Theses and Dissertations - Department of Geography
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Browsing Theses and Dissertations - Department of Geography by Subject "Climate change"
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Item Assessing the influence of climate change on flooding hazards following tropical cyclone events in the southeast United States(University of Alabama Libraries, 2016) Stone, Monica Helen; Cohen, Sagy; University of Alabama TuscaloosaRecent tropical cyclones, like Hurricane Katrina, have been some of the worst the United States has experienced. Tropical cyclones are expected to intensify, bringing about 20% more precipitation, in the near future in response to global climate warming. Further, global climate warming may extend the hurricane season. This study focuses on four major river basins (Neches, Pearl, Mobile, and Roanoke) in the Southeast United States that are frequently impacted by tropical cyclones. The Soil and Water Assessment Tool (SWAT) was used to model flow along these rivers from 1998-2014 with 20% more precipitation during tropical cyclones. The results of this study show that an increase in tropical cyclone precipitation due to future climate change may increase peak flows at the mouths of these Southeast rivers by ~7-18%. Most tropical cyclones that impact these river basins occur during the low discharge season, and thus rarely produce flooding conditions at their mouths. An extension of the current hurricane season of June-November, due to global climate warming, could encroach upon the wet season in these basins and lead to increased flooding. On average, this analysis shows that an extension of the hurricane season to May-December increased flooding susceptibility by 63% for the rivers analyzed in this study. That is, 4-6 more days per year likely would have been above bankfull discharge if an average tropical cyclone had occurred any day (based on 1998-2014 data) in the months May-December than in the current hurricane season months of June-November. More research is needed on the mechanisms and processes involved in the water balance of the four rivers analyzed in this study, and others in the Southeast United States, and how this is likely to change in the near future with global climate warming.Item Population dynamics of sugar maple (Acer saccharum Marsh.) at the southern portion of its range: implications for range migration and succession(University of Alabama Libraries, 2011) Turberville, Craig Marcus; Hart, Justin L.; University of Alabama TuscaloosaEvidence for climate change driven range migration exists for a variety of tree species in eastern North America. Northward range migration for tree species in the region requires a decrease in population density near the southern range boundary coupled with an increase in population density at the northern range boundary. Sugar maple (Acer saccharum Marsh.) is one such species that has been projected by some biogeographic models to shift north in accord with climate. However, a widespread pattern of increased sugar maple density has been reported in the forest science literature from a variety of sites throughout the species' range. This pattern is linked to a complex of interacting factors and has been hypothesized to represent a positive feedback that facilitates sugar maple regeneration. The primary goal of my study was to test which of these hypotheses (range migration or succession) was correct for the southern portion of the sugar maple range. I used Forest Inventory and Analysis program data to compare region-wide population dynamics for this species on a plot-by-plot basis. Changes in frequency, density, and dominance of sugar maple trees and seedlings were compared over multiple years for the states of Alabama, Kentucky, North Carolina, Tennessee, Virginia, and West Virginia. Plot data for all states were combined to determine changes in frequency, density, and dominance for the contiguous and non-contiguous regions of sugar maple's southern range portion. Results indicated increases in frequency, density, and dominance of sugar maple within its contiguous range coupled with decreases outside of the contiguous range. It is postulated based on these data that sugar maple's southern range boundary will remain stabilized while the northern boundary will continue to migrate with increasing global temperatures.Item Synoptic characteristics of intense precipitation events in the southeastern united states(University of Alabama Libraries, 2018) Skeeter, Walker J.; Senkbeil, Jason C.; University of Alabama TuscaloosaThe Southeastern United States is a region where increases in temperature have been largely muted when compared to other regions of the country, although extremes in both temperature and precipitation have become more common over time. In the first part of this research, the strength and recurrence of Southeastern United States intense precipitation events (IPEs) was analyzed annually, seasonally, and sub-regionally with an emphasis on identifying trends and causal mechanisms at each of these temporal and spatial scales. Causal mechanisms responsible for IPE were investigated by utilizing the Spatial Synoptic Classification (SSC) to determine which surface weather types are associated with these events. Furthermore, a case study analysis of the most intense IPE in each physiographic province was performed with archived daily surface maps to classify the type of surface forcing mechanism that was responsible for the most exceptional IPE in each physiographic province. Results showed a statistically significant and regionally variable increase in both the recurrence and strength of IPE. A statistically significant increase in the number of moist tropical (MT) weather type IPEs per year was identified, and attributed to more common northward and inland encroachment of these events. Case study reveals that coastal areas depend heavily on tropical events and stationary fronts, while forcings in inland areas are more evenly distributed. In addition to surface characteristics, the second part of this research explored synoptic patterns found with the most intense IPE across the entire study area. Principal Component Analysis, and Cluster Analysis were employed with 500 and 850 mb geopotential heights and a variety of seed variables in subsequent analyses to discover distinct types of IPE. A manual classification based on IPE origin as either a warm or cold core system, and formation location of the IPE provided the best representation of the synoptic patterns responsible for types of IPE. These IPE types were portrayed via a series of mean flow maps of 500 and 850 mb geopotential height, sea level pressure, and 72 hour mean precipitation. The precipitation amounts of the 72 hour means for the five IPE types were statistically significantly different from each other.