Shallow Katabatic Flow in a Complex Valley: An Observational Case Study Leveraging Uncrewed Aircraft Systems

• Published in: Boundary-layer meteorology Vol. 186; no. 2; pp. 399 - 422
• Main Authors: Bailey, Sean C. C., Smith, Suzanne Weaver, Sama, Michael P., Al-Ghussain, Loiy, Boer, Gijs de
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.02.2023; Springer; Springer Nature B.V
• Subjects: Aircraft; Alliances; Analysis; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Canyons; Case studies; Drone aircraft; Drones; Earth and Environmental Science; Earth Sciences; Initial conditions; Katabatic winds; Lower atmosphere; Meteorology; Meteorology & Atmospheric Sciences; One dimensional models; Remotely piloted aircraft; Research Article; Slopes; Valleys; Topographic impact; Katabatic flow; Cold-air drainage; Valley flows; Uncrewed aircraft systems (UAS)
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1007/s10546-022-00783-w

Multiple fixed-wing and multirotor uncrewed aircraft systems were deployed to measure the early morning katabatic flow along a valley as part of the lower atmosphere profiling studies at elevation a remotely-piloted aircraft team experiment (LAPSE-RATE) campaign. The valley’s topography was that of a narrow canyon emerging into a broader shallow-sloped valley, allowing for an assessment of the suitability of one-dimensional approximations for the broad, flat part of the valley. The one-dimensional integral model predicts growth in the katabatic layer with downslope distance, which was not observed in the broader portions of the valley. Instead, observations revealed thinning of the katabatic layer at the valley centreline, coinciding with oscillatory behavior with a period between 30 and 60 min. These features were attributed to strong asymmetry and three-dimensional features initiating in the narrow part of the valley. These features produced initial conditions upstream of the broad slope flow that were not captured by the one-dimensional model.