An overview of observations of unstable layers during the Turbulent Oxygen Mixing Experiment (TOMEX)

Abstract

[1] The Turbulent Oxygen Mixing Experiment (TOMEX) was designed to measure the atmospheric response to the existence of unstable layers as determined by wind and temperature measurements from 80 to 105 km. TOMEX combined Na lidar measurements, from Starfire Optical Range in Albuquerque, New Mexico, with a launch of a payload from White Sands Missile Range, located between 100 and 150 km south of Starfire. The payload included a trimethyl aluminum chemical release to measure winds and diffusion, a 5-channel ionization gauge to measure neutral density fluctuations at high vertical resolution, and a 3-channel photometer experiment to measure atomic oxygen related airglow. The rocket was launched when the lidar data indicated the presence of convectively and dynamically unstable regions between 80 and 100 km altitude. For several hours prior to the launch, there had existed a large amplitude atmospheric gravity wave or tide which brought the background atmosphere into being nearly convectively unstable over the 85 to 95 km region. In addition a large overturning in Na density, possibly due to a convective roll, existed at altitudes around 100 km. This type of instability had not been previously seen and identified in this altitude region. The TOMEX payload measured the existence of Kelvin-Helmholz billows, enhanced neutral density fluctuations, enhanced energy dissipation, and well-mixed regions. These features were associated with convectively unstable regions, dynamically unstable regions, convective rolls, and the presence of this large wave. The unstable regions were persistent and covered large vertical (and horizontal regions) of the atmosphere. The atmospheric mixing and energy dissipation appeared to be largely determined by the presence and nature of these instabilities.

The Turbopause experiment: atmospheric stability and turbulent structure spanning the turbopause altitude

“…Above 95 km we see indications of neutral and electron density fluctuations, but the scale sizes of a few 100 m are rather large, and an inertial range and inner scale could not be found. The region between 95 and 103 km was characterized by low stability and variable wind shear, again similar to the convective layer observed by Hecht et al (2004). The Richardson number profiles are highly structured and values are much lower than unity throughout the region.…”

Observational evidence for new instabilities in the midlatitude <i>E</i> and <i>F</i> region

“…The billowy appearance of the layers in incoherent scatter radar observations like those presented by Miller and Smith (1978) and Smith and Miller (1980) points to neutral shear (dynamical) instability as the cause (Larsen, 2000;Bernhardt, 2002;Hysell et al, 2004;Bernhardt et al, 2006;Larsen et al, 2007;Hysell et al, 2009). This premise is consistent with results from Larsen (2002) and Hecht et al (2004), and others which suggest that the mesosphere lower thermosphere region is frequently dynamically if not convectively unstable. Hysell et al (2012) combined coherent and incoherent scatter radar measurements in a common volume to test the premise.…”

Turbulence parameter estimations from high-resolution balloon temperature measurements of the MUTSI-2000 campaign

“…Systematic measurements of ε and K at different altitudes were made using MF, MST and UHF radars (e.g. Kurosaki et al, 1996;Naström and Eaton, 1997;Hall et al, 1998;Bertin et al, 1999;Dole and Wilson, 2001;Satheesan and Krishna Murthy, 2002;Kelly et al, 2003;Zink et al, 2004), and with acoustic (Agrovskii and Kukharets, 1998;Furumoto and Tsuda, 2001) and optical measurements (Kao et al, 2002;Hecht et al, 2004). Recently, extensive information about profiles of turbulence characteristics was obtained from optical observations of star scintillations from satellites (Gurvich et al, 2001).…”