Atmosphere & climate

Feliks, Yizhak, Michael Ghil, and Eric Simonnet. “Low-frequency variability in the midlatitude atmosphere induced by an oceanic thermal front.” Journal of the atmospheric sciences 61, no. 9 (2004): 961–981.
Lott, François, Andrew W. Robertson, and Michael Ghil. “Mountain torques and Northern Hemisphere low-frequency variability. Part II: Regional aspects.” Journal of the Atmospheric Sciences 61, no. 11 (2004): 1272–1283.
Lott, François, Andrew W. Robertson, and Michael Ghil. “Mountain torques and Northern Hemisphere low-frequency variability. Part I: Hemispheric aspects.” Journal of the Atmospheric Sciences 61, no. 11 (2004): 1259–1271.
Kahn, Brian H., Annmarie Eldering, Michael Ghil, Simona Bordoni, and Shepard A. Clough. “Sensitivity analysis of cirrus cloud properties from high-resolution infrared spectra. Part I: Methodology and synthetic cirrus.” Journal of Climate 17, no. 24 (2004): 4856–4870.
Kondrashov, Dmitri, K. Ide, and Michael Ghil. “Weather regimes and preferred transition paths in a three-level quasigeostrophic model.” Journal of the Atmospheric Sciences 61, no. 5 (2004): 568–587.
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Bellon, G., H. Le Treut, and Michael Ghil. “Large-scale and evaporation-wind feedbacks in a box model of the tropical climate.” Geophysical Research Letters 30, no. 22 (2003).
Kravtsov, S., Andrew W. Robertson, and Michael Ghil. “Low-Frequency Variability in a Baroclinic Beta-Channel with Land-Sea Contrast*.” Journal of the Atmospheric Sciences 60, no. 18 (2003): 2267–2293.
Koo, Seongjoon, Andrew W. Robertson, and Michael Ghil. “Multiple regimes and low-frequency oscillations in the Southern Hemisphere's zonal-mean flow.” Journal of Geophysical Research: Atmospheres 107, no. D21 (2002).
Gildor, Hezi, and Michael Ghil. “Phase relations between climate proxy records: Potential effect of seasonal precipitation changes.” Geophysical Research Letters 29, no. 2 (2002).
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Kao, C.-Y. J., D. I. Cooper, J. M. Reisner, W. E. Eichinger, and Michael Ghil. “Probing near-surface atmospheric turbulence with high-resolution lidar measurements and models.” Journal of Geophysical Research: Atmospheres 107, no. D10 (2002).
Koo, Seongjoon, and Michael Ghil. “Successive bifurcations in a simple model of atmospheric zonal-flow vacillation.” Chaos: An Interdisciplinary Journal of Nonlinear Science 12, no. 2 (2002): 300–309.
Ghil, Michael, and Andrew W. Robertson. “``Waves'' vs. ``particles'' in the atmosphere's phase space: A pathway to long-range forecasting?Proceedings of the National Academy of Sciences 99 (2002): 2493–2500. Abstract

Thirty years ago, E. N. Lorenz provided some approximate limits to atmospheric predictability. The details—in space and time—of atmospheric flow fields are lost after about 10 days. Certain gross flow features recur, however, after times of the order of 10–50 days, giving hope for their prediction. Over the last two decades, numerous attempts have been made to predict these recurrent features. The attempts have involved, on the one hand, systematic improvements in numerical weather prediction by increasing the spatial resolution and physical faithfulness in the detailed models used for this prediction. On the other hand, theoretical attempts motivated by the same goal have involved the study of the large-scale atmospheric motions’ phase space and the inhomoge- neities therein. These ‘‘coarse-graining’’ studies have addressed observed as well as simulated atmospheric data sets. Two distinct approaches have been used in these studies: the episodic or intermittent and the oscillatory or periodic. The intermittency approach describes multiple-flow (or weather) regimes, their per- sistence and recurrence, and the Markov chain of transitions among them. The periodicity approach studies intraseasonal oscil- lations, with periods of 15–70 days, and their predictability. We review these two approaches, ‘‘particles’’ vs. ‘‘waves,’’ in the quantum physics analogy alluded to in the title of this article, discuss their complementarity, and outline unsolved problems.

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Ide, Kayo, H. Le Treut, Z.-X. Li, and Michael Ghil. “Atmospheric radiative equilibria. Part II: bimodal solutions for atmospheric optical properties.” Climate Dynamics 18, no. 1-2 (2001): 29–49.
Tian, Yudong, Eric R. Weeks, Kayo Ide, J. S. Urbach, Charles N. Baroud, Michael Ghil, and Harry L. Swinney. “Experimental and numerical studies of an eastward jet over topography.” Journal of Fluid Mechanics 438 (2001): 129–157.
Lott, François, Andrew W. Robertson, and Michael Ghil. “Mountain torques and atmospheric oscillations.” Geophys. Res. Lett 28 (2001): 1207–1210.
Smyth, Padhraic, Kayo Ide, and Michael Ghil. “Multiple Regimes in Northern Hemisphere Height Fields via Mixture Model Clustering.” Journal of the Atmospheric Sciences 56, no. 21 (1999): 3704–3723.
Moron, Vincent, Robert Vautard, and Michael Ghil. “Trends, interdecadal and interannual oscillations in global sea-surface temperatures.” Climate Dynamics 14, no. 7 (1998): 545–569. Abstract

This study aims at a global description of climatic phenomena that exhibit some regularity during the twentieth century. Multi-channel singular spectrum analysis is used to extract long-term trends and quasi-regular oscillations of global sea-surface temperature (SST) fields since 1901. Regional analyses are also performed on the Pacific, (Northern and Southern) Atlantic, and Indian Ocean basins. The strongest climatic signal is the irregular long-term trend, characterized by overall warming during 1910–1940 and since 1975, with cooling (especially of the Northern Hemisphere) between these two warming intervals. Substantial cooling prevailed in the North Pacific between 1950 and 1980, and continues in the North Atlantic today. Both cooling and warming are preceded by SST anomalies of the same sign in the subpolar North Atlantic. Near-decadal oscillations are present primarily over the North Atlantic, but also over the South Atlantic and the Indian Ocean. A 13–15-y oscillation exhibits a seesaw pattern between the Gulf-Stream region and the North-Atlantic Drift and affects also the tropical Atlantic. Another 7–8-y oscillation involves the entire double-gyre circulation of the North Atlantic, being mostly of one sign across the basin, with a minor maximum of opposite sign in the subpolar gyre and the major maximum in the northwestern part of the subtropical gyre. Three distinct interannual signals are found, with periods of about 60–65, 45 and 24–30 months. All three are strongest in the tropical Eastern Pacific. The first two extend throughout the whole Pacific and still exhibit some consistent, albeit weak, patterns in other ocean basins. The latter is weaker overall and has no consistent signature outside the Pacific. The 60-month oscillation obtains primarily before the 1960s and the 45-month oscillation afterwards.

Jin, F.-F., J. David Neelin, and Michael Ghil. “El Niño Southern Oscillation and the annual cycle: Subharmonic frequency-locking and aperiodicity.” Physica D 98 (1996): 442–465.
Ghil, Michael, and Pascal Yiou. “Spectral methods: What they can and cannot do for climatic time series.” In Decadal Climate Variability: Dynamics and Predictability, edited by D. Anderson and J. Willebrand, 446–482. Springer-Verlag, Berlin/Heidelberg, 1996.
Plaut, Guy, Michael Ghil, and Robert Vautard. “Interannual and Interdecadal Variability in 335 Years of Central England Temperatures.” Science 268, no. 5211 (1995): 710–713. Abstract

Understanding the natural variability of climate is important for predicting its near-term evolution. Models of the oceans' thermohaline and wind-driven circulation show low-frequency oscillations. Long instrumental records can help validate the oscillatory behavior of these models. Singular spectrum analysis applied to the 335-year-long central England temperature (CET) record has identified climate oscillations with interannual (7- to 8-year) and interdecadal (15- and 25-year) periods, probably related to the North Atlantic's wind-driven and thermohaline circulation, respectively. Statistical prediction of oscillatory variability shows CETs decreasing toward the end of this decade and rising again into the middle of the next.