Size distribution and chemical composition of marine aerosols: a compilation and review

Some 30 years of physical and chemical marine aerosol data are reviewed to derive global-size distribution parameters and inorganic particle compositi on on a coarse 15 degrees x 15 degrees grid. There are large gaps in geogra phical and seasonal coverage and chemical and physical aerosol characterisa tion. About 28% of the grid cells contain physical data while there are com positional data in some 60% of the cells. The size distribution data were p arametrized in terms of 2 submicrometer log-normal distributions. The spars eness of the data did not allow zonal differentiation of the distributions. By segregating the chemical data according to the major aerosol sources, s ea salt, dimethylsulfide, crustal material, combustion processes and other anthropogenic sources, much information on mass concentrations and contribu tion of natural and anthropogenic sources to the marine aerosol can be glea ned from the data base. There are significant meridional differences in the contributions of the different sources to the marine aerosol. Very clearly , we see though that the global marine surface atmosphere is polluted by an thropogenic sulfur. Only in the case of sulfur components did the coverage allow the presentation of very coarse seasonal distributions which reflect the spring blooms in the appropriate parts of the oceans. As an example of the potential value in comparing the marine aerosol data base to chemical t ransport models, global seasonal meridional MSA distributions were compared to modelled MSA distributions. The general good agreement in mass concentr ations is encouraging while some latitudinal discrepancies warrant further investigations covering other aerosol components such as black carbon and m etals.