Atmospheric gravity waves are subject to horizontal ducting in a stably stratified atmosphere that contains levels of wind maximum or minimum, quite apart from any superimposed consequences of vertical variation of stability and quite apart from the existence or otherwise of critical levels. The process, ''Doppler ducting'', is examined here for two prototype cases (an isolated wind maximum and a wind minimum at ground level) and for two more realistic model cases (a strong tropospheric jet and a nocturnal boundary layer jet). The wave structure, modal behavior, and dispersion curves of all four are very similar. It is argued that Doppler ducting is available to a part of the gravity wave spectrum in all real circumstances and that it should be considered as a possible candidate whenever observations indicate that some ducting process is operative. One particular wave event is discussed in some detail, and it is shown that Doppler ducting in its simplest form provides a plausible alternative to a more complicated ducting process (which involved critical levels and energy leakage) previously inferred. Doppler ducting is available equally to gravity waves in the oceans when background currents vary with depth. |