Linear unsteady mountain waves

The object of this paper is to describe the generation of mountain gravity waves when the incident wind is transient. The incident flow is a stably stratified fluid which velocity starts from zero at a given time and returns to zero after a finite time. For the mountain, both a single harmonic and a single ridge topography are considered. The nature of transient effects on the disturbance is discussed according to the value of the parameter, ε = U₀t_f/L, which measures the ratio between the time scale t_f of the temporal variation of the incident wind and the advective time scale L/U₀. L and U₀ characterize the horizontal extension of the mountain and the incident wind intensity respectively. -from Authors