Inertial waves in spherical shells at low Ekman numbers

Abstract

Inertial waves as oscillatory motions in rotating fluids generate internal shear layers at critical latitudes. We investigated the nonlinear interaction of inertial waves for global flows (3D flows) in dependence on the Ekman number. When the value of the Ekman number decreases, the influence of the Ekman layers to the flow pattern increases. Critical latitudes, the attractor flow pattern and certainly internal shear layers are observable mainly at greater values of the Ekman number. Although, with decreasing the Ekman number smaller flow structures become visible, nonlinear interactions in shear layers drive an axisymmetric flow whose amplitude diverges at the limit of the vanishing Ekman number. We show that this conclusion is valid not only for zonal wind driven by inertial modes but also for similarly driven global flows.