Evanescent level
From Glossary of Meteorology
evanescent level
A theoretical boundary between a region in the fluid where waves of some frequency are propagating and a region in the fluid where waves of the same frequency do not propagate (where they are evanescent).
This is
also called a critical level but is distinct from the critical level where the background flow has the same speed as the phase speed of the waves.
also called a critical level but is distinct from the critical level where the background flow has the same speed as the phase speed of the waves.