Multiple gravity-wave breaking levels

Abstract

Gravity waves for which the expression /u(bar)-c/, where u(bar) = mean flow speed and c = wave phase speed, exhibits a sharp minimum in the upper troposphere or lower stratosphere, have decaying amplitudes above this level despite their exponentially decreasing mean density; this decay then ceases and growth resumes. If a gravity wave breaks below the level of /u(bar)-c/min, it will cease breaking above this level, while resuming breaking at some higher, second level which is a lower bound for the level of breaking in the mesosphere. Explicit calculations show the second breaking levels to be close to observed levels of mesospheric gravity wave breaking.