Parforce:Objectives and achievements

O'Dowd, C. D. and Becker, E. and Hoell, C. and Mäkelä, J. M. and Kulmala, M. and Hämeri, K. and Väkevä, M. and Pirjola, L. and Aalto, P. and Hansson, H. C. and Strom, J. and Jennings, S. G. and Geever, M. and De Leeuw, G. and Kunz, G. and Berresheim, H. and Hewitt, C. N. and Sartin, J. and Harrison, R. M. and Allen, A. G. and Viisanen, Y. and Korhonen, P. and Rapsomanikis, S. and Hoffman, T. (2000) Parforce:Objectives and achievements. In: AIP Conference Proceedings. American Institute of Physics. ISBN 1563969580

Abstract

Understanding the formation of natural particles in the atmosphere, and their growth to radiatively active sizes, is critical to quantifying the role of anthropogenic emissions on cloud formation, climate change and public health. Only a few regions have been identified as strong natural sources of aerosols in the boundary layer: in particular, the coastal region seems to be the strongest natural source of these new particles. The PARFORCE program was designed to elucidate and understand the underlying processes leading to observed coastal nucleation and to quantify the factors promoting coastal nucleation. Initial results indicate that nucleation rates in the coastal environment are of the order of 107 cm−3 s−1 and can be explained by ternary nucleation of sulphuric acid, water vapor and ammonia; however, growth to detectable sizes can only be explained by additional condensation of, probably, organic vapor—otherwise these new stable embryos are lost due to coagulation. The primary biogenic condensing species leading to the observed particle concentrations is thought to be a halocarbon derivative. Peak concentration of particles at sizes >3 nm can reach 1,000,000 cm−3 after a coastal nucleation event and these events occur almost on a daily basis over considerable spatial scales.