Vertical propagation, breaking and effects of nonlinear gravity waves in the atmosphere

Two-dimensional nonlinear simulation is used for qualitative examining of vertical propagation and breaking of internal gravity waves (IGWs) in the atmosphere. Monochromatic forcing near the Earth's surface is used as IGW source in the model. Wave amplitude increases when wave propagates upward due to decreasing atmospheric density. The wave may break at some height. Nonlinear effects (increasing when the wave propagates upward) are examined for different amplitudes of the boundary forcing. At small forcing amplitude, the wave does not break and the main nonlinear effect is a horizontal jet flow created by the wave at high altitudes. At moderate forcing amplitudes, the wave can break mainly due to Kelvin-Helmholtz instability of the wind shears created by propagating wave. Convective instability could be a reason of wave breaking at large forcing amplitudes. (c) 2005 Elsevier Ltd. All rights reserved.