Rapid distortion theory

From Glossary of Meteorology

rapid distortion theory

A theory that assumes eddy vorticity is conserved in turbulent air undergoing rapid stretching, while shear production of turbulence remains zero or unchanged.

It is used to help predict the flow of turbulent air over hills and predicts that the vertical velocity variance should increase in the outer layer of accelerated winds flowing over a hill, while longitudinal velocity variance should decrease.