Meteorology Commons^™

A Climatology Of Mesoscale Airmasses With High Theta-E, Charles J. Kropiewnicki

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

A Mesoscale Airmass with High Theta-E (MAHTE) is a narrow region of larger theta-e located on the cool side of an airmass boundary. MAHTEs typically possesses higher CAPE than the warm side of the boundary, creating a more favorable environment for severe convection. MAHTEs can also be characterized by larger low-level shear and lower LCLs and may also have a propensity for supporting tornadogenesis. The majority of MAHTE research to date has been comprised of case studies, and the prevalence of MAHTEs is not well understood. This project fills that knowledge gap by creating a climatology of MAHTE occurrence. This …

An Empirical Examination Of The Environmental Variability That Impacted Supercell Evolution, Longevity, And Severe Weather Production On 22 May 2019 In Oklahoma, Kyle D. Pittman

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

Mesoscale environmental heterogeneity can have significant impacts on thunderstorm organization, evolution, longevity, and severe weather production. This study examines the 22 May 2019 thunderstorm event in Oklahoma, where a relatively broad area of strong instability and vertical wind shear existed along a synoptic boundary and in the open warm sector that would seem to support long-lived supercells and tornadoes. There were two particularly dangerous situation (PDS) tornado watches issued during the event, but few severe reports and no tornadoes formed in the watch that covered the southwestern portion of the state. Several tornadic supercells and many more severe reports occurred …

Radar Signatures In Tropical Cyclone Tornadic And Nontornadic Supercells, Michaela Wood

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

Tropical cyclones (TCs) contain highly-sheared environments that are conducive for supercell thunderstorms. These TC supercells sometimes produce tornadoes, often with little warning. Given the often-close proximity of tornadic and nontornadic TC supercells, environments may not be well-distinguished, pointing to the potential value of radar observations. In this study, dual-polarimetric radar signatures of a sample of TC supercells are examined in the context of known supercell structure and microphysics. Tornadic and nontornadic TC supercells are compared with their midlatitude counterparts, and the environments and characteristic structure of these storms are shown to be notably different. An attempt is made to distinguish …

Impacts Of Physical Parameterization Schemes And Soil Moisture Initialization On Boundary Layer Evolution In The Weather Research And Forecasting (Wrf) Model, Grace Cutting

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

Numerical weather prediction (NWP) models have become a necessary addition to the atmospheric research community over the last several decades, and atmospheric modeling has been used internationally for numerous operational and research purposes. NWP models contain a vast number of combinations of physical and dynamical parameterization schemes; however, they are not always accurate in forecasting weather phenomena at a particular location, as different combinations of parameterization schemes represent differing conditions. Weather Research and Forecasting (WRF) model simulations were run to explore which of the commonly used planetary boundary layer (PBL) schemes best represented upper-air data (as well as PBL evolution) …

Using Remote And In Situ Observations From Torus To Investigate A Preexisting Airmass Boundary And Its Influence On A Tornadic Supercell On 28 May 2019, Kristen Axon

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

During the 2019 field phase of Targeted Observation by Radars and UAS of Supercells (TORUS), a preexisting airmass boundary was sampled on 28 May 2019 in north-central Kansas in close proximity to a tornadic supercell. This work hypothesized that the preexisting airmass boundary was associated with a mesoscale air mass with high theta-E (MAHTE) that favorably interacted with the tornadic supercell to increase the likelihood of tornadogenesis. Observations from TORUS including mobile mesonets, unoccupied aerial vehicles, soundings, and ground-based mobile radar were used along with GOES-16 visible satellite imagery, Kansas mesonet surface stations, and KUEX WSR-88D data to investigate this …

An Investigation Of Water Obstructions And Related Weather Conditions For Nebraska Roadways, Logan Bundy

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

Roadway resilience across the 10,000 miles of road and 3,500 bridges in Nebraska is critical to the economic success of production and logistics. In a state where historical flooding scenarios, such as the one in March 2019 that caused $150 million in damage, could potentially be increasing, it has become essential to understand the spatial and temporal distribution of high-frequency water obstruction areas on roadways. Using Nebraska Department of Transportation (NDOT) historical water obstruction data from June 2016 through August 2021, statistical and spatial analyses were conducted to quantify the relationship between water obstructions and their associated meteorological conditions, and …

Case Studies Of Alberta Clipper Systems And The Impacts On Winter Weather Road Maintenance, Cameron Wunderlin

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

Winter weather can cause profound impacts to a variety of economic sectors in the mid-latitudes. In the Great Plains of North America, one sector that is highly impacted by winter weather is road transportation. The burdens to road transportation caused by winter weather have led to the adoption of a Maintenance Decision Support System (MDSS) by the Nebraska Department of Transportation (NDOT). Using both observational and numerical weather model data, NDOT-MDSS generates both winter weather forecasts and winter road maintenance recommendations. Little is known about how well NDOT-MDSS is forecasting conditions for different winter weather events. Using a case study …

An Observational Study Of Winter Weather-Related Traffic Crashes In Nebraska, Jacob Petr

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

The responsibilities of meteorologists have evolved over time from simply providing a forecast to needing to also understand how those predictions will impact society and then communicating those risks in a clear, concise, and consistent manner. Increased motor vehicle crash numbers due to adverse weather conditions represent one such impact worthy of further study. Snowfall, in particular, significantly increases the overall risk of a crash, which can result in extensive property damage, severe injuries, and even loss of life.This project seeks to supplement traffic crash information in Nebraska by assessing how snowfall impacts crashes across the state. Crash data were …

Quantification Of Cloud Condensation Nuclei Effects On The Microphysical Structure Of Continental Thunderstorms Using Polarimetric Radar Observations, Kun-Yuan Lee

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

Aerosols serving as cloud condensation nuclei (CCN) are crucial to the microphysical structure of thunderstorms. They can also alter the rate of cloud microphysical processes, the moisture profile and the local temperature as a result of latent heating/cooling in the early stage of thunderstorm development. Continental thunderstorms are characterized by high complexity and are highly influenced by environmental conditions. The purpose of this study is to determine the influences of CCN concentration on the microphysics of continental thunderstorms, using a sample of storms from northwestern Oklahoma. The Weather Surveillance Radar-1988 Doppler (WSR-88D) at Vance Air Force Base (KVNX) was upgraded …

Evaluation Of Nocturnal Convective Precipitation Over The Great Plains Using Reanalysis Data And A Wrf-Based Regional Climate Model, Xu Deng

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

This study aims to analyze what processes are mainly responsible for nocturnal convective precipitation during the 1991-2000 period for May-June-July over the Great Plains. Firstly, based on the Weather Research and Forecasting model (WRF) coupled with the NCAR Community Land Model (CLM) and the North American Regional Reanalysis (NARR) reanalysis data, the simulations of the diurnal cycles of LLJ and the convective precipitation are examined. Then, the LLJ-related moisture transport is evaluated since the moisture supply is critical for the development of the heavy rainfall. Results show that the WRF model fails to simulate the nocturnal peak rainfall shown in …

An Observational And Modeling Study Of Mesoscale Airmasses With High Theta-E, Lawrence Wolfgang Hanft

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

Typically, the cool side of an airmass boundary is stable to vertical motions due to its associated negative buoyancy. However, under certain conditions, the air on the cool side of the boundary can undergo a transition wherein it assumes an equivalent potential temperature and surface-based convective available potential energy that is higher than that of the airmass on the warm side of the boundary. The resultant airmass is herein referred to as a mesoscale airmass with high theta-e (MAHTE).

Results are presented from an observational and mesoscale modeling study designed to examine MAHTE characteristics and the processes responsible for MATHE …

Influence Of Land Cover Type And The Reliability Of Selected Land Surface Models: A Comparison Of Wrf Version 3.6 Coupled To Clm Version 4.0, Noah-Mp, And The Bucket Hydrology, Andrew J. Kalin

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

In this study, the validity of 3 LSMs (Community Land Model version 4.0, Noah-MP and the Budyko Bucket Hydrology model [henceforth referred to as ‘Bucket model’]) coupled with the Weather Research and Forecasting model version 3.6 (WRF3.6), was examined in an effort to show the associated strengths and weaknesses of each LSM. This objective was completed by first, developing expected results based on a simple surface energy budget calculation, and by later comparing model output to Parameter-elevation Relationships on Independent Slopes Model (PRISM) data, which serve as gridded observed values of mean monthly temperature and total monthly precipitation. Model output …

Modeling And Satellite Remote Sensing Of The Meteorological Impacts Of Irrigation During The 2012 Central Plains Drought, Clint Aegerter

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

As irrigation is increasingly needed for agricultural production, it is becoming progressively more important to understand not only how irrigation impacts water availability, but how the introduction of this water into the soil impacts weather and climate through land-atmosphere interactions. In the summer of 2012, the Central Plains of the United States experienced one of its most severe droughts on record. This study examines the meteorological impacts of irrigation during this drought through observations and model simulations using the Community Land Model (CLM) coupled to the Weather Research and Forecasting (WRF) model. A simple parameterization of irrigation processes is added …

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 …

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 …

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 …

Cloud Impacts On Pavement Temperature And Shortwave Radiation, Curtis L. Walker

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

Forecast systems provide decision support for end-users ranging from the solar energy industry to municipalities concerned with road safety. Pavement temperature is an important variable when considering vehicle response to various weather conditions. A complex, yet direct relationship exists between tire and pavement temperatures. Literature has shown that as tire temperature increases, friction decreases which affects vehicle performance. Many forecast systems suffer from inaccurate radiation forecasts resulting in part from the inability to model different types of clouds and their influence on radiation. This research focuses on forecast improvement by determining how cloud type impacts pavement temperature and the amount …

Verification And Analysis Of Impact-Based Tornado Warnings In The Central Region Of The National Weather Service, Holly B. Obermeier

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

Tornado warnings are one of the most critical products issued by the National Weather Service (NWS), and favorable verification statistics are desirable. The 2011 NWS statistics for traditional tornado warnings indicate that the probability of detection (POD) is 70%, while the false alarm rate (FAR) is 76%. The recent Joplin, Missouri EF5 tornado event on 22 May 2011, which resulted in massive devastation and loss of life, prompted the NWS to re-evaluate the current tornado warning format. After the Joplin, MO event, the Central Region of the NWS implemented the impact-based tornado warning (IBTW) experiment in 2013. IBTWs consist of …

Eastern Us Dryline Climatology And Synoptic-Scale Environment, Rebecca S. Duell

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

The dryline is an important focal point for convection initiation, and the subject of many studies. While the most common location for drylines is the southern Great Plains, dryline passages and subsequent severe weather outbreaks have been documented in the Mississippi River Valley and into portions of the southeastern United States. Little is known about these “eastern” drylines or how often they occur, as no climatologies or detailed studies have been published on them. This thesis presents a fifteen-year climatology (1999-2013) of eastern drylines in an effort to identify how often and where they typically occur, and to identify synoptic …

Springtime Atmospheric Responses To North Atlantic Sst Anomalies In Idealized Gcm Experiments: Northern Hemisphere Circulation And North American Precipitation, Michael C. Veres

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

In this study, a series of experiments using idealized sea surface temperatures (SST), land and orography are performed to examine the interactions between the Atlantic Multidecadal Oscillation (AMO), continents and major orography. Three sets of experiments are done using an increasingly realistic surface boundary (aqua-planet, land without orography and land with orography) and run using perpetual equinox conditions. For each land surface boundary, the model is forced with a zonally symmetric SST, with additional experiments with an imposed positive or negative SST anomalies in the North Atlantic. The experiments are then compared to determine how these forcings interact and what …

Mesoscale Modeling And Satellite Observation Of Transport And Mixing Of Smoke And Dust Particles Over Northern Sub-Saharan African Region, Zhifeng Yang

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

The transport and vertical distribution of smoke and mineral dust aerosols over the Northern Sub-Saharan African (NSSA) region have important implications for regional and global air quality and climate. This study employs ground-based and satellite observations, and numerical simulations conducted with a fully-coupled meteorology-chemistry-aerosol model, Weather Research and Forecasting model with Chemistry (WRF-Chem). The WRF-Chem simulation is for February 2008 and uses hourly dynamic smoke emissions from the Fire Locating and Modeling of Burning Emissions (FLAMBE) database derived from Moderate Resolution Imaging Spectroradiometer (MODIS) fire products. Model performance of smoke and dust simulation is evaluated using numerous satellite and ground-based …

An Examination Of The Mechanisms And Environments Supportive Of Bow Echo Mesovortex Genesis, George Limpert

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

Low-level mesovortices are associated with enhanced surface wind gusts and high-end wind damage in quasi-linear thunderstorms. Although damage associated with mesovortices can approach that of moderately strong tornadoes, skill in forecasting mesovortices is low. The overarching goal of this work is to understand mesovortices and how they develop, to improve the skill in forecasting them. This was done by developing a climatology of mesovortices, which required a tracking algorithm, and numerical simulations were conducted to answer questions that could not be answered through the observational data. A climatology of mesovortices was constructed from 44 events during 2009 and 2010 to …

A Climatology Of Lake-Effect Snowfall And Evaluation Of The Cobb Method For The Great Lakes Region, Seth Kutikoff

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

Accuracy in snowfall prediction has lagged behind other short-term weather forecasting areas. Errors in quantitative precipitation forecasts ensure that any snow ratio applied to snow may result in inaccurate snowfall amounts, and snowfall observations are not consistent or fully reliable. In this study, the Cobb Method is tested on lake-effect snowfalls to determine if the top-down ice crystal growth modeled in the algorithm can be applied to convective snowfalls. To establish the spatiotemporal and physical characteristics of lake-effect snowfalls at selected study locations near the Great Lakes, snowfall and snow ratio climatologies are produced that separate events by lake-effect and …

Remote Sensing Of Surface Visibility From Space: A Look At The United States East Coast, Amy L. Kessner

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

While important for the management of air quality, human health and transportation, surface visibility data currently are only available through ground-based measurements, such as the Automated Surface Observing System (ASOS), and therefore lack spatial coverage. In analogy to the recent work of using satellite-based aerosol optical depth (AOD) to derive surface dry aerosol mass concentration at continental-to-global scale for cloud-free conditions, this study evaluates the potential of AOD retrieved from the MODerate Resolution Imaging Spectroradiometer (MODIS) for deriving surface visibility. For this purpose of evaluation, the truncated and discrete visibility data from daily weather reports are not suitable and the …

An Examination Of Physical And Empirical Approaches In Forecasting Nonconvective Wind Gusts, Jeramie Lippman

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

Nonconvective winds can be a dangerous and costly weather hazard. For example, over a ten year span from 2002 to 2011, there were over 200 fatalities and nearly 1,000 injuries, as well as over 6.4 billion dollars in monetary losses due to high, nonconvective winds. An important subset to nonconvective winds is the nonconvective wind gust. When winds are already relatively strong, a sudden wind gust can magnify already existing hazards. Three different methods were evaluated to determine if either of two physically based algorithms can outperform an empirical algorithm. The two physically based methods were the Wind Gust Estimate …

An Analysis Of Deep Convection Initiation Environments, Noah Lock

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

Initiation is the part of the convective life cycle which is currently least understood and least well forecast. The inability to properly forecast the timing and/or location of deep convection initiation degrades forecast skill, especially during the warm season. The goals of this research are examine the spatiotemporal distribution of thunderstorm initiation points and to determine which atmospheric parameters (and ultimately processes) are most important for the initiation of thunderstorms. The spatiotemporal distribution of thunderstorm initiation points shows the expected peaks during summer and during the afternoon. The warm season also produces significant concentrations of initiation points near mountains, mainly …

Retrieval Of Sub-Pixel-Based Fire Intensity And Its Application For Characterizing Smoke Injection Heights And Fire Weather In North America, David Peterson

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

For over two decades, satellite sensors have provided the locations of global fire activity with ever-increasing accuracy. However, the ability to measure fire intensity, know as fire radiative power (FRP), and its potential relationships to meteorology and smoke plume injection heights, are currently limited by the pixel resolution. This dissertation describes the development of a new, sub-pixel-based FRP calculation (FRP_f) for fire pixels detected by the MODerate Resolution Imaging Spectroradiometer (MODIS) fire detection algorithm (Collection 5), which is subsequently applied to several large wildfire events in North America. The methodology inherits an earlier bi-spectral algorithm for retrieving sub-pixel …

Periodicities Of Peak Current And Flash Multiplicity In Cloud To Ground Lightning, Alexander R. Gibbs

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

Research on lightning has been conducted on various topics including thunderstorm electrification and climatology of lightning strikes however; there are still some characteristics of lightning that are not well known, such as flash multiplicity and peak current as a function of individual thunderstorms. These characteristics are the leading cause of injuries and damage each year. This study examines a severe weather event in Minnesota on 16 September 2006, in order to determine what may cause peak current and flash multiplicity. Cycles in peak current and flash multiplicity are identified and then associated with CAPE to determine if a thunderstorm’s updraft …

Water And Energy Balance Response Of A Riparian Wetland To The Removal Of Phragmites Australis, Phillip Mykleby

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

Vegetation and climate both play integral roles in water availability, particularly for arid to semi-arid regions. Changes in these variables can lead to extreme shortages in water for regions that rely on water for crop irrigation (i.e., the Great Plains). The objective of this study is to evaluate the impacts of vegetation on water availability in the Republican River basin in central Nebraska. Decreases in streamflow have been observed in the river basin for many years and, as a result, an invasive riparian plant species (Phragmites australis) is being removed in an effort to reduce evapotranspiration and reclaim …

Verification Of The Cobb Snowfall Forecasting Algorithm, Josh Barnwell

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

Forecasting storm total snow accumulation is one of the most difficult aspects of meteorological forecasting. The forecaster has to interpret three main variables in order to forecast snowfall accurately. These forecasting variables are the duration of the snowfall, the amount of liquid water the storm will produce, and the snow density or snow ratio. With the advancement of computer models in recent history, the need for a quick and easy interpretation of these variables has grown, and to improve on previous forecasting techniques’ disadvantages with including the three snow forecasting variables. The Cobb Method snowfall forecasting algorithm utilizes model data …