Nucleation rate of particles in the lower atmosphere: Estimated time needed to reach pseudo‐steady state and sensitivity to H 2 SO 4 gas concentration

Abstract

Using a kinetic model, we estimate the time‐needed ( t 0 ) to establish a pseudo‐steady state nucleation when sulfuric acid concentration ([H 2 SO 4 ]) suddenly increases to a certain fixed level. We find that t 0 is roughly inversely proportional to [H 2 SO 4 ]. The assumption of instantaneously achieved pseudo‐steady state concentration of critical clusters, on which the classical nucleation theories are based, is no longer valid when t 0 is longer than the time period that [H 2 SO 4 ] can be treated as constant. Under the lower marine atmospheric conditions considered in this study, the nucleation rate predicted by ion‐mediated nucleation theory is very sensitive to [H 2 SO 4 ] when [H 2 SO 4 ] is low (