Publications

2004
Kao, Jim, Dawn Flicker, Rudy Henninger, Sarah Frey, Michael Ghil, and Kayo Ide. 2004. “Data assimilation with an extended Kalman filter for impact-produced shock-wave dynamics.” Journal of Computational Physics 196 (2). Elsevier: 705–723.
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Kravtsov, Sergey, and Michael Ghil. 2004. “Interdecadal variability in a hybrid coupled ocean-atmosphere-sea ice model.” Journal of Physical Oceanography 34 (7): 1756–1775.
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Loeuille, Nicolas, and Michael Ghil. 2004. “Intrinsic and climatic factors in North-American animal population dynamics.” BMC Ecology 4 (1). BioMed Central: 1. Publisher's Version
Lott, François, Andrew W. Robertson, and Michael Ghil. 2004. “Mountain torques and Northern Hemisphere low-frequency variability. Part II: Regional aspects.” Journal of the Atmospheric Sciences 61 (11): 1272–1283.
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Lott, François, Andrew W. Robertson, and Michael Ghil. 2004. “Mountain torques and Northern Hemisphere low-frequency variability. Part I: Hemispheric aspects.” Journal of the Atmospheric Sciences 61 (11): 1259–1271.
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Sayag, Roiy, Eli Tziperman, and Michael Ghil. 2004. “Rapid switch-like sea ice growth and land ice–sea ice hysteresis.” Paleoceanography 19 (1). Wiley Online Library.
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Kahn, Brian H., Annmarie Eldering, Michael Ghil, Simona Bordoni, and Shepard A. Clough. 2004. “Sensitivity analysis of cirrus cloud properties from high-resolution infrared spectra. Part I: Methodology and synthetic cirrus.” Journal of Climate 17 (24): 4856–4870.
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Kondrashov, Dmitri, K. Ide, and Michael Ghil. 2004. “Weather regimes and preferred transition paths in a three-level quasigeostrophic model.” Journal of the Atmospheric Sciences 61 (5): 568–587.
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2003
Zaliapin, Ilya, Vladimir Keilis-Borok, and Michael Ghil. 2003. “A Boolean delay equation model of colliding cascades. Part I: Multiple seismic regimes.” Journal of Statistical Physics 111 (3-4). Springer: 815–837.
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Zaliapin, Ilya, Vladimir Keilis-Borok, and Michael Ghil. 2003. “A Boolean delay equation model of colliding cascades. Part II: Prediction of critical transitions.” Journal of Statistical Physics 111 (3-4). Springer: 839–861.
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Ghil, Michael. 2003. “Did celestial chaos kill the dinosaurs?” The Observatory 123 (1177): 328–333.
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Simonnet, Eric, Michael Ghil, Shouhong Wang, and Zhi-Min Chen. 2003. “Hopf Bifurcation in Quasi-geostrophic Channel Flow.” SIAM J. Appl. Math. 64 (1). Society for Industrial & Applied Mathematics (SIAM): 343–368.
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Ghil, Michael, Dmitri Kondrashov, F. Lott, and Andrew W. Robertson. 2003. “Intraseasonal oscillations in the mid-latitudes: observations, theory, and GCM results.” Proceedings ECMWF/CLIVAR Workshop on Simulation and Prediction of Intra-Seasonal Variability with Emphasis on the MJO, 3–6.
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Bellon, G., H. Le Treut, and Michael Ghil. 2003. “Large-scale and evaporation-wind feedbacks in a box model of the tropical climate.” Geophysical Research Letters 30 (22). Wiley Online Library.
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Kravtsov, S., Andrew W. Robertson, and Michael Ghil. 2003. “Low-Frequency Variability in a Baroclinic Beta-Channel with Land-Sea Contrast*.” Journal of the Atmospheric Sciences 60 (18): 2267–2293.
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Simonnet, Eric, Michael Ghil, Kayo Ide, Roger Temam, and Shouhong Wang. 2003. “Low-frequency variability in shallow-water models of the wind-driven ocean circulation. Part II: Time-dependent solutions.” Journal of Physical Oceanography 33 (4). Abstract

The time-dependent wind-driven ocean circulation is investigated for both a rectangular and a North Atlantic– shaped basin. Multiple steady states in a 2 ½ -layer shallow-water model and their dependence on various pa- rameters and other model properties were studied in Part I for the rectangular basin. As the wind stress on the rectangular basin is increased, each steady-state branch is destabilized by a Hopf bifurcation. The periodic solutions that arise off the subpolar branch have a robust subannual periodicity of 4–5 months. For the subtropical branch, the period varies between sub- and interannual, depending on the inverse Froude number F 2 defined with respect to the lower active layer’s thickness H 2 . As F 2 is lowered, the perturbed-symmetric branch is destabilized baroclinically, before the perturbed pitchfork bifurcation examined in detail in Part I occurs. Transition to aperiodic behavior arises at first by a homoclinic explosion off the isolated branch that exists only for sufficiently high wind stress. Subsequent global and local bifurcations all involve the subpolar branch, which alone exists in the limit of vanishing wind stress. Purely subpolar solutions vary on an interannual scale, whereas combined subpolar and subtropical solutions exhibit complex transitions affected by a second, subpolar homoclinic orbit. In the latter case, the timescale of the variability is interdecadal. The role of the global bifurcations in the interdecadal variability is investigated. Numerical simulations were carried out for the North Atlantic with earth topography- 5 minute (ETOPO-5) coastline geometry in the presence of realistic, as well as idealized, wind stress forcing. The simulations exhibit a realistic Gulf Stream at 20-km resolution and with realistic wind stress. The variability at 12-km resolution exhibits spectral peaks at 6 months, 16 months, and 6–7 years. The subannual mode is strongest in the subtropical gyre; the interannual modes are both strongest in the subpolar gyre.

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Simonnet, Eric, Michael Ghil, Kayo Ide, Roger Temam, and Shouhong Wang. 2003. “Low-Frequency Variability in Shallow-Water Models of the Wind-Driven Ocean Circulation. Part I: Steady-State Solution.” Journal of Physical Oceanography 33 (4). Abstract

Successive bifurcations—from steady states through periodic to aperiodic solutions—are studied in a shallow- water, reduced-gravity, 2 ½ -layer model of the midlatitude ocean circulation subject to time-independent wind stress. The bifurcation sequence is studied in detail for a rectangular basin with an idealized spatial pattern of wind stress. The aperiodic behavior is studied also in a North Atlantic–shaped basin with realistic continental contours. The bifurcation sequence in the rectangular basin is studied in Part I, the present article. It follows essentially the one reported for single-layer quasigeostrophic and 1 ½ -layer shallow-water models. As the intensity of the north– south-symmetric, zonal wind stress is increased, the nearly symmetric double-gyre circulation is destabilized through a perturbed pitchfork bifurcation. The low-stress steady solution, with its nearly equal subtropical and subpolar gyres, is replaced by an approximately mirror-symmetric pair of stable equilibria. The two solution branches so obtained are named after the inertial recirculation cell that is stronger, subtropical or subpolar, respectively. This perturbed pitchfork bifurcation and the associated Hopf bifurcations are robust to changes in the interface friction between the two active layers and the thickness H 2 of the lower active layer. They persist in the presence of asymmetries in the wind stress and of changes in the model’s spatial resolution and finite- difference scheme. Time-dependent model behavior in the rectangular basin, as well as in the more realistic, North Atlantic–shaped one, is studied in Part II.

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Varadi, F., B. Runnegar, and Michael Ghil. 2003. “Successive refinements in long-term integrations of planetary orbits.” The Astrophysical Journal 592 (1). IOP Publishing: 620.
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Kao, J., D. Flicker, R. Henninger, Michael Ghil, and K. Ide. 2003. “Using extended Kalman filter for data assimilation and uncertainty quantification in shock-wave dynamics.” Uncertainty Modeling and Analysis, 2003. ISUMA 2003. Fourth International Symposium on, 398–407. IEEE.
2002
Ghil, Michael, M. R. Allen, M. D. Dettinger, Kayo Ide, Dmitri Kondrashov, M. E. Mann, Andrew W. Robertson, et al. 2002. “Advanced spectral methods for climatic time series.” Reviews of Geophysics 40 (1): 1–41.
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