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they couple the zonal and vertical velocities, they are least easily dismissed for motions with the vertical scale significant compared to the horizontal scale. White and Bromley (1995) showed that they are small like 2Ω H cos ϕ / U , compared to the next smallest terms, where Ω is the planetary rotation rate, U and H characteristic horizontal velocity and height scales, and ϕ latitude. In terms of wave modes in a stratified atmosphere or ocean, it has been argued that the neglected terms
they couple the zonal and vertical velocities, they are least easily dismissed for motions with the vertical scale significant compared to the horizontal scale. White and Bromley (1995) showed that they are small like 2Ω H cos ϕ / U , compared to the next smallest terms, where Ω is the planetary rotation rate, U and H characteristic horizontal velocity and height scales, and ϕ latitude. In terms of wave modes in a stratified atmosphere or ocean, it has been argued that the neglected terms
1. Introduction Gravity waves propagating vertically from the lower atmosphere are widely recognized to play important roles in a variety of atmospheric phenomena. Known sources of these gravity waves include mountains, moist convection, fronts, upper-level jets, geostrophic adjustment, and spontaneous generation ( Fritts and Alexander 2003 , and references therein). Among these, jets are often responsible for generating low-frequency inertia–gravity waves with characteristic horizontal
1. Introduction Gravity waves propagating vertically from the lower atmosphere are widely recognized to play important roles in a variety of atmospheric phenomena. Known sources of these gravity waves include mountains, moist convection, fronts, upper-level jets, geostrophic adjustment, and spontaneous generation ( Fritts and Alexander 2003 , and references therein). Among these, jets are often responsible for generating low-frequency inertia–gravity waves with characteristic horizontal
’Sullivan and Dunkerton (1995 , hereafter OSD95) , in which spontaneous imbalance in a nonlinear baroclinic-wave life cycle of type 1 (LC1; e.g., Thorncroft et al. 1993 and references therein) produces internal inertia–gravity waves having small scales close to the grid scale of the numerical model. The small scales seem to put OSD95’s example at an opposite extreme to those in which the Lighthill theory is relevant. The Lighthill theory describes scenarios in which unsteady vortical motion
’Sullivan and Dunkerton (1995 , hereafter OSD95) , in which spontaneous imbalance in a nonlinear baroclinic-wave life cycle of type 1 (LC1; e.g., Thorncroft et al. 1993 and references therein) produces internal inertia–gravity waves having small scales close to the grid scale of the numerical model. The small scales seem to put OSD95’s example at an opposite extreme to those in which the Lighthill theory is relevant. The Lighthill theory describes scenarios in which unsteady vortical motion
dynamics perspective, is the intraseasonal planetary-scale disturbance, known as the Madden–Julian oscillation (MJO) ( Madden and Julian 1972 ), that appears as an envelope of mesoscale to synoptic-scale westward inertio-gravity (WIG) waves with periods of approximately two days, thus known as two-day waves ( Takayabu 1994b ; Haertel and Johnson 1998 ; Haertel and Kiladis 2004 ; Haertel et al. 2009 ), and Kelvin waves that move eastward ( Straub and Kiladis 2002 ; Roundy 2008 ). Accordingly
dynamics perspective, is the intraseasonal planetary-scale disturbance, known as the Madden–Julian oscillation (MJO) ( Madden and Julian 1972 ), that appears as an envelope of mesoscale to synoptic-scale westward inertio-gravity (WIG) waves with periods of approximately two days, thus known as two-day waves ( Takayabu 1994b ; Haertel and Johnson 1998 ; Haertel and Kiladis 2004 ; Haertel et al. 2009 ), and Kelvin waves that move eastward ( Straub and Kiladis 2002 ; Roundy 2008 ). Accordingly
