NONLINEAR PROCESSES OF ENERGY-TRANSFER FROM TRAVELING HURRICANES TO THE DEEP-OCEAN INTERNAL WAVE-FIELD

Generation of large-scale internal waves by a hurricane traveling over the ocean with a uniform velocity is investigated by using a three-di mensional, multilevel numerical model. It is found that two distinctiv e kinds of internal waves are excited in the wake of the hurricane, na mely, near-inertial waves, which can be explained based on the linear theory, and superinertial waves with frequencies 2f(0) and 3f(0) (f(0) is the inertial frequency at the latitude of the hurricane track), wh ich are generated through nonlinear effects. Our special attention is directed to the superinertial waves with frequencies 2f(0) and 3f(0) b ecause these internal waves are considered to be efficient energy sour ces for small-scale mixing in the deep ocean. These superinertial wave s predominantly have low-vertical-mode structures and satisfy the disp ersion relation for lee waves. In areas away from the hurricane track, in particular, the double-inertial frequency waves become larger than the near-inertial waves. The nonlinear resonant triads causing the ge neration of such superinertial waves are examined by calculating the b ispectrum, which clearly shows that the lowest-vertical-mode double-in ertial frequency wave is generated efficiently through the nonlinear i nteraction between the high-vertical-made near-inertial waves.