An empirical model has been developed to predict aerosol particle size distributions from a set of relatively simple meteorological parameters. The model is based on measurements taken at Meetpost Noordwijk (MPN) (North Sea) during the Humidity Exchange Over the Sea Main Experiment in 1986. The air masses at MPN contain a mixture of continental and marine aerosol. The relative contribution of each type of air mass strongly depends on the wind direction. Partitioning the aerosol data set into eight wind sectors based on geographical considerations of the sources of natural, anthropogenic, and industrial aerosols is supported by analysis based on the wind speed dependence of the particle concentrations. For each wind sector the aerosol concentrations in the 0.2--15-μm diameter range were analyzed in terms of relative humidity, wind speed, air-sea temperature difference, and water temperature, that is, those parameters that determine the production, dispersal, and deposition of the aerosol. The model predicts the aerosol concentrations to within a factor of 1.7 (68% confidence limit). Model performance is reduced during frontal passages and in periods of rain and high relative humidity. This is illustrated with two case studies. ¿ American Geophysical Union 1992