Relative intensities of middle atmosphere waves

Abstract

Climatologies of gravity waves, quasi-stationary planetary waves, and tides are compared in the upper stratosphere, mésosphère, and lower thermosphere. Temperature standard deviations from zonal means are used as proxies for wave activity. The sum of the waves is compared to directly measured total temperature fluctuations. The resulting difference is used as a proxy for traveling planetary waves. A preliminary climatology for these waves is proposed. A ranking of the four wave types in terms of their impact on the total wave state of the atmosphere is achieved, which is dependent on altitude and-latitude. At extratropical latitudes, gravity waves mostly play a major role. Traveling planetary waves are found to play a secondary role. Quasi-stationary planetary waves and tides yield a lesser contribution there. Vertical profiles of total temperature fluctuations show a sharp vertical gradient change ("kink".or "bend") in the mesosphere. This is interpreted in terms of a change of wave damping, and the Concept of a "wave turbopause" is suggested. The altitude of this wave turbopause is found to be mostly determined, by the relative intensities of gravity waves and planetary waves. The turbopause is further analyzed, including earlier mass spectrometer data. It is found that the wave turbopause and the mass spectrometer turbopause occur rather close together. The turbopause forms a layer about 8 km thick, and the data suggest an additional 3 km mixing layer on top. Copyright 2009 by the American Geophysical Union.