Meteorology Commons^™

Tropical Cyclone Rapid Intensification In Environments Of Upper-Tropospheric Troughs : Environmental Influences And Convective Characteristics, Michael Fischer

Legacy Theses & Dissertations (2009 - 2024)

Intensity forecasts for tropical cyclones that undergo a period of rapid intensification are particularly susceptible to large errors. For those storms that interact with an upper-tropospheric trough, tropical cyclone intensity forecasts are complicated, as upper-tropospheric troughs can provide unique intensification mechanisms, but are often associated with unfavorable environmental conditions. Although tropical cyclones in environments with nearby upper-tropospheric troughs are associated with lesser intensification rates than tropical cyclones in environments devoid of upper-tropospheric troughs, some tropical cyclone--trough interactions are associated with a period of rapid intensification. This dissertation utilizes reanalysis output, satellite observations, and ensemble modeling simulations to understand whether rapid …

The Upper-Level Turbulence, Static Stability And Tropopause Structure Of Tropical Cyclones, Patrick Duran

Legacy Theses & Dissertations (2009 - 2024)

Upper-tropospheric thermodynamic processes can play an important role in tropical cyclone (TC) structure and evolution. Despite its importance, until recently few in-situ observations were available in the upper levels of TCs. Two recent field campaigns -- the National Aeronautics and Space Administration (NASA) Hurricane and Severe Storm Sentinel (HS3) and the Office of Naval Research Tropical Cyclone Intensity (TCI) experiment -- provided a wealth of high-altitude observations within TCs. These observations revealed that the upper-level static stability and tropopause structure of TCs can change dramatically with both space and time.

Predictability Of African Easterly Waves In An Operational Ensemble Prediction System, Travis J. Elless

Legacy Theses & Dissertations (2009 - 2024)

African easterly waves (AEWs) are the primary synoptic-scale weather feature found in sub-Saharan Africa during boreal summer. Many studies have used observations and idealized models to highlight processes associated with the movement and growth of AEWs, yet there have been few studies documenting the performance of operational ensemble prediction systems (EPSs) for these phenomena. Here, the predictability of AEWs in ECMWF EPS forecasts is assessed during two periods of enhanced AEW activity (July--September 2007--2009 and 2011--2013). Specifically, AEW predictability is analyzed through three main areas of focus: 1) verifying AEW position and intensity forecasts, and assessing their relation to convective …

Informing Responders Using Gis And Gps, Deidre Mccarthy

CHAR

Hurricane Katrina devastated the Gulf Coast in August 2005 and created the single largest disaster for cultural resources that the United States has witnessed since the inception of the National Historic Preservation Act (NHPA) in 1966. Notably, the NHPA created the National Register of Historic Places, our nation’s catalog of important cultural resources. The NHPA also stipulates that any federal undertaking which may adversely affect National Register eligible resources be mitigated. For the Federal Emergency Management Agency (FEMA), Katrina created the largest compliance project ever under Section 106 of the NHPA.

Although causing a great deal of damage, Katrina also …

A Climatological And Multiscale Analysis Of Cold Air Outbreaks In The Northeast United States, Zachary Baker Murphy

Legacy Theses & Dissertations (2009 - 2024)

The results of a climatological and multiscale analysis of cold air outbreaks (CAOs) that impacted the Northeast U.S. during 1948–2015 are presented. This climatological and multiscale analysis was based on daily minimum temperature data extracted from the National Centers for Environmental Information (NCEI) Global Historical Climatology Network-Daily dataset for 53 stations that were distributed throughout nine climate regions defined by the NCEI. A CAO is diagnosed whenever two or more stations within an NCEI climate region experience three or more consecutive days where the daily minimum temperatures at a station fall below the 31-day centered moving average of the fifth …

Ensemble Variability In Rainfall Forecasts Of Hurricane Irene (2011), Molly Becker Smith

Legacy Theses & Dissertations (2009 - 2024)

As tropical cyclones (TCs) move into the midlatitudes, they are often associated with extensive heavy precipitation. This precipitation can lead to widespread flooding events, such as occurred with Hurricane Irene (2011) over the northeastern United States. Despite the high-impact nature of these events, there are relatively few studies that explore the sensitivity of precipitation forecasts to model initial conditions, beyond focusing on the variability in forecast TC track.

Turbulence In The Upper Levels Of Tropical Cyclones, Michaela Leigh Rosenmayer

Legacy Theses & Dissertations (2009 - 2024)

Turbulence in the cirrus canopy of tropical cyclones (TCs) can give an indication about the physical processes that occur in this expansive cloud deck. The low stability and/or large shear that likely coincides with turbulent layers can be produced by radiative forcing, convective forcing, and sublimation of frozen precipitation from the cirrus canopy. As a result, turbulence in the cirrus canopy can give an indication about the impact of various physical processes in tropical cyclones.

Determination And Analysis Of Dscovr-Eipc Satellite-Retrieved Radiance From Cloud Geometric And Optical Properties, Emily Christine Morgan

Legacy Theses & Dissertations (2009 - 2024)

Using simulations and numerical fitting, this work sought to describe the satellite-retrieved radiance of clouds as a function of their thermodynamic and optical properties. Subsequently, this understanding can then be used in a look-up-table to determine the properties of clouds imaged by the EPIC sensor in the NASA DSCOVR satellite. In this study, background oxygen absorption was modeled in a radiative transfer model and convolved with EPIC filter functions for two absorption-reference pairs for Oxygen A- and B-band. This absorption profile was established as the primary vertical coordinate in this study, leveraging the similarity principle to allow for intercomparison of …

Tropical Cyclone Intensification Under Moderate Vertical Wind Shear, Rosimar Rios-Berrios

Legacy Theses & Dissertations (2009 - 2024)

Deep-layer (200–850 hPa) vertical wind shear is generally an inhibiting factor for tropical cyclone intensification. Multiple studies—ranging from case studies to climatological analyses—have consistently shown that the chances of tropical cyclone intensification decrease with increasing vertical wind shear magnitude. However, tropical cyclones can intensify under moderate shear—the range of shear magnitudes that are neither too weak to have negligible influence on intensity nor too strong to completely halt intensification. Intensity, track, and precipitation forecasts of tropical cyclones under moderate shear can be highly uncertain; therefore, explaining how tropical cyclones evolve under seemingly unfavorable conditions is an important step towards improved …

Evolution Of African Easterly Waves And Their Relationship To Tropical Cyclogenesis, Alan Brammer

Legacy Theses & Dissertations (2009 - 2024)

The research in this thesis explores the relationship between African easterly waves (AEWs) and tropical cyclogenesis over the eastern Atlantic. This research utilises 33 years of reanalysis and satellite data to investigate the interaction between AEW troughs, the surrounding environment and the embedded vortex.

Evaluating Preferred Direction Tropical Cyclone Track Variability In An Operational Global Ensemble Prediction System, Travis Elless

Legacy Theses & Dissertations (2009 - 2024)

Ensemble forecasts of Tropical Storm Debby and Hurricane Sandy (2012) highlight instances where variability in tropical cyclone (TC) position forecasts are stretched along a preferred direction. The goal of this thesis is to analyze this stretching of variability in a global ensemble prediction system, particularly the European Centre for Medium-Range Weather Forecasts (ECMWF), to determine how often and under what conditions does variability stretching occur, and ultimately what feature(s) are responsible for generating this variability.

An Analysis Of Surface Air Temperature Trends And Variability Along The Andes, Eric Franquist

Legacy Theses & Dissertations (2009 - 2024)

Climate change is difficult to study in mountainous regions such as the Andes since steep changes in elevation cannot always be resolved by climate models. However, it is important to examine temperature trends in this region as rises in surface air temperature are leading to the melting of tropical glaciers. Local communities rely on the glacier-fed streamflow to get their water for drinking, irrigation, and livestock. Moreover, communities also rely on the tourism of hikers who come to the region to view the glaciers. As the temperatures increase, these glaciers are no longer in equilibrium with their current climate and …

The Motion Of Mesoscale Snowbands In Northeast U.S. Winter Storms, Jaymes Kenyon

Legacy Theses & Dissertations (2009 - 2024)

The distribution of snowfall accumulation attending winter storms is a product of both precipitation intensity and duration. Many heavy snowfall events are associated with distinct mesoscale snowbands that strongly modulate snowfall accumulation. Mesoscale snowbands are known to be favored within environments characterized by frontogenesis in the presence of weak moist symmetric or gravitational stabilities. Although the development of mesoscale snowbands often can be anticipated at 24–36-h ranges, anticipating band residence time at a fixed location remains a forecasting challenge. However, given that snowband residence time is related to characteristics of band motion, improved understanding of band motion presents an opportunity …

Interactions Between African Easterly Waves And Moist Convection, Matthew Adam Janiga

Legacy Theses & Dissertations (2009 - 2024)

African easterly waves (AEWs) over tropical Africa and the East Atlantic influence and are themselves influenced by moist convection. Data from the Tropical Rainfall Measuring Mission (TRMM) satellite, reanalyses, and in-situ observations are used to examine both directions of this two-way interaction.

Evaluating Drought In The United States Using The Emissivity Difference Vegetation Index, Hanisha Hirani

Legacy Theses & Dissertations (2009 - 2024)

As monitoring vegetation and crops becomes increasingly important due to climate change, there arises the need for a monitoring scheme that places more weight on water availability as an indication of vegetation health and vitality. The Emissivity Difference Vegetation Index (EDVI) is the first step towards that type of monitoring scheme. With the potential for diurnal studies, there are applications towards agriculture monitoring, wildfire monitoring, and much more. EDVI is a synergetic product retrieved from microwave, visible, and infrared satellite measurements, as well as reanalysis. Since microwave measurements are more sensitive to vegetation water content, EDVI has the potential to …

A Wrf Simulation Of The Asymmetric Rapid Intensification And Trough Interaction Of Tropical Storm Gabrielle (2001), Diana Elizabeth Thomas-Abernethy

Legacy Theses & Dissertations (2009 - 2024)

Despite 13 ms-1 ambient wind shear, Tropical Storm (TS) Gabrielle underwent 22 hPa pressure falls within 3 hours prior to 0900 UTC 14 September. The rapid intensification of Gabrielle was atypical due to an upper-level trough approaching from the northwest. Additionally, a convective cell developed in the downshear left quadrant of the center, moved cyclonically and inward to the 17 km radius. During this time, The Tropical Rainfall Measurement Mission (TRMM) had one of its most intense 85 GHz scattering measurements ever (Molinari and Vollaro, 2010).

An Analysis Of The Formation And Evolution Of The 1989 Western North Pacific Subtropical Gyre, Brian Andrew Crandall

Legacy Theses & Dissertations (2009 - 2024)

This thesis conducts an observational study of a large cyclonic gyre that developed in the Western North Pacific (WNP) in late July 1989. For a period of six days, azimuthally-averaged winds at 850 hPa remained cyclonic out from the center of circulation to the 2000 km radius, with azimuthally-averaged tangential wind speeds at or greater than 10 m s-1. The gyre exhibited an asymmetric convection pattern, with the center, north and west flanks devoid of large convective areas, but the southern and eastern flanks maintained large-scale convective regions, extending as much as 4000 km in longitude.

Analysis Of Intraseasonal Convective Variability Modes Over West Africa During The Monsoon Season, Jeffrey Ceratto

Legacy Theses & Dissertations (2009 - 2024)

Intraseasonal variability of rainfall within the West African Monsoon has been shown to be an important factor in the weather of this region. Multiple factors have been found to contribute to variability at this timescale. Mounier, et al (2008) use EOF analysis to uncover and describe a quasi-stationary dipole of precipitation between the West African Monsoon system and the West Atlantic/Caribbean Sea. This mode, termed the Quasi Biweekly Zonal Dipole mode, operates on timescales of roughly 13 days. The stationary nature of this dipole is focused upon in their work, while the role of Kelvin waves in the mode are …

Convectively-Coupled Kelvin Waves Over The Tropical Atlantic And African Regions And Their Influence On Atlantic Tropical Cyclogenesis, Michael John Ventrice

Legacy Theses & Dissertations (2009 - 2024)

High-amplitude convectively coupled atmospheric Kelvin waves (CCKWs) are explored over the tropical Atlantic during the boreal summer. Atlantic tropical cyclogenesis is found to be more frequent during the passage of the convectively active phase of the CCKW, and most frequent two days after its passage. CCKWs impact convection within the mean latitude of the inter-tropical convergence zone over the northern tropical Atlantic. In addition to convection, CCKWs also impact the large scale environment that favors Atlantic tropical cyclogenesis (i.e., deep vertical wind shear, moisture, and low-level relative vorticity).

Appalachian Lee Troughs And Their Association With Severe Convective Storms, Daniel Thompson

Legacy Theses & Dissertations (2009 - 2024)

Forecasting convective storms in the mid-Atlantic region of the U.S. (hereafter mid-Atlantic) is important because of the proximity of the convective initiation region to major East Coast cities. These forecasts can be challenging because of the weak synoptic-scale forcing for ascent and abundant convective instability typical of the mid-Atlantic warm season (May-September). As a result, mesoscale boundaries such as the Appalachian lee trough (ALT) play an important role in initiating convective storms. This thesis examines the association between ALTs and warm-season severe convective storms in the mid-Atlantic in order to understand how ALTs modulate the frequency and distribution of severe …

The Influence Of The Great Lakes On Mcs Formation And Development In The Warm Season, Alan Frederick Srock

Legacy Theses & Dissertations (2009 - 2024)

This study focuses on how near-surface thermal boundaries that form near the Great Lakes during the warm season can contribute to the formation of mesoscale convective systems (MCSs). Differential heating across land-water interfaces can create a cold dome of air over the lake; convection may develop when the relatively-cold dome of air becomes deep enough to enable air parcels that intersect these boundaries to reach their level of free convection. A radar-based climatology of MCS events surrounding the Great Lakes for 2002-2005 showed that MCSs frequently form in the vicinity of the Great Lakes. Composites of MCS events over the …

The Investigation Of Snowfall Rate Using Optical Techniques, Gerald J. Mulvey

Atmospheric and Environmental Sciences Theses and Dissertations

Experiments involving the attenuation of light by falling snow, or hydrometeors in general, lend themselves to the study of at least two problems of meteorological interest. The first problem is that of visibility in adverse weather conditions, and the second is that of finding a better method to measure precipitation. From the late 1940's through the late 1960's, various investigators have attempted to apply forward light scattering theory in the geometric optics range (α ≥ 200, where α = (2π_r)/λ, λ=wavelength and r = radius)* to quantitatively describe the attenuation of a light beam, and thereby visibility changes due to …