A highly nonlinear coupled mode of decadal variability in a mid-latitude ocean-atmosphere model

作者：Kravtsov S^*; Dewar W K; Berloff P; McWilliams J C; Ghil M

来源：Dynamics of Atmospheres and Oceans, 2007, 43(3-4): 123-150.

DOI：10.1016/j.dynatmoce.2006.08.001

• inertial recirculations
• mid-latitude jet stream
• bimodality

This study examines mid-latitude climate variability in a model that couples turbulent oceanic and atmospheric flows through an active oceanic mixed layer. Intrinsic ocean dynamics of the inertial recirculation regions combines with nonlinear atmospheric sensitivity to sea-surface temperature (SST) anomalies to play a dominant role in the variability of the coupled system.
Intrinsic low-frequency variability arises in the model atmosphere; when run in a stand-alone mode, it is characterized by irregular transitions between preferred high-latitude and less frequent low-latitude zonal-flow states. When the atmosphere is coupled to the ocean, the low-latitude state Occurrences exhibit a statistically significant signal in a broad 5-15-year band. A similar signal is found in the time series of the model ocean's energy in this coupled simulation. Accompanying uncoupled ocean-only and atmosphereonly integrations are characterized by a decrease in the decadal-band variability, relative to the coupled integration; their spectra are indistinguishable from a red spectrum.
The time scale of the coupled interdecadal oscillation is set by the nonlinear adjustment of the ocean's inertial recirculations to the high-latitude and low-latitude atmospheric forcing regimes. This adjustment involves, in turn, SST changes resulting in long-term ocean-atmosphere heat-flux anomalies that induce the atmospheric regime transitions.

• 出版日期2007-8