Damping mechanisms of internal waves in continuously stratified rotating basins

Damping mechanisms, damping rates and the dissipative modal structure of internalwaves in stratified rotating circular basins are investigated analytically. The dampingis shown to be due to a combination of the internal-wave cancelling, where wavesemitted by the oscillatory boundary layers destructively interact with the parent waveand drain energy from it, and spin-down modified by the periodicity, where the energyis drained by the sinks and sources at the bottom corner caused by a discontinuity inthe Ekman transport. It is shown that super-inertial Poincar´e waves and sub-inertialKelvin waves are damped predominantly by the internal-wave cancelling and modifiedspin-down, respectively. These processes also modify the internal-wave structure; forsuper-inertial waves, the boundary-layer-generated waves intensify the interior flowin the lower part of the water column and delay the phase relative to the isopycnaldisplacements, but for sub-inertial waves, the Ekman pumping and the corner sinksand sources add a horizontal circular flow that slants the crest and trough backwardsnear the wall.