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

ABSTRACT

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.

KEYWORDS:

• Sea spray
• optical particle counter
• aerosol
• air-sea interface
• turbulence
• eddy covariance technique

Acknowledgments

The authors wish to thank Drs. Nakamura and Banno, and the staff of the Port and Airport Research Institute for their excellent support and assistance in setting up and maintaining the instruments. We are grateful to Dr. Matthews for carefully proofreading the manuscript. This work was carried out by the joint research program of the Institute for Space−Earth Environmental Research (ISEE), Nagoya University, and was supported by JSPS KAKENHI Grants 21K18652 and 19H05698 of Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. This research is a contribution to the Surface Ocean Lower Atmosphere Study (SOLAS) which is one of the core projects of the Japanese hub of the Future Earth program.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the joint research program of the Institute for Space−Earth Environmental Research (ISEE), Nagoya University, and the JSPS KAKENHI Grants of Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan [21K18652 and 19H05698].