Parallel Computation of Gravity Wave Turbulence in the Earth’s Atmosphere

Gravity waves (GWs) are ubiquitous internal waves in which the restoring force is buoyancy. In the Earth’s atmosphere, GWs are generated whenever a parcel of air is disturbed from its equilibrium position. Disturbing sources include topographic features (e.g., mountains), convective instabilities (e.g., thunderstorms), frontal motions, and oscillations of jet streams. When the amplitude of a GW approaches its inverse vertical wavenumber, the wave “breaks” and generates a localized region of intense turbulence. Strong GWs near the surface in the lee of mountains are responsible for spectacular down-slope windstorms, such as the Boulder chinook, the Santa Ana winds, and the Yugoslavian bora. Such storms often generate hurricane-force winds and are a serious threat to personal safety, buildings, and surface and air transportation. At higher altitudes, GWs can be of sufficient magnitude to alter the mean state of the atmosphere. The wave drag induced by the breaking of small-scale GWs (~10 km) is now thought to be an important issue in improving subgrid parameterizations for global atmospheric flow models. More generally, the propagation and evolution of GWs may be a key component in determining the spectral energy of the atmosphere at mesoscales (~100 km).