Synergistic Observations of Flow in Complex Terrain: Integrating Lidar and Drones During the TEAMx Campaign

Abstract

Atmospheric boundary layer (ABL) dynamics in complex terrain are inherently three-dimensional, where microscale turbulence plays a critical role in driving larger-scale flow evolution. With numerical weather prediction models approaching sub-kilometer resolutions, it is increasingly important to challenge and validate the models on the small scales with high-resolution observations. Contributing to the TEAMx goal of understanding scale interactions, we present results from an intensive field experiment conducted at the Nafingalm, a pasture at the valley head of a tributary to the Inn Valley (Austria).

The experimental site, a north-south aligned valley system approximately 2x2 km wide and 500 m deep, was instrumented during the Summer 2025 Extended Observation Period (EOP). The setup included two scanning lidars, a profiling lidar, and a network of ground-based meteorological stations. These continuous observations were augmented by the SWUF-3D fleet of multicopter drones (aka Uncrewed Aircraft Systems, UAS) between 1 and 23 July 2025. Up to 30 UAS were operated simultaneously, reaching heights of 220 m above the valley floor to collect distributed measurements of 3D wind, temperature, humidity, and pressure in regions inaccessible to traditional instrumentation.

While continuous lidar scanning mapped the along- and cross-valley flow, the UAS fleet provided direct in situ validation of the assumptions required to derive turbulence statistics from remote sensing. Furthermore, the spatial distribution of the drones allows for direct measurement of shear contributions, buoyancy, and advective tendencies. We present preliminary analyses of two contrasting Intensive Observation Periods (IOPs): one characterized primarily by thermally driven flow and another with increased mesoscale forcing. These cases highlight the strength of synthesizing remote sensing with distributed UAS measurements to resolve scmall-scale dynamics in complex terrain.