First Results from HEFEXIII - current state of the Hintereisferner boundary layer

In the greater TEAMx framework and following HEFEX in 2018 and HEFEXII in 2023, the third HinterEisFerner EXperiment (HEFEXIII) took place in August and September 2025 on Hintereisferner glacier, Tyrol, Austria. During one month, a 9 m tower was deployed on the glacier, equipped with high-frequency measurements of three-dimensional wind components and temperature at five levels (0.5 m, 1 m, 3 m, 5 m and 9 m), as well as low-frequency measurements of two-dimensional wind components, temperature, and relative humidity at three additional levels (2 m, 4 m and 7 m). Furthermore, two lidar systems and a swarm of drones strategically measuring at various locations along the glacier axis, were used to assess the flow conditions in the atmosphere above the glacier. This dataset enables an evaluation of boundary-layer characteristics close to the surface while relating them to the flow in the larger mountain boundary layer above.
Here, we describe the general meteorological conditions observed during the campaign, as well as the turbulence characteristics. We contrast periods with an undisturbed boundary layer with conditions characterised by external disturbances, such as thermally driven upvalley winds or mountain waves on the glacier boundary layer and their influence on the katabatic flow. We focus specifically on vertical profiles of temperature and wind obtained during one of the drone IOPs, as well as the average turbulent fluxes of momentum and heat, and the budget terms of the turbulent kinetic energy at the different measurement heights.