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Understanding Stable Turbulence Profiles in Strong LLJ SBL: Insights and Implications

Explore HRDL-measured turbulence profiles in Strong LLJ SBL for various stability conditions and their implications on NWP. Analyze vertical slice scan data and verification profiles to understand turbulence characteristics and profile shapes in different scenarios.

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Understanding Stable Turbulence Profiles in Strong LLJ SBL: Insights and Implications

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  1. HRDL-Measured Turbulence Profiles for the Strong-LLJ SBL R. Banta and Y. Pichugina Chemical Sciences Division, Earth System Research Lab., NOAA, Boulder

  2. Bulk Ri regimes for the SBL Weakly Stable Strongly Stable

  3. Traditional vs. Upside-Down (a la Mahrt ’99, ’02 w/ Dean)

  4. Background – ancient archives • Genesis • Exodus • Mahrt, Heald, Lenschow, Stankov, Troen, 1979; Caughey et al. 1979 • Deuteronomy • Nieuwstadt 1984 • Lenschow, Li, Zhu, and Stankov, 1988; Sorbjan, 1988

  5. HRDL vertical-slice-scan data

  6. Verification profiles; r2

  7. σu2 ~ TKE, via local scaling Bergström and Smedman (1995) found σu/u* ~ 2.44, σv/u* ~ 1.92, and σw/u* ~ 1.33 using tower time-series data, in approximate agreement with previous work. This would imply σv/ σu ~ 0.79 and σw/ σu ~ 0.54, or • TKE = 0.5 (σu2 + σv2 + σw2 ) = 0.5 (σu2 + 0.792σu2 + 0.542σu2 ) = 0.96 σu2

  8. σu2 ~ TKE - for stable conditions

  9. Vertical profiles – Variety of shapes

  10. Profiles – adjustment to changes

  11. Composite profiles – entire 6-night sample

  12. Height of variance minimum

  13. UX vs. u* scaling – CASES-99 data

  14. σu/ UX maximum valueentire sample + individual nights

  15. U(z) shapes – nose vs. ‘flat’

  16. σu/ UX profile shapes: SX, AX, CX

  17. Height of σmaxfor AX cases

  18. Stability (Ri) dependence of profile shape

  19. Mean = 0.043

  20. Things to chew on • σu2 ~ TKE for stable conditions • UX normalization better than u* • even near sfc, and even though UX measured aloft; u*, in sfc layer • Peak σu/ UX near sfc ~ 0.05 • Profile shapes appear controlled by stability • NWP implications – large-scale control

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