This data set contains atmospheric profile measurements retrieved from 452 radiosonde ascents during FESSTVaL 2021. The data set consits of observations from three data sources: (1) operational 6-hourly radiosonde launches from the Meteorological Observatory Lindenberg - Richard Aßmann Observatory (MOL-RAO) performed by the German Weather Service (sups_rao; 421 sondes); (2) special radiosonde launches from the MOL-RAO performed by the University of Hamburg (fval_uhh; 19 sondes); and (3) special radiosonde launches from the Falkenberg boundary layer measurement site (located about 5 km south of MOL-RAO) performed by the University of Cologne (fval_uzk; 12 sondes). All profiles are stored in seperate files according to the SAMD convention for FESSTVaL. A data file contains the 3-dimensional position information and basic meteorological parameters measured by the radiosonde dependent on time (at 1-s resolution) and typically covers both ascent and descent of the radiosonde flight. The vertical resolution of the measurement data depends on the ascent/descent velocity of the sonde. Date and time in the file names refer to the actual launch time (in UTC) of the respective radiosonde.