HEFEX III: Fixedwing UAS sounding profiles for site F291 and F309 on Hintereisferner glacier (Austria) in August 2025

HEFEX III – Fixedwing UAS Sounding Observations Atmospheric measurements using fixedwing uncrewed aerial systems during IOP1 of the HEFEX III (the third HintEreisFerner EXperiment) field campaign in August 2025 at two locations on the Hintereisferner glacier, a valley glacier in the Rofental catchment in the Ötztal Alps of Austria. DOI: 10.5281/zenodo.22646654 Contact: [e-mail], [e-mail] Sensors: Sensirion-SHT75, UBLOX-M8T Period: 2025-08-06 to 2025-08-10 Locations:name ground-height longitude latitude F291: at 2910 m asl, 10.7571224E, 46.7928514NF309: at 3090 m asl, 10.74449E, 46.79437N Variables: year : year for trajectory points (UTC)month : month for trajectory points (UTC)day : day for trajectory points (UTC)hour : hour for trajectory points (UTC)min : minute for trajectory pointssec : second for trajectory pointsmsec : milliseconds for trajectory pointsheight : height above sea level, corrected by pressure measurements and digtal elevation model (m) height_agl : height above ground level (m)dir : heading direction of flight trajectory in degrees (clock-wise from north) retrieved by GNSS (°)gspeed: ground speed of flight trajectory retrieved by GNSS (m/s)tair : air temperature by SHT75 (direct measurement) (°C)tair_c : time lag corrected air temperatue (°C)tair_vpc : time lag corrected virtual potential temperature reduced to 1000 hPa (°C)rhum : relative humidity by SHT75 (direct measurement) (%)rhum_c : time lag corrected relative humidity (%)shum_c : time lag corrected specify humidity (g/kg)wdir : wind direction determined for slowest ground speed within circular flight circuits at constant throttle (°)wspd : wind speed calculated by ground speed differences between head wind and tail wind within circular flight circuits (m/s)pres : air pressure (hPa) Files: The data are organized in three categories: i) raw data, ii) trajectories and iii) profiles. For each category a bzip2-compressed tar archive is avaliable: - rawdata.tar.bz2 (~75 Mib) - trajectories.tar.bz2 (~13 Mib) - profiles.tar.bz2 (~243 Kib) In order to uncompress under Linux run: tar xvfj rawdata.tar.bz2 ; tar xvfj trajectories.tar.bz2 ; tar xvfj profiles.tar.bz2 The total amount of uncompressed data is ~247 Mib. Each tar archive contains the 34 directories, one for each flight time and location: 2025-08-06_1500_F2912025-08-07_0300_F2912025-08-07_0600_F2912025-08-07_0600_F3092025-08-07_0900_F2912025-08-07_0900_F3092025-08-07_1200_F3092025-08-07_1300_F2912025-08-07_1500_F2912025-08-07_1500_F3092025-08-07_1800_F2912025-08-07_1800_F3092025-08-07_2100_F2912025-08-07_2100_F3092025-08-08_0300_F2912025-08-08_0300_F3092025-08-08_0600_F2912025-08-08_0600_F3092025-08-08_0900_F2912025-08-08_0900_F3092025-08-08_1200_F2912025-08-08_1200_F3092025-08-08_1500_F3092025-08-08_1800_F3092025-08-08_2100_F3092025-08-09_0300_F3092025-08-09_0600_F3092025-08-09_0900_F3092025-08-09_1200_F3092025-08-09_1500_F3092025-08-09_1800_F3092025-08-09_2100_F3092025-08-10_0600_F309 The naming of the directories is YYYY-mm-dd_HHMM_F???, where YYYY is the year, mm the month, dd the day, HH the hour, MM the minute of the planned start of the flight. F stands for Fixedwing and ??? is the location ground level height above sea level in decameters (291 and 309 for the two sites). All dates and times are given in UTC. Data File types: i) raw data are stored on board during the flights by the Paparazzi-UAV autopilot system in fr_????.LOG containing logs from the flight recorder and pprz_????.LOG additionally containing the sensor messages, where ???? is just a running number. In cases where the high frequency on board data are unavailable, telemetry data files are used, which are recorded at the ground control station computer and contain most of the variables, however at a lower frequency. These telemetry data are stored in files named like YY_mm_dd__HH_MM_SS.data containing the messages and an equivalent file ending with *.log containing the flight configuration. More on the file formats can be found e.g at: https://paparazzi-uav.readthedocs.io/en/latest/ ii) Trajectory data of single points in time are stored in csv files named YYYY-mm-dd_HHMM_F???_traj.csv. The trajectory data contain data recorded during sounding flights postprocessed using the software package mmp (mobile measurements postprocessor, see below). The postprocessing steps include time lag correction using estimated air-speed, height correction using atmospheric pressure together with the Austrian digital elevation model (Land Tirol, Abt. Geoinfomation) and estimates for wind direction and wind speed. iii) In order to retrieve representative vertical profiles, trajectory data are aggregated to 5 meter high vertical profile layers by using three different aggregation measures: - YYYY-mm-dd_HHMM_F???_prof05mean.csv : arithmetic mean within each 5-meter layer - YYYY-mm-dd_HHMM_F???_prof05median.csv : median within each 5-meter layer - YYYY-mm-dd_HHMM_F???_prof05mid.csv : center between minimum and maximum within each 5-meter layer The number of avaiable records within each layer is stored in YYYY-mm-dd_HHMM_F???_prof05count.csv Additional details are available in readme.txt