Measurements of oceanic bubble size distributions

For systematic studies of air-sea exchange processes, detailed information is required on the bubble size distributions near the sea surface as function of meteorological and oceanographic conditions. The bubble size distributions should be measured simultaneously with the fluxes of aerosols and gases. Therefore, the authors have developed an optical instrument to measure the sizes of single bubbles and thus derive bubble size distributions at sea. The bubble measuring system uses a laser beam that illuminates a sample volume that is monitored with a simple camera system. A dedicated image processing board is used to derive the bubble spectra on-line. The optics and electronics have been assembled in a water tight housing. Preliminary results are presented that were obtained during the ASGASEX and MAPTIP experiments at the North Sea in the fall of 1993