Radiosoundings were launched every six hours (00, 06, 12 & 18UTC) and additionally before each helicopter flight (if not at one of the normal times), using Vaisala RS92 sondes. Balloons were launched from the helipad of Oden about 13 m above sea level, while the Vaisala DigiCORA receiving station was located on the port side of the 7th deck. Soundings measure pressure, temperature and relative humidity as the balloon roses through the air, at about 4-6 ms-1. From temperature and pressure, altitude is calculated using the hydrostatic relationship. Winds are measured by tracking the sonde using GPS. The data has been through several QC procedures and raw sounding data has been reprocessed using the available surface observation operating in so-called “research mode”; bad or dubious values are replaced by NaN. For a few soundings the RS92 sensor package was complemented either by radioactivity or ozone sensors.