A comparative study of large-amplitude gravity-wave events

The waves were long-lived and maintained their identity over 1000 km, a distance several times their wave-lengths. The synoptic features at the surface were dissimilar. A deep cyclone was present on 5 January, while a leeside trough was present on 14 January. However, the middle- and upper-tropospheric flow patterns were similar. In both cases, the axis of a trough was immediately upstream of the gravity-wave genesis area and a jet streak had just propagated through the base of the trough toward a downstream ridge. Soundings taken near the gravity waves were remarkably similar, with both soundings showing a surface inversion capped by a deep layer or near-neutral stability. The 5 January wave occurred at the back edge of the precipitation associated with a comma cloud, while the wave on 14 January was observed at the leading edge of the synoptic-scale precipitation region. -from Authors