Atmospheric Sciences Commons^™

Predictability Of The Overland Reintensification Of North Atlantic Tropical Cyclone Erin (2007), Ariel Tickner-Ernst

Theses and Dissertations

Tropical cyclones (TC) typically decrease in intensity upon interacting with land because of increased surface roughness and decreased surface evaporation. However, several studies have documented cases in which TCs maintain their intensity or even intensify over land within non- or weakly baroclinic environments. Yet, our understanding of the precise physical processes that support maintenance or intensification over land in non- or weakly baroclinic environments remains limited, and the predictive skill for these outcomes has yet to be quantified.

We begin this process by quantifying the predictive skill and forecast uncertainty of the overland intensification of North Atlantic Tropical Storm Erin …

Decadal Climate Variability In Mesoscale-Resolving Coupled Models, Ilijana Mastilovic

Theses and Dissertations

Most of our knowledge about the causes of 20th-century climate change comes from simulation using numerical models. However, the observed climate variability and the one simulated by the state-of-the-art climate models exhibit substantial discrepancies at the decadal-to-multidecadal time scale and thus it hinders our fundamental understanding of the observed climate change. Evidence is mounting that vigorous intrinsic variability associated with mesoscale oceanic features contributes significantly to large-scale low-frequency climate variability, with fundamental implications for decadal climate low-frequency climate prediction. As of yet, extensive simulation of these decadal effects using high-resolution state-of-the-art coupled climate models has been computationally prohibitive, as it …

A Protocol To Build Trust With Black Box Models, Timothy K. Thielke

Theses and Dissertations

Data scientists are more widely using artificial intelligence and machine learning (ML) algorithms today despite the general mistrust associated with them due to the lack of contextual understanding of the domain occurring within the algorithm. Of the many types of ML algorithms, those that use non-linear activation functions are especially regarded with suspicion because of the lack of transparency and intuitive understanding of what is occurring within the black box of the algorithm. In this thesis, we set out to create a protocol to delve into the black box of an ML algorithm set to predict synoptic severe weather patterns …

Development And Use Of An Agent-Based Model To Assess The Effect Of Forecast Credibility On Urban Traffic During Snow Events, Lillie Farrell

Theses and Dissertations

With the difficulties in snow accumulation prediction, the potential for false alarms and forecast misses arise. These forecast errors can lead to a lack of public trust and poor decisions in responding to future weather hazards. There has been little research on how individuals respond in the future to false alarms and forecast inconsistencies. We developed an agent-based traffic model to demonstrate how snow forecasts and public response interplay. This model factors receptiveness to expertise, forecast severity, and forecast credibility into the agents’ work-related travel decisions. Agents are grouped into three categories: firm workers, service workers, and household workers, where …

Interactions Between Tropical Cyclones And The Midlatitude Waveguide: Downstream Impacts And The Role Of Convective Processes, Kevin Prince

Theses and Dissertations

Significant amplification to the waveguide can occur when a recurving tropical cyclone (TC) interacts with the midlatitude flow, leading to significant downstream impacts. To this point in time, TC-midlatitude waveguide interactions have been conceptualized as primarily being driven by large-scale processes, with convective-scale contributions having been parameterized or neglected. This three-part study diagnoses the impact TC-midlatitude waveguide interactions have on the intensity evolution of downstream TCs and the role convective-scale processes play in TC-midlatitude waveguide interactions. Recurving TCs in both the North Atlantic and western North Pacific basins frequently interact favorably with upstream troughs, where a favorable interaction entails the …

Do State Fairs With Firework Displays Impact Pm2.5 Levels In Nearby Communities?, Victoria Lang

Theses and Dissertations

This study identified state fairs with known firework displays to evaluate whether they impact local air quality. Previous research has shown firework displays are linked with the short-term degradation of local air quality due to increased concentrations of fine particulate matter (PM2.5) as a result of the display. These studies observed increased PM2.5 concentrations associated with widespread firework displays such as the Lantern Festival in China, Diwali Festival in India, and Independence Day in the United States. However, it has not been investigated whether a signal of increased PM2.5 concentrations from firework displays during a state fair could be observed …

An Agent-Based Exploration Of The Hurricane Forecast-Evacuation System Dynamics, Austin Reed Harris

Theses and Dissertations

In the mainland US, the hurricane-forecast-evacuation system is uncertain, dynamic, and complex. As a result, it is difficult to know whether to issue warnings, implement evacuation management strategies, or how to make forecasts more useful for evacuations. This dissertation helps address these needs, by holistically exploring the system’s complex dynamics from a new perspective. Specifically, by developing – and using – an empirically informed, agent-based modeling framework called FLEE (Forecasting Laboratory for Exploring the Evacuation-system). The framework represents the key, interwoven elements to hurricane evacuations: the natural hazard (hurricane), the human system (information flow, evacuation decisions), the built environment (road …

The Influences Of Sea-Surface Temperature Uncertainty On Cool-Season High-Shear, Low Cape Severe Weather Event Predictability In The Southeast United States, Michelle Rose Spencer

Theses and Dissertations

Environments conducive to severe weather and tornadoes occur throughout the southeastern United States, particularly during the cold-season. Throughout the cold-season, severe weather in this region predominantly occurs in environments characterized by high-shear, low-CAPE (HSLC). An important aspect to the production of severe weather in HSLC environments in the southeast United States is that air parcels that help contribute to the limited positive-buoyancy generation originate over areas such as the Gulf of Mexico, western Caribbean Sea, and western Atlantic Ocean. These relatively warm bodies of water, particularly outside of the cooler coastal shelf regions, allow the air parcels to warm and …

An Investigation Into The Thermodynamics Of Overland Tropical Cyclone Intensity Change In Weakly/Non-Baroclinic Environments, Michael Partrick Vossen

Theses and Dissertations

There are two leading theories regarding how tropical cyclones can maintain or increase their intensity over land in weakly to non-baroclinic environments. In the first, tropical cyclones are maintained overland by enhanced upward surface enthalpy fluxes facilitated by the tropical cyclone’s rains, whereas in the second, tropical cyclones are maintained by enhanced enthalpy fluxes under inflowing trajectories at larger radii from the cyclone’s center. These theories have yet to be rigorously tested, however. To rigorously test these hypotheses, this study uses a quasi-idealized version of the Weather Research and Forecasting model lacking parameterized radiation to test the sensitivity of overland …

Verification Of Environmental-Regime–Stratified Gfs Short-Range Vertical Sounding Forecasts, Dillon Blount

Theses and Dissertations

In recent years, the United States’ operational global numerical weather prediction model, the Global Forecast System (GFS), has been upgraded to include a new dynamical core and an updated turbulence parameterization. This updated turbulence parameterization uses a hybrid eddy-diffusivity, countergradient, and mass-flux formulation to approximate near-surface turbulent vertical mixing. The precise formulation used is based on the local stability, with the eddy-diffusivity, countergradient, and mass flux formulations used under stable, weakly unstable, and strongly unstable conditions, respectively. In this study, an objective classification of environmental regimes is used to verify GFS short-range vertical soundings, focusing on the planetary boundary layer …

Investigating The Potential Of A Combined Air Quality-Heat Index In Predicting Mortality, Shayna Fever

Theses and Dissertations

Although the development of the Air Quality Index (AQI) has been significant in informing and protecting the public, it may not be entirely reflective of the health effects from exposure to air pollutants. Meteorological factors that are considered in the heat index (HI), temperature and relative humidity, are not considered when calculating the AQI. It may be important to consider certain meteorological factors when assessing the quality of the air because such factors affect the dynamics of air movement as well as the formation of certain pollutants.Through a series of Quasi-Poisson regression models, we investigated whether the relationship between the …

Biennial And Low-Frequency Components Of El Niño/Southern Oscillation, James Michael Ryan

Theses and Dissertations

El Niño/Southern Oscillation (ENSO) is a coupled oscillation of sea surface temperatures (SSTs), winds, and air pressure in the eastern and central tropical Pacific, that repeats with quasi-regularity, every 2–7 years. Although the ENSO’s spectral peak is found at a 4–7-yr period, composite El Niño events, taken as the 84 months before and after the peak of each El Niño, show that the length of each event, and often the following La Niña if there is one, usually falls within a quasi-biennial (QB) range of around 18–42 months. We argue that the biennial range of ENSO events stems from the …

Predicting Peak Wind Gusts During Specific Weather Types With The Meteorologically Stratified Gust Factor Model, Teresa Jean Turner

Theses and Dissertations

Peak wind gusts were estimated by the meteorologically stratified gust factor model at Milwaukee, WI (KMKE) for eight different weather types during 2010-2017. The gust factor model couples gust factors with wind speed and direction forecast guidance to produce peak gust forecasts. The model evaluated used two model output statistics (MOS) guidance products at lags ranging from 6-24 hr and was compared with peak gust forecasts provided by the Localized Aviation MOS Program (LAMP) as well as observed gusts reported by automated surface observing systems (ASOS).

Compared with climatology, the gust factor model showed skill when coupled with MOS in …

A Feasibility Study Of Microbialites As Paleomagnetic Recorders, Ji-In Jung

Theses and Dissertations

Microbialites are carbonate organosedimentary deposits formed by benthic microbial communities that trap and bind detrital sediments, and/or inorganic and biologically influenced calcification. Any ferromagnetic particles incorporated into the microbialite structure have the potential to preserve variations in Earth’s magnetic field. A paleomagnetic record in microbialites would be useful for reconstructing the geomagnetic field because it may record at a high temporal resolution based on estimated growth rates, thus preserving relatively short-period variations of the Earth’s magnetic field. In addition, microbialites can be found in the geologic record going back ~3.5 Ga, hence potentially providing information on very ancient variations in …

Multidecadal Climate Variability In Observed And Simulated Surface Air Temperature And Sea-Level Pressure, Andrew Aden Westgate

Theses and Dissertations

Accurate estimates of multidecadal climate variability generated internally within the climate system are required to gauge anthropogenic contribution to warming trends and to develop efficient strategies to mitigate climate change. Previous analyses of historical surface air temperatures (SAT) showed that numerical climate prediction models lack a pronounced global mode of observed internal variability — the stadium wave (SW), — which represents a multidecadal undulation originating in the North Atlantic and propagating to other regions of the globe. The present study extends these analyses by exploring co-variability of SAT and sea-level pressure (SLP) within the SW. Addition of SLP data does …

Modeling Of Cloud Droplet Formation: Software Development And Sampling Strategies, Niklas Selke

Theses and Dissertations

Updraft speeds are an important factor in the formation of cloud droplets which play an important role in an atmospheric simulation. The updraft speeds are varying very strongly in small areas of space. Current models do not account for this kind of variability. Support for a probability density function (PDF) based approach in representing the variability of the updraft speeds has been implemented in the Energy Exascale Earth System Model (E3SM). Specifics of the implementation process have been discussed.

Different sampling strategies were tested to analyze the convergence behavior of the new approach to the cloud droplet formation process. It …

An Analysis Of Momentum Flux Budgets And Profiles In A Large-Eddy Model, Steffen Domke

Theses and Dissertations

Momentum fluxes and variances play an important role in the characterization and forecast of weather phenomena, but cannot be measured easily.

A subdivision of the flux changes into budget terms by the underlying physical processes, such as buoyancy transport, can assist in understanding their sources and influences.

Momentum flux and variance budgets for SAM, the System for Atmospheric Modeling, have been implemented and are compared to existing budgets from other simulations.

A tool for the visualization of these quantities from three-dimensional grid data has been developed to show and explain their distribution in conjunction with shallow cumulus and stratocumulus clouds. …

An Analysis Of Momentum Flux Budgets And Profiles In A Large-Eddy Model, Steffen Domke

Theses and Dissertations

Momentum fluxes and variances play an important role in the characterization and forecast of weather phenomena, but cannot be measured easily.

A subdivision of the flux changes into budget terms by the underlying physical processes, such as buoyancy transport, can assist in understanding their sources and influences.

Momentum flux and variance budgets for SAM, the System for Atmospheric Modeling, have been implemented and are compared to existing budgets from other simulations.

A tool for the visualization of these quantities from three-dimensional grid data has been developed to show and explain their distribution in conjunction with shallow cumulus and stratocumulus clouds. …

Using Evolutionary Programming To Generate A Tropical Cyclone Intensity Model, Jesse Schaffer

Theses and Dissertations

An innovative statistical-dynamical tropical cyclone (TC) intensity model is developed from a large ensemble of algorithms through evolutionary programming (EP). EP mimics the evolutionary principles of genetic information, reproduction, and mutation to develop through selective pressure a population of algorithms with skillful predictor combinations. From this process the 100 most skillful algorithms as determined by root-mean square error on cross-validation data is kept and bias corrected. Bayesian model combination is then used to assign individual weights to a subset of ten algorithms from the 100 best algorithms list, which are chosen to minimize mean-absolute error (MAE) and maximize mean-absolute difference …

Using Evolutionary Programming To Generate A Tropical Cyclone Intensity Model, Jesse Schaffer

Theses and Dissertations

An innovative statistical-dynamical tropical cyclone (TC) intensity model is developed from a large ensemble of algorithms through evolutionary programming (EP). EP mimics the evolutionary principles of genetic information, reproduction, and mutation to develop through selective pressure a population of algorithms with skillful predictor combinations. From this process the 100 most skillful algorithms as determined by root-mean square error on cross-validation data is kept and bias corrected. Bayesian model combination is then used to assign individual weights to a subset of ten algorithms from the 100 best algorithms list, which are chosen to minimize mean-absolute error (MAE) and maximize mean-absolute difference …

Multidecadal Variability In Climate Models And Observations, Alex Carl Oser

Theses and Dissertations

Climate change attribution and prediction using state-of-the-art models continue to garner an ever-growing focus amongst both the scientific community and public alike. Recent analyses showing discrepancies in the structure of modeled and observed decadal climate variability (DCV), therefore, have engendered efforts to not only diagnose the dynamics underpinning observed DCV, but also to characterize the behavior of DCV within climate models. In this thesis, we employ Multichannel Singular Spectrum Analysis (M-SSA) to show that while the DCV signal in observations is best described as a coherent oscillation with complex propagation across the globe, modeled DCV lacks this structure altogether. Specifically, …

Using Self-Organizing Maps As A Forecasting Tool, Andrea Honor

Theses and Dissertations

Some extreme weather events, such as the early season heavy snow and cold weather outbreak of early November 2014, can be traced back to the influence of tropical or extratropical cyclones on the planetary scale flow. Such planetary scale reorganization also occurs in conjunction with serial extratropical cyclogenesis. Potential temperature on the dynamic tropopause (defined by the 2 PVU surface) allows for a dynamically compact characterization of the flow. NCEP Climate Forecast Systems Reanalysis data spanning 32 years are used to provide this measure, and Self-Organizing Maps (SOM) are then constructed to identify our atmospheric regimes. Key elements of this …

An Investigation Of The Conditional Practical Predictability Of The 31 May 2013 Heavy-Rain-Producing Mesoscale Convective System, Aidan Kuroski

Theses and Dissertations

On 31 May 2013, strong thunderstorms initiated in west-central Oklahoma with one of the storms eventually creating a very strong tornado near El Reno, OK. The storms then grew upscale into a quasi-stationary mesoscale convective system that produced prolonged heavy rainfall that led to severe flooding across parts of Oklahoma, including the Oklahoma City metropolitan area. A 50-member ensemble of short range (0-24 h) forecasts was conducting using a set of initial conditions generated via cycled data assimilation to quantify event predictability and identify forecast sensitivities, primarily with CI and initial upscale growth. Both a composite and ensemble sensitivity analysis …

Using Advanced Post-Processing Methods With The Hrrr-Tle To Improve The Prediction Of Cold Season Precipitation Type, Timothy Thielke

Theses and Dissertations

In this study we explore advanced statistical methods with the operational High-Resolution Rapid Refresh Model (HRRR) Time-Lagged Ensemble (TLE) to improve the prediction of cold season precipitation type. TLEs are a computationally efficient method to provide a slightly improved probabilistic forecast as the differences between model runs are an approximation of initial condition uncertainty. We apply evolutionary programming, weight-decay bias correction, and Bayesian Model Combination with fifteen HRRR forecast variables that potentially relate to precipitation type for station locations in the contiguous United States that are along and to the east of 100 W longitude to obtain probabilistic precipitation type …

Developing A Probabilistic Heavy-Rainfall Guidance Forecast Model For Great Lakes Cities, Cory Kevin Rothstein

Theses and Dissertations

A method for predicting the probability of exceeding specific warm-season (April-October) 0-24 hour precipitation thresholds is developed based upon daily maximums of meteorological parameters. North American Regional Reanalysis and Daily Unified Precipitation data from 2002-2017 were used to gather meteorological data for the Milwaukee and Chicago County Warning Areas. Individual artificial neural networks and multiple logistic regressions were conducted for daily rainfall thresholds above 0.5'', 1'', 1.5'' and 2'' to determine the probability of threshold exceedances for each County Warning Area. The most important parameters were 1000-500 hPa specific humidity, vertical velocities at various levels, high cloud cover, precipitable water …

Isolating Secular Signals In Observations And Climate Model Simulations Using M-Ssa Based Wiener Filtering, Christian Grimm

Theses and Dissertations

In this thesis, Wiener filtering of gridded surface-temperature time series from observations and climate model simulations is performed by using multi-channel singular spectrum analysis (M-SSA) in order to isolate non-stationary climate signals. The contributions to the singular spectrum from shorter-term internal climate variability, treated in this context as noise, are estimated by fitting to the data spatially extended stochastic models, which are subsequently used to produce synthetic ensembles of surface temperature time series and the corresponding synthetic M-SSA spectra. The full spectra are weighted by the signal-to-noise ratios and transformed back to physical space to obtain reconstructions of the non-stationary …

The Influence Of Vertical Advection Discretization In Wrf-Arw Model On Capping Inversion Representation In Warm-Season, Thunderstorm Supporting Environments, David Nevius

Theses and Dissertations

This study evaluates forecasts of capping inversions and thermodynamic variables for believed areas of possible deep, moist convection initiation during the warm-season using the Weather Research and Forecasting Model (WRF) with the Advanced Research core (WRF-ARW). WRF-ARW was configured nearly identical to the National Severe Storms Laboratory (NSSL) version of WRF (NSSL-WRF). WRF-ARW's default third-order-accurate vertical advection scheme, which is an odd-order-accurate scheme, is known to introduce implicit damping which acts to dampen short wavelength features (Skamarock et al. 2008), such as capping inversions. It is hypothesized that by increasing WRF-ARW's vertical advection to the next higher, even-order-accurate vertical advection …

A Climatology Of Extreme South American Andean Cold Surges, Kevin Prince

Theses and Dissertations

Interactions between the tropics and midlatitudes have been an ongoing area of research since the inception of meteorology. Cold surges represent one of several phenomena by which midlatitude features can modulate the atmosphere, both dynamically and thermodynamically, deep into the tropics. This study performs a climatology of particularly strong South American cold surges that follow along the Andes mountains to quantify the maximum extent to which these surges can modulate the atmosphere from the midlatitudes to the tropics. Data was collected for Austral winter (JJAS) from 1980-2010 (31 years). To identify events, standardized anomalies for 925 hPa meridional wind and …

An Examination Of The Dynamics Of A Rear-Inflow Jet Associated With An Idealized Mesoscale Convective System, Caitlin Crossett

Theses and Dissertations

This study evaluates the main controls on the descent of the rear-inflow jet (RIJ), associated with a mesoscale convective system (MCS), toward the surface. This study employs the Cloud Model 1 (CM1), release 18.3, to simulate idealized MCSs. The model has a horizontal grid spacing of 1 km with 100 vertical levels, and utilizes doubly periodic lateral boundary conditions. The Morrison double-moment explicit moisture scheme is used and Coriolis accelerations are ignored. To initiate convection, a 2 K warm bubble is applied over a limited subset of the domain. Simulations in which the magnitude of vertical wind shear is perturbed, …

Performance Test Of The Pasquill Stability Classification Scheme, Hillary Lin Chapman

Theses and Dissertations

In 1961, Frank Pasquill proposed a method for classifying atmospheric stability based on routinely available surface observations – namely wind speed, cloud cover, and the strength of incoming solar radiation. Stability is classified into six categories: extremely unstable (A); moderately unstable (B); slightly unstable (C); neutral (D); slightly stable (E); and moderately stable (F). These categories are ultimately meant to be used to determine the rate of diffusion of windblown pollutants, but since their inception, the classes have often seen use outside of their originally intended purpose. In this thesis, the performance of the Pasquill scheme is tested in order …