Boundary-Layer Meteorology

, Volume 68, Issue 1–2, pp 193–199 | Cite as

The Ekman momentum approximation and its application

  • Tan Zhemin
  • Wu Rongsheng
Research Notes


In the boundary layer, the flow is basically an equilibrium of three forces: Coriolis, pressure gradient and frictional. This means that it is an Ekman flow while the basic flow in the free atmosphere is an equilibrium of two forces: Coriolis and pressure gradient, and is a geostrophic flow. Therefore, it is natural to try to modify the geostrophic momentum approximation in the free atmosphere to become an Ekman momentum approximation in the boundary layer. The physical explanation and foundation of the Ekman momentum approximation are discussed.


Atmosphere Boundary Layer Pressure Gradient Basic Flow Physical Explanation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Blumen, W.: 1979, ‘Unstable Nonlinear Evolution of an Eady Wave in Time-Dependent Basic Flows and Frontogenesis’,J. Atmos. Sci. 36, 3–11.Google Scholar
  2. Blumen, W. and Wu, R.: 1983, ‘Baroclinic Instability and Frontogenesis with Ekman Boundary Layer Dynamics Incorporation the Geostrophic Momentum Approximation’,J. Atmos. Sci. 39, 1774–1782.Google Scholar
  3. Hoskins, B. J.: 1975, ‘The Geostrophic Momentum Approximation and the Semi-Geostrophic Equations’,J. Atmos. Sci. 32, 233–242.Google Scholar
  4. Hoskins, B. J.: 1976, ‘Barolinic Wave and Frontogenesis, Part: I. Introduction and Eady Wave’,Quart. J. Roy. Meteorol. Soc. 102, 103–122.Google Scholar
  5. Tan, Z. and Wu, R.: 1991, ‘On Ekman Momentum Approximation for Boundary Layer Dynamics’,Acta. Meteor. Sinica 49, 421–429. (in Chinese with English abstract).Google Scholar
  6. Tan, Z. and Wu, R.: 1992, ‘Dynamics of Ekman Momentum Flow and Frontogenesis’,Science in China, Ser B,35, 115–128 (in English).Google Scholar
  7. Wu, R. and W. Blumen: 1982, ‘An Analysis of the Ekman Boundary Layer Dynamics Incorporating the Geostrophic Momentum Approximation’,J. Atmos. Sci. 39, 1774–1782.Google Scholar
  8. Wu, R.: 1984, ‘Dynamics of Semi-Geostrophic Flow’,Scientia Sinica, Ser. B,XXVII, 735–743.Google Scholar
  9. Wu, R. and W. Blumen: 1991, ‘The Ekman Boundary Layer over Orography: An Analysis of Vertical Motion’,Boundary-Layer Meteorol. 54, 315–326.Google Scholar

Copyright information

© Kluwer Academic Publishers 1994

Authors and Affiliations

  • Tan Zhemin
    • 1
  • Wu Rongsheng
    • 1
  1. 1.Department of Atmospheric SciencesNanjing UniversityNanjingP.R. China

Personalised recommendations