Laboratory Simulation of Atmospheric Motions in the Vicinity of Antarctica

Abstract

Laboratory experiments concerned with surface cooling, were conducted to simulate the surface wind patterns and the free atmosphere general circulation in the vicinity of Antarctica. The principal dynamical similarity parameter is shown to be ROT/S, where RoT is the thermal Rossby number and S the Burger number. At parameter values appropriate to the atmosphere, the physical model experiments led to a surface drainage flow and an accompanying polar cyclone that had characteristics similar to atmospheric observations. The simulated polar cyclone contained two low centers and planetary wavelike structures. The interior streamlines near the cyclone centers tended to follow the continental height contours. In the laboratory simulations, eastward-propagating wave troughs were periodically generated in the vicinity of 110°E and developed maximum strengths in the vicinity of the Ross Ice Shelf at 160°W before dissipating by 70°W. Jets in the polar cyclone were observed over regions of the model Antarctic continent having large slope. The boundary drainage flows spread out from the interior of the continent and concentrated in several valleys leading to the oceans. On approaching the model ocean, the drainage flows tended to move around the edge of the continent in an anticlockwise pattern (i.e., an anticyclone) with anticyclonic spiral tongues spreading to the surrounding ocean regions. Experiments conducted by varying RoT and S, while fixing RoT/S, demonstrated that the strength and areal extent of the polar cyclone do not vary greatly in what is in effect a change of season. The results demonstrated that the thermal forcing of the Antarctic continent and the unique nature of the Antarctic orography are important features in determining the principal characteristics of the continental surface winds and the general circulation of the high-latitude Southern Hemisphere atmosphere.