ReviewInternal wave coupling processes in Earth’s atmosphere
Section snippets
Introduction to atmospheric vertical coupling
The structure and dynamics of Earth’s atmosphere are determined by a complex interplay of radiative, dynamical, thermal, chemical, and electrodynamical processes in the presence of solar and geomagnetic activity variations. The lower atmospheric processes are the primary concern of meteorology, while impacts of the Sun and geomagnetic processes on the atmosphere–ionosphere are the subject of space weather research. Thus, the whole atmosphere system is under the continuous influence of
Internal wave characteristics and propagation
To a first approximation, atmospheric waves can be distinguished by their spatial scales. Earth’s atmosphere possesses a broad spectrum of waves ranging from very small- (e.g., gravity waves, GWs) to planetary-scale waves (tides, Rossby waves). Table 1 summarizes quantitatively the range of temporal scales for tides, gravity, planetary Rossby and Kelvin waves. Overall, internal wave periods vary from a few minutes to tens of days. They also have different spatial scales. While small-scale GWs
General characteristics of observations
A variety of techniques is utilized to detect wave signatures in the atmosphere. To date, a combination of in situ and remote sensing observational methods provides an unprecedented view of the local and global state and composition of the atmosphere. Thus, atmospheric temperature, pressure, wind fields, humidity, solar radiation flux, trace substances, electrical properties, and precipitation can be observed by these techniques. A variety of small- and large-scale structures can be identified
Techniques of modeling internal wave processes
Although observations suggest that wave-like structures are continuously present in the upper atmosphere (e.g., Djuth et al., 2004, Livneh et al., 2007), it is not always possible to determine their propagation and dissipation characteristics simultaneously and unambiguously. Theoretical, numerical, and global modeling studies allow for the analysis of various physical processes that influence the propagation of internal waves from their sources to regions where they strongly interact with
Wave propagation and consequences in the upper atmosphere
Internal waves affect the momentum, energy, and composition balance of the middle atmosphere through a variety of effects (e.g., see reviews by Fritts and Alexander, 2003, Becker, 2011). Observational and modeling studies have shown that small-scale GWs (e.g., Yiğit et al., 2009) and solar tides (e.g., Oberheide et al., 2009) can directly propagate to the upper atmosphere as well. We next focus on the upward propagation of these waves from the lower atmosphere to the thermosphere–ionosphere
Vertical coupling during sudden stratospheric warmings
In this section, we focus on the observed and modeled effects of sudden stratospheric warmings (SSWs) on the upper atmosphere. SSWs are spectacular transient events in the winter Northern Hemisphere (NH) first discovered by Scherhag (1952). The winter polar temperature dramatically increases within a few days following the breakdown or weakening of the stratospheric polar vortex as a consequence of planetary wave amplification and breaking. Such warmings are accompanied by deceleration, and
Upper atmosphere variability
The term “variability” implies an existence of a mean state with respect to which deviations s′ are studied. Since any field s is the superposition of the mean and deviations, , the choice of the mean determines the spatio-temporal structure of the variability . The practical importance of variability is that it is a source of uncertainty in the prognosis of the atmosphere–ionosphere. The upper atmosphere is a highly variable region at all temporal and spatial scales ranging from
Open questions and concluding remarks
A concise review of vertical coupling in the atmosphere–ionosphere system has been presented here, focusing on the role of internal waves as the main vertical coupling mechanism. Considerable progress has been made, over the past decade, in the appreciation of the role, which these waves play in the dynamical coupling between the lower and upper atmosphere. Internal waves include planetary Rossby and Kelvin waves, tides, and gravity waves. Due to their ability to propagate vertically, internal
Acknowledgments
The work was partially supported by German Science Foundation (DFG) Grant ME2752/3-1. Erdal Yiğit was partially supported by NASA – United States Grant NNX13AO36G. The authors are grateful to Art Poland at George Mason University’s Space Weather Laboratory for his valuable comments on the manuscript.
References (155)
Direct heating rates associated with gravity wave saturation
J. Atmos. Sol.-Terr. Phys.
(2004)- et al.
Traveling planetary wave ionospheric disturbances and their role in the generation of equatorial Spread-F and GPS phase fluctuations during the last extreme low solar activity and comparison with high solar activity
J. Atmos. Sol.-Terr. Phys.
(2014) - et al.
Numerical modeling of propagation of breaking nonlinear acoustic-gravity waves from the lower to the upper atmosphere
Adv. Space Res.
(2013) - et al.
Directivity and apparent velocity of the coseismic ionospheric disturbances observed with a dense GPS array
Earth Planet. Sci. Lett.
(2005) - et al.
A numerical model for gravity wave dissipation in the thermosphere
J. Atmos. Terr. Phys.
(1988) Forcing of the ionosphere by waves from below
J. Atmos. Sol.-Terr. Phys.
(2006)Lower ionosphere response to external forcing: a brief review
Adv. Space Res.
(2009)Global pattern of trends in the upper atmosphere and ionosphere: recent progress
J. Atmos. Sol.-Terr. Phys.
(2009)- et al.
The nonlinear mechanism of gravity wave generation by meteorological motions in the atmosphere
J. Atmos. Terr. Phys.
(1995) - et al.
Parameterization of gravity wave momentum deposition based on nonlinear wave interactions: basic formulation and sensitivity tests
J. Atmos. Sol.-Terr. Phys.
(2000)