The generation of stratospheric inertia-gravity waves is investigated with the aid of a dry two-dimensional anelastic numerical model. The model calculations follow the development of upper-level and low-level fronts together with their attendant jets. Long-wavelength low-frequency inertia-gravity waves are generated in the model runs. The key constituents of the model basic-state are: (1) a time-dependent shear flow normal to the front in thermal-wind balance with the along-front potential temperature; and (2) a time- and height-independent confluent-deformation wind-field with its axis of dilation parallel to the front. When the cross-front geostrophic wind shear △ is negative, and consequently the upper-level jet advects cold air along the upper front, prominent vertically propagating inertia-gravity waves are evident in the lower stratosphere. Like those observed in the atmosphere, the modelled waves have frequencies close to the inertial frequency, horizontal wavelengths of order 400-1200 km, and vertical wavelengths in the range 2-10 km. Numerical experiments in which △ ≥ 0 showed little gravity-wave activity.
|Number of pages||22|
|Journal||Quarterly Journal of the Royal Meteorological Society|
|Publication status||Published - 1 Jan 1996|
- Gravity-wave drag
- Inertia-gravity waves
- Jet streams