Forcing of secondary waves by breaking of gravity waves in the mesosphere

Abstract

Previous simulations with a two-dimensional cloud-resolving model have shown that gravity waves generated by tropospheric convection can propagate into the mesosphere, where they break and produce local heating and local accelerations. The forcing associated with this wave breaking excites secondary gravity waves that propagate upward and downward away from the wave-breaking region. Typical horizontal and vertical scales of individual centers of forcing caused by wave breaking are ∼25 km and 10-20 km, respectively. Groups of individual forcing centers tend to be aligned along phase lines of the primary waves. In the region east of the storm center the forcing groups move eastward and downward with the primary wave phase lines, while individual forcing centers move upward. To a first approximation, the secondary gravity waves are a linear response to the localized momentum and thermal forcing associated with wave breaking, though the forcing is itself generated by the nonlinear wave-breaking process. The secondary waves can be derived from knowledge of the temporal and spatial variability of the forcing.