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
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. References
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.

3. Content

4. Surface layer and roughness length

5. Parameters controlling z 0u

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 LENGTH in the “meteorological interval” -10 < h0/L <10 after new theory and experimental data Solid line: z0u/z0 versus h0/L Dashed line: traditional formulation z0u = z0

17. Conclusions (roughness length)
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

18. NEUTRAL and STABLE ABL HEIGHT
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

19. References
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,
Zilitinkevich, S.S., and Baklanov, A., 2002: Calculation of the height of stable boundary layers in practical applications. Boundary-Layer Meteorol. 105,
Zilitinkevich S. S., and Esau, I. N., 2002: On integral measures of the neutral, barotropic planetary boundary layers. Boundary-Layer Meteorol. 104,
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,
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,

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)