Using the SWUF-3D UAS fleet to determine heat flux characteristics in an Alpine valley
Keywords
heat flux, verification, diurnal evolution, heat flux divergence, UAS observations
Presenter Abstract
Advancements in uncrewed aerial system (UAS) development and meteorological sensor integration have created a valuable tool to observe turbulence in the atmospheric boundary layer (ABL). Deploying a fleet of UASs allows the flexibility to sample the spatiotemporal structure of turbulence; such observations are particularly useful in complex terrain where it is difficult to sample with classical approaches. During the TEAMx campaign, the DLR SWUF-3D fleet of UAS was operated in a remote Alpine valley. Each SWUF-3D UAS is outfitted with a rapid response temperature sensor and can determine the 3D wind field at high-resolution, and these measurements are calibrated in-field. The 3D box-pattern configuration of a UAS fleet hovers up to 18 min at fixed-position across the valley and allows spatial gradients to be calculated. In July 2025, 88 box-pattern fleet flights were completed across a range of weather conditions. Valley heating mechanisms are unique due to contributions in all three dimensions but rarely have the observations to characterize the volume effects. Evaluating the UAS flux measurements against a nearby eddy-covariance station shows that the turbulence measurements are reliable and within the documented degree of uncertainty. The SWUF-3D measurements show the horizontal heat flux contribution is the same order of magnitude as the vertical heat flux during thermally-driven upvalley flow, contributing to strong temperature variance. Additionally, the UAS box-pattern arrangement provides the opportunity to calculate the heating budget terms that can be combined with surface-based automated weather stations positioned across the valley.
Presentations
Presented in Session 4: New Observations I
Using the SWUF-3D UAS fleet to determine heat flux characteristics in an Alpine valley
Advancements in uncrewed aerial system (UAS) development and meteorological sensor integration have created a valuable tool to observe turbulence in the atmospheric boundary layer (ABL). Deploying a fleet of UASs allows the flexibility to sample the spatiotemporal structure of turbulence; such observations are particularly useful in complex terrain where it is difficult to sample with classical approaches. During the TEAMx campaign, the DLR SWUF-3D fleet of UAS was operated in a remote Alpine valley. Each SWUF-3D UAS is outfitted with a rapid response temperature sensor and can determine the 3D wind field at high-resolution, and these measurements are calibrated in-field. The 3D box-pattern configuration of a UAS fleet hovers up to 18 min at fixed-position across the valley and allows spatial gradients to be calculated. In July 2025, 88 box-pattern fleet flights were completed across a range of weather conditions. Valley heating mechanisms are unique due to contributions in all three dimensions but rarely have the observations to characterize the volume effects. Evaluating the UAS flux measurements against a nearby eddy-covariance station shows that the turbulence measurements are reliable and within the documented degree of uncertainty. The SWUF-3D measurements show the horizontal heat flux contribution is the same order of magnitude as the vertical heat flux during thermally-driven upvalley flow, contributing to strong temperature variance. Additionally, the UAS box-pattern arrangement provides the opportunity to calculate the heating budget terms that can be combined with surface-based automated weather stations positioned across the valley.