Chapter 4: Atmospheric Circulation, Cylindrical Tank Experiments

Laboratory demonstrations show settling of a denser patch of dyed fluid in a cylindrical tank. When the tank is stationary, the dye settles, forming a gravity current, and coats the bottom of the tank. Next we rotate the entire set up on our rotary table. Now the dye does not settle as it is supported by Coriolis forces (i.e., geostrophic balance), and instead forms a dipolar vortex. This structure is then pushed away from the center of the tank by unbalanced centrifugal forces. Analogous to mid- and high-latitude atmospheric dynamics, this demonstration shows the importance of eddies and vortices in regions far from the equator.