A hybrid coupled general circulation model for El Niño
studies.
J. David Neelin
J. Atmos. Sci., 47, 1990.
Paper (PDF 1.9MB)
© Copyright 1990 by the American Meteorological Society.
Abstract. A model is developed for tropical air-sea interaction
studies, which is intermediate in complexity between the large coupled general
circulation models (coupled GCMs) coming into use and the simple two-level models
with which pioneering El Niño-Southern Oscillation studies were carried out.
The model consists of a stripped-down tropical Pacific ocean GCM, coupled to an
atmospheric model which is sufficiently simple that steady state solutions may
be found for low level flow and surface stress, given oceanic boundary conditions.
This hybrid coupling of an ocean GCM to a steady atmospheric model permits
examination of the nature of interannual coupled oscillations in the absence of
atmospheric noise. Tests of the atmospheric model against an atmospheric GCM
simulation of El Niño anomalies are presented, and the ocean model
climatology is examined under several different conditions. Experiments with
the coupled model exhibit a variety of behaviors within a realistic parameter
range. These indicate a partial bifurcation diagram in which the coupled
system undergoes a Hopf bifurcation from a stable climatology, giving rise to
sustained El Niño-period oscillations. The amplitude, period and
eastward extent of these oscillations increase with the strength of coupling
and the El Niño-period oscillation itself becomes unstable to a higher
frequency coupled mode which coexists with it and may affect predictability.
The difference between these flow regimes may be relevant to results found
by other investigators in coupled GCM experiments.
Citation.
Neelin, J. D., 1990: A hybrid coupled general circulation model for
El Niņo studies.
J. Atmos. Sci., 47, 674-693.
Acknowledgments.
This work was supported by NSF Grants ATM-8905164 and ATM-8342482 and by the
Canadian Natinal Science and Engineering Research Foundation. Part of this work
was carried out during a postdoctoral year at the Department of Earth, Atmospheric
and Planetary Sciences, Massachusetts Institute of Technology, during which the
support and encouragement of Richard Lindzen are gratefully acknowledged. The
authour thanks George Philander for much discussion, access ot ocean GCM code
and computing time at the Geophysical Fluid Dynamics Laboratory where some
of the model integrations were carried out. Work on the atmospheric model was
also carried out at GFDL, and thanks are due to Isaac Held and Gabriel Lau for
discussins important to this section. Ron Pacanowski provided advice on GCM code
and Frabrice Cuq assisted with compter graphics. Conversations with Michael Ghil,
Mark Cane and David Battisti are also appreciated. Acknowledgement is made to
the National Center for Atmospheric Research, which is sponsored by the National Science
Foundation, for computing time used in this research. This work, like many others, owes
a debt to the memory of Michael Cox and his contribution to ocean model development.
© Copyright 1990 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in
scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined
to be "fair use" under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of
the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS's permission. Republication, systematic reproduction,
posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above
statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the
AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or
copyrights@ametsoc.org.