Comment on "Size distribution of sea-salt emissions as a function of relative humidity"

Zhang et al. (2005) present a parameterization for what they term the "growth factor" of a sea salt aerosol particle relative to its formation diameter, which they assert "is a function of relative humidity alone" and independent of an arbitrary reference relative humidity. Here we note that this growth factor implicitly assumes an arbitrary reference relative humidity through the salinity of the seawater from which the particle is produced and thus that the diameter at formation does not uniquely represent the amount of solute mass contained in a sea salt aerosol particle, in contrast to the equivalent dry radius (or diameter) or to the radius (or diameter) of the particle in equilibrium at a given relative humidity, typically used for this purpose. We present an alternative parameterization for the RH growth factor of sea salt aerosol particles that is physically based, of more general applicability, more accurate, and valid at higher relative humidity. The dependence of the size of sea salt aerosol particles on relative humidity is important to numerous processes of interest: light scattering, gas-liquid exchange of water and trace gases, dry deposition, particle sampling, and the like, the accurate description of which requires accurate knowledge and representation of this dependence. Zhang et al. present a parameterization of the growth factor, which they define as the ratio of the diameter of a sea salt aerosol particle at formation from seawater having salinity 35, D form,35 , to the diameter of the same particle in equilibrium with a given