Low-frequency variability and heat transport in a low-order nonlinear coupled ocean-atmosphere model
Discipline
Earth and related Environmental sciences
Audience
Scientific
Date
2015-07Publisher
Elsevier
Metadata
Show full item recordDescription
We formulate and study a low-order nonlinear coupled ocean–atmosphere model with an emphasis on
the impact of radiative and heat fluxes and of the frictional coupling between the two components. This
model version extends a previous 24-variable version by adding a dynamical equation for the passive
advection of temperature in the ocean, together with an energy balance model.
The bifurcation analysis and the numerical integration of the model reveal the presence of lowfrequency
variability (LFV) concentrated on and near a long-periodic, attracting orbit. This orbit combines
atmospheric and oceanic modes, and it arises for large values of the meridional gradient of radiative input
and of frictional coupling. Chaotic behavior develops around this orbit as it loses its stability; this behavior
is still dominated by the LFV on decadal and multi-decadal time scales that is typical of oceanic processes.
Atmospheric diagnostics also reveals the presence of predominant low- and high-pressure zones, as well
as of a subtropical jet; these features recall realistic climatological properties of the oceanic atmosphere.
Finally, a predictability analysis is performed. Once the decadal-scale periodic orbits develop, the coupled
system’s short-term instabilities – as measured by its Lyapunov exponents – are drastically reduced,
indicating the ocean’s stabilizing role on the atmospheric dynamics. On decadal time scales, the recurrence
of the solution in a certain region of the invariant subspace associated with slow modes displays
some extended predictability, as reflected by the oscillatory behavior of the error for the atmospheric
variables at long lead times.
Citation
Vannitsem, Stéphane; Demaeyer, Jonathan; De Cruz, Lesley; Ghil, Michael (2015-07). Low-frequency variability and heat transport in a low-order nonlinear coupled ocean-atmosphere model. , Physica D, Vol. 309, 71-85, Elsevier, DOI: http://dx.doi.org/10.1016/j.physd.2015.07.006.Identifiers
Type
Article
Peer-Review
Yes
Language
eng