New laboratory experiments to study the large-scale circulation and climate dynamics

  • Harlander, Uwe (BTU Cottbus-Senftenberg)
  • Sukhanovskii, Andrei (Institute of Continuous Media Mechanics)

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The large-scale flows of the oceans and the atmosphere are driven by a non-uniform surface heating over latitude and rotation. The former is responsible for large-scale convective processes like the Hadley cell. The latter generates the atmospheric westerlies. The differentially heated rotating annulus experiment includes both effects, convection and rotation, and is considered as an analog to the large-scale atmospheric circulation. In this experiment, in contrast to the Taylor-Couette (TC) setup, the azimuthal mean flow is generated by the radial heating contrast and not by differential rotation. The experiment has much in common with radially heated TC systems. However, to reach similarity with the atmosphere, the aspect ratio between height and width needs to be small. Here we contrast two rather new experiments particularly designed for studying the atmospheric large-scale circulation. One of the experiments, the differentially heated rotating annulus at BTU Cottbus, has a classical ``Hide-setup'' with an cooled inner cylinder and a heated outer wall.mHowever, the atmosphere is characterized by heating at the bottom in the tropics and cooling at the top of the polar latitudes. This particular forcing is not correctly reproduced in the Hide-setup and this motivates to use a design that includes heating and cooling at different vertical levels. We compare results from both experimental designs, showing common features but also qualitative and quantitative differences. We further present data that highlight the usefulness of the experiments in the context of climate dynamics and extreme events.