+publisher:"Georgia Tech" +contributor:("Di Lorenzo, Emanuele")

1. Hsu, Wei-Ching. The variability and seasonal cycle of the Southern Ocean carbon flux.

Degree: MS, Earth and Atmospheric Sciences, 2013, Georgia Tech

► Both physical circulation and biogeochemical characteristics are unique in the Southern Ocean (SO) region, and are fundamentally different from those of the northern hemisphere. Moreover,… (more)

▼ Both physical circulation and biogeochemical characteristics are unique in the Southern Ocean (SO) region, and are fundamentally different from those of the northern hemisphere. Moreover, according to previous research, the oceanic response to the trend of the Southern Annual Mode (SAM) has profound impacts on the future oceanic uptake of carbon dioxide in the SO. In other words, the climate and circulation of the SO are strongly coupled to the overlying atmospheric variability. However, while we have understanding on the SO physical circulation and have the ability to predict the future changes of the SO climate and physical processes, the link between the SO physical processes, the air-sea carbon flux, and correlated climate variability remains unknown. Even though scientists have been studying the spatial and temporal variability of the SO carbon flux and the associated biogeochemical processes, the spatial patterns and the magnitudes of the air-sea carbon flux do not agree between models and observations. Therefore, in this study, we utilized a modified version of a general circulation model (GCM) to performed realistic simulations of the SO carbon on seasonal to interannual timescales, and focused on the crucial physical and biogeochemical processes that control the carbon flux. The spatial pattern and the seasonal cycle of the air-sea carbon dioxide flux is calculated, and is broadly consistent with the climatological observations. The variability of air-sea carbon flux is mainly controlled by the gas exchange rate and the partial pressure of carbon dioxide, which is in turn controlled by the compensating changes in temperature and dissolved inorganic carbon. We investigated the seasonal variability of dissolved inorganic carbon based on different regional processes. Furthermore, we also investigated the dynamical adjustment of the surface carbon flux in response to the different gas exchange parameterizations, and conclude that parameterization has little impact on spatially integrated carbon flux. Our simulation well captured the SO carbon cycle variability on seasonal to interannual timescales, and we will improve our model by employ a better scheme of nutrient cycle, and consider more nutrients as well as ecological processes in our future study. Advisors/Committee Members: Ito, Taka (advisor), Di Lorenzo, Emanuele (committee member), Jones, Daniel (committee member).

Subjects/Keywords: Carbon flux; Southern Ocean; Seasonal cycle; Antarctic Ocean; Geological carbon sequestration; Ocean circulation; Atmospheric circulation; Mathematical models; Computer simulation

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APA (6^th Edition):

Hsu, W. (2013). The variability and seasonal cycle of the Southern Ocean carbon flux. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/49079

Chicago Manual of Style (16^th Edition):

Hsu, Wei-Ching. “The variability and seasonal cycle of the Southern Ocean carbon flux.” 2013. Masters Thesis, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/49079.

MLA Handbook (7^th Edition):

Hsu, Wei-Ching. “The variability and seasonal cycle of the Southern Ocean carbon flux.” 2013. Web. 06 Mar 2021.

Vancouver:

Hsu W. The variability and seasonal cycle of the Southern Ocean carbon flux. [Internet] [Masters thesis]. Georgia Tech; 2013. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/49079.

Council of Science Editors:

Hsu W. The variability and seasonal cycle of the Southern Ocean carbon flux. [Masters Thesis]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/49079

2. Cardona, Yuley. Mesoscale variability in the Gulf of Mexico, its impact and predictability.

Degree: PhD, Earth and Atmospheric Sciences, 2013, Georgia Tech

URL: http://hdl.handle.net/1853/52189

► The circulation of the Gulf of Mexico is controlled by presence of large mesoscale structures (10-500 km). We investigate its variability and predictability from interannual… (more)

▼ The circulation of the Gulf of Mexico is controlled by presence of large mesoscale structures (10-500 km). We investigate its variability and predictability from interannual to intraseasonal time scales, and the dynamical interactions between physical circulation and biological productivity. We do so by analyzing an ensemble of numerical integrations using the Regional Ocean Modeling System and hydrographic and biogeochemistry observations collected during summer field campaigns in 2010, 2011, and 2012. First, we explore the potential relationships and linkages between Mississippi-Atchafalaya River runoff, nutrient loads, and ocean dynamics from our field data. A negative correlation between nutrient concentration and salinity was confirmed at the surface and in the upper 60m of the water column for nitrite, nitrate, phosphate and silicate. No major changes in the nutrient concentrations were found between our data and previous measurements from twenty years ago. The biological activity in the stations sampled (northern Gulf) is nitrogen limited in 79% of them and phosphorus limited in 8%. Besides the direct input of nutrients from river discharges, the distribution of nutrients in intermediate and high salinity waters in the euphotic layer is influenced by dynamical processes at the ocean mesoscales such as eddies, coastal upwelling events and Loop Current (LC) intrusions. Then, using an ensemble of four model integrations we investigate how mesoscale motions dominate the variability of the Gulf of Mexico circulation both at the surface and in deep waters on intraseasonal time scales. We focus on its predictability by exploring the impact of small variations in the initial conditions and the role of the boundary conditions in the circulation evolution. In all runs, the model provides a good representation of the mean circulation features. However, the shedding of the Loop Current Eddies (LCE) differs in each run considered, and our analysis shows that the detachment of the LCE is a stochastic process. We show that the interannual variability at the model boundaries affects the representation of the LC strength and of the Yucatan Channel transport. On the other hand, the circulation in the LATEX Shelf, TAVE Shelf, and Bay of Campeche is insensitive to the details of the model boundaries, is not affected by the LC, but depends only on the wind variability, and it is therefore predictable if the atmospheric conditions are known. On the contrary, the circulation in the central basin is affected by the LC extension and by the Rings, and dominated by mesoscale features. In most of the basin, mesoscale features are coherent in the top ~ 1000 m of the water column, and below it, but not correlated between the surface and the deep layer. Coherency throughout the whole water column is attributed to particular topographic features such as the south-west corner of the Sigsbee Deep. The chaotic behavior associated with the propagation of the LCE and the elevated mesoscale activity restricts the predictability of the system… Advisors/Committee Members: Bracco, Annalisa (advisor), Curry, Judith (committee member), Di Lorenzo, Emanuele (committee member), Deng, Yi (committee member), Subramaniam, Ajit (committee member).

Subjects/Keywords: Mesoscale; Gulf of Mexico; Predictability; High frequency winds; Model

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APA (6^th Edition):

Cardona, Y. (2013). Mesoscale variability in the Gulf of Mexico, its impact and predictability. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52189

Chicago Manual of Style (16^th Edition):

Cardona, Yuley. “Mesoscale variability in the Gulf of Mexico, its impact and predictability.” 2013. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/52189.

MLA Handbook (7^th Edition):

Cardona, Yuley. “Mesoscale variability in the Gulf of Mexico, its impact and predictability.” 2013. Web. 06 Mar 2021.

Vancouver:

Cardona Y. Mesoscale variability in the Gulf of Mexico, its impact and predictability. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/52189.

Council of Science Editors:

Cardona Y. Mesoscale variability in the Gulf of Mexico, its impact and predictability. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/52189

3. Agaiby, Shehab. Advancements in the interpretation of seismic piezocone tests in clays and other geomaterials.

Degree: PhD, Civil and Environmental Engineering, 2018, Georgia Tech

URL: http://hdl.handle.net/1853/59848

► Seismic piezocone testing (SCPTu) offers an economic and expedient means for the modern collection of geotechnical data during site investigation of soils. It is actually… (more)

▼ Seismic piezocone testing (SCPTu) offers an economic and expedient means for the modern collection of geotechnical data during site investigation of soils. It is actually a hybrid test that has all the advantages and the merits of classic cone penetration testing (CPT) where it obtains three continuous readings with the depth: cone tip resistance (qt), sleeve friction (fs), and porewater pressure (u2); plus geophysical component involving downhole testing, where shear wave velocity (Vs) measurements are recorded at 1-m depth intervals. The conducted study aims at making full usage of the four main readings obtained from the seismic piezocone test: cone tip resistance, cone sleeve friction, porewater pressure and downhole shear wave velocity. New links between undrained shear strength and shear wave velocity are investigated and previous relationships between stress history and shear wave velocity are revisited and improved. A unified approach for estimating stress history of wide variety of geomaterials using net cone tip resistance is presented. Predictive equations for detecting sensitive clays from seismic shear wave velocity are introduced with a focus on sensitive and structured clays within North America. Modification of a hybrid spherical cavity expansion theory- critical state soil mechanics solution is introduced addressing the stress history of sensitive and structured clays. A new analytical approach allows the direct assessment of undrained rigidity index from CPTu data which finds value in assessing undrained shear strength, yield stress, and coefficient of consolidation, the latter from piezodissipation tests. The special nature and difficulties of organic clays are discussed and an indirect means of detecting their existence using piezocone testing is presented. Finally, an effort is undertaken to calibrate an analytical model for evaluating the undrained shear strength and stress history of clays using two large databases. Advisors/Committee Members: Mayne, Paul W. (advisor), Frost, James D. (committee member), Burns, Susan E. (committee member), Dai, Sheng (committee member), Di Lorenzo, Emanuele (committee member).

Subjects/Keywords: Seismic cone penetration tests

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APA (6^th Edition):

Agaiby, S. (2018). Advancements in the interpretation of seismic piezocone tests in clays and other geomaterials. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/59848

Chicago Manual of Style (16^th Edition):

Agaiby, Shehab. “Advancements in the interpretation of seismic piezocone tests in clays and other geomaterials.” 2018. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/59848.

MLA Handbook (7^th Edition):

Agaiby, Shehab. “Advancements in the interpretation of seismic piezocone tests in clays and other geomaterials.” 2018. Web. 06 Mar 2021.

Vancouver:

Agaiby S. Advancements in the interpretation of seismic piezocone tests in clays and other geomaterials. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/59848.

Council of Science Editors:

Agaiby S. Advancements in the interpretation of seismic piezocone tests in clays and other geomaterials. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/59848

Georgia Tech

4. Grothe, Pamela R. A coral ensemble record of the El Niño southern oscillation over the mid-to-late holocene.

Degree: PhD, Earth and Atmospheric Sciences, 2017, Georgia Tech

URL: http://hdl.handle.net/1853/60185

► The El Niño-Southern Oscillation (ENSO) represents the largest source of year-to-year global climate extremes. However, its sensitivity to external climate forcing, whether natural or anthropogenic,… (more)

▼ The El Niño-Southern Oscillation (ENSO) represents the largest source of year-to-year global climate extremes. However, its sensitivity to external climate forcing, whether natural or anthropogenic, is difficult to assess with available records. Paleoclimate reconstructions from the central tropical Pacific provide much-needed targets for climate models that are used to simulate future projections of ENSO variability under enhanced greenhouse emissions. Coral oxygen isotopes track variations in sea surface temperature and sea surface salinity, which is largely driven by ENSO. To date, paleo records rely on rare but decades-long fossil coral sequences that date to the last 7,000 years [Cobb et al., 2013]. This study turns to using abundant but shorter sequences (7-20yrs-long) of fossil coral rubble samples to produce a more statistically robust reconstruction of ENSO from the central tropical Pacific through the last 7,000 years. In Chapter 1, I provide relevant background information on ENSO in order to place this dissertation into broader scientific context. This includes the basics on ENSO dynamics and the different spatial patterns of El Niño events. I also explain the different proxies that have evolved our understanding of ENSO throughout the Holocene. Lastly, I mention where we currently are in understanding future projections of ENSO behavior under greenhouse gas emissions. In Chapter 2, I address one of the largest challenges in using a large number of fossil corals for paleoclimate reconstruction, which involves dating hundreds of coral samples cheaply and quickly. I compared the coral dating results from a rapid radiocarbon (14C) dating method, developed at the University of California Irvine, to high precision uranium-thorium (U/Th) dates, considered the gold standard of coral dating. The rapid 14C dating method allows for ~300 samples to be analyzed per week at 40/sample versus ~30 samples per week at 500/sample for U/Th dating. My results demonstrate the utility of employing 14C dating to screen large numbers of corals, followed by more limited U/Th dating on samples chosen for paleoclimate reconstruction. In addition, my extensive fossil coral dating has provided a map of fossil coral age distributions across Christmas Island in the central tropical Pacific. In Chapter 3, we extend the paleo-ENSO record through the generation of 16 new fossil coral δ18O timeseries, averaging 15yrs each, for a total of 233 years of data that greatly augment the available paleo-ENSO archive. Combining this new dataset with published data, we quantify the differences in natural variations in ENSO from the early mid-Holocene to present. In this study, we document a significant increase in recent ENSO variance as compared to the last 7,000 years, implying a role for greenhouse gases in driving an intensification of ENSO. We also find a significant reduction in ENSO variance of roughly 20% from 3,000-5,000yr before present, relative to the preceding and subsequent intervals of data. The causes of the late mid-Holocene… Advisors/Committee Members: Cobb, Kim (advisor), Lynch-Stieglitz, Jean (committee member), Di Lorenzo, Emanuele (committee member), Ito, Taka (committee member), Capotondi, Antonietta (committee member).

Subjects/Keywords: Radiocarbon; Uranium; Thorium; Dating; Coral; Diagenesis; Paleoclimate; El Nino; La Nina; ENSO; Global warming; Holocene; Oxygen isotopes

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Grothe, P. R. (2017). A coral ensemble record of the El Niño southern oscillation over the mid-to-late holocene. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60185

Chicago Manual of Style (16^th Edition):

Grothe, Pamela R. “A coral ensemble record of the El Niño southern oscillation over the mid-to-late holocene.” 2017. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/60185.

MLA Handbook (7^th Edition):

Grothe, Pamela R. “A coral ensemble record of the El Niño southern oscillation over the mid-to-late holocene.” 2017. Web. 06 Mar 2021.

Vancouver:

Grothe PR. A coral ensemble record of the El Niño southern oscillation over the mid-to-late holocene. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/60185.

Council of Science Editors:

Grothe PR. A coral ensemble record of the El Niño southern oscillation over the mid-to-late holocene. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60185

Georgia Tech

5. Lu, Yi. Dynamical footprints of aerosols in extratropical atmospheric disturbances and circulation: A modeling analysis.

Degree: PhD, Earth and Atmospheric Sciences, 2017, Georgia Tech

URL: http://hdl.handle.net/1853/60651

► Synoptic-scale atmospheric disturbances occupy extratropics in wintertime and form extratropical “storm tracks”. These disturbances not only influence day-to-day weather variability but also modulate regional climates.… (more)

▼ Synoptic-scale atmospheric disturbances occupy extratropics in wintertime and form extratropical “storm tracks”. These disturbances not only influence day-to-day weather variability but also modulate regional climates. The region of the North Pacific storm track is also known to be characterized by high concentrations of atmospheric aerosols, making it an ideal location for investigating the interaction between aerosols and extratropical disturbances. In the first part of the study, we investigate the aerosol indirect effects on the development of idealized baroclinic waves in the Weather Research and Forecasting (WRF) model. Doubling of cloud droplet number concentration (to mimic the aerosol indirect effects) in the model increases total cloud water in the model, enhances local latent heating and leads to a statistically significant strengthening of the wave. To take into account the effects of aerosol-convection interaction that had been omitted in the WRF experiments, the Superparameterized Community Atmosphere Model (SP-CAM) is adopted to examine the aerosol effects on developing extratropical cyclones in a more realistic environment. The result suggests that the growth rate of the cyclone is temporarily reduced with increased environmental aerosol concentrations. A convection–advection–moisture self-adjustment (CAMS) mechanism of aerosol–cyclone interaction is proposed to explain this finding. The last part of the study explores the collective effects of aerosols on multiple aspects of the northern extratropical circulation in boreal winter based on long-term perpetual winter simulations conducted with the SP-CAM. Analyses of local energetics of atmospheric disturbances reveal the underlying processes that lead to the strengthened activity of high-frequency (less than 10 days) disturbances and weakened activity of low-frequency (10 to 30 days) disturbances with an elevated level of aerosol emission. Also discussed are the implications of these findings for the short-term prediction of weather and long-term projection of climate change in the northern extratropics. Advisors/Committee Members: Deng, Yi (advisor), Black, Robert X. (committee member), Wang, Yuhang (committee member), Di Lorenzo, Emanuele (committee member), Wang, Jingfeng (committee member).

Subjects/Keywords: Extratropical cyclone; Aerosol effects; Storm track

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lu, Y. (2017). Dynamical footprints of aerosols in extratropical atmospheric disturbances and circulation: A modeling analysis. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60651

Chicago Manual of Style (16^th Edition):

Lu, Yi. “Dynamical footprints of aerosols in extratropical atmospheric disturbances and circulation: A modeling analysis.” 2017. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/60651.

MLA Handbook (7^th Edition):

Lu, Yi. “Dynamical footprints of aerosols in extratropical atmospheric disturbances and circulation: A modeling analysis.” 2017. Web. 06 Mar 2021.

Vancouver:

Lu Y. Dynamical footprints of aerosols in extratropical atmospheric disturbances and circulation: A modeling analysis. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/60651.

Council of Science Editors:

Lu Y. Dynamical footprints of aerosols in extratropical atmospheric disturbances and circulation: A modeling analysis. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60651

Georgia Tech

6. Pozo Buil, Maria Mercedes. Exploiting subsurface ocean dynamics for decadal predictability in the upwelling systems of the Eastern North Pacific.

Degree: PhD, Earth and Atmospheric Sciences, 2017, Georgia Tech

URL: http://hdl.handle.net/1853/60704

► Given the strong recent interest in the decadal timescale variability and the potential for its predictability, it is critical to identify dynamics that carry inherent… (more)

▼ Given the strong recent interest in the decadal timescale variability and the potential for its predictability, it is critical to identify dynamics that carry inherent decadal-scale predictability. This work enhances our understanding and prediction capability of the subsurface signature of the decadal variability in the eastern North Pacific upwelling systems using reanalysis products and a set of eddy-resolving ocean model simulations. We show that subsurface temperature anomalies propagated by mean advection along the North Pacific Current significantly contribute through mean upwelling to decadal changes of surface temperature in the Gulf of Alaska. We also show that this influence is comparable to the contribution associated with variations in atmospheric winds. We find that subsurface anomalies in the core of the North Pacific Current propagate temperature, salinity, and oxygen signals downstream into the coastal California Current upwelling system, following the path of the mean gyre circulation with a time scale of 10 years. We suggest these propagation dynamics lead to potential predictability of ocean tracers, specifically oxygen and nutrients. Using reanalysis products and a set of eddy-resolving ocean model simulations, we provide evidence that supports the proposed inherent decadal predictability associated with the propagation of subsurface anomalies. We quantify the predictability of impacts associated with the arrival of the subsurface anomalies in the California Current upwelling system. We find a region of strong deterministic, predictable variance in the core of the North Pacific Current and in the sub-polar gyre region. Finally, we propose a dynamical subsurface connection between the western and eastern boundary, with subsurface anomalies generating and propagating eastward from the Kuroshio-Oyashio Extension region in the Western Pacific all the way to the California Current region in the Eastern Pacific. Advisors/Committee Members: Di Lorenzo, Emanuele (advisor), Bracco, Annalisa (committee member), Ito, Taka (committee member), Cobb, Kim (committee member), Bograd, Steven (committee member).

Subjects/Keywords: Subsurface ocean dynamics; Decadal predictability; California current system; Gulf of Alaska; ROMS ensemble

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APA (6^th Edition):

Pozo Buil, M. M. (2017). Exploiting subsurface ocean dynamics for decadal predictability in the upwelling systems of the Eastern North Pacific. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60704

Chicago Manual of Style (16^th Edition):

Pozo Buil, Maria Mercedes. “Exploiting subsurface ocean dynamics for decadal predictability in the upwelling systems of the Eastern North Pacific.” 2017. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/60704.

MLA Handbook (7^th Edition):

Pozo Buil, Maria Mercedes. “Exploiting subsurface ocean dynamics for decadal predictability in the upwelling systems of the Eastern North Pacific.” 2017. Web. 06 Mar 2021.

Vancouver:

Pozo Buil MM. Exploiting subsurface ocean dynamics for decadal predictability in the upwelling systems of the Eastern North Pacific. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/60704.

Council of Science Editors:

Pozo Buil MM. Exploiting subsurface ocean dynamics for decadal predictability in the upwelling systems of the Eastern North Pacific. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60704

Georgia Tech

7. Woolfe, Katherine F. Passive acoustic monitoring of the deep ocean using ambient noise.

Degree: PhD, Mechanical Engineering, 2015, Georgia Tech

URL: http://hdl.handle.net/1853/53910

► In the ocean, changes in the speed of sound can be related to changes in water temperature. By leveraging this relationship, acoustic methods – namely… (more)

▼ In the ocean, changes in the speed of sound can be related to changes in water temperature. By leveraging this relationship, acoustic methods – namely acoustic tomography- have been used to monitor temperature changes in the deep ocean for the purposes of providing inputs to climate change models. Traditionally, these acoustic methods involve loud, active sound sources which can be logistically challenging to operate and have been criticized for potentially disturbing marine animals. Therefore, this work demonstrates a passive acoustic method - previously only used in shallow water for short monitoring durations- that uses only recordings of low-frequency (1-40 Hz) ambient noise to continuously monitor variations in deep ocean temperature with an unprecedented degree of precision and temporal resolution. Numerical simulations were conducted to show the portions of the ocean that are monitored with this passive method. This work also provides recommendations (regarding sensor placement around the world) for future development of a global passive acoustic sensor network that makes use of distant noise sources (sea-ice or seismic sources) to extract meaningful information (whether temperature, currents, etc.) about the ocean. Finally, an optimization method is proposed to overcome one of the fundamental limitations of previous applications of this passive monitoring method: tracking oceanic fluctuations that occur over short time scales. Hence, the results of this study may assist in the development of more reliable climate models that include an enhanced understanding of the ocean’s role as a global heat sink. Finally, an optimization method was proposed to enhance the emergence rate of coherent arrivals from ambient noise correlations, thus allowing this passive monitoring method to track acoustic medium fluctuations on a shorter time scale. This optimization could also be used in other applications of noise-based passive monitoring in a rapidly fluctuating medium (seismic, structural health monitoring, biomedical, etc.). Advisors/Committee Members: Sabra, Karim (advisor), Degertekin, F. Levent (committee member), Di Lorenzo, Emanuele (committee member), Meaud, Julien (committee member), Kuperman, William (committee member).

Subjects/Keywords: Acoustic; Oceanography

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APA (6^th Edition):

Woolfe, K. F. (2015). Passive acoustic monitoring of the deep ocean using ambient noise. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53910

Chicago Manual of Style (16^th Edition):

Woolfe, Katherine F. “Passive acoustic monitoring of the deep ocean using ambient noise.” 2015. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/53910.

MLA Handbook (7^th Edition):

Woolfe, Katherine F. “Passive acoustic monitoring of the deep ocean using ambient noise.” 2015. Web. 06 Mar 2021.

Vancouver:

Woolfe KF. Passive acoustic monitoring of the deep ocean using ambient noise. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/53910.

Council of Science Editors:

Woolfe KF. Passive acoustic monitoring of the deep ocean using ambient noise. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53910

Georgia Tech

8. Westby, Rebecca Marie. Extreme temperature regimes during the cool season: Their trends, variability, triggers and physical connections to low frequency modes.

Degree: PhD, Earth and Atmospheric Sciences, 2015, Georgia Tech

URL: http://hdl.handle.net/1853/54899

► During the boreal cool season (December – February) extreme temperature regimes (ETRs), including cold air outbreaks (CAOs) and warm waves (WWs), affect regional economies and… (more)

▼ During the boreal cool season (December – February) extreme temperature regimes (ETRs), including cold air outbreaks (CAOs) and warm waves (WWs), affect regional economies and human safety via their significant impacts on energy consumption, local agriculture and human health. This work aims to improve our understanding of the trends and variability in ETRs, their physical connections to low frequency modes, and the dynamical mechanisms leading to ETR onset. Earlier studies on ETR trends and variability do not consider the last decade. Further, little is known about the physical and dynamical nature of ETR onset. These unknowns motivate this dissertation and are particularly important for WWs, which have rarely been studied. This study begins with an updated analysis of the long-term trends and interannual variability in ETRs. Even with the inclusion of the last decade, no significant trends in either WW or CAO occurrence are identified over the continental United States between 1949-2011. The accompanying correlation analysis reveals that on interannual time scales, ETRs in specific regions of the U.S. tend to be modulated by certain low frequency modes. This analysis highlights an important regional asymmetry in the low frequency mode modulation of ETRs, and also indicates that the influence of ENSO upon ATRs is mainly limited to a modest modulation of WWs over the southeast US. Further, a multiple linear regression analysis reveals that the regional collective influence of low-frequency modes accounts for as much as 50% of interannual ETR variability. A synoptic-dynamic characterization of ETR onset over the southeast US is then performed using composite time-evolution analyses of events occurring between 1949-2011 to provide a qualitative indication of the role of low frequency modes. During CAO (WW) onset, negative (positive) geopotential height anomalies are observed in the upper troposphere over the Southeast with oppositely-signed anomalies in the lower troposphere over the central US. In most cases, there is a surface east-west height anomaly dipole, with anomalous northerly (CAO) or southerly (WW) flow into the Southeast leading to cold or warm surface air temperature anomalies, respectively. Companion potential vorticity anomaly analyses reveal prominent features in the mid- to upper-troposphere consistent with the geopotential height anomaly patterns. The composite analyses reveal significant roles for both synoptic and large-scale disturbances in ETR development. Synoptic-scale disturbances serve as dynamic triggers for ETR events, while low-frequency modes can provide a favorable environment for ETR onset. A suite of diagnostic analyses is conducted next and aims to identify the primary thermodynamic processes and dynamical mechanisms responsible for ETR development over the Southeast US. Heat budget analyses implicate linear temperature advection as the primary contributor to ETR development, while nonlinear advection plays a smaller role. Both the linear and the nonlinear terms contribute positively… Advisors/Committee Members: Black, Robert X. (advisor), Deng, Yi (committee member), Di Lorenzo, Emanuele (committee member), Belanger, James (committee member), Evans, Katherine (committee member).

Subjects/Keywords: Extreme temperature regimes; Cold-air outbreaks; Warm waves; Variability; Triggers; Low frequency modes

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APA (6^th Edition):

Westby, R. M. (2015). Extreme temperature regimes during the cool season: Their trends, variability, triggers and physical connections to low frequency modes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54899

Chicago Manual of Style (16^th Edition):

Westby, Rebecca Marie. “Extreme temperature regimes during the cool season: Their trends, variability, triggers and physical connections to low frequency modes.” 2015. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/54899.

MLA Handbook (7^th Edition):

Westby, Rebecca Marie. “Extreme temperature regimes during the cool season: Their trends, variability, triggers and physical connections to low frequency modes.” 2015. Web. 06 Mar 2021.

Vancouver:

Westby RM. Extreme temperature regimes during the cool season: Their trends, variability, triggers and physical connections to low frequency modes. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/54899.

Council of Science Editors:

Westby RM. Extreme temperature regimes during the cool season: Their trends, variability, triggers and physical connections to low frequency modes. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/54899

Georgia Tech

9. Lin, Liao-Fan. Data assimilation and dynamical downscaling of remotely-sensed precipitation and soil moisture from space.

Degree: PhD, Civil and Environmental Engineering, 2016, Georgia Tech

URL: http://hdl.handle.net/1853/54974

► Environmental monitoring of Earth from space has provided invaluable information for understanding the land-atmosphere water and energy exchanges. However, the use of satellite observations in… (more)

▼ Environmental monitoring of Earth from space has provided invaluable information for understanding the land-atmosphere water and energy exchanges. However, the use of satellite observations in hydrologic applications is often limited by coarse space-time resolutions. This study aims to develop a data assimilation system that integrates remotely-sensed precipitation and soil moisture observations into physically-based models to produce fine-scale precipitation, soil moisture, and other relevant hydrometeorological variables. This is particularly useful with the active Global Precipitation Measurement and Soil Moisture Active Passive missions. The system consists of two major components: (1) a framework for dynamic downscaling of satellite precipitation products using the Weather Research and Forecasting (WRF) model with four-dimensional variational data assimilation (4D-Var) and (2) a variational data assimilation system using spatio-temporally varying background error covariance for directly assimilating satellite soil moisture data into the Noah land surface model coupled with the WRF model. The WRF 4D-Var system can effectively assimilate and downscale six-hour precipitation products of a spatial resolution of about 20 km (i.e., those derived from the National Centers for Environmental Prediction Stage IV data and the Tropical Rainfall Measuring Mission (TRMM) 3B42 dataset) to hourly precipitation with a spatial resolution of less than 10 km. The system is able to assimilate and downscale daily soil moisture products at a gridded 36-km resolution obtained from the Soil Moisture and Ocean Salinity (SMOS) mission to produce hourly 4-by-4 km surface soil moisture forecasts with a reduction of mean absolute error by 35% on average. The results from the system with coupled components show that assimilation of the TRMM 3B42 precipitation improves the quality of both downscaled precipitation and soil moisture analyses, while the effect of SMOS soil moisture data assimilation is largely on the soil moisture analyses. The downscaled WRF precipitation, with and without assimilation of TRMM precipitation, was preliminarily tested with a spatially distributed simulation of streamflow using the TIN (Triangular Irregular Network)-based Real-time Integrated Basin Simulator (tRIBS). Advisors/Committee Members: Bras, Rafael (advisor), Wang, Jingfeng (committee member), Georgakakos, Aris (committee member), Di Lorenzo, Emanuele (committee member), Flores, Alejandro (committee member).

Subjects/Keywords: Precipitation; Soil moisture; Data assimilation; Dynamical downscaling; Weather research and forecasting; Land-atmosphere interaction; Remote sensing; Hydrometeorology; Hydrology

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APA (6^th Edition):

Lin, L. (2016). Data assimilation and dynamical downscaling of remotely-sensed precipitation and soil moisture from space. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54974

Chicago Manual of Style (16^th Edition):

Lin, Liao-Fan. “Data assimilation and dynamical downscaling of remotely-sensed precipitation and soil moisture from space.” 2016. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/54974.

MLA Handbook (7^th Edition):

Lin, Liao-Fan. “Data assimilation and dynamical downscaling of remotely-sensed precipitation and soil moisture from space.” 2016. Web. 06 Mar 2021.

Vancouver:

Lin L. Data assimilation and dynamical downscaling of remotely-sensed precipitation and soil moisture from space. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/54974.

Council of Science Editors:

Lin L. Data assimilation and dynamical downscaling of remotely-sensed precipitation and soil moisture from space. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/54974

Georgia Tech

10. Takano, Yohei. Understanding the mechanisms of dissolved oxygen trends and variability in the ocean.

Degree: PhD, Earth and Atmospheric Sciences, 2016, Georgia Tech

URL: http://hdl.handle.net/1853/54994

► A widely observed tracer in the field of oceanography is dissolved oxygen (O2). A tracer crucial to ocean biogeochemical cycles, O2 plays an active role… (more)

▼ A widely observed tracer in the field of oceanography is dissolved oxygen (O2). A tracer crucial to ocean biogeochemical cycles, O2 plays an active role in chemical processes, marine life, and ecosystems. Recent advances in observation and numerical simulation have introduced opportunities for furthering our understanding of the variability and long-term changes in oceanic O2. This work examines the underlying mechanisms driving O2 variability and long-term changes. It focuses on two distinct time-scales: intra-seasonal variability (i.e., a time scale of less than a month) and centennial changes in O2. The first half of this work analyzes state-of-the-art observations from a profiling float in an investigation of the mechanisms driving the intra-seasonal variability of oceanic O2. Observations from the float show enhanced intra-seasonal variability (i.e., a time scale of about two weeks) that could be driven by isopycnal heaving resulting from internal waves or tidal processes. Observed signals could result from aliased signals from internal waves or tides and should be taken into account in analyses of the growing observational dataset. The methods proposed in this study may be useful for future analyses of high-frequency tracer variability associated with mesoscale and sub-mesoscale processes. Using outputs from state-of-the-art earth system models and a suite of sensitivity experiments based on a general circulation and biogeochemistry ocean model, the second half of this work focuses on investigating mechanisms regulating centennial changes in O2. It explores the aspect of anthropogenic climate change (e.g., changes in the sea surface temperature and wind stress fields) that significantly impacts oceanic O2, focusing specifically on tropical oxygen minimum zones. Results suggest that ocean heating induces a water mass shift, leads to decrease apparent oxygen utilization (AOU) in the tropical thermocline. The AOU decrease compensates the effect of decrease in oxygen saturation due to the ocean warming. Our sensitivity experiments show that both physically (i.e., age) and biologically (i.e., the oxygen utilization rate) driven AOU will contribute almost equally to controlling changes in oceanic O2 in the next century. However, additional sensitivity experiments indicate that physically and biologically driven AOU balance has regional characteristics. We need to address the unanswered question of how varying large-scale oceanic circulations regulate this balance and answer fundamental questions that lead to a more comprehensive understanding of the mechanisms that control the variability and the future evolution of oceanic O2. Advisors/Committee Members: Ito, Takamitsu (advisor), Di Lorenzo, Emanuele (committee member), Bracco, Annalisa (committee member), Deutsch, Curtis (committee member), Montoya, Joseph (committee member).

Subjects/Keywords: Dissolved oxygen; Climate change; Temporal spectrum

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APA (6^th Edition):

Takano, Y. (2016). Understanding the mechanisms of dissolved oxygen trends and variability in the ocean. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54994

Chicago Manual of Style (16^th Edition):

Takano, Yohei. “Understanding the mechanisms of dissolved oxygen trends and variability in the ocean.” 2016. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/54994.

MLA Handbook (7^th Edition):

Takano, Yohei. “Understanding the mechanisms of dissolved oxygen trends and variability in the ocean.” 2016. Web. 06 Mar 2021.

Vancouver:

Takano Y. Understanding the mechanisms of dissolved oxygen trends and variability in the ocean. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/54994.

Council of Science Editors:

Takano Y. Understanding the mechanisms of dissolved oxygen trends and variability in the ocean. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/54994

11. El Sharif, Husayn Ahmad. Integrated assessment of multi-sensor gridded data products for agricultural and hydrological applications.

Degree: PhD, Civil and Environmental Engineering, 2019, Georgia Tech

URL: http://hdl.handle.net/1853/61090

► New remote sensing and gridded reanalysis data products from sources including the NASA Soil Moisture Active Passive (SMAP) Mission, Global Precipitation Measurement (GPM) Mission, North… (more)

Subjects/Keywords: Remote sensing; Agriculture; Gridded data; SMAP; GPM

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APA (6^th Edition):

El Sharif, H. A. (2019). Integrated assessment of multi-sensor gridded data products for agricultural and hydrological applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/61090

Chicago Manual of Style (16^th Edition):

El Sharif, Husayn Ahmad. “Integrated assessment of multi-sensor gridded data products for agricultural and hydrological applications.” 2019. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/61090.

MLA Handbook (7^th Edition):

El Sharif, Husayn Ahmad. “Integrated assessment of multi-sensor gridded data products for agricultural and hydrological applications.” 2019. Web. 06 Mar 2021.

Vancouver:

El Sharif HA. Integrated assessment of multi-sensor gridded data products for agricultural and hydrological applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/61090.

Council of Science Editors:

El Sharif HA. Integrated assessment of multi-sensor gridded data products for agricultural and hydrological applications. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/61090

Georgia Tech

12. Joh, Youngji. PACIFIC TELECONNECTIONS DYNAMICS IN A CHANGING CLIMATE: THEORIES, OBSERVATIONS, AND MODELS.

Degree: PhD, Earth and Atmospheric Sciences, 2020, Georgia Tech

URL: http://hdl.handle.net/1853/64102

► Pacific climate and weather extreme events such as heatwaves, drought, and hydrological extremes are dynamically linked large-scale climate variability. This work aims at improving the… (more)

▼ Pacific climate and weather extreme events such as heatwaves, drought, and hydrological extremes are dynamically linked large-scale climate variability. This work aims at improving the current understanding of the role of climate coupling within the Pacific system and investigating their changes to anthropogenic forcing. Using observational reanalyses and global climate model ensemble, we show that prolonged multi-year marine heatwaves are linked to the dynamics of the two dominant modes of winter sea surface temperature variability in the North Pacific, the Pacific Decadal Oscillation (PDO) and the North Pacific Gyre Oscillation (NPGO). Specifically, we find a significant correlation between winter NPGO anomalies and the following winter PDO arising from extra-tropical/tropical teleconnections. Our work reports that marine heatwaves in the North Pacific are becoming stronger in amplitude with a larger area as well as more persistent under anthropogenic forcing. We next propose that a preferred decadal timescale in the Kuroshio Extension (KE) may arise from the interaction between the KE and the extra-tropical/tropical Pacific variability. We show that changes in the KE states apply a persistent downstream atmospheric response that projects on the atmospheric forcing of the Pacific Meridional Modes (PMM) over 9 months timescales. Subsequently, the PMM energizes the central Pacific El Niño Southern Oscillation (CP-ENSO), which in turn excites oceanic Rossby waves in the central North Pacific that propagate westward changing the KE (~3 years). We provide a cross-correlation function between the KE and the PMM/CP-ENSO indices exhibiting a significant sinusoidal shape corresponding to a preferred spectral power at decadal timescales (~10 years). Finally, through combining observations, numerical simulations, and empirical dynamical models, we confirm that KE and the tropical Pacific are dynamically linked, especially during the recent decades. The statistical differences between the KE properties before and after the mid-1980 suggest non-stationary decadal KE variability. Moreover, the KE interaction with the CP-ENSO has been increasing in a changing climate. We discuss the link of the enhanced extratropical-tropical coupled KE system with the potential impact of anthropogenic forcing and changes in the KE downstream response with stronger subtropical wind forcing and subsequent favorable conditions for Pacific Meridional modes and CP-ENSO. Advisors/Committee Members: Di Lorenzo, Emanuele (advisor), Ito, Taka (committee member), He, Jie (committee member), Capotondi, Antonietta (committee member), Kirtman, Ben (committee member).

Subjects/Keywords: Pacific Climate; Teleconnections

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APA (6^th Edition):

Joh, Y. (2020). PACIFIC TELECONNECTIONS DYNAMICS IN A CHANGING CLIMATE: THEORIES, OBSERVATIONS, AND MODELS. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/64102

Chicago Manual of Style (16^th Edition):

Joh, Youngji. “PACIFIC TELECONNECTIONS DYNAMICS IN A CHANGING CLIMATE: THEORIES, OBSERVATIONS, AND MODELS.” 2020. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/64102.

MLA Handbook (7^th Edition):

Joh, Youngji. “PACIFIC TELECONNECTIONS DYNAMICS IN A CHANGING CLIMATE: THEORIES, OBSERVATIONS, AND MODELS.” 2020. Web. 06 Mar 2021.

Vancouver:

Joh Y. PACIFIC TELECONNECTIONS DYNAMICS IN A CHANGING CLIMATE: THEORIES, OBSERVATIONS, AND MODELS. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/64102.

Council of Science Editors:

Joh Y. PACIFIC TELECONNECTIONS DYNAMICS IN A CHANGING CLIMATE: THEORIES, OBSERVATIONS, AND MODELS. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/64102

Georgia Tech

13. Arnold, Hannes. Plasma Interaction Signatures of Plumes at Europa.

Degree: PhD, Earth and Atmospheric Sciences, 2020, Georgia Tech

URL: http://hdl.handle.net/1853/64130

► We present a systematic modeling framework for the identification of water vapor plumes in plasma and magnetic field data from spacecraft flybys of Jupiter's moon… (more)

Subjects/Keywords: Jupiter; Europa; Plumes; Plasma Physics

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APA (6^th Edition):

Arnold, H. (2020). Plasma Interaction Signatures of Plumes at Europa. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/64130

Chicago Manual of Style (16^th Edition):

Arnold, Hannes. “Plasma Interaction Signatures of Plumes at Europa.” 2020. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/64130.

MLA Handbook (7^th Edition):

Arnold, Hannes. “Plasma Interaction Signatures of Plumes at Europa.” 2020. Web. 06 Mar 2021.

Vancouver:

Arnold H. Plasma Interaction Signatures of Plumes at Europa. [Internet] [Doctoral dissertation]. Georgia Tech; 2020. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/64130.

Council of Science Editors:

Arnold H. Plasma Interaction Signatures of Plumes at Europa. [Doctoral Dissertation]. Georgia Tech; 2020. Available from: http://hdl.handle.net/1853/64130

14. Davis, Andrew Murphy. The spatial structure and interannual variability of California current system.

Degree: PhD, Earth and Atmospheric Sciences, 2014, Georgia Tech

URL: http://hdl.handle.net/1853/52236

► The California Current is the Eastern Boundary Current associated with the North Pacific Subtropical Gyre, transporting cold, nutrient-rich water equatorward. It is also an area… (more)

Subjects/Keywords: Physical oceanography; Climate

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APA (6^th Edition):

Davis, A. M. (2014). The spatial structure and interannual variability of California current system. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52236

Chicago Manual of Style (16^th Edition):

Davis, Andrew Murphy. “The spatial structure and interannual variability of California current system.” 2014. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/52236.

MLA Handbook (7^th Edition):

Davis, Andrew Murphy. “The spatial structure and interannual variability of California current system.” 2014. Web. 06 Mar 2021.

Vancouver:

Davis AM. The spatial structure and interannual variability of California current system. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/52236.

Council of Science Editors:

Davis AM. The spatial structure and interannual variability of California current system. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/52236

15. Zhong, Yisen. Submesoscale dynamics and transport properties in the Gulf of Mexico.

Degree: PhD, Earth and Atmospheric Sciences, 2013, Georgia Tech

URL: http://hdl.handle.net/1853/50385

► Submesoscale processes, characterized by O(1km) horizontal scale and O(1) Rossby number, are ubiquitous in the world ocean and play an important role in the vertical… (more)

Subjects/Keywords: Ocean submesoscales; Lagrangian transport; Tracer distribution; Sargassum pattern; Oceanography; Ocean waves

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APA (6^th Edition):

Zhong, Y. (2013). Submesoscale dynamics and transport properties in the Gulf of Mexico. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50385

Chicago Manual of Style (16^th Edition):

Zhong, Yisen. “Submesoscale dynamics and transport properties in the Gulf of Mexico.” 2013. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/50385.

MLA Handbook (7^th Edition):

Zhong, Yisen. “Submesoscale dynamics and transport properties in the Gulf of Mexico.” 2013. Web. 06 Mar 2021.

Vancouver:

Zhong Y. Submesoscale dynamics and transport properties in the Gulf of Mexico. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/50385.

Council of Science Editors:

Zhong Y. Submesoscale dynamics and transport properties in the Gulf of Mexico. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50385

16. Nekouee, Navid. Dynamics and numerical modeling of river plumes in lakes.

Degree: PhD, Civil and Environmental Engineering, 2010, Georgia Tech

URL: http://hdl.handle.net/1853/41104

► Models of the fate and transport of river plumes and the bacteria they carry into lakes are developed. They are needed to enable informed decisions… (more)

▼ Models of the fate and transport of river plumes and the bacteria they carry into lakes are developed. They are needed to enable informed decisions about beach closures to avoid economic losses, and to help design water intakes and operate combined sewer overflow schemes to obviate exposure of the public to potential pathogens. This study advances our understanding of river plumes dynamics in coastal waters by means of field studies and numerical techniques. Extensive field measurements were carried out in the swimming seasons of 2006 and 2007 on the Grand River plume as it enters Lake Michigan. They included simultaneous aerial photography, measurements of lake physical properties, the addition of artificial tracers to track the plume, and bacterial sampling. Our observed results show more flow classes than included in previous studies (e.g. CORMIX). Onshore wind can have a significant effect on the plume and whether it impacts the shoreline. A new classification scheme based on the relative magnitude of plume-crossflow length scale and Richardson number based on the wind speed is devised. Previous studies on lateral spreading are complemented with a new relationship in the near field. The plume thickness decreased rapidly with distance from the river mouth and a new non-dimensional relationship to predict thickness is developed. Empirical near field models for surface buoyant plumes are reviewed and a near field trajectory and dilution model for large aspect ratio surface discharge channels is devised. Bacterial reductions due to dilution were generally small (less than 10:1) up to 4.5 km from the river mouth. E. coli decay rates were significantly affected by solar radiation and ranged from 0.2 to 2.2 day-1 which were within the range of previous studies in Lake Michigan. Total coliform survived longer than E. coli suggesting different die-off mechanisms. Mathematical models of the bacterial transport are developed that employ a nested modeling scheme to represent the 3D hydrodynamic processes of surface river discharges in the Great Lakes. A particle tracking model is used that provides the capability to track a decaying tracer and better quantify mixing due to turbulent diffusion. Particle tracking models have considerable advantages over gradient diffusion models in simulating bacterial behavior nearshore that results in an improved representation of bacteria diffusion, decay and transport. Due to the complexity and wide variation of the time and length scale of the hydrodynamic and turbulent processes in the near field (where plume mixing is dominated by initial momentum and buoyancy) and far field (where plume mixing is dominated by ambient turbulence), a coupling technique is adapted. The far field random walk particle tracking model incorporates the empirical near field model. It simulates the transport, diffusion and decay of bacteria as discrete particles and employs the near field output as the source and transports the particles based on ambient currents predicted by the 3D hydrodynamic model.… Advisors/Committee Members: Roberts, Philip (Committee Chair), Di Lorenzo, Emanuele (Committee Member), Schwab, David (Committee Member), Stoesser, Thorsten (Committee Member), Webster, Donald (Committee Member).

Subjects/Keywords: Beach forecasting; Particle tracking; Hybrid model; Nearshore bacterial transport; Coastal diffusion and dispersion; Mass transport; Empirical model; Plumes (Fluid dynamics); Fluid dynamics; Mathematical models; Plumes (Fluid dynamics) Mathematical models

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APA (6^th Edition):

Nekouee, N. (2010). Dynamics and numerical modeling of river plumes in lakes. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/41104

Chicago Manual of Style (16^th Edition):

Nekouee, Navid. “Dynamics and numerical modeling of river plumes in lakes.” 2010. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/41104.

MLA Handbook (7^th Edition):

Nekouee, Navid. “Dynamics and numerical modeling of river plumes in lakes.” 2010. Web. 06 Mar 2021.

Vancouver:

Nekouee N. Dynamics and numerical modeling of river plumes in lakes. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/41104.

Council of Science Editors:

Nekouee N. Dynamics and numerical modeling of river plumes in lakes. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/41104

17. Yang, Xiufeng. Ocean current energy resource assessment for the United States.

Degree: PhD, Civil and Environmental Engineering, 2013, Georgia Tech

URL: http://hdl.handle.net/1853/50352

► Ocean currents are an attractive source of clean energy due to their inherent reliability, persistence and sustainability. The Gulf Stream system is of particular interest… (more)

▼ Ocean currents are an attractive source of clean energy due to their inherent reliability, persistence and sustainability. The Gulf Stream system is of particular interest as a potential energy resource to the United States with significant currents and proximity to the large population on the U.S. east coast. To assess the energy potential from ocean currents for the United States, the characterization of ocean currents along the U.S. coastline is performed in this dissertation. A GIS database that maps the ocean current energy resource distribution for the entire U.S. coastline and also provides joint velocity magnitude and direction probability histograms is developed. Having a geographical constraint by Florida and the Bahamas, the Florida Current has the largest ocean current resource which is fairly stable with prevalent seasonal variability in the upper layer of the water column (~200m). The core of the Florida Current features higher stability than the edges as a result of the meandering and seasonal broadening of the current flow. The variability of the Gulf Stream significantly increases as it flows past the Cape Hatteras. The theoretical energy balance in the Gulf Stream system is examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for quasi-geostrophic subtropical gyres. Additional turbine drag is formulated and incorporated in the model to represent power extraction by turbines. Parameters in the model are calibrated against ocean observational data such that the model can reproduce the volume and kinetic energy fluxes in the Gulf Stream. The results show that considering extraction over a region comprised of the entire Florida Current portion of the Gulf Stream system, the theoretical upper bound of averaged power dissipation is around 5.1 GW, or 45 TWh/yr. If the extraction area comprises the entire portion of the Gulf Stream within 200 miles of the U.S. coastline, the theoretical upper bound of averaged power dissipation becomes approximately 18.6 GW or 163 TWh/yr. The impact of the power extraction is primarily constrained in the vicinity of the turbine region, and includes a significant reduction of flow strength and water level drop in the power extraction site. The turbines also significantly reduce residual energy fluxes in the flow, and cause redirection of the Gulf Stream. A full numerical simulation of the ocean circulation in the Atlantic Ocean is performed using Hybrid Coordinate Ocean Model (HYCOM) and power extraction from the Florida Current is modeled as additional momentum sink. Effects of power extraction are shown to include flow rerouting from the Florida Strait channel to the east side of the Bahamas. Flow redirection is stronger during peak summer flow resulting in less seasonal variability in both power extraction and residual fluxes in the Florida Current. A significant water level drop is shown at the power extraction site, and so is a slight water level rise along the coasts of Florida and the Gulf. The sum of extracted… Advisors/Committee Members: Haas, Kevin A. (advisor), Fritz, Hermann M. (committee member), Roberts, Philip J. (committee member), Di Lorenzo, Emanuele (committee member), Work, Paul A. (committee member).

Subjects/Keywords: Ocean current energy; Gulf Stream system; Resource assessment; Renewable energy sources; Ocean energy resources; Ocean wave power; Gulf Stream

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APA (6^th Edition):

Yang, X. (2013). Ocean current energy resource assessment for the United States. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/50352

Chicago Manual of Style (16^th Edition):

Yang, Xiufeng. “Ocean current energy resource assessment for the United States.” 2013. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/50352.

MLA Handbook (7^th Edition):

Yang, Xiufeng. “Ocean current energy resource assessment for the United States.” 2013. Web. 06 Mar 2021.

Vancouver:

Yang X. Ocean current energy resource assessment for the United States. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/50352.

Council of Science Editors:

Yang X. Ocean current energy resource assessment for the United States. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/50352

18. He, Jia. The nature and dynamics of rapid spring onset in the Arctic.

Degree: PhD, Earth and Atmospheric Sciences, 2017, Georgia Tech

URL: http://hdl.handle.net/1853/58225

► The Arctic atmospheric circulation undergoes a systematic rapid seasonal transition each year from late winter to early spring. At stratospheric and upper-tropospheric levels, this transition… (more)

▼ The Arctic atmospheric circulation undergoes a systematic rapid seasonal transition each year from late winter to early spring. At stratospheric and upper-tropospheric levels, this transition is dominated by an abrupt break down of the circumpolar vortex, which is related to upward planetary wave propagation. At the surface, this rapid spring onset transition is manifested by a dramatic increase in air temperature within a short time period. Very limited prior research efforts exist on the nature and physics of the rapid near-surface warming during Arctic spring onset (ASO). The current dissertation provides a thorough investigation of the abrupt transition of ASO events from the perspective of near-surface air temperature increase. In contrast to conventional measures of spring onset timing (often defined in terms of temperature thresholds related to regional phenology), our investigation views the abrupt transition as either an acceleration of air temperature increase or a transition from a steady winter state into a warming spring state. Thus, the first part of this dissertation provides a comprehensive exploration of three novel techniques for identifying ASO via the rapid increase in the 2-meter temperature (T2m). A 2-phase linear regression model is first employed to identify a transition from an approximately steady winter state to a warming spring state. The other two methods, the time derivative (d2T/dT) and radius of curvature (RoC) techniques, isolate periods of large T2m acceleration. Although all three approaches are largely successful in isolating the state transition associated with ASO, the RoC method is most effective in capturing the most rapid temperature increases and is this adopted in the remainder of the dissertation. It is determined that ASO timing exhibits strong interannual variability but with no significant long-term trend. The Arctic-mean composite evolution reveals T2m increases notably faster than the climatological seasonal trends, which indicates the likelihood of a dynamical driving mechanism. Spatial patterns of T2m changes occurring during ASO events are shown via a composite analysis. The rapid warming observed over Polar latitudes during ASO is roughly zonally symmetric while concomitant warming patterns observed further south distinguish North Siberia as the critical region (CR) in which robust warming occurs during most ASO events. Besides such common structures isolated in the composite, individual events demonstrate distinct primary warming structures that may occur outside the CR region. A hierarchical cluster analysis and a synoptic classification technique are applied to the individual ASO T2m change maps leading to the identification of four subsets of events distinguished by their primary regional warming signature. The synoptic behavior of ASO events is studied via a parallel composite analysis of sea level pressure (SLP) anomalies. This analysis reveals that, during ASO events, changes in the regional semi-permanent surface pressure features provide favorable… Advisors/Committee Members: Black, Robert X. (advisor), Deng, Yi (committee member), Belanger, James (committee member), Di Lorenzo, Emanuele (committee member), Robinson, Walter A. (committee member).

Subjects/Keywords: Spring onset; Arctic; Atmospheric dynamics; Synoptic eddy; Heat budget; Linear/nonlinear effect

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APA (6^th Edition):

He, J. (2017). The nature and dynamics of rapid spring onset in the Arctic. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58225

Chicago Manual of Style (16^th Edition):

He, Jia. “The nature and dynamics of rapid spring onset in the Arctic.” 2017. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/58225.

MLA Handbook (7^th Edition):

He, Jia. “The nature and dynamics of rapid spring onset in the Arctic.” 2017. Web. 06 Mar 2021.

Vancouver:

He J. The nature and dynamics of rapid spring onset in the Arctic. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/58225.

Council of Science Editors:

He J. The nature and dynamics of rapid spring onset in the Arctic. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/58225

19. Liguori, Giovanni. The role of meridional modes in pacific climate variability and change.

Degree: PhD, Earth and Atmospheric Sciences, 2018, Georgia Tech

URL: http://hdl.handle.net/1853/60760

► Decadal changes in Pacific climate affect long-term transitions in marine ecosystems and influence the statistics of weather including ocean and atmosphere extremes such as strong… (more)

▼ Decadal changes in Pacific climate affect long-term transitions in marine ecosystems and influence the statistics of weather including ocean and atmosphere extremes such as strong droughts, hurricanes and marine heatwaves. However, the physical mechanisms that generate decadal variance and how these dynamics will change under anthropogenic forcing remains unknown. This research utilizes statistical and physical modeling to investigate the role of extratropical El Niño-Southern Oscillation (ENSO) precursors such as Pacific Meridional Modes (PMMs) in driving Pacific decadal variability and change. In the first part of this dissertation, we develop an interpretative framework for the Pacific decadal variability (PDV) in which the stochastic variability of the North Pacific Oscillation (NPO) energizes the decadal-scale sea surface temperature anomalies (SSTa) variability in the extratropics through PMM dynamics. The spatial evolution of the North PMM (NPMM) dynamics injects decadal variance into the tropics where the SSTa anomalies are amplified by the feedback dynamics characteristic of the ENSO system along the equatorial plane. After the SSTa are amplified in the tropics, ENSO teleconnections project the decadal-scale variance onto the climate modes of the extratropics (e.g., Pacific Decadal Oscillation and North Pacific Gyre Oscillation). The coupling between extra-tropics/tropics/extra-tropics acts as a primary mechanism to redden (e.g. energize the low frequency) the Pacific climate spectrum by prolonging the memory of the system to stochastic perturbation from the ENSO precursors. In the second part of this dissertation, we use the interpretative framework to explore how the PDV has changed in the observational record, and how it is expected to change according to the Community Earth System Model (CESM) Large Ensemble (LENS) under the RCP8.5 radiative forcing scenario. After designing a set of diagnostics to measure the interaction dynamics between NPMM and ENSO, we found that the variance of the NPMM increases in a warming climate because of an intensification of the thermodynamic coupling of the ocean and atmosphere, also known as the wind-evaporations-SST (WES) feedback. This feedback is dependent on the mean background state (i.e., warming of SST generates a stronger response in evaporation) and modulates the amplitude of the growth of NPMM. In the third part of this dissertation, we investigate the relative importance of the NPMM and South PMM (SPMM) in ENSO and tropical Pacific decadal variability (TPDV) by performing experiments with the CESM model in which the NPMM and SPMM are selectively suppressed. We find that both meridional modes energize the tropical variance independently on different timescales. The absence of NPMM leads to a significant reduction of the tropical interannual variability (~35%), while the absence of the SPMM has no appreciable impact on ENSO but significantly reduces the TPDV (~30%). While the relative importance of the NPMM and SPMM may be model dependent, the stochastic… Advisors/Committee Members: Di Lorenzo, Emanuele (advisor), Ito, Takamitsu (committee member), Lynch-Stieglitz, Jean (committee member), He, Jie (committee member), Capotondi, Antonietta (committee member).

Subjects/Keywords: Pacific meridional modes; Pacific climate variability; Pacific decadal variability; El Niño–Southern oscillation; ENSO

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APA (6^th Edition):

Liguori, G. (2018). The role of meridional modes in pacific climate variability and change. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60760

Chicago Manual of Style (16^th Edition):

Liguori, Giovanni. “The role of meridional modes in pacific climate variability and change.” 2018. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/60760.

MLA Handbook (7^th Edition):

Liguori, Giovanni. “The role of meridional modes in pacific climate variability and change.” 2018. Web. 06 Mar 2021.

Vancouver:

Liguori G. The role of meridional modes in pacific climate variability and change. [Internet] [Doctoral dissertation]. Georgia Tech; 2018. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/60760.

Council of Science Editors:

Liguori G. The role of meridional modes in pacific climate variability and change. [Doctoral Dissertation]. Georgia Tech; 2018. Available from: http://hdl.handle.net/1853/60760

20. Furtado, Jason C. On the uncertainties and dynamics of Pacific interannual and decadal climate variability and climate change.

Degree: PhD, Earth and Atmospheric Sciences, 2010, Georgia Tech

URL: http://hdl.handle.net/1853/37302

► Tropical and extratropical Pacific decadal climate variability substantially impact physical and biological systems in the Pacific Ocean and strongly influence global climate through teleconnection patterns.… (more)

▼ Tropical and extratropical Pacific decadal climate variability substantially impact physical and biological systems in the Pacific Ocean and strongly influence global climate through teleconnection patterns. Current understanding of Pacific decadal climate variability centers around the El Niño-Southern Oscillation (ENSO), the Aleutian Low (AL), and the Pacific Decadal Oscillation (PDO). However, recent literature has highlighted the emerging roles of secondary modes of variability of the tropical and extratropical Pacific atmosphere and ocean in global climate change: the Central Pacific Warming (CPW) phenomenon, the North Pacific Oscillation (NPO), and the North Pacific Gyre Oscillation (NPGO). This work analyzes the statistics and uncertainties behind Pacific interannual and decadal-scale climate variability, and focuses on better understanding the roles of the CPW, NPO, and NPGO in the climate system. The study begins by examining the dynamics of the NPO and its role in Pacific interannual and decadal climate variability. Results illustrate that the individual poles of the NPO have relations at high frequencies, but only the southern node contains a deterministic low-frequency component, which is forced by tropical Pacific sea surface temperature (SST) variability, as shown with a modeling experiment. The NPO-induced variability by the tropical Pacific SST is then integrated by the underlying ocean surface to form the decadal-scale NPGO signal. Thus, a new link between the CPW, the NPO, and the NPGO is formed, expanding the current framework of Pacific decadal variability and its implications for weather and climate. The new framework of North Pacific decadal variability (NPDV) is then evaluated in 24 state-of-the-art coupled climate models. Results indicate that the models in general have difficulty reproducing the leading modes of NPDV in space and time, particularly the NPGO mode and its connection to the NPO. Furthermore, most models lack the proper connections between extratropical and tropical Pacific, for both the ENSO/AL/PDO and CPW/NPO/NPGO connections. Improvements in these teleconnections are thus needed to increase confidence in future climate projections. The last part of the dissertation explores further the importance of the CPW mode by comparing and contrasting two popular paleoclimate SST anomaly reconstruction methods used for tropical Indo-Pacific SSTs. The first method exploits the high correlation between the canonical ENSO mode and tropical precipitation; the second method uses a multi-regression model that exploits the multiple modes of covariability between tropical precipitation and SSTs, including the CPW mode. The multi-regression approach demonstrates higher skill throughout the tropical Indo-Pacific than the first approach, illustrating the importance of including the CPW phenomenon in understanding past climates. Advisors/Committee Members: Di Lorenzo, Emanuele (Committee Chair), Anderson, Bruce T. (Committee Member), Black, Robert X. (Committee Member), Cobb, Kim M. (Committee Member), Webster, Peter J. (Committee Member).

Subjects/Keywords: North Pacific; Atmospheric circulation; Coupled climate models; IPCC; North Pacific oscillation; Tropical Pacific; Climate change; ENSO; Climatology; Climatic changes; Tropospheric circulation

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APA (6^th Edition):

Furtado, J. C. (2010). On the uncertainties and dynamics of Pacific interannual and decadal climate variability and climate change. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/37302

Chicago Manual of Style (16^th Edition):

Furtado, Jason C. “On the uncertainties and dynamics of Pacific interannual and decadal climate variability and climate change.” 2010. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/37302.

MLA Handbook (7^th Edition):

Furtado, Jason C. “On the uncertainties and dynamics of Pacific interannual and decadal climate variability and climate change.” 2010. Web. 06 Mar 2021.

Vancouver:

Furtado JC. On the uncertainties and dynamics of Pacific interannual and decadal climate variability and climate change. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/37302.

Council of Science Editors:

Furtado JC. On the uncertainties and dynamics of Pacific interannual and decadal climate variability and climate change. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/37302

21. Ahn, Seongho. Wave energy resource characterization and classification for the United States & numerical simulation of coastal circulation near Point Sal, California.

Degree: PhD, Civil and Environmental Engineering, 2019, Georgia Tech

URL: http://hdl.handle.net/1853/61793

► This thesis contains two different topics: 1) Wave energy resource assessments, characterizations, and classiﬁcations for US coastal waters, 2) Numerical studies for three-dimensional circulation during… (more)

▼ This thesis contains two different topics: 1) Wave energy resource assessments, characterizations, and classiﬁcations for US coastal waters, 2) Numerical studies for three-dimensional circulation during coastal upwelling favorable winds on the inner shelf near Point Sal, California. Ocean waves are a largely abundant and untapped renewable source of energy with limited environmental impact and high energy density. Although ocean waves have signiﬁcant energy potential, the technology is in early stages of development due to high costs from lower conversion efﬁciencies as well as risks to operations, maintenance and survival. This study characterizes and classifies the wave energy resource by performing a comprehensive resource assessment of the wave energy for the US. The work for this portion includes three parts. The ﬁrst part focuses on describing the wave energy resource parameters or metrics for characterization, e.g., wave energy potential, dominant frequency, directional and temporal variability. Partitioned wave parameters generated from a 30-year WaveWatch III model hindcast are used to estimate the total wave energy potential as an annual available energy (AAE), which is a theoretical annual energy production per unit energy capture length without considering energy conversion efficiencies. The distribution of AAE by peak period, wave direction, month, and year are important attributes of the wave energy resource that can be quantified using simple summary metrics (indices), including spectral width, energy-weighted period, directionality coefficient, and direction of maximum directionally resolved AAE. These metrics are used to characterize long-term AAE trends, including inter-annual and seasonal variability. These temporal attributes of the wave energy resource can be parameterized by simple indices as measures of the variability, or constancy, of the resource, which can affect the capacity factor and annual energy production of a wave energy generation project. Geographical distributions of the AAE and these seven resource parameters delineate distinct wave climates and wave energy resource regions within US coastal waters, which supports regional energy planning and project development. The second part uses these parameters to delineate and describe eleven distinct US wave climates or wave energy resource regions based on the key attributes of the resource, wave energy potential, resource attributes, assessed from the part 1. In order to gain a high-level wave resource characteristics, marginal and joint energy distributions of the wave energy in terms of the peak period, wave direction and month, and corresponding resource parameters are provided. The frequency dependence, directional and temporal variability of the conditional wave energy resources at each region is characterized, e.g., the spectral width of the wave energy from a particular direction or month, directionality coefficient of the wave energy within a particular frequency or month. These assessments and characteristics of the conditional… Advisors/Committee Members: Haas, Kevin A. (advisor), Fritz, Hermann M. (committee member), Webster, Donald R. (committee member), Di Lorenzo, Emanuele (committee member), Neary, Vincent S. (committee member).

Subjects/Keywords: Wave energy resource characterization; Wave energy resource classification; Wave energy resource parameter; Coastal circulation; Coastal upwelling; Lagrangian tracking; Momentum analysis; ROMS simulation

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APA (6^th Edition):

Ahn, S. (2019). Wave energy resource characterization and classification for the United States & numerical simulation of coastal circulation near Point Sal, California. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/61793

Chicago Manual of Style (16^th Edition):

Ahn, Seongho. “Wave energy resource characterization and classification for the United States & numerical simulation of coastal circulation near Point Sal, California.” 2019. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/61793.

MLA Handbook (7^th Edition):

Ahn, Seongho. “Wave energy resource characterization and classification for the United States & numerical simulation of coastal circulation near Point Sal, California.” 2019. Web. 06 Mar 2021.

Vancouver:

Ahn S. Wave energy resource characterization and classification for the United States & numerical simulation of coastal circulation near Point Sal, California. [Internet] [Doctoral dissertation]. Georgia Tech; 2019. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/61793.

Council of Science Editors:

Ahn S. Wave energy resource characterization and classification for the United States & numerical simulation of coastal circulation near Point Sal, California. [Doctoral Dissertation]. Georgia Tech; 2019. Available from: http://hdl.handle.net/1853/61793

Georgia Tech

22. Widlansky, Matthew Johnson. Variability of the South Pacific Convergence Zone and its influence on the general atmospheric circulation.

Degree: MS, Earth and Atmospheric Sciences, 2007, Georgia Tech

URL: http://hdl.handle.net/1853/19766

► Intense atmospheric convection associated with the South Pacific Convergence Zone (SPCZ) significantly impacts basin-scale circulation patterns over the Pacific. We explore dynamical processes which foster… (more)

▼ Intense atmospheric convection associated with the South Pacific Convergence Zone (SPCZ) significantly impacts basin-scale circulation patterns over the Pacific. We explore dynamical processes which foster changes in convection along the convergence zone. These forcings include strong moisture convergence and accumulation of wave energy in the boundary layer, as well as dynamical instability associated with moderate cross-equatorial wind bursts. A focus is applied to observing the dominant modes of variability on synoptic to intraseasonal timescales using a combination of satellite observations and NCEP reanalysis data. Accumulation of energy, due to negative stretching deformation, occurs with both tropical and extratropical modes suggesting that the SPCZ is an artifact of wide ranging modes. Signals of the dominant modes (inferred from fields of outgoing longwave radiation: OLR) are isolated using bandpass filtering techniques, which are then mapped in space and time using Principal Components from Empirical Orthogonal Function analyses. Variability of convective systems in the SPCZ is found to be significantly correlated with changes in the regional Hadley Circulation and the Pacific Walker cell. This co-variability presents the possibility of important teleconnection routes between the tropical West and East Pacific, as well as with the mid-latitude regions of the Northern and Southern Hemispheres. We test these interaction hypotheses by developing composites of the circulation patterns using dates of maximum convection events (regions of minimum OLR) in the SPCZ. Intensities of the large-scale circulations are measured using observations of stream function mass fluxes. Results suggest that deep convection maxima (minima) are associated with an increase (decrease) in the Walker Circulation. It is also illustrated how off-equatorial convection anomalies in the subtropical portion of the SPCZ may induce changes to the Hadley Circulation. Interactions with the zonal (Walker) and meridional (Hadley) circulations appear to have important consequences on the ability for wave energy to propagate through the tropical Pacific atmosphere. Examples include Northern Hemisphere cross-equatorial teleconnections through the Westerly Wind Duct in the upper branch of the Walker circulation and Rossby wave trains in the SPCZ, which may be partially governed by characteristics of the regional Hadley circulation. Advisors/Committee Members: Webster, Peter (Committee Chair), Di Lorenzo, Emanuele (Committee Member), Fu, Rong (Committee Member).

Subjects/Keywords: Madden-Julian oscillation; Atmospheric circulation; Convection (Meteorology)

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APA (6^th Edition):

Widlansky, M. J. (2007). Variability of the South Pacific Convergence Zone and its influence on the general atmospheric circulation. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/19766

Chicago Manual of Style (16^th Edition):

Widlansky, Matthew Johnson. “Variability of the South Pacific Convergence Zone and its influence on the general atmospheric circulation.” 2007. Masters Thesis, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/19766.

MLA Handbook (7^th Edition):

Widlansky, Matthew Johnson. “Variability of the South Pacific Convergence Zone and its influence on the general atmospheric circulation.” 2007. Web. 06 Mar 2021.

Vancouver:

Widlansky MJ. Variability of the South Pacific Convergence Zone and its influence on the general atmospheric circulation. [Internet] [Masters thesis]. Georgia Tech; 2007. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/19766.

Council of Science Editors:

Widlansky MJ. Variability of the South Pacific Convergence Zone and its influence on the general atmospheric circulation. [Masters Thesis]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/19766

Georgia Tech

23. Ceballos, Lina Isabel. North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems.

Degree: MS, Earth and Atmospheric Sciences, 2008, Georgia Tech

URL: http://hdl.handle.net/1853/26552

► Recent studies have identified the North Pacific Gyre Oscillation (NPGO) as a decadal mode of climate variability that is linked to previously unexplained fluctuations of… (more)

Subjects/Keywords: NPGO; Kuroshio; Decadal variability; North Pacific; Ocean currents

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APA (6^th Edition):

Ceballos, L. I. (2008). North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/26552

Chicago Manual of Style (16^th Edition):

Ceballos, Lina Isabel. “North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems.” 2008. Masters Thesis, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/26552.

MLA Handbook (7^th Edition):

Ceballos, Lina Isabel. “North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems.” 2008. Web. 06 Mar 2021.

Vancouver:

Ceballos LI. North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems. [Internet] [Masters thesis]. Georgia Tech; 2008. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/26552.

Council of Science Editors:

Ceballos LI. North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems. [Masters Thesis]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/26552

Georgia Tech

24. Young, Carina Saxton. Decadal variability of the Pacific subtropical cells and equatorial sea surface temperature.

Degree: MS, Earth and Atmospheric Sciences, 2009, Georgia Tech

URL: http://hdl.handle.net/1853/31671

► This thesis investigates possible dynamical pathways through which variability in the extra-tropical Pacific Ocean influences decadal fluctuations of tropical Pacific sea surface temperatures (SST). Specifically,… (more)

Subjects/Keywords: Decadal variability; Subtropical cells; Ocean-atmosphere interaction; Marine meteorology; Ocean temperature

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APA (6^th Edition):

Young, C. S. (2009). Decadal variability of the Pacific subtropical cells and equatorial sea surface temperature. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/31671

Chicago Manual of Style (16^th Edition):

Young, Carina Saxton. “Decadal variability of the Pacific subtropical cells and equatorial sea surface temperature.” 2009. Masters Thesis, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/31671.

MLA Handbook (7^th Edition):

Young, Carina Saxton. “Decadal variability of the Pacific subtropical cells and equatorial sea surface temperature.” 2009. Web. 06 Mar 2021.

Vancouver:

Young CS. Decadal variability of the Pacific subtropical cells and equatorial sea surface temperature. [Internet] [Masters thesis]. Georgia Tech; 2009. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/31671.

Council of Science Editors:

Young CS. Decadal variability of the Pacific subtropical cells and equatorial sea surface temperature. [Masters Thesis]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/31671

Georgia Tech

25. Combes, Vincent. Upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary.

Degree: PhD, Earth and Atmospheric Sciences, 2010, Georgia Tech

URL: http://hdl.handle.net/1853/34814

► The upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary is explored using a high resolution ocean model for the last 60 years. Three… (more)

Subjects/Keywords: Eastern boundary current systems; Pacific; Large scale climate variability; Offshore transport; Upwelling; Mesoscale eddy; Ocean currents; Ocean currents Pacific Ocean; Upwelling (Oceanography) North Pacific Ocean; Climatic changes

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APA (6^th Edition):

Combes, V. (2010). Upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/34814

Chicago Manual of Style (16^th Edition):

Combes, Vincent. “Upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary.” 2010. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/34814.

MLA Handbook (7^th Edition):

Combes, Vincent. “Upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary.” 2010. Web. 06 Mar 2021.

Vancouver:

Combes V. Upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/34814.

Council of Science Editors:

Combes V. Upwelling and cross-shelf transport dynamics along the Pacific Eastern Boundary. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/34814

Georgia Tech

26. Nurhati, Intan Suci. Coral records of central tropical Pacific sea-surface temperature and salinity variability over the 20th century.

Degree: PhD, Earth and Atmospheric Sciences, 2010, Georgia Tech

URL: http://hdl.handle.net/1853/34775

► Accurate forecasts of future regional temperature and rainfall patterns in many regions largely depend on characterizing anthropogenic trends in tropical Pacific climate. However, strong interannual… (more)

▼ Accurate forecasts of future regional temperature and rainfall patterns in many regions largely depend on characterizing anthropogenic trends in tropical Pacific climate. However, strong interannual to decadal-scale tropical Pacific climate variability, combined with sparse spatial and temporal coverage of instrumental climate datasets in this region, have obscured potential anthropogenic climate signals in the tropical Pacific. In this dissertation, I present sea-surface temperature (SST) and salinity proxy records that span over the 20th century using living corals from several islands in the central tropical Pacific. I reconstruct the SST proxy records via coral Sr/Ca, that are combined with coral oxygen isotopic (d18O) records to quantify changes in seawater d18O (hereafter d18Osw) as a proxy for salinity. Chapter 2 investigates the spatial and temporal character of SST and d18Osw-based salinity trends in the central tropical Pacific from 1972-1998, as revealed by corals from Palmyra (6ºN, 162ºW), Fanning (4ºN, 159ºW) and Christmas (2ºN, 157ºW) Islands. The late 20th century SST proxy records exhibit warming trends that are larger towards the equator, in line with a weakening of equatorial Pacific upwelling over this period. Freshening trends revealed by the salinity proxy records are larger at those sites most affected by the Inter-Tropical Convergence Zone (ITCZ), suggesting a strengthening and/or an equatorward shift of the ITCZ. Taken together, the late 20th century SST and salinity proxy records document warming and freshening trends that are consistent with a trend towards a weakened tropical Pacific zonal SST gradient under continued anthropogenic forcing. Chapter 3 characterizes the signatures of natural and anthropogenic variability in central tropical Pacific SST and d18Osw-based salinity over the course of 20th century using century-long coral proxy records from Palmyra. On interannual timescales, the SST proxy record from Palmyra tracks El Niño-Southern Oscillation (ENSO) variability. The salinity proxy record tracks eastern Pacific-centered ENSO events but is poorly correlated to central Pacific-centered ENSO events - the result of profound differences in precipitation and ocean advection that occur during the two types of ENSO. On decadal timescales, the coral SST proxy record is significantly correlated to the North Pacific Gyre Oscillation (NPGO), suggesting that strong dynamical links exist between the central tropical Pacific and the North Pacific. The salinity proxy record is significantly correlated to the Pacific Decadal Oscillation (PDO), but poorly correlated to the NPGO, suggesting that, as was the case with ENSO, these two modes of Pacific decadal climate variability have unique impacts on equatorial precipitation and ocean advection. However, the most striking feature of the salinity proxy record is a prominent late 20th century freshening trend that is likely related to anthropogenic climate change. Taken together, the coral data provide key constraints on tropical Pacific… Advisors/Committee Members: Cobb, Kim (Committee Chair), Bracco, Annalisa (Committee Member), Di Lorenzo, Emanuele (Committee Member), Lynch-Stieglitz, Jean (Committee Member), Webster, Peter (Committee Member).

Subjects/Keywords: Tropical Pacific climate; Sr/Ca; Global warming; ENSO; Coral; Hydrological changes; Climatic changes; Climatic changes Research

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APA (6^th Edition):

Nurhati, I. S. (2010). Coral records of central tropical Pacific sea-surface temperature and salinity variability over the 20th century. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/34775

Chicago Manual of Style (16^th Edition):

Nurhati, Intan Suci. “Coral records of central tropical Pacific sea-surface temperature and salinity variability over the 20th century.” 2010. Doctoral Dissertation, Georgia Tech. Accessed March 06, 2021. http://hdl.handle.net/1853/34775.

MLA Handbook (7^th Edition):

Nurhati, Intan Suci. “Coral records of central tropical Pacific sea-surface temperature and salinity variability over the 20th century.” 2010. Web. 06 Mar 2021.

Vancouver:

Nurhati IS. Coral records of central tropical Pacific sea-surface temperature and salinity variability over the 20th century. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1853/34775.

Council of Science Editors:

Nurhati IS. Coral records of central tropical Pacific sea-surface temperature and salinity variability over the 20th century. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/34775

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