Articles | Volume 12, issue 6
Nonlin. Processes Geophys., 12, 1033–1041, 2005
https://doi.org/10.5194/npg-12-1033-2005

Special issue: Turbulent transport in geosciences

Nonlin. Processes Geophys., 12, 1033–1041, 2005
https://doi.org/10.5194/npg-12-1033-2005

  20 Dec 2005

20 Dec 2005

Experiments on transitions of baroclinic waves in a differentially heated rotating annulus

Th. von Larcher and C. Egbers Th. von Larcher and C. Egbers
  • Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus, 03046 Cottbus, Germany

Abstract. Experiments of baroclinic waves in a rotating, baroclinic annulus of fluid are presented for two gap widths. The apparatus is a differentially heated cylindrical gap, rotated around its vertical axis of symmetry, cooled from within, with a free surface, and filled with de-ionised water as working fluid. The surface flow was observed with visualisation technique while thermographic measurements gave a detailed understanding of the temperature distribution and its time-dependent behaviour. We focus in particular on transitions between different flow regimes. Using a wide gap, the first transition from axisymmetric flow to the regular wave regime was characterised by complex flows. The transition to irregular flows was smooth, where a coexistence of the large-scale jet-stream and small-scale vortices was observed. Furthermore, temperature measurements showed a repetitive separation of cold vortices from the inner wall. Experiments using a narrow gap showed no complex flows but strong hysteresis in the steady wave regime, with up to five different azimuthal wave modes as potential steady and stable solutions.