Particle nucleation in the tropical boundary layer and its coupling to marine sulfur sources.

New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area.

Measurements of the humidification processes of hydroscopic particles.

A number of pure salt aerosols were produced in the laboratory, subjected to a controlled humidity environment. The magnitude of the electrooptic response was measured continuously over a range of relative humidity (RH), which was varied from 20 to 90%, with an integrating electrooptical nephelometer. From such observations the influence of water vapor on the salt aerosols, especially the process of phase transition that occurs at the deliquescent point, can be monitored.

Characterization of nonspherical atmospheric aerosol particles with electrooptical nephelometry.

An integrating nephelometer was adapted electronically to study the electrooptical properties of aerosol particles. The increase in light scattering coefficient due to orientation of nonspherical particles in the pulsed electric field and the decay of this signal were measured. Examples of the data for laboratory generated aerosols and atmospheric aerosols are presented.