Start Submission Become a Reviewer

Reading: Dynamical structures for southwesterly airflow over southern Norway: the role of dissipation

Download

A- A+
Alt. Display

Original Research Papers

Dynamical structures for southwesterly airflow over southern Norway: the role of dissipation

Authors:

Idar Barstad ,

Department of Geology and Geophysics, Yale University, CT, US; Geophysical Department, University of Bergen, 5007 Bergen, NO
X close

Sigbjørn Grønås

Geophysical Department, University of Bergen, 5007 Bergen, NO
X close

Abstract

Earlier studies have revealed mesoscale structures in southwesterly flows over the mountains of southern Norway (Rossby number ∼1): a left-side jet and an upstream wind minimum as signs of the influence of rotation; a downstream wind shadow connected to inertio-gravity waves; a weak jet on the right side of the wind shadow and a shallow coastal wind shadowbetween the left-side jet and the main wind shadow. In the present study, the dynamics of the structures have been further examined from the results of experiments performed by a mesoscale numerical model and computations using a linear model with rotation included. Ideal atmospheric conditions for a large-scale wind direction from southwest have been used to initialize the numerical model. The sensitivity of mesoscale structures was studied with respect to dissipation from wave breaking and surface friction. Nonlinearity and dissipation in breaking waves are needed to explain the location, depth and strength of the downstream wind shadow. Increased wind to the right of the shadow was found to be generated by the effect of the Coriolis force as air was pulled towards the low-pressure perturbation behind the mountains. The coastal wind shadow was found to be a direct result of differential friction between land and ocean. Nonlinear experiments and an attempt to include boundary layer effects in linear theory showed that friction is reducing the effective height of the mountain and the signal of the mesoscale structures.

How to Cite: Barstad, I. and Grønås, S., 2006. Dynamical structures for southwesterly airflow over southern Norway: the role of dissipation. Tellus A: Dynamic Meteorology and Oceanography, 58(1), pp.2–18. DOI: http://doi.org/10.1111/j.1600-0870.2006.00152.x
  Published on 01 Jan 2006
 Accepted on 16 May 2005            Submitted on 12 Jun 2004

References

  1. Barstad , I. and Gronas , S. 2005 . Southwesterly flows over southern Norway-mesoscale sensitivity to large-scale wind direction and speed . Tellus 57A , 136 – 152 .  

  2. Burk , S. and Thompson , H. 1989 . A vertically nested regional numerical prediction model with second-order closure physics. Mon. Wea. Re v . 117 , 2305 – 2324 .  

  3. Doyle , J. D. and Shapiro , M. A. 1999 . Flow response to large-scale topography: the Greeland tip jet . Tellus 51A , 728 – 748 .  

  4. Eliassen , A. and Palm , E. 1960 . On the transfer of energy in the stationary mountain waves . Geofys. Publ . 22 , 1 – 23 .  

  5. Gill , A. E. 1982 . Atmosphere-Ocean Dynamics . International Geo-physics series , Academic Press , NY , 662 .  

  6. Grell , G. , Dudhia , J. and Stauffer , D. 1994. A Description of the Fifth-Generation Penn State/NCAR Mesoscale Model (MM5). NCAR tech-nical note NCAR/TNN-398±STR, Boulder, CO, U.S.A.  

  7. Grubigié , V. , Smith , R. B. and Schär , C. 1995 . The effect of bottom friction on shallow-water flow past an isolated obstacle. J. Atmos. Sc i . 50 , 1985 – 2005 .  

  8. Klemp , J. B. and Lilly , D. K. 1978 . Numerical Simulation of Hydrostatic Mountain Waves . J. Atmos. Sci . 35 , 78 – 107 .  

  9. Lott , E and Miller , M. J. 1997 . A new subgrid-scale orographic drag parameterization: Its formulation and testing . Quart. J. R. Met. Soc . 123 , 101 – 127 .  

  10. O´lafsson , H. 2000 . The impact of flow regimes on asymmetry of oro-graphic drag at moderate and low Rossby numbers . Tellus 52A , 365 – 379 .  

  11. O´lafsson , H. and Bougeault , P. 1997 . The effect of rotation and surface friction on orographic drag . J. Atmos. Sci . 54 , 193 – 210 .  

  12. Peng , M. S. , Li , S.-W. , Chang , S. W. and Williams , R. T. 1995 . Flow over mountains: coriolis force, transient troughs and three dimensionality . Q.J.R. MeteoroL Soc . 121 , 593 – 613 .  

  13. Pierrehumbert , R. T. 1986 . Chapter 21 in Mesoscale meteorology and forecasting (ed . P. S. Ray), Publ. American Meteorological Society , Boston .  

  14. Pierrehumbert , R. and Wyman , B. 1985 . Upstream effects of Mesoscale Mountains . J. Atmos. Sci . 42 , 977 – 1003 .  

  15. Schneider , T. , Held , I. M. and Garner , S. T. 2003 . Boundary Effects in Potential Voracity Dynamics . J. Atmos. Sci . 60 , 1024 – 1040 .  

  16. Schär , C., 1993 . A generalization of Bernoulli Theorem , J. Atmos. Sci . 50 , 1437 – 1443 .  

  17. Schär , C. and Smith , R. B. 1993 . Shallow water flow past isolated to-pography. Part I: Voracity production and wake formation . J. Atmos. Sci . 50 , 1373 – 1400 .  

  18. Schär , C. , Sprenger , M. , Liithi , D. , Jiang , Q. , Smith , R. B. and Benoit , R . 2003 . Structure and dynamics of an Alpine potential-vorticity banner . Q.J.R. Meteorol. Soc . 129 ( Part B ), 825 – 855 .  

  19. Smith , R. B. 1979 . The influence of the Earth’s rotation on mountain wave drag . J. Atmos. Sci . 36 , 177 – 180 .  

  20. Smith , R. B. 1989a . Hydrostatic airflow over mountains . Adv. Geophys . 31 , 59 – 81 .  

  21. Smith , R. B. 1989b . Comment on “Low Froude number flow past three dimensional obstacles. Part I: Baroclinically generated lee vorticies” byP. K. Smolarlciewicz and R . Rotunno. J. Atmos. Sci . 46 , 3611 – 3613 .  

  22. Smith , R. B. 2001 . Stratified airflow over Mountains, Ch.6 in Environ-mental Stratified Flows. Vol. 3 . In: Topics in Environmental Fluid Mechanics (ed. R. Grimshaw ), Kluwer Publishing , Boston .  

  23. Smith , R. B. and Gronhs , S. 1993 . Stagnation points and bifurcation in 3-D mountain flow . Tellus 45A , 28 – 43 .  

  24. Smith , R. B. , Jiang , Q. and Doyle J. D. 2005 . A theory of gravity wave absorption in boundary layer . J. Atmos. Sci ., in press .  

  25. Smolarkiewicz , P. K. and Rotunno , R. 1989 . Low froude number past three-dimensional obstacles. Part I: Baroclinically generated lee vor-tices . J. Atmos. Sci . 46 , 1154 – 1164 .  

  26. Thorsteinsson , S. and Sigurdsson , S. 1996 . Orogenic blocking and deflection of stratified air flow over an f-plane . Tellus 48A , 578 – 583 .  

  27. Tr¨ub , J. and Davies , H. 1995 . Flow over mesoscale ridge: pathways to regime transition . Tellus 47A , 502 – 524 .  

comments powered by Disqus