Atmosphere & climate

2007
Camargo, Suzana J., Andrew W. Robertson, Scott J. Gaffney, Padhraic Smyth, and Michael Ghil. 2007. “Cluster analysis of typhoon tracks. Part II: Large-scale circulation and ENSO.” Journal of Climate 20 (14): 3654–3676.
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Feliks, Yizhak, Michael Ghil, and Eric Simonnet. 2007. “Low-frequency variability in the midlatitude baroclinic atmosphere induced by an oceanic thermal front.” Journal of the Atmospheric Sciences 64 (1): 97–116.
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Kondrashov, Dmitri, Jie Shen, Richard Berk, Fabio D'Andrea, and Michael Ghil. 2007. “Predicting weather regime transitions in Northern Hemisphere datasets.” Climate Dynamics 29 (5). Springer: 535–551.
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Deloncle, Axel, Richard Berk, Fabio D'Andrea, and Michael Ghil. 2007. “Weather regime prediction using statistical learning.” Journal of the Atmospheric Sciences 64 (5): 1619–1635.
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2006
Kondrashov, Dmitri, S. Kravtsov, and M. Ghil. 2006. “Empirical Mode Reduction in a Model of Extratropical Low-Frequency Variability.” Journal of the Atmospheric Sciences 63 (7): 1859-1877. Publisher's Version
Kondrashov, Dmitri, S Kravtsov, and M Ghil. 2006. “Empirical mode reduction in a model of extratropical low-frequency variability.” Journal of the Atmospheric Sciences 63 (7): 1859–1877. Abstract

This paper constructs and analyzes a reduced nonlinear stochastic model of extratropical low-frequency variability. To do so, it applies multilevel quadratic regression to the output of a long simulation of a global baroclinic, quasigeostrophic, three-level (QG3) model with topography; the model's phase space has a dimension of O(104). The reduced model has 45 variables and captures well the non-Gaussian features of the QG3 model's probability density function (PDF). In particular, the reduced model's PDF shares with the QG3 model its four anomalously persistent flow patterns, which correspond to opposite phases of the Arctic Oscillation and the North Atlantic Oscillation, as well as the Markov chain of transitions between these regimes. In addition, multichannel singular spectrum analysis identifies intraseasonal oscillations with a period of 35–37 days and of 20 days in the data generated by both the QG3 model and its low-dimensional analog. An analytical and numerical study of the reduced model starts with the fixed points and oscillatory eigenmodes of the model's deterministic part and uses systematically an increasing noise parameter to connect these with the behavior of the full, stochastically forced model version. The results of this study point to the origin of the QG3 model's multiple regimes and intraseasonal oscillations and identify the connections between the two types of behavior.

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Kravtsov, S., Andrew W. Robertson, and Michael Ghil. 2006. “Multiple regimes and low-frequency oscillations in the Northern Hemisphere's zonal-mean flow.” Journal of the Atmospheric Sciences 63 (3): 840–860.
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Bellon, G., Michael Ghil, and H. Le Treut. 2006. “Scale separation for moisture-laden regions in the tropical atmosphere.” Geophysical Research Letters 33 (1). Wiley Online Library.
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2005
Kravtsov, S., Andrew W. Robertson, and Michael Ghil. 2005. “Bimodal behavior in the zonal mean flow of a baroclinic beta-channel model.” Journal of the Atmospheric Sciences 62 (6): 1746–1769.
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Koo, Seongjoon, Andrew W. Robertson, and Michael Ghil. 2005. “A Multiple-Regime Approach to Atmospheric Zonal-Flow Vacillation”.
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Kondrashov, Dmitri, Yizhak Feliks, and Michael Ghil. 2005. “Oscillatory modes of extended Nile River records (A.D. 622–1922).” Geophysical Research Letters 32 (10). AGU: L10702. Abstract

The historical records of the low- and high-water levels of the Nile River are among the longest climatic records that have near-annual resolution. There are few gaps in the first part of the records (A.D. 622-1470) and larger gaps later (A.D. 1471-1922). We apply advanced spectral methods, Singular-Spectrum Analysis (SSA) and the Multi-Taper Method (MTM), to fill the gaps and to locate interannual and interdecadal periodicities. The gap filling uses a novel, iterative version of SSA. Our analysis reveals several statistically significant features of the records: a nonlinear, data-adaptive trend that includes a 256-year cycle, a quasi-quadriennial (4.2-year) and a quasi-biennial (2.2-year) mode, as well as additional periodicities of 64, 19, 12, and, most strikingly, 7 years. The quasi-quadriennial and quasi-biennial modes support the long-established connection between the Nile River discharge and the El-Niño/Southern Oscillation (ENSO) phenomenon in the Indo-Pacific Ocean. The longest periods might be of astronomical origin. The 7-year periodicity, possibly related to the biblical cycle of lean and fat years, seems to be due to North Atlantic influences.

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2004
Feliks, Yizhak, Michael Ghil, and Eric Simonnet. 2004. “Low-frequency variability in the midlatitude atmosphere induced by an oceanic thermal front.” Journal of the atmospheric sciences 61 (9): 961–981.
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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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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
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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2002
Koo, Seongjoon, Andrew W. Robertson, and Michael Ghil. 2002. “Multiple regimes and low-frequency oscillations in the Southern Hemisphere's zonal-mean flow.” Journal of Geophysical Research: Atmospheres 107 (D21). Wiley Online Library.
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Gildor, Hezi, and Michael Ghil. 2002. “Phase relations between climate proxy records: Potential effect of seasonal precipitation changes.” Geophysical Research Letters 29 (2). Wiley Online Library.
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