Turning latitude

From Glossary of Meteorology

turning latitude

The latitude below which the meridional structure of an equatorial gravity or Rossby wave is wavelike and beyond which the meridional structure is decaying.

With the β-plane approximation, the turning latitude (one in each hemisphere) is defined as
where n is the meridional mode number, c is the phase speed of a given vertical mode Kelvin wave, and β is the derivative of Coriolis parameter f with respect to latitude.