| Summary: | Bubble size distributions were measured at open sea with optical bubble measuring systems(BMS)deployed from buoys at depths from 0.4 to l.5m. The BMS measures the bubbles in a small sample volume that is monitored with a video camera. The images are analyzed to obtain bubble size distributions in the diameter range from 30 to 1000 um. The BMS was deployed in the North sea from the research tower Meetpost Noordwijk and from ships in the North Atlantic, yielding a validated data set of circa 300 bubble spectra obtained during seven cruises in different seasons. The measurements were made in a variety of wind speeds, water temperatures and atmospheric stability's. Bubble concentations vary by 2 orders of magnitude, the spectra peak at diameters of 50-80 pm, and the slope varies from -l.8 to -5. often a second peak is observed at 200-300 pm. The largest variations were observed between different experiments, while during a single experiment the spectra showed less variation, indicating seasonal influences. Wind speed dependencies were observed during single experiments, while in other experiments such effect was not statistically significant. The measurements were all made with the same technique, and the results are similar to data presented in the literature obtained with different techniques.
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