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P. H. Haynes, D. A. Poet, and E. F. Shuckburgh

.) rather than the last barrier transition. Here we compare a particular kinematic model, in which the flow is given by the streamfunction: representing a time-periodic flow with period 2 π /0.3, with a corresponding dynamical model, based on the two-dimensional equations on a β plane with topographic forcing: where the total streamfunction ψ = −0.5 y + ψ̃ and β has been taken to be 0.5. The topographic forcing h ( x , y , t ) is given by The flow is taken to be 2 π periodic in the x

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P. B. Rhines

gravest mode, κR =8.77, according to the approximate theory above, has a period of 10.8 s compared to the forcing period of 8.3 s The paraboloid in this case is rather big, however, with δh m /h m ∼1, so quantitative comparisons require a more complete solution. The figure suggests the presence of mean zonal flow as well as waves. This is the classic result of stirring a PV gradient, shown so clearly by Whitehead (1975) and elaborated by Rhines (1977) . Westward, anticyclonic circulation

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Semion Sukoriansky, Nadejda Dikovskaya, and Boris Galperin

transfer of energy from small to large scales takes place in such a way that most of the energy is directed to the zonal jets. The rest of the aforementioned issues, however, remain controversial, particularly when compounded with other complicating factors such as the friction, continuous forcing, effects of the boundaries, effects of stratification, etc. Let us consider, for example, a realistic system in which the bottom friction acts like a large-scale drag. One can introduce a wavenumber

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I. G. Watterson

anthropogenic aerosol are included through a surface albedo adjustment. b. Simulation and datasets The simulation of the model that is analyzed here is one of an ensemble contributed to the “IPCC [Intergovernmental Panel on Climate Change] model output” dataset (available from ). It represents climate over the years 1871–2200, with observationally based “forcing” for the years to 2000 (as described by Watterson and Dix 2005 ). Forcing in the twenty-first century follows the A1B scenario

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Thomas Jung and Peter B. Rhines

tendency (westerly force on the atmosphere; Brown 2004 ). This arises not from Greenland but from the Aleutian low and its interaction with the upslope of the Coast Range of Alaska. The global angular momentum of the atmosphere responds primarily to pressure torque from the Rocky Mountains, Andes, and Tibetan Plateau. Pressure-drag variability on these topographies is associated with distinct atmospheric response patterns (e.g., Lott et al. 2004a , b ). This paper explores Greenland’s effect on the

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Yoshi-Yuki Hayashi, Seiya Nishizawa, Shin-ichi Takehiro, Michio Yamada, Keiichi Ishioka, and Shigeo Yoden

resolution of T85, in which variables are evaluated by the sum of spherical harmonics up to total wavenumber 85, and nonlinear terms are calculated on 256 × 128 longitude–latitude grids. A full spherical version of forced turbulence was investigated by Nozawa and Yoden (1997a , b ) for the same setup as Williams (1978) , and by Huang and Robinson (1998) for a different type of forcing to realize a constant energy input rate. They reconfirmed the spontaneous formation of a banded structure of zonal

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Gang Chen, Isaac M. Held, and Walter A. Robinson

of the jet shift can be understood in terms of Rossby wave refraction and reflection. Orlanski (2003) , in contrast, finds that a transition from LC1 to LC2 can be obtained in a shallow water model by increasing the amplitude of the forcing, and shows high-resolution life cycles in dry and moist 3D atmospheres that highlight this amplitude effect. The midlatitude storm tracks are composed of many growing and decaying waves, often having a nonmodal character. Rather than thinking in term of

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Robert X. Black and Brent A. McDaniel

subseasonal variability in the NAM. First, the transformed Eulerian mean (TEM) dynamical framework is used to study the net eddy-forcing (wave driving) of the zonal mean flow. The quasigeostrophic (QG) form of the TEM zonal mean momentum equation is given by where u is the zonally averaged zonal wind, f is the Coriolis parameter, υ r is the residual mean meridional velocity, z is a log-pressure coordinate with scale height H , ϕ is latitude, r is the radius of the earth, D x is a frictional

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O. Martius, C. Schwierz, and H. C. Davies

occur when strong anticyclonic vortices deform a cyclonic vortex and vice versa for the cyclonic life cycles ( Orlanski 2003 ). Because of asymmetries in the growth of vortices, stronger low-level forcing will lead to cyclonic life cycles and weaker forcing to anticyclonic life cycles ( Orlanski 2003 ). Third, previous studies that have identified the flow settings favoring the various life cycles have, on the one hand, highlighted the seminal influence of the relative meridional location of the

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Yohai Kaspi and Glenn R. Flierl

forcing and large-scale friction Huang et al. (2001) and Galperin et al. (2001) suggest a scaling law to the energy spectra of the jets and show ( Galperin et al. 2001 , 2006 ) that it matches the spectrum of the observed jets on Jupiter. Smith (2004) shows multiple jets emerging from stochastically forced quasigeostrophic (QG) turbulence in an equivalent barotropic system. As applied to a gas giant’s atmosphere, these shallow water or quasigeostrophic models have several flaws exemplified by

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