Abstract

In this seminar I will introduce the CERN CLOUD chamber experiment studying atmospheric new particle formation and the associated gas-phase chemistry. About half of cloud-forming aerosol particles (‘cloud condensation nuclei’) in the atmosphere originate from new particle formation. The formation process, and the growth of new nanoparticles to the sizes needed to seed cloud droplets, can depend on organic chemistry, often involving peroxy radicals, and this has been a particular focus of the CLOUD experiment in recent years. I will discuss work we have done to parameterize new particle formation and growth rates for atmospheric models. I will discuss the implementation of the parameterizations into the models and the implications of the results from these models for estimated cloud condensation nuclei concentrations and indirect aerosol radiative forcing. The uncertainties in modelling new particle formation remain large, and I will outline how we are moving forward to try to reduce them.