Patterns of Bubble Clouds organized by Langmuir Circulation

Abstract A commonly observed property of near-surface bubble distributions is their collective organization into long rows aligned with the wind under the influence of Langmuir circulation. Time series observations with sonars having fixed orientation reveal the temporal evolution of bubble distributions as they drift through the sonar measurement path, Here this concept is extended to provide a time sequence, at 37-s intervals, of two-dimensional images generated by horizontally rotating sonars. Observations obtained during a storm in the Strait of Georgia show individual Langmuir convergence zones as they evolve above the freely drifting sonar. The resulting images are processed to generate a binary representation of the convergence zone patterns from which their orientation, length, spacing, and other properties can be extracted. Although there is some angular spreading, most convergence lines are aligned within 20° of the wind. The spacing between convergence lines reveals a wide range of scales, but ...