[세미나] Dr. Andreas Dornbrack

Transient Tropopause Waves

Dr. Andreas Dornbrack

2023년 10월 10일 (화) 16:00

과학관 B102호

Abstract

Flight level airborne observations have often detected horizontal short waves near the tropopause. Here, in situ and remote sensing aircraft data during a mountain wave event over southern Scandinavia are used to quantify the spectral energy and energy fluxes of the observed waves and to identify non-stationary modes. A series of two-dimensional numerical simulations are performed to explain the origin of these transient wave modes and to investigate the parameters on which they depend. It turns out that the interaction between wave breaking in the middle atmosphere and tropospheric flow is the essential factor in explaining the origin of these transient short modes. In agreement with previous results from the T REX field program, secondary downward-propagating gravity waves are responsible for the excitation of horizontally short gravity waves near the tropopause. Intermittent and periodic breaking of mountain waves in the lower stratosphere reinforces a wave duct directly above the tropopause where the short gravity waves are trapped. The characteristics of the trapped, downstream-propagating waves are controlled by the sharpness of the tropopause inversion layer, the strength of the orographic forcing of the primary mountain waves, and, to a lesser extent, by the underlying orography that excites the vertically propagating mountain waves.