Eddy Covariance measurements of the sea-spray aerosol flux: parameterization in terms of a wave roughness Reynolds number

Sea spray aerosol forms a dominant contribution to the total aerosol loading of the atmosphere over the open ocean. The aerosol originates from spray droplets generated by the bursting of bubbles following wave breaking events. Most parameterizations of the source flux are formulated in terms of wind speed alone; the order of magnitude uncertainty that remains in these parameterizations, and the different functions obtained by various studies strongly suggest that other factors contribute to the variability in aerosol production.

Here we use direct eddy covariance measurements of the sea spray aerosol flux in the North Atlantic to formulate a source function for the aerosol size range 0.18 μm to 6.6 μm in terms of a wave roughness Reynolds number. This takes account of both wind speed and significant wave height. It explains up to twice the variance in the observations than does wind speed alone.

The Reynolds number parametrization and a wind speed only parametrization derived from the same data set are forced with ECMWF operational mode fields. They differ substantially in regions where the wave field is substantially under- or over-developed compared to a wave state in equilibrium with the local wind.