Effects of Short Scale Roughness and Wave Breaking Efficiency on Sea Spray Aerosol Production: Multisensor Field Observations

TL;DR

This study uses multisensor field data to analyze how short-scale roughness and wave breaking efficiency influence sea spray aerosol production, highlighting turbulence and wind conditions as key factors.

Contribution

It introduces a comprehensive analysis linking surface roughness and wave breaking to SSA production using multi-scale parameters and field observations.

Findings

Surface roughness correlates strongly with SSA properties.

Wave breaking efficiency varies with wind direction and sea state.

Turbulence and wind conditions significantly impact SSA generation.

Abstract

Simultaneous measurements of sea spray aerosol (SSA), wind, wave, underwater acoustic noise, and microwave brightness temperature are obtained in the open ocean. These data are analyzed to clarify the ocean surface processes important to SSA production. Parameters are formulated to represent surface processes with characteristic length scales over a broad range, from tens of meters to a few centimeters. The result shows that the correlation coefficients between SSA properties (number, volume and flux) and surface process parameters improve toward the shortest length scale. This suggests that whereas surface wave breaking is a necessary initial and boundary condition, the final state of the atmospheric SSA properties is controlled primarily by turbulent processes characterized by the ocean surface roughness. The investigation also reveals distinct differences of the SSA properties in rising winds and falling winds, with higher efficiency of breaking production in low or falling winds. Previous studies show that the length scale of breaking waves is shorter in mixed seas than in wind seas. Combining the observations together, it is suggestive that larger air cavities are entrained in rising winds (with wind seas more likely). The larger air cavities escape before they can be fully broken down into small bubbles for the subsequent SSA production. In contrast, the shorter breakers in low or falling winds (with mixed seas more likely) trap smaller air cavities that stay underwater longer for more efficient bubble breakup by turbulence.