Group 1. Nucleation working group (McMurry & Clarke)

The discussion focused on nucleation-related papers that are being considered. The following topics were mentioned:

For the June 1, JGR submission:

• Rodney Weber, Peter McMurry, Eisele and coworkers, Bradshaw and coworkers; Kreidenweis and coworkers: Rodney Weber is working on a paper that describes the nucleation event observed downwind of Macquarie Island. The paper will examine the relationship between particle production and precursor gases such as H2SO4 and NH3, and will investigate particle production rates as well as particle growth rates. Measurements on Macquarie Island will be incorporated in this paper to provide information about initial conditions.

Work planned for the future:

• Sonia Kreidenweis and coworkers: 2-D cloud dynamics model with coupled chemical model to investigate processes that lead to nucleation at outflow regions from convective clouds.

• Lynn Russell and John Seinfeld: 1-D hybrid cloud dynamics model with coupled chemical model to investigate processes that lead to nucleation at outflow regions from convective clouds.

• Doug Davis and Gao: Model for nucleation induced by mixing and chemical transformations in cloud outflow regions. High time resolution data from the C-130 fro species including 03, H2O, H2SO4, and Nox should be useful in evaluating model predictions.

• Tony Clarke: Is working on a "nucleation climatology" survey paper that will summarize conditions (aerosol surface areas, local events such as cloud outflow, etc.) That lead to nucleation.

• Allen Bandy and coworkers: Have developed an alternative model for nucleation based on chemical arguments that reactions between H2SO4 and clusters are kinetically limited. They plan to compare predictions of their model with data acquired in ACE-1.

• Jingxia Zhao, Tony Clarke, and Jamie Li: Jingxia Zhao has developed a theory for nucleation in the atmosphere. She plans to work in collaboration with Clarke and coworkers to compare model predictions with ACE-1 data.

• Rodney Weber, Peter McMurry, Eisele and coworkers, etc: This group is planning to study data for nucleation in cloud outflow regions in an effort to determine the relationship between particle production and growth rates and concentrations of gas phase precursors.

• Rodney Weber plus other groups with CNC data: Rodney has compared data from CNCs on the C-130. This comparison provided useful insights, for example, into conditions that lead to droplet shatter. Because droplet shatter produced particles in the nanoparticle range, there is a potential for confusing droplet shatter events with nucleation events. Although this paper is not aimed at nucleation, this work must be completed before the C-130 data can be used to obtain information about nucleation. Rodney has also compared C-130 data with data from Macquarie, the Discoverer, and Cape Grim for periods when the aircraft was in the vicinity. He does not plan to compare CNC data of the Discoverer and ground sites when the ship was upwind of those sites.

• Rodney Weber, Mark Stolzenburg, Spyros Pandis, and Peter McMurry: A paper on the inversion of pulse height data to obtain size distributions in the 3-10 nm diameter range will be submitted to the Journal of Aerosol Science by mid April for review for inclusion in a special issue on nanoperticles. Some of the Macquarie Island data will be included in this paper to illustrate distributions that are obtained when nucleation is occurring. This paper will not include an in depth discussion of the Macquarie Island data.