+publisher:"Texas A&M University" +contributor:("Lin, Xiaopei")

Texas A&M University

1. Liu, Xue. Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics.

Degree: PhD, Oceanography, 2018, Texas A&M University

URL: http://hdl.handle.net/1969.1/173790

► As resolution of observations and climate models continues to improve, it has become increasingly evident that mesoscale eddies – a ubiquitous feature of the world… (more)

▼ As resolution of observations and climate models continues to improve, it has become increasingly evident that mesoscale eddies – a ubiquitous feature of the world ocean – can interact with the overlying atmosphere, potentially affecting large-scale atmospheric and oceanic circulation and climate. Improving our understanding of this ocean mesoscale eddy – atmosphere (OME-A) interaction has important implications for improving climate simulations and predictions. This dissertation contributes to this understanding by focusing on two elements of OME-A interaction. The first element deals with the influence of ocean mesoscale eddies on rainfall. By comparing three different satellite-derived rainfall datasets, we examined the robustness of the rainfall response to ocean eddy induced mesoscale sea-surface temperature anomalies (SSTAs). The three datasets are the Tropical Rainfall Measurement Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA), NOAA Climate Prediction Center (CPC) Morphing Technique (CMORPH) global precipitation and newly available Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) that is based on the latest remote sensing technology with finer spatial and temporal resolution. The results show that 1) all datasets exhibit a similar rainfall response to ocean eddies, but the amplitude of the rainfall response varies among datasets with IMERG producing the strongest and most coherent rainfall response, despite the weakest time-mean rainfall, 2) eddy-induced precipitation response is significantly stronger in winter than in summer and over warm eddies than cold eddies, and these asymmetries in rainfall response is more robust in IMERG than in the other two datasets. Documenting and analyzing these asymmetric rainfall responses are important for understanding the potential role of ocean eddies in forcing the large-scale atmospheric circulation and climate. The second element examines the effect of OME-A interaction on ocean eddy wind power that plays a vital role in dissipating eddy kinetic energy (EKE). By using a scaling analysis and analyzing eddy-resolving coupled climate model simulations, we not only quantify the impact of OME-A interaction on eddy wind power, but also provide a mechanistic understanding of the underlying process. Results show that the impact of OME-A feedback on eddy wind power, albeit smaller than that due to ocean current feedback, is significant and amounts to about 30-40% reduction of the value without OME-A interaction. Therefore, in the absence of OME-A interaction, eddy wind power is significantly overestimated, thus providing a too-strong sink for EKE. Advisors/Committee Members: Chang, Ping (advisor), Lin, Xiaopei (advisor), Saravanan, Ramalingam (committee member), Szunyogh, Istvan (committee member).

Subjects/Keywords: Oceanic Mesoscale Eddies; Air-Sea Interaction; Rainfall; Wind Power

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APA (6^th Edition):

Liu, X. (2018). Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/173790

Chicago Manual of Style (16^th Edition):

Liu, Xue. “Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics.” 2018. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/173790.

MLA Handbook (7^th Edition):

Liu, Xue. “Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics.” 2018. Web. 18 Jan 2021.

Vancouver:

Liu X. Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics. [Internet] [Doctoral dissertation]. Texas A&M University; 2018. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/173790.

Council of Science Editors:

Liu X. Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics. [Doctoral Dissertation]. Texas A&M University; 2018. Available from: http://hdl.handle.net/1969.1/173790

Texas A&M University

2. Ma, Xiaohui. A Study of Frontal-Scale Air-Sea Interaction in Midlatitude Western Boundary Current Regimes.

Degree: PhD, Oceanography, 2014, Texas A&M University

URL: http://hdl.handle.net/1969.1/153332

► Frontal-scale air-sea interactions during boreal winter season in midlatitude western boundary current (WBC) regimes, including the Kuroshio Extension Region (KER) and Gulf Stream Region (GSR),… (more)

▼ Frontal-scale air-sea interactions during boreal winter season in midlatitude western boundary current (WBC) regimes, including the Kuroshio Extension Region (KER) and Gulf Stream Region (GSR), are investigated using both observational (reanalysis) data and regional climate model simulations. The focus of the study is on the KER in the North Pacific. Extreme flux events associated with cold air outbreaks (CAOs) in boreal winter in the KER of the Northwestern Pacific and the GSR of the Northwestern Atlantic are analyzed and compared based on different reanalysis datasets. A close relationship between extreme flux events over the KER/GSR and the Pacific Decadal Oscillation (PDO)/East Atlantic Pattern (EAP) is found with more frequent occurrence of extreme flux events during a positive PDO/EAP phase. Furthermore, the PDO/EAP may be explained as the rectified effects of the synoptic winter storms accompanied with the extreme flux events. A lag-composite analysis shows that event-day storms tend to have a preferred southeastward propagation path, potentially contributing to the southward shift of the storm track over the eastern North Pacific/Atlantic basin during positive PDO/EAP phase. Using an atmosphere-only model (Weather Research Forecasting, WRF) at 27 km, two ensembles of simulations were conducted for boreal winter season in the North Pacific to study the possible local and remote influence of meso-scale oceanic eddies in the KER on the atmosphere. Filtering out meso-scale oceanic eddies results in a deep tropospheric response along and downstream of the KER, including a significant decrease (increase) in winter season mean rainfall along the KER (west coast of US), a reduction of storm growth rate in the KER, and a southward shift of the jet stream and North Pacific storm track in the eastern North Pacific. A mechanism invoking moist baroclinic instability is proposed to link meso-scale oceanic eddies in the KER to largescale atmospheric circulations and weather patterns in the North Pacific. Using a high-resolution (9 km) coupled regional climate model (CRCM), three sets of experiment were performed to investigate potential feedbacks of ocean-eddy induced atmospheric response to the ocean. Filtering out meso-scale oceanic eddies during coupling causes a surface warming and a weak Kuroshio strength. Advisors/Committee Members: Chang, Ping (advisor), Lin, Xiaopei (committee member), Saravanan, R. (committee member), Hetland, Robert D. (committee member).

Subjects/Keywords: Frontal-Scale; Meso-Scale; Air-Sea Interaction; Kuroshio Extension; Gulf Stream; Storm Track; Extreme Flux Event; Eddy

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APA (6^th Edition):

Ma, X. (2014). A Study of Frontal-Scale Air-Sea Interaction in Midlatitude Western Boundary Current Regimes. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/153332

Chicago Manual of Style (16^th Edition):

Ma, Xiaohui. “A Study of Frontal-Scale Air-Sea Interaction in Midlatitude Western Boundary Current Regimes.” 2014. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/153332.

MLA Handbook (7^th Edition):

Ma, Xiaohui. “A Study of Frontal-Scale Air-Sea Interaction in Midlatitude Western Boundary Current Regimes.” 2014. Web. 18 Jan 2021.

Vancouver:

Ma X. A Study of Frontal-Scale Air-Sea Interaction in Midlatitude Western Boundary Current Regimes. [Internet] [Doctoral dissertation]. Texas A&M University; 2014. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/153332.

Council of Science Editors:

Ma X. A Study of Frontal-Scale Air-Sea Interaction in Midlatitude Western Boundary Current Regimes. [Doctoral Dissertation]. Texas A&M University; 2014. Available from: http://hdl.handle.net/1969.1/153332

Texas A&M University

3. Xu, Zhao. Oceanic Origins of Southwest Tropical Atlantic Biases.

Degree: PhD, Oceanography, 2013, Texas A&M University

URL: http://hdl.handle.net/1969.1/149583

► The SST bias in the tropical Atlantic exists in the early to latest generation of coupled general circulation models. The maximum bias is not on… (more)

▼ The SST bias in the tropical Atlantic exists in the early to latest generation of coupled general circulation models. The maximum bias is not on the equator but at 16°S, the cause of which has not been thoroughly studied. Newly released CMIP5 models provide a useful tool to investigate the contributions of different physical processes to the SST bias in this area in the coupled system. We tested three existing mechanisms and found that: 1) there is no significant relationship between the SST bias and surface heat flux bias; 2) deficient coastal upwelling is a contributing but not the sole source of the bias; and 3) the SST bias is correlated with temperature biases in the upstream equatorial region. The Angola-Benguela front is displaced southward by more than 10° in latitude in many CIMP5 models. Due to the huge temperature contrasts on two sides of the front, such a frontal displacement generates a very strong SST bias. The correlation between the SST bias and frontal location error in this region is significant at the 99% level, demonstrating that the SST bias in coupled GCMs is attributable to the models’ inability to reproduce a realistic position of the front and the consequent erroneous advection by the southward Angola current. This is due to both errors in the simulated surface wind field and systematic errors in ocean models. Ocean reanalysis datasets and a high-resolution regional model simulation suffer a similar pattern of SST biases. Although they produce a more realistic ocean circulation than coarser resolution simulations and alleviate some of the severe SST bias near the front, a warm bias overlies on a northward current to the south of the front, which actually comes from the north of the front through a subsurface passage. We identify a strong subsurface temperature bias caused by a too-deep and diffused simulated thermocline along the coast of Angola, originating from the equatorial thermocline, advected by the Angola Current and an undercurrent beneath the Benguela current, and then brought to the surface by the coastal upwelling along the Benguela coast, contributing to the warm SST bias south of the front. Advisors/Committee Members: Chang, Ping (advisor), Lin, Xiaopei (advisor), Saravanan, R. (committee member), Hetland, Robert (committee member).

Subjects/Keywords: GCM; Southeast Tropical Atlantic; SST bias; oceanic current

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

APA (6^th Edition):

Xu, Z. (2013). Oceanic Origins of Southwest Tropical Atlantic Biases. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/149583

Chicago Manual of Style (16^th Edition):

Xu, Zhao. “Oceanic Origins of Southwest Tropical Atlantic Biases.” 2013. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/149583.

MLA Handbook (7^th Edition):

Xu, Zhao. “Oceanic Origins of Southwest Tropical Atlantic Biases.” 2013. Web. 18 Jan 2021.

Vancouver:

Xu Z. Oceanic Origins of Southwest Tropical Atlantic Biases. [Internet] [Doctoral dissertation]. Texas A&M University; 2013. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/149583.

Council of Science Editors:

Xu Z. Oceanic Origins of Southwest Tropical Atlantic Biases. [Doctoral Dissertation]. Texas A&M University; 2013. Available from: http://hdl.handle.net/1969.1/149583

Texas A&M University

4. Liu, Xue. Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics.

Degree: PhD, Oceanography, 2018, Texas A&M University

URL: http://hdl.handle.net/1969.1/173883

► As resolution of observations and climate models continues to improve, it has become increasingly evident that mesoscale eddies – a ubiquitous feature of the world… (more)

▼ As resolution of observations and climate models continues to improve, it has become increasingly evident that mesoscale eddies – a ubiquitous feature of the world ocean – can interact with the overlying atmosphere, potentially affecting large-scale atmospheric and oceanic circulation and climate. Improving our understanding of this ocean mesoscale eddy – atmosphere (OME-A) interaction has important implications for improving climate simulations and predictions. This dissertation contributes to this understanding by focusing on two elements of OME-A interaction. The first element deals with the influence of ocean mesoscale eddies on rainfall. By comparing three different satellite-derived rainfall datasets, we examined the robustness of the rainfall response to ocean eddy induced mesoscale sea-surface temperature anomalies (SSTAs). The three datasets are the Tropical Rainfall Measurement Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA), NOAA Climate Prediction Center (CPC) Morphing Technique (CMORPH) global precipitation and newly available Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) that is based on the latest remote sensing technology with finer spatial and temporal resolution. The results show that 1) all datasets exhibit a similar rainfall response to ocean eddies, but the amplitude of the rainfall response varies among datasets with IMERG producing the strongest and most coherent rainfall response, despite the weakest time-mean rainfall, 2) eddy-induced precipitation response is significantly stronger in winter than in summer and over warm eddies than cold eddies, and these asymmetries in rainfall response is more robust in IMERG than in the other two datasets. Documenting and analyzing these asymmetric rainfall responses are important for understanding the potential role of ocean eddies in forcing the large-scale atmospheric circulation and climate. The second element examines the effect of OME-A interaction on ocean eddy wind power that plays a vital role in dissipating eddy kinetic energy (EKE). By using a scaling analysis and analyzing eddy-resolving coupled climate model simulations, we not only quantify the impact of OME-A interaction on eddy wind power, but also provide a mechanistic understanding of the underlying process. Results show that the impact of OME-A feedback on eddy wind power, albeit smaller than that due to ocean current feedback, is significant and amounts to about 30-40% reduction of the value without OME-A interaction. Therefore, in the absence of OME-A interaction, eddy wind power is significantly overestimated, thus providing a too-strong sink for EKE. Advisors/Committee Members: Chang, Ping (advisor), Lin, Xiaopei (advisor), Saravanan, Ramalingam (committee member), Szunyogh, Istvan (committee member).

Subjects/Keywords: Oceanic Mesoscale Eddies; Air-Sea Interaction; Rainfall; Wind Power

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APA (6^th Edition):

Liu, X. (2018). Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/173883

Chicago Manual of Style (16^th Edition):

Liu, Xue. “Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics.” 2018. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/173883.

MLA Handbook (7^th Edition):

Liu, Xue. “Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics.” 2018. Web. 18 Jan 2021.

Vancouver:

Liu X. Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics. [Internet] [Doctoral dissertation]. Texas A&M University; 2018. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/173883.

Council of Science Editors:

Liu X. Elements of Ocean Mesoscale Eddy-Atmosphere Interactions in Extratropics. [Doctoral Dissertation]. Texas A&M University; 2018. Available from: http://hdl.handle.net/1969.1/173883

Texas A&M University

5. Li, Pin. Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region.

Degree: PhD, Oceanography, 2018, Texas A&M University

URL: http://hdl.handle.net/1969.1/174045

► In current-generation climate models, the warm sea surface temperature (SST) bias problem is most commonly seen in the eastern boundary upwelling systems (EBUSs), and is… (more)

▼ In current-generation climate models, the warm sea surface temperature (SST) bias problem is most commonly seen in the eastern boundary upwelling systems (EBUSs), and is most pronounced and most prevalent in the Southeast Tropical Atlantic (SETA) region. Previous studies have shown that the coastal wind pattern in this region, namely the Benguela low-level coastal jet (BLLCJ), is of great importance for the generation of such SST bias, because the coastal ocean circulation is highly sensitive to the off-shore structure of the wind forcing. Using an eddy-resolving regional ocean model, we first show that the SST bias in the region is drastically reduced when forced with simulated winds from a high-resolution regional atmospheric model. We subsequently demonstrate that the SST bias is highly sensitive to the spatial structure of the wind stress curl (WSC). We also find that when the ocean model is forced by a realistic high-resolution wind, the ocean model resolution is of second order importance in reducing the SST bias. Furthermore, we use a double-time average (DTA) method to quantify the contribution of heat budget terms, and show that the horizontal advection contributes significantly to the SST bias. We then examined the question: To what extent do ocean eddies play a role in balancing the coastal ocean heat budget and affecting the SST bias? By experimenting with a submesoscale eddy-permitting regional ocean model, we show that ocean eddies in the Southeast Tropical Atlantic region are most energetic near the Angola-Benguela Front (ABF), the Lüderitz Upwelling Cell region and the Agulhas Leakage region. In these three regions, comparisons between the two model simulations forced with the low- vs high-resolution winds suggest that the SST bias is mainly generated by mean flow advection with ocean eddies playing the role of counteracting the warming induced by the mean flow advection in this region. Advisors/Committee Members: Chang, Ping (advisor), Lin, Xiaopei (committee member), Hetland, Robert (committee member), Stössel, Achim (committee member), Saravanan, Ramalingam (committee member).

Subjects/Keywords: Climate model; SST bias; southeast tropical Atlantic; Benguela low-level coastal jet; Angola Current; Benguela Current; upwelling; eddy advection

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APA (6^th Edition):

Li, P. (2018). Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/174045

Chicago Manual of Style (16^th Edition):

Li, Pin. “Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region.” 2018. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/174045.

MLA Handbook (7^th Edition):

Li, Pin. “Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region.” 2018. Web. 18 Jan 2021.

Vancouver:

Li P. Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region. [Internet] [Doctoral dissertation]. Texas A&M University; 2018. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/174045.

Council of Science Editors:

Li P. Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region. [Doctoral Dissertation]. Texas A&M University; 2018. Available from: http://hdl.handle.net/1969.1/174045

Texas A&M University

6. Li, Bo. Stratification Limited Vertical Ventilation: Effects of Water-column Stabilities on the Formation of Hypoxia on the Texas-Louisiana Shelf.

Degree: PhD, Oceanography, 2013, Texas A&M University

URL: http://hdl.handle.net/1969.1/151781

► I examine the vertical structure of water-column stability and its relationship to near-bottom dissolved oxygen (DO) concentration in the hypoxic zone of the Texas-Louisiana Shelf… (more)

▼ I examine the vertical structure of water-column stability and its relationship to near-bottom dissolved oxygen (DO) concentration in the hypoxic zone of the Texas-Louisiana Shelf using observations collected between year 2003 and 2009. A threshold of N=0.06 s^(-1) is defined to represent the lower limit of the stratification strength for existence of hypoxia. An idealized one-dimensional model with parameterized respiration was applied to study stratification structure associated hypoxia development. The simulation results showed that the bottom mixed layer could enhance the bottom DO depletion and favor the development of hypoxia. A secondary pycnocline was above the bottom mixed layer and performed as a barrier to inhibit the vertical extension of hypoxia and vertical DO flux through it. Furthermore, I discussed possible mechanisms causing bottom mixed layer on the continental shelf, including return flow caused by upwelling, inertial motions and tidal currents. Diapycnal diffusivity was calculated using hourly continuous observations in the hypoxic zone on the Texas-Louisiana Shelf. The estimated time-averaged diapycnal diffusivity was 3 × 10^(-6) m^(2) s^(-1) along the pycnocline. Averaged cross-pycnocline vertical dissolved oxygen flux was calculated in a two-layer stratified water column with subpycnocline hypoxia. The estimated cross-pycnocline dissolved oxygen flux was 156.8 ml l^(-1) d^(-1), which resupplied 45% dissolved oxygen consumption in the subpycnocline layer. Continuous observations at the South Marsh Mooring showed the first highly resolved observations of short timescale fluctuations in the DO concentrations in the seasonal hypoxic waters on the Louisiana Shelf. There were 19 ventilation events in the DO records with a time period of 1~3 days. Analysis of the time series of DO, salinity and temperature at different levels of the mooring demonstrated that most of the ventilation-intervals were associated with increased vertical mixing, which contributed 58% of the total ventilation intervals. It suggests that mixing events dominate the ventilation-intervals. Comparison of the time derivative of the low-frequency part of the near-bottom DO concentration to observations of the wind and significant wave height suggests that local wind events are responsible for the enhanced vertical mixing. Advisors/Committee Members: DiMarco, Steven F. (advisor), Hetland, Robert D. (committee member), Jackson, George A. (committee member), Lin, Xiaopei (committee member), Quigg, Antonietta S. (committee member).

Subjects/Keywords: hypoxia; stratification

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APA (6^th Edition):

Li, B. (2013). Stratification Limited Vertical Ventilation: Effects of Water-column Stabilities on the Formation of Hypoxia on the Texas-Louisiana Shelf. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/151781

Chicago Manual of Style (16^th Edition):

Li, Bo. “Stratification Limited Vertical Ventilation: Effects of Water-column Stabilities on the Formation of Hypoxia on the Texas-Louisiana Shelf.” 2013. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/151781.

MLA Handbook (7^th Edition):

Li, Bo. “Stratification Limited Vertical Ventilation: Effects of Water-column Stabilities on the Formation of Hypoxia on the Texas-Louisiana Shelf.” 2013. Web. 18 Jan 2021.

Vancouver:

Li B. Stratification Limited Vertical Ventilation: Effects of Water-column Stabilities on the Formation of Hypoxia on the Texas-Louisiana Shelf. [Internet] [Doctoral dissertation]. Texas A&M University; 2013. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/151781.

Council of Science Editors:

Li B. Stratification Limited Vertical Ventilation: Effects of Water-column Stabilities on the Formation of Hypoxia on the Texas-Louisiana Shelf. [Doctoral Dissertation]. Texas A&M University; 2013. Available from: http://hdl.handle.net/1969.1/151781

Texas A&M University

7. Zhang, Wenxia. Stratification Prediction and Bottom Boundary Layer Dynamics over the Texas-Louisiana Continental Shelf.

Degree: PhD, Oceanography, 2015, Texas A&M University

URL: http://hdl.handle.net/1969.1/155027

► The bottom boundary layer is an unstratified thin layer above the sea floor, separated from the more strongly stratified interior. Formation of a thin bottom… (more)

▼ The bottom boundary layer is an unstratified thin layer above the sea floor, separated from the more strongly stratified interior. Formation of a thin bottom boundary layer in the presence of stratification and a sloping bottom is common, and well characterized by theory. This thin layer is an important source of mixing over the continental shelf, and it plays a fundamental role in several continental shelf physical and biogeochemical processes, such as buoyancy advection, bottom material transport and hypoxia formation. In this research, Both observations and numerical models are used to study models' ability of reproducing observed stratification and bottom boundary layer dynamics over the Texas-Louisiana shelf. Simulated vertical stratification, which is also representing the vertical density structure, was first evaluated since it directly controls the bottom boundary layer structure itself and is important for other bottom boundary layer dynamics. A new metric, the histogram of vertical stratification, is introduced in this research to evaluate the models' ability of reproducing observed stratification in a bulk sense. The improvement in model performance is attributed to the finer horizontal and temporal resolutions of a model, while factors like open boundary conditions and vertical resolutions are modified without any improvement in the ability of the model to simulate observed stratification. Towed, undulating CTD profiles collected during Mechanisms Controlling Hypoxia (MCH) program also detected mid-water oxygen minima in many transects. These intrusions are connected with the bottom boundary layer and follows the pycnocline seaward as a mid-water column tongue of low oxygen. We calculate convergence within the bottom boundary layer relative to density surfaces using the simulated results; there is a convergence in the bottom boundary layer at the location where the pycnocline intercepts the bottom, creating an injection of bottom boundary layer water into the pycnocline. Convergent flow at the bottom, relative to isopycnal surfaces, is strongest in the density classes associated with the oxygen minimum layer. We believe these mid-water oxygen minima are actually intrusions of low oxygen protruding from the bottom boundary layer via buoyancy advection driven convergence, following the main pycnocline. Advisors/Committee Members: Hetland, Robert D. (advisor), Lin, Xiaopei (advisor), DiMarco, Steven F. (committee member), Socolofsky, Scott A. (committee member).

Subjects/Keywords: stratification; bottom boundary layer

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APA (6^th Edition):

Zhang, W. (2015). Stratification Prediction and Bottom Boundary Layer Dynamics over the Texas-Louisiana Continental Shelf. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/155027

Chicago Manual of Style (16^th Edition):

Zhang, Wenxia. “Stratification Prediction and Bottom Boundary Layer Dynamics over the Texas-Louisiana Continental Shelf.” 2015. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/155027.

MLA Handbook (7^th Edition):

Zhang, Wenxia. “Stratification Prediction and Bottom Boundary Layer Dynamics over the Texas-Louisiana Continental Shelf.” 2015. Web. 18 Jan 2021.

Vancouver:

Zhang W. Stratification Prediction and Bottom Boundary Layer Dynamics over the Texas-Louisiana Continental Shelf. [Internet] [Doctoral dissertation]. Texas A&M University; 2015. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/155027.

Council of Science Editors:

Zhang W. Stratification Prediction and Bottom Boundary Layer Dynamics over the Texas-Louisiana Continental Shelf. [Doctoral Dissertation]. Texas A&M University; 2015. Available from: http://hdl.handle.net/1969.1/155027

8. Zhang, Zhaoru. Wind- and Buoyancy-modulated Along-shore Circulation over the Texas-Louisiana Shelf.

Degree: PhD, Oceanography, 2013, Texas A&M University

URL: http://hdl.handle.net/1969.1/151180

► Numerical experiments are used to study the wind- and buoyancy-modulated along-shore circulation over the Texas-Louisiana continental shelf inshore of 50-m water depth. Most attention is… (more)

▼ Numerical experiments are used to study the wind- and buoyancy-modulated along-shore circulation over the Texas-Louisiana continental shelf inshore of 50-m water depth. Most attention is given to circulation in the non-summer flow regime. A major focus of this study is on a unique along-shore flow phenomenon – convergent along- shore flows, which is controlled jointly by wind forcing and buoyancy fluxes from the Mississippi-Atchafalaya river plume. The second problem addresses the forcing effect of buoyancy on the general along-shore circulation pattern over the shelf in non-summer. The convergent along-shore flows are characterized by down-coast flow from the northern shelf encountering up-coast flow from the southern shelf. This phenomenon is explored for both weather band and seasonal timescales. For the weather band, investigations are focused on non-summer convergent events. The formation of convergent flows is primarily caused by along-coast variation in the along-shore component of wind forcing, which in turn is due to the curvature of the Texas-Louisiana coastline. In general, along-shore currents are well correlated with along-shore winds. However, the points of convergence of currents and winds are not co-located; but rather, points of convergence of currents typically occur down-coast of points of convergence of wind. This offset is mainly caused by buoyancy forcing that forces down-coast currents and drives the point of convergence of currents further down-coast. No specific temporal shift pattern is found for the weather-band convergence, whereas monthly monthly mean convergence exhibits a prominent pattern of seasonal along-coast migration. Buoyancy forcing in the non-summer along-shore flow is investigated in detail in the second part of this study. During non-summer, under down-coast wind forcing, the Mississippi-Atchafalaya river plume exhibits a bottom-advected pattern, for which isopycnals strongly interact with the sea floor. The density front is fairly wide and spans nearly across the entire shelf. Within the front, vertical shear of the alongshore flow is in thermal wind balance with the cross-shore density gradient, and the shear causes a slight reversal of alongshore flow near the bottom. An alongshore flow estimated by the thermal wind relation, along with an assumption of zero bottom reference velocity, agrees well with the actual alongshore flow. Advisors/Committee Members: Hetland, Robert D. (advisor), Lin, Xiaopei (advisor), Chang, Ping (committee member), Stossel, Achim (committee member), Szunyogh, Istvan (committee member).

Subjects/Keywords: Texas-Louisiana shelf; alongshore circulation; wind; buoyancy

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APA (6^th Edition):

Zhang, Z. (2013). Wind- and Buoyancy-modulated Along-shore Circulation over the Texas-Louisiana Shelf. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/151180

Chicago Manual of Style (16^th Edition):

Zhang, Zhaoru. “Wind- and Buoyancy-modulated Along-shore Circulation over the Texas-Louisiana Shelf.” 2013. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/151180.

MLA Handbook (7^th Edition):

Zhang, Zhaoru. “Wind- and Buoyancy-modulated Along-shore Circulation over the Texas-Louisiana Shelf.” 2013. Web. 18 Jan 2021.

Vancouver:

Zhang Z. Wind- and Buoyancy-modulated Along-shore Circulation over the Texas-Louisiana Shelf. [Internet] [Doctoral dissertation]. Texas A&M University; 2013. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/151180.

Council of Science Editors:

Zhang Z. Wind- and Buoyancy-modulated Along-shore Circulation over the Texas-Louisiana Shelf. [Doctoral Dissertation]. Texas A&M University; 2013. Available from: http://hdl.handle.net/1969.1/151180

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