3 years ago

A comparison of small and medium-scale gravity wave interactions in the linear and nonlinear limits

C. J. Heale, J. B. Snively
A 2D numerical model is used to compare interactions between small (25km horizontal wavelength, 10 min period) and medium scale (250km horizontal wavelength, 90 min period) gravity waves in the Mesosphere and Lower Thermosphere (MLT) within three different limits. First, the medium-scale wave is specified as a static, horizontally homogeneous ambient atmospheric feature; second, a linear interaction is investigated between excited, time-dependent small and medium scale waves and, third, a fully nonlinear interaction at finite amplitudes is considered. It is found that the finite amplitude wave interactions can cause small-scale wave breaking aligned with the phase fronts of the medium scale waves, which induces a permanent mean flow and shear that is periodic in altitude. This impedes small-scale wave propagation into in the upper thermosphere and dissipation by molecular diffusion, when compared to linear amplitude simulations. Linear cases also omit self-acceleration-related instabilities of the small-scale wave and secondary wave generation, which modulate the medium-scale wave field. Neither the linear or nonlinear cases resemble the static approximation, which, by reducing a dynamic wave interaction to a static representation that is vertically varying produces variable momentum flux distributions that depend strongly upon the amplitude and phase of the larger scale wave. This is an approximation made by gravity wave parameterization schemes, and results suggest that including time dependent effects and feedback mechanisms for interactions between resolved and parameterized waves will be an important area for future investigations especially as General Circulation Models (GCMs) begin to resolve medium scale gravity waves explicitly.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/2017JD027590

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.