The Role of Stratified Turbulence in the Cold Summer Mesopause Region

Abstract

AbstractThe summer mesopause at middle and high latitudes is the coldest place on Earth, and atmospheric gravity waves are responsible for the emergence of this extreme thermal phenomenon. Although the main physical mechanism behind the latter is understood, a deeper insight into it can be gained from the investigation of the mesoscale energy spectrum. In this work, we decompose the frequency spectra into divergent and rotational parts and find that their energy contributions are equipartitioned at high frequencies. This mesoscale energy equipartition is a feature of stratified turbulence and illustrates the complexity of the mesoscale dynamics in the summer mesopause region. We also analyze the power spectra of observed and simulated mesoscale zonal and meridional winds at middle latitudes in the Southern Hemisphere and show that stratified turbulence plays a role in the mesopause region during summer.