Dissertation
IMPACTS OF LARGE-SCALE TURBULENT MOTIONS ON TURBULENCE STRUCTURES AND FLUX EXCHANGE IN A DISTURBED ATMOSPHERIC SURFACE LAYER
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/117193
Abstract
The atmospheric surface layer (ASL) is intermittently subjected to disturbance by non-local, large-scale turbulent motions (hereafter large eddies). In this dissertation, using turbulence data collected from two field experiments, large eddies are examined in terms of their impacts on turbulence structures and flux exchange of momentum, heat, and water vapor in a disturbed ASL (i.e., the ASL disturbed by large eddies). The first chapter presents the motivations and objectives for this research, and a background review of large eddies and their impacts on turbulence structures and flux exchange in the ASL. In the second chapter, large eddies are shown to modulate flux convergence and divergence under unstable atmospheric conditions. Large eddies may either increase or decrease turbulent fluxes by enhancing or depressing the vertical velocity spectra in the middle- to low-frequency ranges, and thus improve or degrade the surface energy balance closure in the ASL. In the third chapter, the impacts of large eddies on the widely reported non-closure of the surface energy balance in the ASL are investigated. The phase difference between the vertical velocity and water vapor density associated with large eddies reduces latent heat fluxes, especially in conditions where advection prevails. The enlarged phase difference of large eddies linked to entrainment or advection occurrence leads to increased residuals in the surface energy balance. The fourth chapter focuses on the impacts of large eddies on the dissimilarity of turbulent transport of heat and water vapor in the unstable ASL over an open water surface. The degree to which large eddies impact the temperature-humidity dissimilarity is affected by the wind shear and stability, as wind shear and stability can modulate the structures of large eddies in the ASL. Last, a summary of this dissertation and suggestions for future studies are provided in the fifth chapter.
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Details
- Title
- IMPACTS OF LARGE-SCALE TURBULENT MOTIONS ON TURBULENCE STRUCTURES AND FLUX EXCHANGE IN A DISTURBED ATMOSPHERIC SURFACE LAYER
- Creators
- Zhongming Gao
- Contributors
- Heping Liu (Advisor)Brian Lamb (Committee Member)Shelley Pressley (Committee Member)B. Thomas Jobson (Committee Member)Steven Oncley (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 156
- Identifiers
- 99900581515101842
- Language
- English
- Resource Type
- Dissertation