Inferring Stratospheric Mountain Wave Breaking through Observations at the Tropopause
Several characteristics of the simulated secondary waves were unexpected. First, the secondary waves are generated with good efficiency, approaching 20% of the upgoing wave momentum flux. Second, while most of the secondary waves are downward, the shorter components reflect upward from the tropopause, giving a kind of lee wave trapping in the lower stratosphere. Third, the phase speed of the secondary waves is nearly zero so that they satisfy the Eliassen-Palm relationship between momentum and energy flux. While the 2-D results are robust to grid size and sub-grid parametrization, an extension of the modeling to three dimensions is disappointing. The secondary waves amplitudes in the 3-D runs are much smaller than observed.