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Norihiko Sugimoto, Keiichi Ishioka, and Katsuya Ishii

; Fritts and Alexander 2003 ). There are many studies on gravity waves, and several sources for these waves (topography, convection, jets, fronts, cyclones, and so on) have been identified ( Fritts and Nastrom 1992 ; Sato 2000 ). From several observational studies it has been suggested that inertial gravity waves are radiated from strong rotational flows, such as polar night jets ( Yoshiki and Sato 2000 ), subtropical jets ( Uccelini and Koch 1987 ; Kitamura and Hirota 1989 ; Sato 1994 ; Plougonven

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David A. Schecter

radiation, a DVRW simultaneously stirs PV in its critical layer. Such stirring efficiently transfers angular pseudomomentum from the DVRW into the critical layer, and thereby acts to damp the wave. Damping will prevail over radiative pumping if the radial gradient of PV in the critical layer is sufficiently large ( SM04 ; SM06 ). Figure 2 illustrates the two potential fates of a DVRW in an MC. Section 4 will demonstrate that a precise growth rate formula for the DVRW is readily extracted from an

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Paul D. Williams, Thomas W. N. Haine, and Peter L. Read

the peak of their generation. We discuss the consequences of this energy flux for the atmosphere and ocean in section 6 . For comparison, Afanasyev (2003) estimates that approximately 4% of the energy is radiated as inertia–gravity waves in a nonrotating, linearly stratified laboratory fluid during the adjustment after the collision of two translating vortex dipoles. 5. Variation of inertia–gravity wave activity with Rossby number We now extend the life cycle analysis of section 4 , which was

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Y. D. Afanasyev, P. B. Rhines, and E. G. Lindahl

adjustment the flow radiates waves. Since the waves can propagate far away without significant decay, they can be dynamically important despite the fact that their energy is relatively small. The exact circumstances through which the wave radiation takes place are yet to be established. It is also important to measure the amount of energy radiated in these events. Acoustic wave generation by turbulence in a compressible fluid is analogous, and Lighthill’s (1952) classic analysis regards compact regions

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Kaoru Sato and Motoyoshi Yoshiki

frequency approaches zero. Another important finding was the dominance of downward energy flux associated with gravity waves in the polar night jet (PNJ) region, suggesting gravity wave sources in the polar stratosphere. Yoshiki and Sato (2000) examined seasonal variation of gravity waves in the polar stratosphere using operational radiosonde data from 33 stations over a period of 10 yr. It was shown that both potential and kinetic energies of gravity waves per unit mass are maximized in austral spring

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Dong L. Wu and Stephen D. Eckermann

radiated from jet imbalance (see, e.g., section 7h of Kim et al. 2003 ). Direct measurements of GWs by advanced satellite remote sensors can reduce some of these uncertainties ( Wu et al. 2006a ). One of the first satellite instruments to provide global measurements of stratospheric GWs was the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite ( UARS ; Wu and Waters 1996 , 1997 ). Those measurements provided initial insights into some of the major orographic and deep

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Chris Snyder, David J. Muraki, Riwal Plougonven, and Fuqing Zhang

b , the initial conditions for the simulation are the geostrophic winds, potential temperature θ , and hydrostatic pressure from the QG dipole solution of Muraki and Snyder (2007) . These initial conditions do not directly yield a steadily propagating solution of the primitive equations for two reasons. First, because the initial conditions are purely geostrophic, the solution undergoes transient adjustment in which strong inertia–gravity waves radiate away from the dipole. These waves are

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Yonghui Lin and Fuqing Zhang

Mesoscale Model (MM5; Dudhia 1993). Three two-way-nested model domains (D1, D2, and D3) respectively use 90-, 30-, and 10-km horizontal grid spacing, and 60 vertical layers are used with 360-m vertical spacing. D1 is configured in the shape of a channel 27 000 km long ( x direction) and 8010 km wide ( y direction), and D2 (D3) is a rectangular subdomain 9300 (3100) km long and 4500 (2500) km wide centered at x = 6150 (17 000) km and y = 2850 (6700) km within D1 (D2). Radiative top boundary

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Vladimir Zeitlin

/ c 0 ) r , Eq. (26) takes the form of the Bessel equation: The pressure is proportional to the time derivative of the complex potential for the wave field. Hence, the matching condition is Only the n = 2 harmonics should be present in the wave field, and the following choice of its amplitude ensures the matching (29) : Here, H (2) n is the Hankel function of the second kind, a solution of (28) corresponding to the outward energy flux. 2) The effects of rotation In the rotating case at

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