From AMS Glossary
An analytic approximation to the internal gravity wave spectrum (for ocean waves with large horizontal extent compared with the vertical extent) that is observed to have the same structure throughout the deep ocean.
The energy density spectrum is proportional to
for waves of frequency ω in which f is the Coriolis parameter and E is a nondimensional parameter empirically determined to be E ≈ 6 × 10-5. For a wide range of observations E has been found to vary by no more than a factor of 2.