From AMS Glossary
A wavenumber in the turbulence kinetic energy spectrum that separates the buoyancy subrange from the inertial subrange.
This wavenumber kB is given by
where N is the Brunt–Väisälä frequency and ε is the rate of dissipation of turbulence kinetic energy. Some measurements indicate that there is a relative minimum or gap in the spectrum at this wavenumber.