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Jadwiga H. Beres

1. Introduction Parameterization of gravity wave drag force (GWD) is critical to the proper representation of the circulations of the middle and upper atmosphere in general circulation models (GCMs; e.g., Lindzen 1981 ; Boville 1995 ). Parameterized GWD is proportional to the vertical divergence of momentum flux carried by the spectrum of upward-propagating gravity waves specified in the model. Proper representation of this quantity is dependent on the specification of the gravity wave phase

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Sylvain Mailler and François Lott

distinction between the drag forces that are opposed to the low-level winds and the lift forces that are perpendicular to them. At the mesoscale, where the mountain flow dynamics is controlled by gravity waves and includes low-level flow blocking, the drag force is very important, whereas at the synoptic and planetary scales the lift force plays a key role and causes vortex compression over mountains ( Smith 1979 ). By triggering baroclinic wave development and forcing planetary-scale waves, these lift

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Paul F. Fanelli and Peter R. Bannon

1. Introduction A variety of perturbations frequently force the compressible atmosphere out of its approximate hydrostatic and geostrophic state. The atmosphere must adjust to these imbalances toward a new equilibrium state. This atmospheric adjustment process involves the generation of both buoyancy and acoustic modes that act to redistribute mass, momentum, and entropy so that a new balance is reached. Chagnon and Bannon (2005a) provide a recent survey of the literature. Chagnon and Bannon

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Werner Metz

15JULY 1986 WERNER METZ 1467Transient Cyclone-Scale Vorticity Forcing of Blocking Highs WERNER METZMeteorological Institute, University of Ml~nchen, FRG(Manuscript received 10 July 1985, in final form 5 February 1986)ABSTRACT The forcing of Northern Hemisphere blocking highs by the transient vorticity transfer from the cyclone-scaleeddies into the planetary flow is investigated

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Hong-Li Ren, Fei-Fei Jin, and Jong-Seong Kug

atmospheric circulation? Previous studies have concluded that the LFV is internal to atmospheric dynamics. The internal dynamics in atmospheric models without external forcing can display significant LFV and the pure nonlinear eddy–mean flow interactions can generate a substantial amount of LFV (e.g., Held 1983 ; Egger and Schilling 1983 ; Hendon and Hartmann 1985 ; Cai and Mak 1990 ; Cai and van den Dool 1991 ; Lau and Nath 1991 ; Robinson 1991 ; Branstator 1995 ; Whitaker and Barcilon 1995

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Gerald Schubert and Richard E. Young

Atmospheres.The 4-Day Venus Circulation Driven by Periodic Thermal Forcing GERALD SCHUBERT AND RICHARD E. YOUNgDept. of Planetary and Space Science, University of California at Los A ngdes(Manuscript received 30 March 1970)ABSTRACT It has been proposed that the observed 4-day retrograde rotation of the Venus atmosphere is a zonalmotion of at least the upper atmosphere driven by periodic solar thermal forcing. We have assessed therelative importance of periodic thermal forcing for the atmospheres of

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Volkmar Wirth and Timothy J. Dunkerton

hurricane the eye secondary circulation must be mechanically forced ( Emanuel 1997 ). Both Smith (1980) and Emanuel (1997) refer to turbulent exchange of angular momentum across the eyewall when talking about mechanical forcing. By contrast, the hurricane theory of Emanuel (1986) is effectively inviscid in the interior of the atmosphere, leaving Ekman pumping from the frictional boundary layer as the only possible source of mechanical forcing. The above quoted theoretical approaches are not

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Kaushik Srinivasan and W. R. Young

1. Introduction In this work we consider a canonical linear problem: the stochastically forced, linearized β -plane vorticity equation with a background mean shear γ : The eddy vorticity is related to the eddy streamfunction by , and the eddy velocities are . The random forcing ξ ( x , y , t ) is spatially homogenous and white noise in time and is characterized more precisely in section 2 . Drag, with coefficient μ , is the dissipative mechanism. Our main concern is the eddy transport

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Rajul E. Pandya and M. Joan Alexander

detailed vertical profile of the heating. Thus many features of the observations of convectively forced planetary-scale waves can be accounted for within a linear framework using only the depth of the convective heating and the zonal mean wind variations. A similar approach has been applied to smaller-scale waves in the inertia-gravity wave portion of the spectrum ( Manzini and Hamilton 1993 ; Bergman and Salby 1994 ). Manzini and Hamilton (1993) examined the role of convective heating in forcing

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James W. Hurrell

2286 JOURNAL OF THE ATMOSPHERIC SCIENCES VoL, 52, No. 12Transient Eddy Forcing of the Rotational Flow during Northern Winter JAMES W. HURRELLNational Center for Atmospheric Research,* Boulder, Colorado(Manuscript received 20 September 1994, in final form 23 January 1995) ABSTRACT The total direct transient eddy forcing of the vorticity

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