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STRATIFICATION EFFECT ON THE ROUGHNESS LENGTH

STRATIFICATION EFFECT ON THE ROUGHNESS LENGTH . S. S. Zilitinkevich 1,2,3 , I. Mammarella 1,2 , A. Baklanov 4 , and S. M. Joffre 2 1. Atmospheric Sciences, University of Helsinki, Finland 2. Finnish Meteorological Institute, Helsinki, Finland

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STRATIFICATION EFFECT ON THE ROUGHNESS LENGTH

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  1. STRATIFICATION EFFECT ON THE ROUGHNESS LENGTH • S. S. Zilitinkevich1,2,3, I. Mammarella1,2, • A. Baklanov4, and S. M. Joffre2 • 1. Atmospheric Sciences, University of Helsinki, Finland • 2. Finnish Meteorological Institute, Helsinki, Finland • 3. Nansen Environmental and Remote Sensing Centre / • Bjerknes Centre for Climate Research, Bergen, Norway • 4. Danish Meteorological Institute, Copenhagen, Denmark

  2. S. S. Zilitinkevich, I. Mammarella, A. A. Baklanov, and S. M. Joffre, 2007: The roughness length in environmental fluid mechanics: the classical concept and the effect of stratification. Submitted to Boundary-Layer Meteorology. References

  3. Content

  4. Surface layer and roughness length

  5. Parameters controlling z0u

  6. Stability Dependence of Roughness Length For urban and vegetation canopies with roughness-element heights (20-50 m) comparable with the Monin-Obukhov turbulent length scale, L, the surface resistance and roughness length depend on stratification

  7. Background physics and effect of stratification

  8. Recommended formulation

  9. Experimental datasets Sodankyla Meteorological Observatory, Boreal forest (FMI) BUBBLE urban BL experiment, Basel, Sperrstrasse (Rotach et al., 2004) h ≈ 13 m, measurement levels 23, 25, 47 m h ≈ 14.6 m, measurement levels 3.6, 11.3, 14.7, 17.9, 22.4, 31.7 m

  10. Stable stratification

  11. Stable stratification

  12. Stable stratification

  13. Unstable stratification

  14. Unstable stratification

  15. Unstable stratification

  16. STABILITY DEPENDENCE OF THE ROUGHNESS LENGTHin the “meteorological interval” -10 < h0/L <10 after new theory and experimental dataSolid line: z0u/z0versus h0/L Dashed line: traditional formulation z0u = z0

  17. Traditional concept: roughness length fully characterised by geometric features of the surface New theory and data: essential dependence on hydrostatic stability especially strong in stable stratification Applications: to urban and terrestrial-ecosystem meteorology Practically sound: urban air pollution episodes in very stable stratification Conclusions(roughness length)

  18. Sergej Zilitinkevich 1,2,3, Igor Esau3 and Alexander Baklanov4 1 Division of Atmospheric Sciences, University of Helsinki, Finland 2 Finnish Meteorological Institute, Helsinki, Finland 3 Nansen Environmental and Remote Sensing Centre / Bjerknes Centre for Climate Research, Bergen, Norway 4 Danish Meteorological Institute, Copenhagen, Denmark NEUTRAL and STABLE ABL HEIGHT

  19. Zilitinkevich, S., Baklanov, A., Rost, J., Smedman, A.-S., Lykosov, V., and Calanca, P., 2002: Diagnostic and prognostic equations for the depth of the stably stratified Ekman boundary layer. Quart, J. Roy. Met. Soc., 128, 25-46. Zilitinkevich, S.S., and Baklanov, A., 2002: Calculation of the height of stable boundary layers in practical applications. Boundary-Layer Meteorol.105, 389-409. Zilitinkevich S. S., and Esau, I. N., 2002: On integral measures of the neutral, barotropic planetary boundary layers. Boundary-Layer Meteorol. 104, 371-379. Zilitinkevich S. S. and Esau I. N., 2003: The effect of baroclinicity on the depth of neutral and stable planetary boundary layers. Quart, J. Roy. Met. Soc. 129, 3339-3356. Zilitinkevich, S., Esau, I. and Baklanov, A., 2007: Further comments on the equilibrium height of neutral and stable planetary boundary layers. Quart. J. Roy. Met. Soc., 133, 265-271. References

  20. Factors controlling PBL height

  21. Scaling analysis

  22. Dominant role of the smallest scale

  23. How to verify h-equations?

  24. Stage I: Truly neutral ABL

  25. Stage I: Transition TNCN ABL

  26. Stage I: Transition TNNS ABL

  27. Stage II: General case

  28. Conclusions (SBL height)

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