Physical Sciences and Mathematics Commons^™

Estimation Of Deep Drainage Differences Between Till And No-Till Irrigated Agriculture, Justin P. Gibson

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Deep drainage was monitored under two center pivot irrigation sites located in south-central Nebraska during the 2013, and part of the 2014, growing seasons. Both fields underwent similar land management except for tillage practice: no-till in one and disk till in the other. Long term deep drainage rates were also estimated from chemical analysis of extracted soil cores, with the aid of the chloride mass balance equation. Mechanisms underpinning differences in deep drainage between the two fields were investigated through the use of unsaturated zone numerical modeling.

Deep drainage estimates from field monitoring indicated that a greater amount of deep …

Rear-Flank Outflow Dynamics And Thermodynamics In The 10 June 2010 Last Chance, Colorado Supercell, Curtis J. Riganti

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

On 10 June 2010, the second Verification of the Origins of Tornadoes Experiment (VORTEX2) armada observed the non-tornadic phase of a supercell thunderstorm near Last Chance, Colorado. Tempest unmanned aircraft system (UAS) data collected in the rear-flank outflow revealed what appeared to be an elevated outflow head, turbulent wake, and a cold secondary outflow surge. Surface thermodynamic and kinematic data collected by StickNets and mobile mesonets suggested that the outflow wake may have extended to or very near the surface, perhaps cutting off the leading edge of the outflow at times. Single-Doppler data collected by the NOAA X-Pol Mobile Polarimetric …

Sequence Stratigraphic Framework Of Carbonate Diagenesis Within Neogene Glaciomarine Sandstones Of The Victoria Land Basin, Antarctica: Insights Into Reservoir Quality In Polar Settings, Daniel P. Dunham

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

The controls on reservoir quality of most clastic sedimentary deposits are well-documented and understood. However, comparatively little is known about the reservoir potential of glaciogenic and glaciomarine deposits. This study investigates the Neogene strata of the AND-2A core recovered by the ANDRILL-Southern McMurdo Sound Project in the Victoria Land Basin, Antarctica, as an analog for assessing controls on reservoir quality in glaciomarine deposits. A petrographic analysis was conducted on 60 sandstone samples from various depths throughout the core, and carbonate diagenetic phases and morphologies were documented. Four sequences were examined in detail. Point counting on all samples was done to …

Perceptions Of Tornadoes, Tornado Warnings, Safety Actions, And Risk: Effects On Warning Response Among Undergraduates In Nebraska, Sabrina T. Jauernic

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Few studies show how university students perceive and respond to tornado warnings, or how they gain tornado-related knowledge. Lacking in the literature are investigations of how perceptions of tornado risk may influence actions. Using two separate surveys and two large samples of undergraduates enrolled in the University of Nebraska, the author determined significant relationships between student demographics, perceptions, and response actions. Incorrect perceptions were found, such as overpasses and southwest corners of buildings being safe, and cities being invulnerable to tornadoes. International students, especially, assumed cities were safe from tornadoes. Students had a tendency to confirm their risk instead of …

Evaluation Of Regional Climate Models With Remotely Sensed Evapotranspiration Data, Doruk Ozturk

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Water is one of the most precious resources on Earth. Managing water resources is a complex discipline that requires accurate data, which in turn means that the management of water resources is limited by the availability and quality of these datasets. Evapotranspiration (ET) is one of these key datasets, but is also one that is lacking in large-scale spatial distribution with traditional methods such as weighing lysimeters or Bowen ratio. This is a quantity that needs to be evaluated in regional and global climate models since it is a substantial component of the land surface-atmosphere interaction. In order to overcome …

Retrieval Of Aerosol Microphysical Properties From Aeronet Photopolarimetric Measurements, Xiaoguang Xu

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Atmospheric aerosols play an important role in earth climate by scattering and absorbing solar and terrestrial radiation, and indirectly through altering the cloud formation, life- time, and radiative properties. However, accurate quantification of these effects is in no small part hindered by our limited knowledge about the particle size distribution (PSD) and refractive index, the aerosol microphysical properties essentially pertain to aerosol optical and cloud-forming properties. The research goal of this thesis is to obtain the aerosol microphysical properties of both fine and coarse modes from the polarimetric solar radiation measured by the SunPhotometer of the Aerosol Robotic Network (AERONET). …

Ecology And Morphology Of The Late Miocene Musk Deer, Longirostromeryx Wellsi (Artiodactyla: Moschidae: Blastomerycinae), Katheryn Y. C. Chen

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Longirostromeryx wellsi, one of the latest surviving members of the extinct clade Blastomerycinae (Artiodactyla: Moschidae), possesses highly derived craniodental morphology that deviates from typical musk deer form. Previous work suggests that the unique anatomy of L. wellsi represents adaptations for occupying open savannas. To test this hypothesis I conduct principal components analysis on five postcranial bones of L. wellsi, comparing them to that of several extant ruminant artiodactyls, which are divided among seven habitat categories. These elements are also compared with the postcrania of other blastomerycines. These analyses indicate that L. wellsi anatomy is most similar to that of other …

Improving Nocturnal Fire Detection With The Viirs Day-Night Band, Thomas N. Polivka

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

As an important component in the Earth-atmosphere system, wildfires are a serious threat to life and property that—despite improving warning systems—have exacted greater costs in recent years. In addition, they impact global atmospheric chemistry by releasing potent trace gasses and aerosols. Using the Visible Infrared Imaging Radiometer Suite (VIIRS), this study investigates the adjustment of fire pixel selection criteria to include visible light signatures at night, creating the Firelight Detection Algorithm (FILDA). This allows for greatly improved detection of smaller and cooler fires from satellite observations. VIIRS scenes with coincident Advanced Spaceborne Thermal Emission and Reflection (ASTER) overpasses are examined …

Springtime Melt Onset On Arctic Sea Ice From Satellite Observations And Related Atmospheric Conditions, Angela C. Bliss

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

The timing of snowmelt onset (MO) on Arctic sea ice derived from passive microwave satellite data is examined by determining the melting area (in km²) on a daily basis for the spring and summer melt season months over the 1979 – 2012 data record. The date of MO on Arctic sea ice has important implications for the amount of total solar energy absorbed by the ice-ocean system in a given year. Increasingly early mean MO dates have been recorded over the 34-year data record as evidenced by statistically significant trends of 6.6 days decade^-1 over the extent …

Unraveling Controls On Fracture Stratigraphy In Carbonates: The Influence Of Regional Stress, Mechanical Properties, And Diagenesis, Matthew H. Peppers

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Fracture characteristics analyzed from outcrops provide key insights into the migration pathways of subsurface hydrocarbons, and allow for a detailed understanding of the tectonic history in an area. This study looks to assess the impacts that various controlling factors have on the development of fracture characteristics. To complete this objective, a succession of Ordovician to Mississippian rocks was examined. The logged section includes the Cotter Dolomite, Chattanooga Shale, St. Joe Formation, and the Boone Formation (subdivided into informal Upper and Lower members). Located in northwestern Arkansas and southwestern Missouri, data were collected from roadcut exposures along Highway 71. Collected fracture …

Stratigraphy And Depositional Environment Of The Mesaverde Group In The Northern Bighorn Basin Of Wyoming, Gordon Adams

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

A sedimentological, stratigraphical and palynological study was conducted on the upper Cretaceous (Campanian) Mesaverde Group over 27.5 km of a north-south-orientated outcrop belt in the northern Bighorn Basin, Wyoming. During the Campanian, the study area lay in the western part of the Cretaceous Western Interior Seaway. The study aims to provide a stratigraphic and paleoenvironmental analysis of the Mesaverde Group and to integrate findings with data from outcrop belts to the south (southern Bighorn Basin), north (Montana) and east (Powder River Basin).

The Mesaverde Group (371 - 515 m thick) comprises a succession of mainly coarsening-upward stratal cycles, with some …

Climate Effects On Mammalian Body Size And Grassland Composition Inferred From Late Quaternary Grazers In The Great Plains Of North America, Tom Baldvins

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Several mammalian taxa exhibited a diminution during the Pleistocene-Holocene transition. Two hypotheses have been proposed to explain this phenomenon: (1) human hunting and (2) climate change along with its effects on grasslands. I use stable isotopes from a variety of Quaternary grazing mammals to measure grassland changes following the Last Glacial Maximum (LGM) in Nebraska and to develop a climate proxy to compare with mammalian body size. Results indicate that latest Pleistocene equids and mammoths have δ¹³C values indicative of a C₃ or mixed C₃/C₄ diet. However, Holocene bison have greatly elevated δ^{13 …}