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Boundary Layer Structure and Depth

Boundary Layer Structure and Depth. The treatment here largely follows the work by Kaimal and Finnigan ( Atmospheric Boundary Layer Flows: Their Structure and Measurement , 1993, Oxford University Press, 304 pp.).

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Boundary Layer Structure and Depth

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  1. Boundary Layer Structure and Depth The treatment here largely follows the work by Kaimal and Finnigan (Atmospheric Boundary Layer Flows: Their Structure and Measurement, 1993, Oxford University Press, 304 pp.) Surface layer – analogous to inner layer of wall-bounded turbulent shear flows (e.g., in pipes or channels) and in laboratory flows – velocity fluctuations here scale with the distance from the surface Boundary layer – analogous to outer layer – velocity fluctuations here scale with the thickness of the boundary layer Above – the flow asymptotically approaches Geostrophic/gradient balance in the free atmosphere

  2. For neutral stratification, Sutton (1953) approximated the depth as which was based on the premise that Km was constant with height (i.e., an Ekman layer), which turned out to not be the case – so this approach was no longer tenable. Tennekes (1982) showed that the depth (when shear dominated) was proportional to u*/f, such that with C ~ 0.25 – again, unrealistic as subsidence (which limits boundary layer growth) and buoyancy changes often overwhelm changes of u*/f.

  3. Definitions As the field of boundary layer evolution and prediction has evolved, studies have converged on definitions related turbulent characteristics that are different between day and night, such that

  4. The Mixed Layer and Adjacent Layers

  5. The Stable Boundary Layer and Environs

  6. Evolutionary Boundary Layers

  7. Stability Considerations

  8. Convective Mixed Layers and Entrainment

  9. Structures of the Stable Boundary Layer

  10. The Surface Layer

  11. K Theory

  12. Logarithmic Wind Profile

  13. Eddy Correlations and Fluxes

  14. Scaling for the Boundary Layer

  15. Similarity Functions - Surface Layer

  16. Eddy Diffisivity and Richardson Number formulations for surface layer

  17. Scaling Equations

  18. The Outer Layer - Convective Mixed Layer

  19. Convective Scaling Parameterizations

  20. Convective Matching Layer

  21. Stable Outer Layer

  22. Budgets TKE - already covered

  23. Project! • Part One - PBL Model (introduce next time) - team project to investigate aspects of PBL structure using an interactive 1D model of the PBL valid for stable and unstable boundary layers • Part Two - individual project with abstract, presentation, and 2 page preprint style paper (AGU/AMS style), to be presented last two weeks of classes, including finals week.

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