Whitaker, J. S., and A. Barcilon, 1995:
Low-frequency variability and wavenumber selection in models with zonally symmetric forcing. J.
Atmos. Sci., 52, 491-503.
ABSTRACT
Low-frequency variability and wavenumber selection in models with zonally
symmetric forcing
Jeffrey S. Whitaker
CIRES, University of Colorado, Boulder, CO
Albert Barcilon
Dept. of Meteorology and Geophysical Fluid Dynamics Institute, The Florida State
University, Tallahassee, FL
Abstract
The authors consider a two-layer quasi-geostrophic model with linear surface
drag and forcing that relaxes to a zonal baroclinically unstable equilibrium
state consisting of a meridionally confined temperature gradient. It is
observed that the most energetic wave in the time-mean climate has near zero
frequency and is not driven by upscale nonlinear energy transfers. This wave
has a zonal scale near the long wave cutoff of the equilibrium state, and its
energy balance is mainly between baroclinic generation and dissipation. This
maintenance mechanism is different from that suggested by beta-plane,
two-dimesional, and quasi-geostrophic turbulence arguments and may be relevant
to the dynamics of zonally asymmetric low-frequency variability in the
atmosphere, particularly in the Southern Hemisphere.