Parameterization for Atmospheric New-Particle Formation: Application to a System Involving Sulfuric Acid and Condensable Water-Soluble Organic Vapors

A new parameterization for atmospheric new-particle formation has been developed. The parameterization takes into account the early growth of nucleated clusters by condensation of sulfuric acid and water-soluble organic vapors, as well as the scavenging of the growing nuclei by coagulation into larger pre-existing particles. The main input parameters are the nucleation rate, the concentration of sulfuric acid and organic vapor(s) contributing to the nuclei growth, and the pre-existing particle size distribution. The resulting output quantity is the formation rate of particles at a desired size, typically a few nanometers of particle diameter. Comparisons to detailed numerical simulations demonstrated that the parameterization is relatively accurate when the nucleation rate, condensable vapor concentrations, and nuclei growth rate change sufficiently slowly with time, and when the nucleation rate is not very high. As such, the parameterization is most applicable to“regional nucleation events,”in which new-particle formation occurs over distances of tens to hundreds of kilometers. The main obstacle in applying the new parameterization is that organic vapors contributing to the early growth of nucleated clusters have not been identified so far. A couple of solutions to this problem are proposed.