An experimental study of laboratory-scale atmospheric and oceanic jets

Atmospheric and oceanic jets can significantly influence global climate events. Understanding the jet characteristics is therefore useful in furthering available climate models, and provide an improved understanding and prediction. Here. we present an experimental study of a barotropic jet in an annular rotating-tank with a beta-slope. The top boundary includes an independently controlled annular forcing ring which creates an azimuthal, meandering jet. The Rossby numbers are in the range 0.05-0.3 and Ekman number is of the order 1e-04. From full-field 2D Particle Image Velocimetry data at mid-depth, we look at the effect of forcing on the steady-state flow field. An azimuthal jet velocity scale, over which Rossby waves propagate, is obtained using energy balance considerations, and it is found to be in good agreement with the measured mean jet profile. It is further observed that with increasing forcing, the dominant mode number of the Rossby wave decreases. In addition, we also report two different regimes in the experiments - the locked and unlocked regimes, using spatio-temporal velocity data. A physical interpretation of the observations based on the dispersion relation for Rossby waves propagating on an azimuthal jet is provided.