Spectral measurements of turbulence and gravity waves, part 4.2A

Recently, it has become widely recognized that gravity waves play an important role in determining the large-scale circulation of the middle atmosphere. This realization has come about, in large measure, from the realization that Rayleigh friction plays an important role in the dynamics of the middle atmosphere. Since Rayleigh friction is intimately related to the saturation of vertically propagating gravity waves, an understanding of the saturation process has become a focal point for theoretical studies. With the advent of MST radar studies of the middle atmosphere, it has become possible to determine the spectrum of horizontal atmospheric velocity fluctuations over the range of scales which comprise the gravity-wave spectrum. It has been suggested that these spectra are comprised of buoyancy waves. The controversial interpretation of these spectra is discussed.