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Richardson number

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In the stability of continuously stratified parallel shear flows the ratio of (the squares of) the buoyancy frequency to the background velocity gradient is known as the (gradient) Richardson number.

Ri = \frac{N^2}{U_z^2}

N = \mbox{Buoyancy frequncy} = -\frac{g}{\rho_0} \frac{\partial \bar{\rho}}{\partial z}

Here  \rho_0 is the reference density and  \bar{\rho} is the background density field.


  • Hunt, J C R (1998), Lewis Fry Richardson and his contributions to mathematics, meteorology, and models of conflict, Annual Review of Fluid Mechanics, Vol. 30, 1998, pp. xiii–xxxvi.
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