During extreme marine weather conditions, the wind can tear off small droplets from the wave crests, also termed sea spray spume. While these droplets are small, the sheer number of droplets generated significantly increases the surface area between the ocean and atmosphere, thereby impacting the fluxes of momentum, mass and heat across the air-sea interface. Great uncertainty currently exists in quantifying the amount of sea spray spume produced, largely due to the difficulties in measuring sea spray in-situ and near the ocean surface.
Here, we present an acoustic method to measure sea spray spume droplets in-situ during extreme marine weather conditions. Specifically, we use the resonance response of a hydrophone to droplet impact to quantify the sea spray droplet number flux. The method was calibrated and validated using laboratory experiments of free-falling and wind-driven spray droplets. We find good agreement between the droplet number flux estimated from the acoustic recordings and that measured using a stroboscopic imaging system. The acoustic method provides significant opportunities in measuring sea spray spume droplets in-situ and should provide observation-based support for sea spray induced fluxes in weather and climate forecasting models.