Direct measurements of sea spray particle fluxes using a high temporal resolution optical particle counter over the coastal ocean

Atmospheric aerosols affect the global radiation balance both directly and indirectly (IPCC, Masson-Delmotte et al. 2021). In order to understand the spatial and temporal variations of these aerosol-related effects, field observations of aerosol properties over a range of atmospheric conditions need to be performed (e.g. de Leeuw et al. 2011; Pryor et al. 2008). Sea spray particles play a key role in transferring momentum, heat, and gas across the atmosphere–ocean interface at high wind speeds and represent an important source of cloud condensation nuclei which affect the genesis, chemistry, and radiative properties of marine clouds. Here, we present direct measurements of sea spray particle fluxes obtained using an eddy covariance technique through the use of a newly developed high temporal resolution optical particle counter. With this instrumentation measurements were made over the coastal ocean during a 5-week field campaign conducted at an observation pier from November to December 2021. Our optical particle counter was capable of measuring size spectra at a rate of 10 Hz in 8 channels covering a range of mean radii between 0.3 and 15. The power spectra of particle number density followed the Kolmogorov −2/3 power law. The shape of the cospectrum of the particle number density flux was basically similar to that of the cospectra of the heat and gas fluxes. The measured sea spray particle fluxes at mean wind speeds of up to 21 m s⁻¹ were dominated by an upward flux, which likely represents aerosol production caused by the bursting of bubbles at the ocean surface.