mode Climatology Of Tennessee Tornado Events And Effect On National Weather Service Warning Processes, Kelly Nicole Gassert

Masters Theses

Tennessee resides in the Southeastern United States, a region prone to violent tornadoes on a year-round basis. With one of the highest tornado fatality rates in the country, and a climatology that varies across the state, analysis of storms resulting in Tennessee tornadoes is necessary for improving forecasting techniques and decreasing loss of life. This study analyzed convective modes responsible for Tennessee tornadoes from 2003 to 2014 to determine an association with fatalities, seasonality, day and night, tornado magnitude, regionality, and multiple-tornado days. Chi-squared tests were conducted to determine if these patterns were significant. National Weather Service forecasters from the …

Trends In Location Of Lifetime Maximum Intensity Of Tropical Cyclones In The North Atlantic And West Pacific Oceans, Sarah Ann Bleakney

Masters Theses

Tropical cyclones threaten coastal populations around the world each year. Thus, the climatology of tropical cyclones is an immediate research need, specifically to better understand their long-term patterns and elucidate their future in a changing climate. One important pattern that has recently been detected is the poleward shift of the lifetime maximum intensity (LMI) of tropical cyclones in the Northern Hemisphere. My study further assesses the recent spatial changes in the LMI of tropical cyclones in the Northern Atlantic and Western Pacific basins since 1964. I explored relationships between the intensity and location of LMI with respect to landfall location …

Knoxville Microclimates: Spatial And Temporal Variability In Ambient Air Temperature Across Four Urban Neighborhoods, David Andrew Howe

Masters Theses

The urban heat island (UHI), has been studied extensively over the past 30 to 40 years, yet questions remain regarding the spatiotemporal variability of the UHI, and what factors influence this variability. More recent studies have emphasized the microclimates within an urban setting, but most do not have the high resolution climate or land cover data necessary to truly understand the interactions taking place at a neighborhood-level scale. This study used a network of 10 identical weather stations and high resolution land use data in Knoxville, Tennessee to analyze the microclimates of a medium-sized city with a temperate climate over …

Rare Occurrences Of Free-Living Bacteria Belonging To Sedimenticola From Subtidal Seagrass Beds Associated With The Lucinid Clam, Stewartia Floridana, Aaron M. Goemann

Masters Theses

Lucinid clams and their sulfur-oxidizing endosymbionts comprise two compartments of a three-stage, biogeochemical relationship among the clams, seagrasses, and microbial communities in marine sediments. A population of the lucinid clam, Stewartia floridana, was sampled from a subtidal seagrass bed at Bokeelia Island Seaport in Florida to test the hypotheses: (1) S. floridana, like other lucinids, are more abundant in seagrass beds than bare sediments; (2) S. floridana gill microbiomes are dominated by one bacterial operational taxonomic unit (OTU) at a sequence similarity threshold level of 97% (a common cutoff for species level taxonomy) from 16S rRNA genes; …

Elucidating The Impact Of Roseophage On Roseobacter Metabolism And Marine Nutrient Cycles, Nana Yaw Darko Ankrah

Doctoral Dissertations

As the most abundant biological entities in marine environments, viruses are an important component of marine food webs. The activity of viruses contributes significantly to the mortality of marine microorganisms, ultimately influencing biological function and chemical composition of aquatic systems by impacting species composition and flow of carbon, nitrogen and other nutrients. Despite the growing recognition that viral activity contributes to marine biogeochemical cycles, the extent to which virus infection reshapes host metabolism and the effect of this alteration on the composition of host lysate remains poorly understood. Additionally, the degree to which natural bacterioplankton communities metabolise the released lysate …

Detecting Tropical Cyclone Signals In Tree Rings Of Longleaf Pine (Pinus Palustris Mill.), Valdosta, Georgia, U.S.A., Savannah Anne Collins

Masters Theses

The study of past hurricanes to help interpret the patterns of current and future tropical storms is vital to our economy, society, and infrastructure. Understanding how hurricanes are influenced by a warm climate is critical, and hurricane reconstructions from former periods of the Holocene (the last ~11,500 yr) will be beneficial. Paleotempestology is the study of past tropical cyclones and uses historical, biological, and geological proxies to reconstruct tropical cyclone activity to create a record of historical hurricane patterns. A tropical cyclone (TC) is a chaotic weather event that is influenced by several elements, including warm ocean waters from which …

Measuring Carbon Dioxide (Co2) Flux Of Agricultural Practices In Sub-Saharan Africa, Debra Blumberg O'Dell

Masters Theses

Agriculture has an important role in addressing two of the world’s most pressing problems: meeting global food demand and mitigating climate change. If agriculture is not practiced sustainably it will fail to meet future food demand and likely intensify the pace of global climate change. There are some agricultural practices, such as Conservation Agriculture, that can produce food sustainably and have the potential to mitigate climate change. However it is not clear which agricultural practices contribute to climate mitigation and by how much. By measuring the carbon dioxide (CO2) emissions of specific agricultural practices, the ability of practices to sequester …

Evaluating Predictability In The Community Earth System Model In Response To The Eruption Of Mount Pinatubo, Abigail Laurel Gaddis

Doctoral Dissertations

A central goal of climate research is to determine the perceptible effects of climate change on humans; in other words, the regional and decadal scale effects of carbon dioxide forcing. Identifying the most pronounced and long-lasting responses of climate variables to forcing is important for decadal prediction since forcing terms are a source of predictability on those time scales. Powerful volcanic eruptions provide a transient forcing on the climate system, creating a test bed for climate models. In this study, the Mount Pinatubo eruption is simulated in the Community Earth System Model, CESM1.0, for three model configurations: fully coupled T85 …

Quorum Sensing And Metabolism In Marine Environments, Amanda May

Doctoral Dissertations

Quorum sensing (QS) is a phenomenon that allows bacteria to communicate with each other. Small molecules known as autoinducers are synthesized and released by bacteria, and once enough members of the community are around to ensure survival, i.e. quorum, a phenotype, e.g. bioluminescence, is expressed. There are two types of QS molecules, intra- and inter-species.

S-4,5-Dihydroxy-2,3-pentanedione (DPD) is a byproduct of the activated methyl cycle which recycles methionine. This has led to the discussion as to whether DPD is a metabolic byproduct or is the interspecies signal as proposed previously. The detection and quantitation of DPD however, has not …

An Evaluation Of Disturbance-Induced Nutrient Changes And Climate Responses Of Loblolly Pine Xylem, Rebecca Lynne Stratton

Doctoral Dissertations

Dendrochronological techniques are currently limited to the identification of visible fire scars. However, through the development of new dendrochemical techniques, the potential exists to provide insight into a broader array of pyric ecosystems. In addition, the ability to identify historic climate-growth responses provides a better understanding of the conditions under which historic fire regimes occurred.

This study provides the groundwork for the identification of a dendrochemical nutrient fire signature in xylem and identifies the climate-radial growth responses of loblolly pine (Pinus taeda L.) on five sites in the Piedmont of South Carolina. Changes in N, P, K, Ca, Mg, …

Oceanic-Atmospheric And Hydrologic Variability In Long Lead-Time Forecasting, Abdoul Aziz Oubeidillah

Doctoral Dissertations

Water managers throughout the world are challenged with managing scarce resources and therefore rely heavily on forecasts to allocate and meet various water demands. The need for improved streamflow and snowpack forecast models is of the utmost importance. In this research, the use of oceanic and atmospheric variables as predictors was investigated to improve the long lead-time (three to nine months) forecast of streamflow and snowpack. Singular Value Decomposition (SVD) analysis was used to identify a region of Pacific and Atlantic Ocean SSTs and a region of 500 mbar geopotential height (Z500mb) that were teleconnected with streamflow and snowpack. The …

A 7600-Year Record Of Environmental History From The Sediments Of Laguna Tortuguero, Puerto Rico, Alice Renee Schoen

Masters Theses

In 1987, Burney and collaborators (Journal of Archaeological Science (1994) 21, 273–281) recovered a ca. 8 m sediment core from the western basin of Laguna Tortuguero, Puerto Rico that spanned the last ca. 7000 calibrated years. They produced a detailed microscopic charcoal record, and from an initial peak in charcoal at ca. 5300 cal yr B.P. suggested that humans had colonized the island some 2000 years earlier than documented by the archaeological evidence then available. In 2008, two sediment cores were recovered from the eastern basin of Laguna Tortuguero. AMS dates on macrofossils indicate the profile extends to 7600 calibrated …

Use Of Remote Sensing, Hydrologic Tree-Ring Reconstructions, And Forecasting For Improved Water Resources Planning And Management, Cody Lee Moser

Doctoral Dissertations

Uncertainties were analyzed in three areas (remote sensing, dendroclimatology, and climate modeling) relevant to current water resources management. First, the research investigated the relationships between remotely sensed and in situ Snow Water Equivalent (SWE) datasets in three western U.S. basins. Agreement between SWE products was found to increase in lower elevation areas and later in the snowpack season. Principal Components Analysis (PCA) revealed two distinct snow regions among the datasets and Singular Value Decomposition (SVD) was used to link both data products with regional streamflow. Remotely sensed SWE was found to be sufficient to use in statistically based forecast models …

Wind Regimes In Complex Terrain Of The Great Valley Of Eastern Tennessee, Kevin Ray Birdwell

Doctoral Dissertations

This research was designed to provide an understanding of physical wind mechanisms within the complex terrain of the Great Valley of Eastern Tennessee to assess the impacts of regional air flow with regard to synoptic and mesoscale weather changes, wind direction shifts, and air quality. Meteorological data from 2008–2009 were analyzed from 13 meteorological sites along with associated upper level data. Up to 15 ancillary sites were used for reference. Two-step complete linkage and K-means cluster analyses, synoptic weather studies, and ambient meteorological comparisons were performed to generate hourly wind classifications. These wind regimes revealed seasonal variations of underlying physical …

The ‘Helper’ Phenotype: A Symbiotic Interaction Between Prochlorococcus And Hydrogen Peroxide Scavenging Microorganisms, James Jeffrey Morris

Doctoral Dissertations

The unicellular cyanobacterium Prochlorococcus is the numerically dominant photosynthetic organism throughout the temperate and tropical open oceans, but it is difficult to grow in pure cultures. We developed a system for rendering spontaneous streptomycin-resistant mutants of Prochlorococcus axenic by diluting them to extinction in the presence of “helper” heterotrophic bacteria, allowing them to grow to high cell concentrations, and then killing the helpers with streptomycin. Using axenic strains obtained in this fashion, we demonstrated that Prochlorococcus experiences a number of growth defects in dilute axenic culture, including reduced growth rate, inability to form colonies on solid media, and higher incidence …

An Investigation Of Atmospheric Turbulence Probes With Ground Test Comparisons Of Probe Head Designs And Evaluation Of Suitability To Instrumented Aircraft, Charles F Lams

Masters Theses

A comparison of methods to determine the flow angle components of atmospheric velocity vectors is presented. The atmospheric turbulence probes used to measure behavior of the atmosphere use different methods to obtain this information and there is some confusion as to which method is best. Although the methods are all based upon potential flow theory, the details about how the atmospheric and flight parameters are measured makes a difference to the design of an atmospheric turbulence probe and carrier research aircraft. This paper presents the mathematical theory behind five methods of obtaining atmospheric flow angle measurements from a moving aircraft. …

Niche Of Harmful Alga Aureococcus Anophagefferens Revealed Through Ecogenomics, Christopher Gobler, Dianna Berry, Sonya Dyhrman, Steven Wilhelm

Microbiology Publications and Other Works

Harmful algal blooms (HABs) cause significant economic and ecological damage worldwide. Despite considerable efforts, a comprehensive understanding of the factors that promote these blooms has been lacking, because the biochemical pathways that facilitate their dominance relative to other phytoplankton within specific environments have not been identified. Here, biogeochemical measurements showed that the harmful alga Aureococcus anophagefferens outcompeted co-occurring phytoplankton in estuaries with elevated levels of dissolved organic matter and turbidity and low levels of dissolved inorganic nitrogen. We subsequently sequenced the genome of A. anophagefferens and compared its gene complement with those of six competing phytoplankton species identified through metaproteomics. …

Aquatic Habitat Mapping Within The Obed Wild And Scenic River For Threatened And Endangered Species Habitat Delineation, Joseph Ross Candlish

Masters Theses

There is a need to define a more efficient and accurate approach to aquatic habitat mapping. Traditional approaches have focused on intense biological/non-biological sampling and observation analysis within specific and restrained scales. Therefore, an underwater video mapping system (UVMS) has been developed in efforts to identify federally protected aquatic species’ habitats within the Obed Wild and Scenic River (OBRI). The UVMS kayak apparatus provides georeferenced video footage correlated with GPS (global positioning systems) for GIS (geographic information systems) mapping applications. Based on its fluvial and geomorphological trends, OBRI was dissected quantitatively and integrated into databases for species-specific GIS habitat queries. …

An Empirical Model Of Thermal Updrafts Using Data Obtained From A Manned Glider, Christopher E. Childress

Masters Theses

Various methods have been used, including airborne radars, LIDAR, observation of flying birds, towers, tethered balloons, and aircraft to gain both a qualitative and quantitative representation of how heat and moisture are transported to higher altitudes and grow the boundary or mixing layer by thermal updrafts. This paper builds upon that research using an instrumented glider to determine the structure and build a mathematical model of thermals in a desert environment. During these flights, it was discovered that the traditional view of a thermal as a singular rising plume of air did not sufficiently explain what was being observed, but …