Zonal winds

Zonal winds are axisymmetric flows in rotating geophysical systems such as atmopheres, oceans or cores. We’d like to understand the physical mechanism responsible of their presence, their amplitude and their geometry.
The zonal flows are east-west wind (along lines parallel to the equator of a sphere) which turns around the axis of rotation of the planet. An image of Jupiter gives us a clear representation of what they are.

Jupiter observed by Voyager, NASA

We mainly focus in deep layer systems where the rotation (through the Coriolis forces) imposes a geometrical constraint on the flow, known as geostrophic constraint. The zonal flows are quite peculiar because they cannot originate from radial forcing such as boyancy forces but are produced by non linear interaction of the flow in presence of rotation. Result of rotating turbulence, these flows are difficult to compute.

Equatorial view of the longitudinal velocities (in Reynolds number) in rapidly rotating convection showing multiple azimuthal jets. from Guervilly et al (GJI 2017)

In ISTerre, we built an experimental set up, called ZoRo (for Zonal flows in Rotating fluids), to study zonal flows. We study the flow of aire embedded inside a rotating spheroidal cavity (up to 30Hz). In order to measure the flow, we develop a velocimetry method based on pertubations of acoustic modes.

Photograp of the experimental setup - Max Solazzo