Dissipative effects on internal gravity waves in geophysical fluids

Summary In the present paper we develop a systematic analysis of the dispersion and dissipation effects on internal gravity waves in fluids of geophysical interest. Dissipation induces a cut-off in the short wavelengths, leading to an admissible range of waves. Defining a suitable criterion for detection of waves, an observable wave range results, in which the frequency dispersion is nearly the same as for the inviscid case, whereas the amplitude is damped. The peculiar behaviour displayed by the dispersion relationship for Prandtl number equal to one is discussed.