A review of the sea spray generation function for the open ocean

The sea spray generation function quantifies the rate at which sea spray droplets of initial radius r₀ are produced at the sea surface--as a function of wind speed, for example. Spray droplets are important to air-sea interaction and marine meteorology because they are the source of the marine aerosol, may evolve into cloud condensation nuclei, and can affect the optical properties of the marine boundary layer. But my own personal interest is in how or whether spray droplets can alter the exchange of heat, moisture, and momentum across the air-sea interface. At least a dozen versions of the spray generation function for r₀ values, nominally, between 1 and 500 µm are available in the literature; but at any given r₀, these various functions range over six orders of magnitude. Clearly, a six-order-of-magnitude uncertainty in this essential function impedes our attempts to understand the role of spray in air-sea interaction. Some of the differences between functions undoubtedly result from the difficulty in making the required measurements, some result from varying definitions of the function, and some functions are simply incorrect. In this presentation, I will summarize the published spray generation functions; present theoretical guidelines to help us judge which have realistic magnitude and behavior; and, finally, suggest which are the most reliable in terms of spectral shape and wind speed dependence.