On the Theory of the Long-Term Variability of the Atmosphere

Egger, Joseph; Schilling, Heinz-Dieter

doi:10.1175/1520-0469(1983)040<1073:ottotl>2.0.co;2

Cited by 58 publications

(24 citation statements)

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“…High-frequency synoptic activity interacts with lowfrequency variability through nonlinear rectification (Egger and Schilling 1983;Lau and Holopainen 1984;Lau 1988;Vautard and Legras 1988;Cai and Mak 1990a;Lau and Nath 1991;Branstator 1990Branstator , 1995Limpasuvan andHartmann 1999, 2000). Cai and Mak (1990a) demonstrated that planetary low-frequency flow and synoptic eddy flow depend on each other.…”

Section: Introductionmentioning

confidence: 99%

Eddy-Induced Instability for Low-Frequency Variability

Jin

2010

Journal of the Atmospheric Sciences

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Synoptic eddy-mean flow interaction has been recognized as one of the key sources for extratropical lowfrequency variability. In this paper, the underlying dynamics of this interaction are examined from the perspective of a synoptic eddy-induced dynamic instability. To delineate this instability, a barotropic model is used that is linearized with respect to a stochastic basic flow prescribed with both climatologic-mean flow and synoptic eddy statistics. This linear model captures the dynamics of feedback between synoptic eddy and lowfrequency flow through a dynamic closure that relates the anomalous eddy vorticity forcing to low-frequency flow anomalies. After reducing this dynamic closure to its fundamental components, this stability is elucidated with analytical results under the most idealized consideration of basic flow. It is shown that through systematic alteration of the synoptic eddy structures in the basic flow, a low-frequency planetary-scale perturbation generates anomalous eddy vorticity forcing positively proportional to the vorticity of the perturbation. Such a perturbation amplifies itself; the energy source for its growth comes from the reservoir residing in the basic synoptic eddy activity. Thus, the growth rate of the synoptic eddy-induced dynamic instability depends primarily on the kinetic energy level of the basic synoptic eddy activity. Moreover, this instability is scale selective with preference for zonal symmetric and asymmetric planetary-scale modes, whose meridional and zonal scales are roughly in the range of those of the observed leading low-frequency patterns. Analysis of this synoptic eddy-induced instability provides insight into the origin of extratropical low-frequency variability.

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Section: Introductionmentioning

confidence: 99%

Eddy-Induced Instability for Low-Frequency Variability

Jin

2010

Journal of the Atmospheric Sciences

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“…It is well recognized that two‐way interaction between synoptic eddies and low‐frequency flow plays an important role in the formations of climate mean state and low‐frequency climate modes [ Lau and Wallace , 1979; Egger and Schilling , 1983; Lau and Holopainen , 1984; Lau , 1988; Cai and Mak , 1990; Lau and Nath , 1991; Cai and Van den Dool , 1991; Qin and Robinson , 1992; Whitaker and Barcilon , 1992a, 1992b, 1995; Branstator , 1995; Limpasuvan and Hartmann , 1999, 2000; Robinson , 2000]. In particular, Lau [1988] first demonstrated that the predominant climate modes are closely related to the storm track variability and that the vorticity fluxes by synoptic eddies give a positive feedback to the dominant low‐frequency mode.…”

Section: Introductionmentioning

confidence: 99%

Role of synoptic eddies on low‐frequency precipitation variation

2010

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[1] This study investigates a contribution of the synoptic-eddy moisture feedback to low-frequency precipitation variability. On one hand, synoptic-eddy moisture flux is systematically controlled by monthly mean flow. On the other hand, anomalous synopticeddy moisture fluxes can positively contribute to low-frequency precipitation anomalies. The eddy moisture convergence exhibits a considerable magnitude compared to that of precipitation variability, so their ratio is more than 0.5 over several extratropical regions. In addition, the moisture convergence induced by synoptic eddies is significantly correlated to precipitation variability. We also showed eddy-induced moisture convergence plays an important role in the variability of PNA (Pacific North America Pattern)-related precipitation and polar precipitation.

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“…For (1) to be a closed system, F can represent only stochastic forcing with externally specified amplitudes; otherwise, a second model of F would be needed. Such a simple model can reproduce the gross features of observed low-frequency variance statistics if L is a linearized barotropic operator (e.g., Egger and Schilling 1983;Newman et al 1997;Branstator and Frederikson 2003). However, as Newman et al (1997) stressed, it does a poor job of explaining the evolution of climate anomalies and related statistics, such as lag covariances.…”

Section: Introductionmentioning

confidence: 99%

Tropical and Stratospheric Influences on Extratropical Short-Term Climate Variability

Newman

Sardeshmukh

2008

Journal of Climate

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The relative impacts of tropical diabatic heating and stratospheric circulation anomalies on wintertime extratropical tropospheric variability are investigated in a linear inverse model (LIM) derived from the observed zero lag and 5-day lag covariances of 7-day running mean departures from the annual cycle. The model predicts the covariances at all other lags. The predicted and observed lag covariances are generally found to be in excellent agreement, even at the much longer lag of 21 days. This validates the LIM's basic premise that the dynamics of weekly averages are effectively linear and stochastically driven, which justifies further linear diagnosis of the system.Analysis of interactions among the LIM's variables shows that tropical diabatic heating greatly enhances persistent variability over most of the Northern Hemisphere, especially over the Pacific Ocean and North America. Stratospheric effects are largely confined to the polar region, where they ensure that the dominant pattern of sea level pressure variability is the annular Arctic Oscillation rather than the more localized North Atlantic Oscillation. Over the North Atlantic, both effects are important, although some of the stratospheric influence is ultimately traceable to tropical forcing. In general, the tropically forced anomalies extend through the depth of the troposphere and into the stratosphere, whereas stratospherically generated anomalies tend to be largest at the surface and relatively weak at midtropospheric levels. Some persistent variability is, however, found even in the absence of these "external" forcings, especially near the amplitude maxima of the leading eigenmodes of the internal extratropical tropospheric evolution operator. One of these eigenmodes has a circumglobal zonal wavenumber-5 structure with maxima over the Arabian Sea and the central Pacific, and two others are associated with north-south dipole variations across the North Atlantic jet. Overall, tropical influences are generally found to be larger than stratospheric influences on extratropical tropospheric variability and have a pronounced impact on the persistent, and therefore the potentially predictable, portion of that variability.

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On the Theory of the Long-Term Variability of the Atmosphere

Cited by 58 publications

References 0 publications

Eddy-Induced Instability for Low-Frequency Variability

Eddy-Induced Instability for Low-Frequency Variability

Role of synoptic eddies on low‐frequency precipitation variation

Tropical and Stratospheric Influences on Extratropical Short-Term Climate Variability

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