Observation and modeling of a gap flow in the Wipp valley

A case of gap flow has been observed with the airborne lidar LEANDRE 2 in the Wipptal valley in the framework of the Mesoscale Alpine Programme. An analytical fluid mechanics model is used to interpret lidar observations in connection with in situ measurements. This model, which generalizes the reduced-gravity shallow-water theory for stratified flows over topography, is diagnostic and uses boundary conditions defined in terms of Riemann invariants.