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1. Introduction Gravity waves (GWs) play a key role in the global meteorology, climate, chemistry, and microphysics of the stratosphere and mesosphere ( Fritts and Alexander 2003 ). Because finite computational resources force global climate–chemistry and weather prediction models to run at spatial resolutions that do not adequately resolve GW dynamics, these important GW-induced effects must be parameterized (e.g., McLandress 1998 ; Kim et al. 2003 ). Arguably the greatest weakness in
1. Introduction Gravity waves (GWs) play a key role in the global meteorology, climate, chemistry, and microphysics of the stratosphere and mesosphere ( Fritts and Alexander 2003 ). Because finite computational resources force global climate–chemistry and weather prediction models to run at spatial resolutions that do not adequately resolve GW dynamics, these important GW-induced effects must be parameterized (e.g., McLandress 1998 ; Kim et al. 2003 ). Arguably the greatest weakness in
1. Introduction Gravity waves are atmospheric waves with a restoring force of buoyancy, which are characterized by their small spatial scales and short periods. Gravity waves have the ability to transport momentum, mostly in the vertical, over a long distance and deposit it in the mean field through dissipation and breaking processes. Since the importance of this ability of gravity waves in the middle atmosphere was recognized in early 1980s, many observational, numerical, and theoretical
1. Introduction Gravity waves are atmospheric waves with a restoring force of buoyancy, which are characterized by their small spatial scales and short periods. Gravity waves have the ability to transport momentum, mostly in the vertical, over a long distance and deposit it in the mean field through dissipation and breaking processes. Since the importance of this ability of gravity waves in the middle atmosphere was recognized in early 1980s, many observational, numerical, and theoretical
of the DVRW equals the angular rotation frequency of the mean flow. The central radius r * of the critical layer is precisely defined by the resonance condition Figure 3a illustrates a typical set of critical layers for the DVRWs of a shallow-water MC. Through the extension of its velocity field, the DVRW can stir fluid everywhere beyond the core. Outside of the critical layer, fluid parcels moving with the mean flow experience rapid oscillations of positive and negative wave forcing, which
of the DVRW equals the angular rotation frequency of the mean flow. The central radius r * of the critical layer is precisely defined by the resonance condition Figure 3a illustrates a typical set of critical layers for the DVRWs of a shallow-water MC. Through the extension of its velocity field, the DVRW can stir fluid everywhere beyond the core. Outside of the critical layer, fluid parcels moving with the mean flow experience rapid oscillations of positive and negative wave forcing, which
-scale imbalance in generating mesoscale gravity waves were further examined most recently in Plougonven and Zhang (2007) . However, as noted in Lane et al. (2004) , without a sophisticated wave source analysis it is often difficult to determine unambiguously whether mesoscale structures, such as jets and upper-level fronts, are the source of the gravity waves or a response to some other forcing that also generates the waves. The ray-tracing technique has been widely used to investigate gravity wave sources
-scale imbalance in generating mesoscale gravity waves were further examined most recently in Plougonven and Zhang (2007) . However, as noted in Lane et al. (2004) , without a sophisticated wave source analysis it is often difficult to determine unambiguously whether mesoscale structures, such as jets and upper-level fronts, are the source of the gravity waves or a response to some other forcing that also generates the waves. The ray-tracing technique has been widely used to investigate gravity wave sources
interaction between the flow and a physical obstruction (e.g., generation in the wake of a ship; Lighthill 1978 ), which is the mechanism by which mountains generate atmospheric gravity waves ( Hines 1989 ). Direct forcing of the ocean by the atmosphere is a known source of oceanic gravity waves ( Wunsch and Ferrari 2004 ). Finally, inertia–gravity waves are also radiated during the geostrophic adjustment of a hypothetical fluid ( Rossby 1938 ), in which geostrophic balance is approached from an
interaction between the flow and a physical obstruction (e.g., generation in the wake of a ship; Lighthill 1978 ), which is the mechanism by which mountains generate atmospheric gravity waves ( Hines 1989 ). Direct forcing of the ocean by the atmosphere is a known source of oceanic gravity waves ( Wunsch and Ferrari 2004 ). Finally, inertia–gravity waves are also radiated during the geostrophic adjustment of a hypothetical fluid ( Rossby 1938 ), in which geostrophic balance is approached from an
