A Nearly Global-Scale In Situ Atlas of Sea Salt Aerosol Vertical Profiles

Seasalt‐derived aerosol (SSA) particles are the largest contributor to aerosol mass on a global basis. Particularly in areas of the remote ocean, they are important contributors to light scattering and cloud droplet nuclei. Vertically‐resolved atmospheric concentrations of sea‐spray aerosol over the open ocean are sparse and are not well represented in chemical transport models. We have analyzed particle size distribution data from 16 NASA and NSF‐sponsored airborne projects to assemble a collection of latitude‐, longitude‐, altitude‐, and time‐referenced SSA size distributions stretching over 20 years and including most of the world’s ocean basins. Where possible, chemical determinations of SSA are included, but size distributions are inferred from a variety of aerodynamic and optical particle sizing instruments. Thus there is some ambiguity when other aerosol constituents are present. For coarse particles, dust is the only important confounding factor. Accumulation mode SA is inferred using a thermal denuder, but dust, soot and some organic material survive along with the seasalt, so the data presented should be regarded as an upper bound. The majority presented here are from aerodynamic and optical particle sizers, the latter with intermittent thermal treatment to remove most volatile aerosol components. including thermal treatment to drive off volatile materials. Where possible, they are referenced to chemical measurements and are generally correct to within 30%. Due to the difficulty of sampling large particles through airborne inlets, only particles <10 μm are considered and considerable corrections are required above 4 µm.

We show that chemical transport models often have large, systematic errors in both mixed layer SSA and the efficiency with which they are transported higher in the boundary layer and the free troposphere.

A preliminary version of the data is available at https://www.soest.hawaii.edu/higear/data
It has only the most recent projects. Files are Matlab format and are divided into profiles (200 m vertical bins) and level legs (better data quality) flight by flight. Each level leg and altitude bin has size distributions from individual instruments; merged size distributions from all available instruments; integral quantities (total and submicron mass and number); data quality flags; ancillary data including black carbon from PSAPs or SP2s, CO, organic mass from an aerosol mass spectrometer; latitude, longitude, altitude, and time.