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Early laboratory experiments of shear flow by Thorpe (Thorpe, 2002) provided evidence of Kelvin-Helmholtz Instability (KHI) billow interactions either due to misaligned adjacent billow cores or varying phases along the adjacent billow axes. Similar evidence has been found in the observations of tropospheric clouds, airglow, and Polar Mesospheric Clouds (PMC) imagery data in the mesosphere. Initial High-Resolution Direct Numerical Simulations (DNS) studies performed at Reynolds Number of 5000 (Fritts et al., 2021a, Fritts et al., 2021b) have demonstrated the that misaligned KH billow cores exhibit strong and complex vortex interactions inducing ‘Tubes and Knots’ (T&K) structures (Thorpe, 2002). These T&K structures were observed to accelerate transition to small-scale turbulence in contrast to previously known notable transitional mechanisms such as secondary KHI and convective instabilities emerging in individual KH billows. Also, the KHI T&K dynamics evidently yield intense turbulence dissipation rates contrasting that of secondary KHI and convective instabilities in billow cores.More recent high-resolution imaging of OH airglow (Hecht et al., 2021) provide concrete evidence of KHI billows with wavelength ranging between 7-10 km modulated by atmospheric Gravity Waves (GWs) of dominant horizontal wavelengths ∼ 30km and oriented orthogonal to KH billow axes and propagate along the billow cores which result in apparent T&K dynamics rapidly driving KH billow breakdown. Similar evidence has been found in recent PMC imaging. This is the central theme of the idealized DNS discussed in this talk.We conducted DNS studies to demonstrate the turbulence energetics of KHI billow interactions when subject to modulations due to monochromatic atmospheric gravity waves of small perturbation amplitudes and intrinsic frequency of N/5 (where N is the background Brunt-Vaisala Frequency). Preliminary analyses of our DNS results indicate that GW modes with modest amplitudes promote KHI billow misalignments resulting in complex multi-scale T&K dynamics fixed at specific GW phases. An increase in the GW amplitude resulted in noticeable reduction of KHI billow wavelengths further promoting KH billow misalignments. The resulting turbulence is expected to consist of broader scale ranges of intense turbulence dissipation rate and diffusivity.References[Fritts et al., 2021a] Fritts, D. C., Wang, L., Lund, T. S., and Thorpe, S. A. (2021a). Multi-Scale Dynamics of Kelvin-Helmholtz Instabilities . Part 1 : Secondary Instabilities and the Dynamics of Tubes and Knots. pages 1–27.[Fritts et al., 2021b] Fritts, D. C., Wang, L., Thorpe, S. A., and Lund, T. S. (2021b). Multi-Scale Dynamics of Kelvin-Helmholtz Instabilities . Part 2 : Energy Dissipation Rates , Evolutions , and Statistics. pages 1–39.[Hecht et al., 2021] Hecht, J. H., Fritts, D. C., Gelinas, L. J., Rudy, R. J., Walterscheid, R. L., and Liu, A. Z. (2021). Kelvin-Helmholtz Billow Interactions and Instabilities in the Mesosphere Over the Andes Lidar Observatory: 1. Observations. Journal of Geophysical Research: Atmospheres, 126(1):e2020JD033414. Publisher: John Wiley & Sons, Ltd.[Thorpe, 2002] Thorpe, S. A. (2002). The axial coherence of Kelvin–Helmholtz billows. Quarterly Journal of the Royal Meteorological Society, 128(583):1529–1542. Publisher: John Wiley & Sons, Ltd.