Bubble Formation and Modification in the Sea and its Meteorological Significance

Abstract

It is believed that the vast majority of the airborne salt nuclei arise from bursting bubbles at the air—sea water interface. Four natural mechanisms for the production of these bubbles have been studied. These are whitecaps, rain, snow and supersaturation of the surface waters of the sea due to spring warming. The bubble spectra from whitecaps and snowflakes have been measured and semi-quantitative and qualitative observations have been made on the bubble spectrum produced by raindrops. No evidence of bubble production by spring warming has been obtained. All of the measurements show that a majority of the bubbles are < 200 microns diameter and, in the case of bubbles from snowflakes, < 50 microns. In the vicinity of a breaking wave the bubble production rate is about 30 cm−2 sec−1. Due to the effects of surface tension in increasing the bubble internal pressure all bubbles < 300 microns will go into solution even at sea water air saturations of 102 percent. Bubbles < 20 microns will go into solution at saturations up to 115 percent! The solution time for small bubbles of about 10 microns is about 10 sec and is not markedly affected by the water saturation percentage. It is concluded that the effects of the rate of solution of bubbles in sea water can, under some conditions, play a significant role in modifying the initial bubble spectrum. This, in turn, should influence the spectrum of airborne nuclei.