The vertical coordinate has a special significance, since all the reciprocal lattice points which a have constant value lie in the plane normal to the rotation axis.

The vertical coordinate is handled in various ways.

Some models, such as Richardson's 1922 model, use geometric height () as the vertical coordinate.

It was a matter of moving mere fractions of a degree through vertical and horizontal coördinates.

Therefore, a transformation of the vertical coordinate to a terrain-following one is performed.

This version revealed that the use of an integrated model based on a generic vertical coordinate is a very powerful tool.

Lewis Fry Richardson's 1922 model used geometric height () as the vertical coordinate.

Thereafter, the Boussinesq approximation is applied to the remaining flow equations, in order to eliminate the dependence on the vertical coordinate.

As an example, consider potential flow over a horizontal bed in the (x,z) plane, with x the horizontal and z the vertical coordinate.

In this expression μ is the molar chemical potential, g the gravitational acceleration, and z the vertical coordinate.