Air-sea gas transfer velocities in the Baltic Sea measured with the Active Controlled Flux Technique

Heat transfer velocities measured during three different campaigns in the Baltic Sea using the Active Controlled Flux Technique (ACFT) with wind speeds ranging from 5.3 to 14.8 m s−1 are presented. Careful scaling of the heat transfer velocities to gas transfer velocities using Schmidt number exponents measured in a laboratory study allows to compare the measured transfer velocities to existing gas transfer velocity parameterizations, which use wind speed as the controlling parameter. The measured data and other field data clearly show that some gas transfer velocities are much lower than the empirical wind speed parametrizations. This indicates that the dependencies of the transfer velocity on the fetch, i.e., the history of the wind and the age of the wind wave field, and the effects of surface active material need to be taken into account. Data set contains: Measured heat transfer velocities kheat in dependency of time, position, wind speed and water and air temperature for the measurements on RV Alkor and RV Aranda in 2009 and 2010. Furthermore the Prandtl number Pr, the Schmidt number exponent n and the scaled transfer velocity k600 are given. The given times are approximate starting times in UTC. Each measurements lasted about 20 min.