Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Atmospheric Sciences

Theses and Dissertations

2018

Articles 1 - 13 of 13

Full-Text Articles in Physical Sciences and Mathematics

Multidecadal Variability In Climate Models And Observations, Alex Carl Oser Dec 2018

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, …

Go to article

Using Self-Organizing Maps As A Forecasting Tool, Andrea Honor Sep 2018

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 …

Go to article

Developing A Probabilistic Heavy-Rainfall Guidance Forecast Model For Great Lakes Cities, Cory Kevin Rothstein Aug 2018

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 …

Go to article

An Investigation Of The Conditional Practical Predictability Of The 31 May 2013 Heavy-Rain-Producing Mesoscale Convective System, Aidan Kuroski Aug 2018

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 …

Go to article

Using Advanced Post-Processing Methods With The Hrrr-Tle To Improve The Prediction Of Cold Season Precipitation Type, Timothy Thielke Aug 2018

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 …

Go to article

Isolating Secular Signals In Observations And Climate Model Simulations Using M-Ssa Based Wiener Filtering, Christian Grimm May 2018

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 …

Go to article

A Climatology Of Extreme South American Andean Cold Surges, Kevin Prince May 2018

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 …

Go to article

The Influence Of Vertical Advection Discretization In Wrf-Arw Model On Capping Inversion Representation In Warm-Season, Thunderstorm Supporting Environments, David Nevius May 2018

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 …

Go to article

A New Analysis Of The Gálvez-Davison Index For Convective Forecasts In Northern Africa, Gabriel D. Donndelinger Mar 2018

A New Analysis Of The Gálvez-Davison Index For Convective Forecasts In Northern Africa, Gabriel D. Donndelinger

Theses and Dissertations

Severe wind gusts and thunderstorms have been difficult to forecast in Africa. Traditional convective forecast tools (e.g. Total Totals Index, Lifted Index, K Index (KI) and Convective Available Potential Energy) do not accurately portray potential for thunderstorms in Africa. This research effort used the Gálvez-Davison Index (GDI), a convective index created for the tropics, and assess its applicability to northern Africa. GDI was produced for the Caribbean and Central America, and utilized temperature, moisture, mid-level stability, dry air entrainment and an elevation factor to calculate convective potential. In this research, GDI and KI were calculated using Global Forecast System (GFS) …

Go to article

Impacts Of Sub-Auroral Polarization Streams On High Frequency Operations As A Function Of Modeled Particle Energy Flux, Nathan D. Smith Mar 2018

Impacts Of Sub-Auroral Polarization Streams On High Frequency Operations As A Function Of Modeled Particle Energy Flux, Nathan D. Smith

Theses and Dissertations

Space weather events can cause irregularities within the ionosphere; in particular, this research examines sub-auroral polarization streams (SAPS), as their accompanying irregularities and effects can degrade high-frequency (HF) signal propagation. It is known that the strongest westerly current drifts delineating SAPS are associated with a deep ionospheric trough, which in turn contaminates HF data with clutter from the non-standard ionosphere. Having a methodology to track and identify these occurrences on current computational architecture would provide operators enhanced situational awareness in knowing to expect degradation in HF processes. This study has discovered a weak, yet significant, exponentially decaying correlation between maximum …

Go to article

The Geographic Distribution Of Downburst Frequency Across Spaceport Florida, Tania M. Garza Mar 2018

The Geographic Distribution Of Downburst Frequency Across Spaceport Florida, Tania M. Garza

Theses and Dissertations

Strong winds from downbursts pose a significant hazard to personnel and launch operations at Cape Canaveral Air Force Station (CCAFS) and NASA Kennedy Space Center (KSC). The CCAFS/KSC complex has a robust mesonet from which an 18 year (1995-2012) warm-season convective wind climatology (WSCWC) was developed (Koermer 2017). While the frequency of downbursts in the area has been determined, the frequency at the individual tower locations has not. The 5-minute peak wind data from the WSCWC was analyzed to determine the geographic distribution of downburst frequency across Spaceport Florida. For this project a downburst was determined by the threshold of …

Go to article

Evaluation Of A Cloud Detection Technique Using Spatial And Radiometric Thresholds For Near Infrared Satellite Imagery, William J. Graff Mar 2018

Evaluation Of A Cloud Detection Technique Using Spatial And Radiometric Thresholds For Near Infrared Satellite Imagery, William J. Graff

Theses and Dissertations

Knowledge of cloud location in near infrared (NIR) imagery is of interest to the meteorological community given the wavelengths greater spatial resolution compared to longwave infrared and its potential nighttime applications. This method consists of an algorithm that can be employed by multiple instrument platforms. It analyzes changes between satellite image radiances and a seasonal synthetic background radiance image. The NIR sensor bands of the Sentinel-2 Multispectral Instrument (MSI) and Suomi National Polar-Orbiting Partnership (Suomi NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) satellite instruments are used to evaluate the performance of a monochromatic change detection technique designed to locate areas …

Go to article

Forecasting Lightning Initiation Utilizing Dual-Polarization Radar Parameters Over Washington, D.C., Sarah A. Olsen Mar 2018

Forecasting Lightning Initiation Utilizing Dual-Polarization Radar Parameters Over Washington, D.C., Sarah A. Olsen

Theses and Dissertations

Accurate forecasts of thunderstorms are vital to space launch, aviation, and public safety. Prior studies by Woodard (2011), Thurmond (2014), and Travis (2015) show that dual-polarization radar can be utilized to identify the presence of hydrometeors necessary for cloud charging. These studies emphasized that a combination of radar reflectivity (Z) and differential reflectivity (ZDR) predictors have the potential to improve forecast skill of lightning initiation over methods that rely on Z alone (Roeder and Pinder, 1998; Yang and King, 2010). Travis (2015) discovered two parameters, when used together, produced the best results: Z ≥ 36.5 dBZ and ZDR …

Go to article