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THE VARIABILITY OF DROUGHT DYNAMICS IN THE SOUTHWEST UNITED STATES AND AN ANALYSIS OF DROUGHT RISK IN THE NORTHEASTERN UNITED STATES

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Abstract

This work is the culmination of my studies at Cornell University in the Department of Earth and Atmospheric Sciences under the tutelage of Dr. Toby Ault as a member of the Emergent Climate Risk Lab. Herein, I used a variety of tools to analyze the variability of hydroclimate teleconnections of the southwest United States (SWUS) to El Niño Southern Oscillation (ENSO), which included observations, paleoclimate records, general circulation models, and statistical models. To categorize the hydroclimate of the SWUS, we used the Palmer Drought Severity Index (PDSI). This analysis investigated the inherent century-scale teleconnection variability between PDSI in the SWUS and the Niño3.4 index of anomalous sea surface temperatures in the tropical Pacific Ocean. Our analysis concluded that there is a large amount of inherent variability in the system and that GCMs are unable to accurately capture this variability, even with the most recent models included in the Coupled Model Intercomparison Project Phase 6 (CMIP6). My attention was then turned towards the northeastern United States (NEUS) where drought dynamics are understudied in the available literature. This work used reanalysis products to compose a moisture budget analysis of the NEUS, to study both the climatology and case studies of individual drought events in the region. Our analysis showed that neither the advection of moisture into the region nor a lack of mass convergence over the region are responsible for droughts in the NEUS. While anomalously low winter snowpack during the winter months that establishes soil moisture deficits that are unable to recover and recharge may be a factor, much more consequential seems to be a potential shift of evaporative regimes. Finally, we analyzed the future risk of droughts and heat waves in the NEUS and found that GCMs, from both the last millennium ensemble (LME) and CMIP6, have a wet bias in the northeast. Radiation at the surface of the Earth is a balance between incoming solar radiation and outgoing longwave radiation. The surface may also lose energy through sensible heat loss and outgoing latent energy. This important balance is highly sensitive to soil moisture content. Because of the wet bias in the GCMs, future climate projections therefore underestimate the near-term-future heat wave and drought risk in the NEUS. The results provided by this dissertation shed useful insights into drought for stakeholders in both the SWUS and NEUS, especially as we continue to face a changing climate.

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131 pages

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2022-12

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Ault, Toby

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Allmon, Warren
Steinschneider, Scott
Degaetano, Arthur

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Atmospheric Science

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Ph. D., Atmospheric Science

Degree Level

Doctor of Philosophy

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Government Document

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Attribution 4.0 International

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dissertation or thesis

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