On Pressure Perturbations Caused by a Moving Heat Source of Frontal Type (Hydrostatic Mode)

Resumo

The problem of surface-pressure perturbations caused by a moving nonstationary heat source (localized along one horizontal coordinate and periodic along the other) is considered. Pressure perturbations are associated with internal gravity waves (IGWs). It is shown that, during the source movement throughout a finite-height atmospheric layer (atmospheric waveguide), when a discrete set of vertical IGW modes is excited, there may be three types of time surface-pressure variations at a fixed observation point. A time amplitude-modulated signal; a Doppler frequency-modulated signal; and a signal that occurs only after the passage of the source correspond to these three types, respectively. Each of these types is implemented for certain source oscillation frequencies and Mach numbers (ratio between the movement rate of source and the phase velocity of IGWs). At \(M < 1\), a nonstationary source always excites wave precursors—disturbances observed before the source arrival. The movement of the source in a semi-infinite atmosphere leads to additional generation of waves that transport energy into the upper atmospheric layers.