Diagnostics of internal atmospheric wave saturation and determination of their characteristics in Earth's stratosphere from radiosonde measurements

Abstract

Internal gravity waves (IGW) significantly affect the structure and circulation of Earth’s atmosphere by transporting wave energy and momentum upward from the lower atmosphere. Since IGW can propagate freely through a stably stratified atmosphere, similar effects may occur in the atmospheres of Mars and Venus. Observations of temperature and wind speed fluctuations induced by internal waves in Earth’s atmosphere have shown that wave amplitudes increase with height, but not quickly enough to correspond to the amplitude increase due to an exponential decrease in the density without energy dissipation. The linear theory of IGW explains the wave amplitude growth rate as follows: any wave amplitude exceeding the threshold value leads to instability and produces turbulence, which hinders further amplitude growth (internal wave saturation). The mechanisms that contribute most to the energy dissipation and saturation of IGW in the atmosphere are thought to be the dynamical (shear) and convective instabilities. The assumption of internal wave saturation plays a key role in radio occultation monitoring of IGW in planetary atmospheres. A radiosonde study of wave saturation processes in Earth’s atmosphere is therefore actual and important task. We report the results of determination of actual and threshold amplitudes, saturation degree, and other characteristics for the identified IGW in Earth’s atmosphere obtained from the analysis of SPARC (Stratospheric Processes And their Role in Climate) radiosonde measurements of wind speed and temperature [http://www.sparc.sunysb.edu/].

Keywords

• Earth’s atmosphere
• internal gravity waves
• saturation
• radiosonde measurements
• wind speed
• temperature