# Turner angle

From Glossary of Meteorology

## Turner angle

A parameter used to define the local stability of an inviscid water column to double-diffusive convection.

Defined as where tan

^{−1}is the four-quadrant arctangent,*α*is the coefficient of thermal expansion,*β*is the equivalent coefficient for the addition of salinity (sometimes referred to as saline contraction because the addition of salinity reduces the volume),*T*is temperature, and*S*is salinity. If −45° < Tu < 45°, the column is statically stable. If −90° > Tu or Tu > 90°, the column is statically unstable to Rayleigh–Taylor instability. If −90° < Tu < −45°, the column is unstable to diffusive convection. If 45° < Tu < 90°, the column is unstable to salt fingering.*Term edited 1 March 2021*