Evidence of gravity wave breaking in lidar data from the mesopause region

Abstract

[1] An outstanding question about the dynamics of the mesosphere is the temporal and spatial distribution of nonlinear events such as wave-breaking, wave saturation, and wave-critical layer interactions. A climatology of these events will help us understand how the mesoscale dynamical features, such as gravity waves, interact with the background mean wind and temperature structure. New lidar systems have the resolution to show us a height versus time ''picture'' of the dynamics so that identifying individual events within the observation window of the instrument is now possible. At the Starfire Optical Range (SOR) a sodium resonance lidar provides simulataneous sodium density, temperature, and three components of the winds. In this paper we present ''pictures'' of individual wave events apparent in the lidar data using the temperature (plotted as potential temperature and spectra) to show the time evolution of the wave structure.

Evidence of mesospheric bore formation from a breaking gravity wave event: simultaneous imaging and lidar measurements

“…This behavior is evidence of large-scale adiabatic vertical motion (of 6-8 km in extent). Similar behavior in the potential temperature during breaking gravity wave events has been reported previously from Na lidar temperature measurements (Williams et al (2002) and Franke and Collins (2003), for example). It should be noted that the downward advection of enhanced Na and K seen in Figs.…”

Evidence of damping and overturning of gravity waves in the Arctic mesosphere: Na lidar and OH temperature observations

“…However, overturning structures are detected in the bottomside of the Na layer during 20 of these 24 events. These overturning structures are indicative of convective instabilities as reported in several recent studies Fritts et al, 1997;Williams et al, 2002;Franke and Collins, 2003). We conclude that the overturning arises from instabilities due to superposition of large-and small-scale waves, rather than breaking of the large-scale waves, similar to the interaction reported by Hecht et al (1997) and modeled by Fritts et al (1997).…”

“…We ÿnd that large-scale gravity waves with associated overturning signatures are a relatively common feature at this site. Finally, we discuss these observations in terms of recent observational studies of wave breaking in the Na layer (Williams et al, 2002;Franke and Collins, 2003).…”

“…Williams et al (2002) and Franke and Collins (2003) have reported lidar observations of wave breaking and overturning in the Na layer at Fort Collins (41 • N; 105 • W) and at Starÿre Optical Range (35 • N; 107 • W). In both these studies the authors calculated the potential temperature from the temperature measurements (Fig.…”

Signature of an overturning gravity wave in the mesospheric sodium layer: Comparison of a nonlinear photochemical‐dynamical model and lidar observations

“…Early studies, based on sodium density measurements alone, determined the characteristics of tides and gravity waves under the assumption that the metal density acted as a tracer of the fluid motions [e.g., Batista et al , 1985; Gardner and Shelton , 1985; Senft and Gardner , 1991; Collins et al , 1996]. Recent studies have used observations (employing various combinations of metal density, temperature and wind measurements as well as different contributions from lidar, radar, and airglow systems) of the sodium layer to investigate gravity‐wave instability in the mesopause region [e.g., Hecht et al , 1997; Fritts et al , 1997; Hecht et al , 2000; Williams et al , 2002; Franke and Collins , 2003; Bishop et al , 2004; Collins and Smith , 2004; Liu et al , 2004; Larsen et al , 2004; Hecht et al , 2004; Li et al , 2005a].…”