The life cycle of a mesoscale gravity wave as observed by a network of Doppler wind profilers

For the first time, an analysis has been made of the evolving vertical stru cture of a long-lived mesoscale gravity wave that exerted a strong influenc e upon the precipitation distribution across a large area. This paper descr ibes this gravity wave system on 14 February 1992, which was observed using a combination of a surface mesonetwork, digital satellite and radar imager y, and several Doppler wind profilers. The resulting vertical structures ar e compared to the predictions of linear stability theory. Since the signature of the gravity waves in the profiler vertical beam data was often complicated by the presence of precipitation, a kinematic method was developed for estimating the vertical air motions during these periods . The resultant time-height fields show vertical and horizontal winds that are consistent with a gravity wave conceptual model, the microbarograph tra ces, and the cloud and precipitation patterns. In the early stages of devel opment, a strong vertically erect wave of depression was observed in southw estern Kansas. A few hours later, in central Kansas, a distinct discontinui ty had developed at the 4-km level. This phase shift and the vertical motio n profiles are both shown to be consistent with linear theory, as well as t he notion that the critical level at 5.4 km acted as a nodal surface for a complex ducted wave mode. Precipitation patterns were strongly affected by the waves. According to th e profiler analysis, the sharp back edge to the associated rainband was pro vided by strong low-level subsidence ahead of the wave of depression. The w aves and precipitation strengthened in a synergistic fashion-as strong conv ection developed along the wave, the wave of depression evolved into a wave train in which the leading wave crest eventually dominated over the initia l wave of depression. The profiler results reveal the existence of the inci pient wave land other waves) at midlevels several hours before the surface mesonet stations detected the presence of the waves. Thus, an important and unexpected finding from the profiler analysis is that surface microbarogra ph detection of mesoscale gravity waves may be limited to those waves that primarily affect the lower troposphere.