Binary Homogeneous Nucleation: Temperature and Relative Humidity Fluctuations, Nonlinearity, and Aspects of New Particle Production in the Atmosphere

Abstract

Binary homogeneous nucleation of sulfuric acid and water vapor is thought to be the primary source of new particles in the marine atmosphere. The rate of binary homogeneous nucleation depends strongly on temperature and the gas-phase concentrations of both sulfuric acid and water vapor. This paper investigates the effects of these nonlinear dependencies on the rate of formation of new particles. An increase of 2°-3°C can reduce the particle formation rate by an order of magnitude. Large-scale fluctuations such as those characteristic of a well-mixed boundary layer can alternately “turn on” and “shut off” the nucleation process, giving rise to regions of new particle formation that are quite localized. These “bursts” of nucleation correspond to higher altitudes in the boundary layer. Small-scale fluctuations, more typical of normal atmospheric turbulence, can increase the binary homogeneous nucleation rate severalfold above the rate calculated based on mean conditions.