Richardson number

The dimensionless ratio of buoyant suppression of turbulence to shear generation of turbulence. It is defined as

where g is the acceleration of gravity, β a representative vertical stability (commonly ∂θ/∂z, where θ is potential temperature), and ∂u/∂z is a characteristic vertical shear of the wind. It is used as a dynamic stability measure to determine if turbulence will exist.
See gradient Richardson number, bulk Richardson number, critical Richardson number, flux Richardson number.