Observations of diurnal mountain valley flow utilizing dual Doppler lidar virtual tower technique

In April 2006 during the Terrain-induced Rotor Experiment, dual coherent Doppler lidars were used to study the diurnal cycle of the mountain valley flow in the Owens Valley. An overview of the observed phenomena as well as a discussion of the virtual tower dual Doppler lidar technique will be presented. The main observational objective of the Terrain-induced Rotor Experiment was the comprehensive study of mountain waves and rotors. The secondary objective was the observation of thermally driven mountain valley flows. During quasi-quiescent periods EOP's where carried out to achieve this secondary objective. Phenomena of interest during EOP's included morning and evening transitions, coupled slope and valley wise flows, and boundary layer evolution. Virtual tower Doppler lidar scaning techniques were used during specific EOP's to observe the diurnal mountian valley flow phenomena. This technique utilises two Doppler lidars performing range height indicator (RHI) scans in tandum over a given geographic location. The resulting intersection of the two RHI planes is refered to as a virtual tower. Several towers were established in a plane in the cross valley direction. The resulting data set allows for characterization of the diurnal mountain valley flow cycle in Owens Valley as well as lending itself to model comparison and comparison to vertical profilers also used during the experiment.