The 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.
N2 - Plain Language Summary: Given its complexity to be measured at different spatio‐temporal scales, the exploration of the mesosphere and lower thermosphere remains an active area of research. In this work, we have applied velocity filtering techniques to both multistatic specular meteor radar measurements and global circulation model simulations to analyze horizontal wind frequency spectra over southern Patagonia. We consider the theory of layered anisotropic stratified turbulence to study the summer mesopause region and hypothesize that this type of turbulence (in the statistical sense) plays a role in the transition of internal gravity waves to small‐scale turbulence. N2 - Key Points:Spatially filtered horizontal wind residuals are explored for the first time at mesopause altitudes over Patagonia
Frequency spectra of horizontal wind residuals follow a −2 slope
Simulated divergent and rotational parts of the mesoscale kinetic energy are equipartitioned at high frequencies