Estimation of sea spray aerosol surface area over the Southern Ocean using scattering measurements

Aerosol SA is used in many models' ice nucleating particle (INP) parameterizations, as well as influencing particle light scattering, hygroscopic growth, and reactivity, but direct observations are scarce in the Southern Ocean (SO). Two campaigns jointly conducted in austral summer 2018 provided co-located measurements of aerosol SA from particle size distributions and lidar to evaluate SA estimation methods in this region.

Mie theory calculations based on measured size distributions were used to test a proposed approximation for dry aerosol SA, which relies on estimating effective scattering efficiency (Q) as a function of angstrom ngstrom exponent (a). For distributions with dry a 1, an assumption of Q = 3 as in some prior studies underestimates dry aerosol SA by a factor of 2 or more. We propose a new relationship between dry a and Q, which can be used for -0.2 < a < 2, and suggest a = 0.8 as the cutoff between primary and secondary marine aerosol-dominated distributions.