The influence of random fluctuations on the behaviour of an aerosol

The purpose of the paper is to assess in a general manner the influence of random fluctuations in the local velocity, deposition rate, growth rate and coagulation constant on the behaviour of an aerosol. Using stochastic methods of probability theory we have shown that fluctuations in the local velocity lead to a broadening of the volume distribution which increases with time. The fluctuation in the deposition rate has a destabilizing effect and reduces the deterministically calculated rate of decay. Fluctuations in growth rate lead to the broadening of an initially monodisperse distribution and allow for evaporation and condensation. The rate of increase of suspended mass arising from this condensation-evaporation process is greater than the corresponding deterministic value.The effect of fluctuations in the coagulation constant leads to a decrease in the usual rate of removal of particles, although this is a small effect.The fluctuations are assumed to be stationary, random functions of time or position and in most cases are taken to be Gaussian variables. However, it is found that the infinite range of the Gaussian can lead to certain unphysical results and other distributions are examined.