High-Resolution Simulations of Internal Gravity-Wave Fine Structure Interactions and Implications for Atmospheric Turbulence Forecasting

In this paper, we present new results from recent coupled gravity-wave-breaking simulations involving gravity waves (GWs) whose wavelengths differ by an order of magnitude. Several scenarios are investigated, all with waves that are individually statically stable (Ri≥0.25). Nevertheless, turbulence outbreaks are observed as the periodic motion of the larger GW induces a parametric instability in the shorter wavelength fine structure wave, and the coupling produces a massive instability response at multiple scales, yielding a layering of the potential temperature field resembling "sheet and layer" structures observed in the atmosphere and oceans. Such interactions among large-scale GWs and fine structure due to small-scale inertia-GWs or superposed regions of decaying or fossil turbulence events are likely ubiquitous throughout the atmosphere and may account for sporadic bursts of turbulence and its persistence in regions of high apparent static stability. The implications for these new results are discussed for our probabilistic turbulence forecasting methods.