Material Type  

 학위논문

 

0016934927

Date and Time of Latest Transaction  

20240214101832

ISBN  

9798380333917

DDC  

551.46

Author  

Zheng, Zhihua.

Title/Author  

Impacts of Surface Waves on Turbulence in Ocean Surface Boundary Layers: Observations and Scaling - [electronic resource]

Publish Info  

[S.l.] : University of Washington., 2023

Publish Info  

Ann Arbor : ProQuest Dissertations & Theses, 2023

Material Info  

1 online resource(140 p.)

General Note  

Source: Dissertations Abstracts International, Volume: 85-03, Section: B.

General Note  

Advisor: Harcourt, Ramsey R.

학위논문주기  

Thesis (Ph.D.)--University of Washington, 2023.

Restrictions on Access Note  

This item must not be sold to any third party vendors.

Abstracts/Etc  

요약Turbulence in the ocean surface boundary layer (OSBL) drives mixing, brings nutrients from depth, and mediates the air-sea exchange of heat, momentum, and gases and is thus a key player in the weather and climate system. The current generation of global climate models typically have large errors in the predictions of surface ocean properties, such as the mixed layer depth and the sea surface temperature. These errors are potentially caused by an implicit, or incomplete representation of surface wave effects in the OSBL mixing parameterization that is largely based on turbulence scaling relations for the atmospheric boundary layer (ABL) over land. Turbulence driven by the breaking surface waves and Langmuir circulations arising from the interaction between current and surface wave Stokes drift are the two major mechanisms by which the surface waves contribute to vertical mixing. Although progress has been made in quantifying some of their effects on vertical mixing under certain forcing conditions, our understanding of their roles in the vertical mixing process is still far from complete. To address knowledge gaps about the surface wave impacts on turbulence and vertical mixing, this study makes use of measurements collected from a number of locations with distinct forcing conditions and examines them from a scaling perspective. The research is presented in two parts. Part I takes measurements of temperature profile to infer the vertical mixing of heat while part II concentrates on vertical velocity measurements to diagnose the turbulence intensity. The first research component of this dissertation (Chapter 2) evaluates the conventional Monin-Obukhov scaling for the mean vertical temperature gradient in surface layers under destabilizing surface buoyancy fluxes and investigates the modifications of the Monin-Obukhov scaling by wave breaking and Langmuir turbulence. Measurements from two mooring sites are compared with predictions from the Monin-Obukhov scaling. The observational data consistently show smaller unstable thermal gradients under weakly destabilizing conditions, indicating stronger vertical mixing of heat. These deviations are discussed in the context of a simplified theoretical framework for boundary layer turbulence to understand the influence of surface wave breaking and Langmuir turbulence on the mean temperature gradient scaling.The second research component of this dissertation focuses on the scaling of turbulent vertical velocity in both the surface layer (Chapter 3) and the boundary layer (Chapter 4). In both chapters, a large collection of archived Lagrangian float data are used to compare the vertical turbulence kinetic energy (TKE) from a wide variety of aquatic environments to the conventional scaling relations in the ABL. The observational data exhibits substantial variations under similar conditions of wind stress and surface buoyancy flux. These variations cannot be explained by conventional ABL scaling relations and are shown to depend on the surface wave Stokes drift forcing. Additionally, Chapter 3 details the data processing and extends the surface layer scaling of vertical TKE to incorporate the Langmuir turbulence effect. Chapter 4 combines the effect of wind stress, surface buoyancy flux, and Stokes drift to give a generalized scaling of the boundary layer averaged vertical TKE. Chapter 4 also discusses the depth-dependent scaling of vertical TKE and vertical velocity skewness to highlight the importance of Langmuir turbulence in enhancing the vertical turbulence intensity, modifying the vertical mixing length scale, and promoting the vertical transport of TKE.

Subject Added Entry-Topical Term  

Physical oceanography.

Subject Added Entry-Topical Term  

Fluid mechanics.

Subject Added Entry-Topical Term  

Geophysics.

Index Term-Uncontrolled  

Langmuir turbulence

Index Term-Uncontrolled  

Ocean surface boundary layers

Index Term-Uncontrolled  

Similarity scaling

Index Term-Uncontrolled  

Surface wave

Added Entry-Corporate Name  

University of Washington Oceanography

Host Item Entry  

Dissertations Abstracts International. 85-03B.

Host Item Entry  

Dissertation Abstract International

Electronic Location and Access  

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소장사항  

202402 2024

Control Number  

joongbu:643180