An experimental study of regime transitions in a differentially heated baroclinic annulus with flat and sloping bottom topographies

Abstract

Abstract.A series of laboratory experiments has been carried out in a thermally driven rotating annulus to study the onset of baroclinic instability, using horizontal and uniformly sloping bottom topographies. Different wave flow regimes have been identified and their phase boundaries -expressed in terms of appropriate non-dimensional parameters -have been compared to the recent numerical linear stability analysis of von Larcher et al. (2013). In the flat bottom case, the numerically predicted alignment of the boundary between the axisymmetric and the regular wave flow regime was found to be consistent with the experimental results. However, once the sloping bottom end wall was introduced, the detected behaviour was qualitatively different from that of the simulations. This disagreement is thought to be the consequence of nonlinear wave-wave interactions that could not be resolved in the framework of the numerical study. This argument is supported by the observed development of interference vacillation in the runs with sloping bottom, a mixed flow state in which baroclinic wave modes exhibiting different drift rates and amplitudes can co-exist.

Benchmarking in a rotating annulus: a comparative experimental and numerical study of baroclinic wave dynamics

“…We note, that in a previous experimental series carried out in the same set-up with the addition of sloping bottom topography, marked wave dispersion was observed. In that case, the stable baroclinic wave patterns emerged in the form of so-called resonant triads (VINCZE et al, 2014). Moreover, PFEFFER and FOWLIS (1968) also found dispersion in their flat bottom experiment, and HARLANDER et al (2011) reported dispersion in the wave transition region of the T a − Ro T diagram at lower ∆T .…”

“…The very same experi-mental apparatus that was used in the present work setup has already been used to test and validate subgridscale parametrization methods of two of the numerical models also used here (see the paper of BORCHERT et al (2014) in the present issue). In another recent comparative study, the effect of the addition of a sloping bottom topography to this set-up was analyzed both experimentally and numerically (VINCZE et al, 2014). However, to the best of our knowledge, the present study is the very first to systematically compare different numerical schemes and two series of experiments with different initial conditions.…”

Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing

“…The archetypal laboratory experiment used in studies of baroclinic instability is the rotating annulus which involves a fluid held between two vertical, coaxial cylinders, the outer of which is heated whilst the inner is cooled and the entire system is uniformly rotated. This setup has been studied extensively through both experiment [4][5][6][7][8][9][10] and numerical models [5,[11][12][13][14]. The success of annulus experiments as laboratory analogues to planetary atmospheres has been confirmed as many flow structures, including the mid latitude baroclinic zone, familiar from the atmosphere may be observed [14,15].…”

A rotating annulus driven by localized convective forcing: a new atmosphere-like experiment

“…Thus, this setup has proven to be a simple enough system to capture the fundamental physics and with enough complexity to represent nonlinear features and transition sequences to chaos similar to those of atmospheric dynamics (Hignett et al 1985;Früh and Read 1997;Bastin and Read 1998;Read 2003;Von Larcher and Egbers 2005;Wordsworth et al 2008;Vincze et al 2014). It has also proved valuable as a tractable 'test bed' within which to test numerical codes and methods (Harlander et al 2011;Vincze et al 2015) as well as to benchmark statistical-dynamical analysis methods in widespread use in meteorology, such as data assimilation (Young and Read 2013).…”