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1. Introduction Equatorially trapped inertia–gravity waves were first identified in the ocean by Wunsch and Gill (1976) through analysis of Pacific Ocean island tide gauge records. Peaks in the frequency spectra at periods of about 3, 4, and 5.5 days were found to be common to islands over a large range of latitudes and longitudes. The oscillations at these periods were coherent with large-scale equatorial winds, but the available frequency spectra of winds showed either no peaks at these
1. Introduction Equatorially trapped inertia–gravity waves were first identified in the ocean by Wunsch and Gill (1976) through analysis of Pacific Ocean island tide gauge records. Peaks in the frequency spectra at periods of about 3, 4, and 5.5 days were found to be common to islands over a large range of latitudes and longitudes. The oscillations at these periods were coherent with large-scale equatorial winds, but the available frequency spectra of winds showed either no peaks at these
1. Introduction Inertia–gravity waves (IGWs) are ageostrophic oscillations that are forced by rotation and buoyancy ( Holton 1992 ). They may modify the weather at the surface and contribute to extreme weather events ( Bosart and Cussen 1973 ; Bosart et al. 1998 ; Koch and Dorian 1988 ). In the middle atmosphere, such waves may trigger polar stratospheric clouds ( Dörnbrack et al. 1999 ; Buss et al. 2004 ; Hitchman et al. 2003 ), local ozone reduction ( Kühl et al. 2004 ) and noctilucent
1. Introduction Inertia–gravity waves (IGWs) are ageostrophic oscillations that are forced by rotation and buoyancy ( Holton 1992 ). They may modify the weather at the surface and contribute to extreme weather events ( Bosart and Cussen 1973 ; Bosart et al. 1998 ; Koch and Dorian 1988 ). In the middle atmosphere, such waves may trigger polar stratospheric clouds ( Dörnbrack et al. 1999 ; Buss et al. 2004 ; Hitchman et al. 2003 ), local ozone reduction ( Kühl et al. 2004 ) and noctilucent
particular, we discuss the relation of the MTs with inertia–gravity waves (IGWs). Geller et al. (2013) compared gravity wave absolute momentum fluxes estimated by the data from high-resolution satellite, isopycnic balloon, and high-resolution radiosonde observations, as well as climate models having parameterized gravity waves and gravity wave–resolving general circulation models. Observations and gravity wave–resolving models show that absolute momentum fluxes have a strong peak around the latitude of
particular, we discuss the relation of the MTs with inertia–gravity waves (IGWs). Geller et al. (2013) compared gravity wave absolute momentum fluxes estimated by the data from high-resolution satellite, isopycnic balloon, and high-resolution radiosonde observations, as well as climate models having parameterized gravity waves and gravity wave–resolving general circulation models. Observations and gravity wave–resolving models show that absolute momentum fluxes have a strong peak around the latitude of
1. Introduction Inertia–gravity waves (IGWs) can carry momentum and heat over considerable distances and effectively couple the atmospheric layers. They control the circulation in the mesosphere with momentum deposition, which is exported from the lower atmosphere ( Fritts and Alexander 2003 ). Observations indicate that their generation is often linked with localized jet streaks in the upper troposphere. The synoptic situation in most of these cases is characterized by a warm front just under
1. Introduction Inertia–gravity waves (IGWs) can carry momentum and heat over considerable distances and effectively couple the atmospheric layers. They control the circulation in the mesosphere with momentum deposition, which is exported from the lower atmosphere ( Fritts and Alexander 2003 ). Observations indicate that their generation is often linked with localized jet streaks in the upper troposphere. The synoptic situation in most of these cases is characterized by a warm front just under
1961 ; Howard 1961 ). Later, Klostermeyer (1983) showed how weak viscosity affects the growth rates and spatial scales of the leading unstable modes, a relevant point since in the mesosphere the kinematic viscosity and thermal diffusivity are relatively large because of the very low ambient density. The above studies neglect the effect of rotation, which becomes significant for steeply propagating waves, so-called inertia–gravity waves (IGWs). Because of their very low frequencies and near
1961 ; Howard 1961 ). Later, Klostermeyer (1983) showed how weak viscosity affects the growth rates and spatial scales of the leading unstable modes, a relevant point since in the mesosphere the kinematic viscosity and thermal diffusivity are relatively large because of the very low ambient density. The above studies neglect the effect of rotation, which becomes significant for steeply propagating waves, so-called inertia–gravity waves (IGWs). Because of their very low frequencies and near
et al. 2003 ; Hoskins and James 2014 ; De Vries et al. 2010 ; Davies 2015 ). The present study is concerned with the inverse problem of using the balanced omega equation to estimate diabatic forcing for the processes involving inertia–gravity waves (IGWs) associated with unbalanced motion and their parameterization. As gravity waves modified by Earth’s rotation ( Holton and Hakim 2013 ), the IGWs play an important role in the atmosphere by transferring momentum and energy ( Fritts and
et al. 2003 ; Hoskins and James 2014 ; De Vries et al. 2010 ; Davies 2015 ). The present study is concerned with the inverse problem of using the balanced omega equation to estimate diabatic forcing for the processes involving inertia–gravity waves (IGWs) associated with unbalanced motion and their parameterization. As gravity waves modified by Earth’s rotation ( Holton and Hakim 2013 ), the IGWs play an important role in the atmosphere by transferring momentum and energy ( Fritts and
applicable to quasi-stationary Rossby waves in zonally asymmetric flow using the wave activity density and wave energy conservation laws. Their flux can be calculated without first computing the time mean to eliminate the wave phase structure, and their flux is equal to the product of the group velocity and the generalized wave activity density for QG perturbations. From the primitive equations, Miyahara (2006) and Kinoshita et al. (2010) derived a 3D wave activity flux applicable to inertia–gravity
applicable to quasi-stationary Rossby waves in zonally asymmetric flow using the wave activity density and wave energy conservation laws. Their flux can be calculated without first computing the time mean to eliminate the wave phase structure, and their flux is equal to the product of the group velocity and the generalized wave activity density for QG perturbations. From the primitive equations, Miyahara (2006) and Kinoshita et al. (2010) derived a 3D wave activity flux applicable to inertia–gravity
1. Introduction The question of “spontaneous” emission of inertia–gravity waves (IGWs), which is being actively discussed in the literature, starting from the pioneering paper ( O’Sullivan and Dunkerton 1995 ), in the context of realistic (e.g., Plougonven and Snyder 2007 ) or idealized (e.g., Dritschel and Viúdez 2007 ) numerical simulations, is a question of the limits of decoupling of fast (waves) and slow (vortices) motions in geophysical fluid dynamics and, therefore, a question of the
1. Introduction The question of “spontaneous” emission of inertia–gravity waves (IGWs), which is being actively discussed in the literature, starting from the pioneering paper ( O’Sullivan and Dunkerton 1995 ), in the context of realistic (e.g., Plougonven and Snyder 2007 ) or idealized (e.g., Dritschel and Viúdez 2007 ) numerical simulations, is a question of the limits of decoupling of fast (waves) and slow (vortices) motions in geophysical fluid dynamics and, therefore, a question of the
periods, nearly diurnal periods have been filtered from each wave signal after the expansion. This is achieved by applying a low-pass Lanczos window with a cutoff period of 36 h to the time series of modal coefficients χ ν for each ν . 3. Average energy distribution in inertia-gravity waves In Part I we showed the average spectra of IG energy separately for the eastward- and westward-propagating modes in order to stress the important contribution of the KW to the global energetics. Now we present
periods, nearly diurnal periods have been filtered from each wave signal after the expansion. This is achieved by applying a low-pass Lanczos window with a cutoff period of 36 h to the time series of modal coefficients χ ν for each ν . 3. Average energy distribution in inertia-gravity waves In Part I we showed the average spectra of IG energy separately for the eastward- and westward-propagating modes in order to stress the important contribution of the KW to the global energetics. Now we present
1. Introduction Inertia–gravity waves are observed ubiquitously throughout the stratified parts of the atmosphere (e.g., Eckermann and Vincent 1993 ; Sato et al. 1997 ; Dalin et al. 2004 ) and ocean (e.g., Thorpe 2005 ). Orthodox mechanisms for inertia–gravity wave generation include dynamical instability (e.g., Kelvin–Helmholtz shear instability; Chandrasekhar 1961 ), which is a known source of atmospheric gravity waves ( Fritts 1982 , 1984 ). Another possible mechanism is the
1. Introduction Inertia–gravity waves are observed ubiquitously throughout the stratified parts of the atmosphere (e.g., Eckermann and Vincent 1993 ; Sato et al. 1997 ; Dalin et al. 2004 ) and ocean (e.g., Thorpe 2005 ). Orthodox mechanisms for inertia–gravity wave generation include dynamical instability (e.g., Kelvin–Helmholtz shear instability; Chandrasekhar 1961 ), which is a known source of atmospheric gravity waves ( Fritts 1982 , 1984 ). Another possible mechanism is the
