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The distribution of sea-salt aerosol in the global troposphere

Murphy, D., K. Froyd, H. Bian, C. Brock, J. Dibb, J. P. DiGangi, G. S. Diskin, M. Dollner, A. Kupc, E. Scheuer, G. Schill, B. Weinzierl, C. Williamson, and P. Yu (2019), The distribution of sea-salt aerosol in the global troposphere, Atmos. Chem. Phys., 19, 4093-4104, doi:10.5194/acp-19-4093-2019.

We present the first data on the concentration of sea-salt aerosol throughout most of the depth of the troposphere and over a wide range of latitudes, which were obtained during the Atmospheric Tomography (ATom) mission. Sea-salt concentrations in the upper troposphere are very small, usually less than 10 ng per standard m3 (about 10 parts per trillion by mass) and often less than 1 ng m−3 . This puts stringent limits on the contribution of sea-salt aerosol to halogen and nitric acid chemistry in the upper troposphere. Within broad regions the concentration of sea-salt aerosol is roughly proportional to water vapor, supporting a dominant role for wet scavenging in removing sea-salt aerosol from the atmosphere. Concentrations of sea-salt aerosol in the winter upper troposphere are not as low as in the summer and the tropics. This is mostly a consequence of less wet scavenging in the drier, colder winter atmosphere. There is also a source of sea-salt aerosol over pack ice that is distinct from that over open water. With a well-studied and widely distributed source, sea-salt aerosol provides an excellent test of wet scavenging and vertical transport of aerosols in chemical transport models.

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Tropospheric Composition Program (TCP)