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Robert A. Pearson

weather maps.strictions, the equations of motion can be written asDu Op---fv ....DtDv--+ fu= 0, (2)Dtop--= --~, (3)OzDo'---~2w =/~ &,~,t), (4)Dt--+---- 0. (5)Ox Oz These equations are those used by Geisler andBretherton (1969) with the addition of rotation. Thevariables u, v, w are the velocity fields, f the Coriolisparameter, N the Brunt-Viiisiilii frequency given byN~= --(g/Oo)(dOo/dz) where Oo(z) is the

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Lee-Or Merkine
and
Moshe Israeli

the lee side of the topography. It is found thatwhen the amplitude of the stationary Rossby wave is sufficiently large a flow which is stable upstream maybecome unstable downstream. The influence of the baroclinlc shear is to reduce the growth rate of the instability in comparison to the corresponding barotropic case. Nonetheless, the growth rates obtained can besign/ficant!y larger than those obtained for a baroclinlc parallel zonal flow, possessing the same baroclinicity.1. Introduction It

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Jason K. S. Ching

speed, l=[olopainen (1967) also stated that: "If calculations of the surface stress curl from the vorticity budget of the atmosphere were made on a, daily basis~ it might be possible.,, to produce a map of some kind of empirical stress coefficient which then could be used~ for example, in the numerical weather prediction mode]s?' Studies of frictionally induced vertical velocitybased on actnal observations have been sparse. Thisstate of affairs is understandable because accuratemeasurements in

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Qin Xu
and
Jie Cao

balance constraints from (2.1c) and (2.3) and one algebraic constraint from (2.2) for the remaining three primary-flow variables ( ϕ , α , θ ); and (iii) the vector diagnostic equation (3.10) for Ψ with computed from Ψ via (3.9) . 4. Conclusions In this paper, the SBM of X94 is rederived in terrain-following pressure coordinates: the η coordinates. The rederived SBM truncates only the secondary-flow vorticity advection and stretching–tilting terms from the vector vorticity

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R. J. Purser

formulations exactly Legendre transformable. The Legendre-transformable representations of the vortex models appear superficially not to preserve the angular symmetry since the concentric circles of the vortex are mapped to sectors of concentric hyperbolas in each transformed horizontal plane. The symmetry breaking is illusory, however; the new representation does preserve the symmetry, provided the space of points x̂ of the Legendre-transformable representation is regarded as being furnished with the

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Nadir Jeevanjee
and
David M. Romps

changing the resolution. All data in the next section are from the end of this run. We diagnose directly from CRM output via the Poisson equation (10) . We compute slightly indirectly by first computing the inertial pressure from CRM output via (B2) and then using . We solve both Poisson equations by Fourier transforming in the horizontal, which yields systems of algebraic equations that can be solved by inverting a tridiagonal matrix. As discussed in section 2a , the fact that at model

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J. G. Charney
,
Bruce Gilchrist
, and
F. G. Shuman

distinguish the present approximation from others in whichcertain partial linearizations are made. In all versions, however,the non-linearity of the advective terms is retained.0~~0~~~1956 J. G. CHARNEY, BRUCE GILCHRIST, AND F. G. SCHUMAN 49 1equationae D- aqDo(13)__--_- 0.ap Dt ap DtUsing the finite-difference approximations for thevertical derivatives of cp, we have84/89 = (2 AP)-l((ok+l - Pk),a2P/ap2 = (Afi)-2((ok+1 f Pk-1 - 2Pk).The spherical earth is mapped conformally onto aplane with the Cartesian

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Mary L. Parlance
and
Terrence R. Nathan

= [TA' + (ik-~Tc + yt)B']eikx sinTry + *, (2.9b)where A' and B' are constants and y~ = (cgc/cgk) evaluated at (U~)m~. Although the wave exhibits no exponential growth at this order (i.e., c~ --- 0), the linearsystem predicts that the wave will grow algebraically.This type of algebraic growth, termed "direct resonance'' by Akylas and Benney (1980, 1982), manifests itself in the nonlinear problem, as shown in section3, through the emergence of

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Paul D. Reasor
and
Michael T. Montgomery

b ). The vortex precesses about the stationary midlevel centroid with no obvious sign of alignment over the 4 τ e period (where τ e denotes a mean vortex circulation period at the RMW, which is approximately 2.9 days for this vortex). The precession period of the vortex is approximately 12.5 days, or just over 4 τ e . As evident from comparison of the two simulations, the interaction between vertical modes is not crucial to understanding the vortex evolution for the small tilts considered

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R. J. Zammett
and
A. C. Fowler

-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5), adapted for use in a polar environment ( Bromwich et al. 2001 ), and hereafter referred to as Polar MM5. Although we make this comparison to show that the parameterized model can fit observations, we do not seek to establish that in all circumstances, the neglect of moisture, Coriolis force, and external pressure gradient is quantitatively accurate. 2. The Prandtl model We consider two

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