Rossby number

from Wikipedia, the free encyclopedia
Physical key figure
Surname Rossby number
Formula symbol
dimension dimensionless
characteristic speed
characteristic length
Coriolis parameters
Named after Carl-Gustaf Rossby
scope of application geophysics

The Rossby number (after Carl-Gustaf Rossby ; not ) is a dimensionless number that is mainly used in geophysics for oceanographic and atmospheric phenomena. It can be used to assess the influence of the Coriolis effect on a rotating movement. The Rossby number describes the ratio of inertial force to Coriolis force :

It is defined as:

in dependence of

  • the characteristic speed
  • the characteristic length over which the observed phenomenon takes place on the earth's surface
  • the Coriolis parameter ,

where is the latitude.

Depending on the phenomenon under consideration, the Rossby number can differ by several orders of magnitude. A small Rossby number means that the Coriolis force has a large influence on the system under consideration, while other forces predominate when the value is larger. For example, the value of the Rossby number in tornadoes is large (≈ 10 3 ), in low pressure areas it is small (≈ 0.1 to 1). The earth's rotation can be neglected for large Rossby numbers ( ).


  • Helmut Kraus: The Rossby number similarity . In: Ders .: Basics of boundary layer meteorology. Introduction to the physics of the atmospheric boundary layer and micrometeorology . Springer, Berlin 2008, ISBN 978-3-540-75980-5 , pp. 97-102.
  • Horst Kurz: Turbulent diffusion in an atmospheric boundary layer with a Rossby number similarity . Dissertation, Technical University Darmstadt 1978.

Individual evidence

  1. Lakshmi H. Kantha & Carol Anne Clayson: Numerical Models of Oceans and Oceanic Processes . Academic Press, 2000, ISBN 0-12-434068-7 , Table 1.5.1, pp. 56 ( limited preview in Google Book search).