Axially asymmetric rotating tank experiments for thermally forced stationary waves in geophysical fluids

Fluid dynamical experiments using a rotating tank with an imposed radial temperature gradient provide classical examples of the realization of large-scale atmospheric circulation in a laboratory setting. The last decade has seen a revival of such experiments for research and education. Classical rotating tank experiments have adopted axially symmetric boundary conditions to maintain a zonally uniform ``pole-to-equator'' temperature gradient. Symmetry breaking arises from internal dynamics of baroclinic instability. A notable exception is the class of experiments for topographic effects, in which an isolated obstacle is added to the bottom boundary. This study explores a new type of experiments that are axially asymmetric due to an imposed, zonally non-uniform, temperature in the lateral boundary. This mimics the contrast of warm pool versus cold tongue in the tropical Pacific Ocean. The experiments produced thermally forced quasi-stationary waves with their wavelength comparable to the scale of the localized thermal boundary forcing. The applications of this new type of experiments to understanding Earth's climate will be discussed.