Near-Inertial Wave Energetics Modulated by Background Flows in a Global Model Simulation.

We study the generation, propagation, and dissipation of wind-generated near-inertial waves (NIWs) in a global 1/258 Hybrid Coordinate OceanModel (HYCOM) simulation with realistic atmospheric forcing and background circulation during 30 days in May-June 2019. The time-mean near-inertial wind power input and depth-integrated energy balance terms are computed for the total fields and the fields decomposed into vertical modes to differentiate between the radiative and (locally) dissipative components of NIWenergy. Only 30.3%of the near-inertial wind input projects onto the first five modes, whereas the sum of the NIW energy in the first five modes adds up to 58% of the total NIW energy. Almost all of the depth-integrated NIW horizontal energy flux projects on the first five modes. The global distribution of dissipation and decay distances of NIW modes confirm that lower latitudes are a sink for NIW energy generated at higher latitudes. The locally dissipated fraction of NIW energy qlocal is found to be uniform throughout the global ocean, with a global mean value of 0.79. The horizontal NIW fluxes diverge from areas with cyclonic vorticity and converge in areas with anticyclonic vorticity; that is, anticyclonic eddies are a sink for NIWenergy fluxes}in particular, for higher modes. Most of the residual energy that does not project onto modes propagates downward in anticyclonic eddies. The global near-inertial wind power input is 0.21 TW for the 30 days, of which only 19%is transmitted below 500-m depth. [ABSTRACT FROM AUTHOR]