Transitions Between Blocked and Zonal Flows in a Rotating Annulus with Topography
Eric R. Weeks,
Yudong Tian,
J. S. Urbach,
*
Kayo Ide,
Harry L. Swinney,
Michael Ghil
The mid-latitude atmosphere is dominated by westerly, nearly zonal
flow. Occasionally, this flow is deflected poleward by blocking
anticyclones that persist for 10 days or longer. Experiments in a
rotating annulus used radial pumping to generate a zonal jet under the
action of the Coriolis force. In the presence of two symmetric ridges
at the bottom of the annulus, the resulting flows were nearly zonal at
high forcing or blocked at low forcing. Intermittent switching between
blocked and zonal patterns occurs because of the jet's interaction
with the topography. These results shed further light on previous
atmospheric observations and numerical simulations.
E. R. Weeks, J. S. Urbach, H. L. Swinney, Center
for Nonlinear Dynamics and Department of Physics, University of Texas
at Austin, Austin, TX 78712, USA.
Y. Tian, K. Ide, M. Ghil, Department of Atmospheric Sciences and
Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, CA 90095, USA.
*
Present address: Department of Physics, Georgetown University,
Washington, DC 20057, USA.
To whom correspondence should be addressed. E-mail:
swinney{at}chaos.ph.utexas.edu
