Abstract
Observations of the ionosphere with the airglow, GPS-TEC, and HF radar techniques reveal a resonant response of the middle and upper atmosphere to broad-band excitation by earthquakes, volcano eruptions, and convective storms. The resonances occur at such frequencies that an atmospheric wave, which is radiated at the ground level and is reflected from a turning point in the middle or upper atmosphere, upon return to the ground level satisfies boundary conditions on the ground. Using asymptotic and numerical models of atmospheric waves, this paper investigates atmospheric resonances and their excitation by seismic waves and infragravity waves in the ocean. It is found that “buoyancy” resonances with periods up to several hours arise in addition to “acoustic” resonances with periods of about 3–5 min. The acoustic and buoyancy resonances occur, respectively, on the acoustic and gravity branches of the dispersion curve of acoustic-gravity waves. Buoyancy of the atmosphere is important for the resonances of both kinds. Acoustic resonances are found to be sensitive to the temperature profile, especially around mesopause and tropopause, and are predicted to be a seasonal phenomenon in polar atmosphere. Unlike acoustic resonances, buoyancy resonances exhibit high sensitivity to the wind velocity profile and its variations. The resonances correspond to most efficient coupling between the atmosphere and its lower boundary and are promising for detection of such coupling.
Highlights
Atmosphere is known to respond in a resonant way to broad-band excitation associated with earthquakes (Shinagawa et al 2007; Choosakul et al 2009; Saito et al 2011; Rolland et al 2011; Ogawa et al 2012; Cahyadi and Heki 2014; Jin 2018), volcanic eruptions (Widmer and Zürn 1992; Kanamori et al 1994; Tahira 1995; Zürn and Widmer 1996; Watada and Kanamori 2010; Aoyama et al 2016; Nakashima et al 2016), turbulence in mountain regions (Bedard 1978), and severe meteorological events such as convective storms (Chimonas and Peltier 1974; Jones and Georges 1976; Pilger et al 2013) and tornados (Nishioka et al 2013)
Further research is necessary to determine whether the difference in the altitude extent of the high correlation bands below and above ~ 1.6 mHz in Fig. 8c is related to the change in the position of Acoustic-gravity wave (AGW) turning point in the buoyancy resonances
Resonance oscillations occur in the atmosphere when upward propagating waves are strongly refracted by temperature and wind velocity gradients, reach a turning point at some altitude, and the resulting combination of the upward and downward propagating waves satisfies the boundary conditions at the lower boundary of the atmosphere
Summary
Atmosphere is known to respond in a resonant way to broad-band excitation associated with earthquakes (Shinagawa et al 2007; Choosakul et al 2009; Saito et al 2011; Rolland et al 2011; Ogawa et al 2012; Cahyadi and Heki 2014; Jin 2018), volcanic eruptions (Widmer and Zürn 1992; Kanamori et al 1994; Tahira 1995; Zürn and Widmer 1996; Watada and Kanamori 2010; Aoyama et al 2016; Nakashima et al 2016), turbulence in mountain regions (Bedard 1978), and severe meteorological events such as convective storms (Chimonas and Peltier 1974; Jones and Georges 1976; Pilger et al 2013) and tornados (Nishioka et al 2013). In “Asymptotic modeling of atmospheric resonances”, the WKB approximation for AGWs (Godin 2015) is used to quantify the conditions necessary for resonances to occur in a continuously stratified atmosphere with gradually varying temperature and wind velocity and to determine the frequency of resonant oscillations of the atmosphere excited by waves traveling along its lower boundary.
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