The Effects of Middle Atmosphere Turbulence on Coupling between Atmospheric Regions

Abstract

Neutralatmosphere turbulence exists almost ubiquitously throughout the atmosphere up to heights of about 100 km, and then completely disappears above about 120 km altitude. It's importance in providing coupling in the lower regions of the atmosphere (troposphere and stratosphere) is well known, but its importance for coupling between the middle atmosphere and ionosphere is not so well understood. In this review, we will concentrate on the role that turbulence plays in the coupling between the middle atmosphere and the low levels of the ionosphere. The discussion will include a review of some of the important principles of turbulence, as well as some of the unique features about middle atmospheric turbulence.A detailed collection of measurements of turbulent eddy diffusion coefficients will be presented, along with some warnings about how these data should be interpreted. The need to understand turbulence at a very fundamental level in order to apply measurements of such "diffusion coefficients" is stressed.

The structure of turbulence in the middle and lower atmosphere seen by and deduced from MF, HF and VHF radar, with special emphasis on small-scale features and anisotropy

“…It is possible to produce a statistical investigation of the likelihood of such levels developing, and thereby obtain a statistical summary of the likely depths of these layers, their frequency of occurrence, and their likely vertical spacing. Figure 2 shows an example of such statistics (Hocking, 1991, after adaptation from Desaubies and Smith, 1982). Similar calculations have been performed by Fairall et al (1991) for the troposphere, and by Hines (1991a, b, c) for the mesosphere.…”

“…Several authors have recognized this (e.g. Peltier et al, 1978;Röttger et al, 1981;Hocking, 1985;Woodman and Chu, 1989;Hocking, 1991). Figure 9 shows one such illustration of the expected variation of anisotropy across the layer, with more Fig.…”

“…Thus, the rate of vertical diffusion over scales deeper than the typical layer depths depends on factors including the depth of the layers, and the frequency of occurrence of the layers, (as well as the strength of turbulence within the layers). More details about this process can be found in Dewan (1981), Woodman and Rastogi (1984), and Hocking (1991Hocking ( , 1999, among others. This understanding of turbulent diffusion has been developed, in part, due to the contributions of radar observations which offer one of the best tools to implement calculations of diffusion in this manner, as described by Woodman and Rastogi (1984).…”

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

“…4a. The eddy diffusivity profile of Hocking (Hocking, 1991) that is presented in Marks and Eckermann (1995) is also superimposed for comparison. Note that Hocking's profile corresponds mainly to midlatitudes.…”

Measurements of Intermittency in the Upper Stratosphere and Mesosphere

“…Hocking (1991) The parametric models independently estimate the driving noise variance of the input process. Hence, it seems reasonable that the amount of saturation, or gain, of the spectrum relates to the ratio of the input driving noise variance to the average power of the output power spectral density.…”