Thermal infrared measurements on a projection screen at Hintereisferner

In this study, an InfraTec VarioCAM HD thermal infrared (TIR) camera (1024 × 768 pixels) was used to monitor air temperature dynamics near a glacier surface. The camera targeted two vertically mounted polyester screens (with emissivity 0.94), which rapidly equilibrate with ambient air temperature and thus serve as reliable proxies for air temperature. Screen 1 (1.9 m × 3 m) was used for along-flow measurements, while Screen 2 (3.8 m × 1.9 m) captured vertical temperature profiles. This analysis focuses on Screen 2 to examine vertical air temperature dynamics in relation to katabatic winds. The screens were aligned with the glacier wind to measure temperature patterns along and across the katabatic jet, typically located 1.7–2.3 m above the ice surface (based on prior HEFEX I data). The TIR camera, positioned at a distance yielding a resolution of ~6 mm/pixel, recorded at 30 Hz. To ensure data accuracy, TIR values were averaged across pixels to account for material variability and contamination. Due to possible solar heating, absolute temperature readings may be positively biased, so the study emphasizes relative temperature changes. TIR measurements were conducted during the Intensive Observation Period (IOP) of the HEFEX II campaign (August 22–24, 2023). Five representative data sequences from August 22–23 2023 were selected, each lasting from one to several hours. These sequences demonstrate the method’s effectiveness in capturing high-resolution spatial and temporal temperature variations during both stable katabatic and disturbed flow conditions. Combining TIR and turbulence data enables estimation of jet height.