Although mechanisms leading to the formation of thermally-driven circulations in alpine valleys are well understood, questions concerning the along-valley initialization and structure of the valley flow as well as interactions with the flow aloft remain. This is partly due to the difficulty of obtaining detailed enough observations with traditional in-situ instrumentation.

A fair weather period during MAP-SOP provided the opportunity to study day-time thermally driven flows in the Wipptal. High resolution measurements were obtained with the NOAA/ETL TEACO2 Doppler lidar along a 12 km section of the valley.

In this poster presentation, lidar images are presented which show the along-valley structure of the valley flow during the morning transition period and the fully developed stage. Analysis of VAD and RHI scans indicates that the valley flow aloft developed more rapidly up-valley from the lidar, and that during the fully developed stage, the valley flow typically accelerated in the up-valley direction, reaching winds speeds of 8 m/s at 300 m AGL. Hypotheses for the flow divergence in this valley segment are presented and the implications are discussed.