Application of a mixed-layer model to aerosols in the marine boundary layer

A mixed-layer model for the concentration and evolution of marine aerosols is presented. The ambient aerosol spectrum is divided into continental and sea-salt components and transformed to a reference saturation ratio. The temporal evolution of the aerosol spectrum is predicted from rate equations that require specification of the mixed-layer depth. particle production at the surface, and particle entrainment into the mixed layer from aloft. The model was tested against a marine data set obtained off Southern California during the CEWCOM-78 experiment. The test was carried out with two different methods of obtaining the relevant meteorological and aerosol parameters: (i) actual measurements and (ii) dynamic boundary layer model prediction and parameterization. In the first case. the model reproduced the aerosol data within a factor of 1.5m while in the second case, the uncertainty factor was 2.0. In either case, the model only modestly out-performs a much simpler model, which uses only local specification of the wind speed and humidity.