The TRR 181 seminar is held by Yohei Onuki (Kyushu University) on February 27, 11 am at Universität Hamburg, Bundesstr. 53, Room 22/23.
It has long been discussed that resonant interaction among internal waves plays a vital role in the energy transfer from wind- or tide-generated large-scale motions to small-scale turbulent dissipation in the ocean interior. In recent years special attention is directed to the latitudinal dependence of the energy loss of internal tides; semidiurnal internal tides promptly lose their energy to near-inertial waves through a class of resonant interaction named parametric subharmonic instability (PSI) at the equatorial sides of 29N/S. In this talk, qualitative and quantitative aspects of PSI are elucidated by using some theoretical models, including simple deterministic stability analysis as well as an elaborated statistical equation originally derived by Klaus Hasselmann. Our newly developed calculation method for the statistical equation gives a new estimate of the decay rate of wave energy due to PSI, successfully resolving the discrepancy between the past theoretical and observational studies. The decay parameter of internal waves thus obtained will become useful for the internal tide models to reproduce deep mixing in the global ocean.