AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Determination of the 3nm Particle Formation Rates at Puijo (Finland) Site Using an Analytical Formula Linking “Real” and “Apparent” Formation Rates
ELHAM BARANIZADEH, Tuomo Nieminen, Tuukka Petäjä, Markku Kulmala, Taina Yli-Juuti, Kari Lehtinen, PhD candidate
Abstract Number: 306 Working Group: Aerosols, Clouds, and Climate
Abstract Atmospheric new particle formation (NPF) events, i.e. nucleation and the subsequent growth of the newly formed particles has received increasing attention due to its impact on climate and human health. Several features at the nucleation level including the actual mechanism, the vapors involved, and the actual rates are not well-understood. At several locations particle size distribution measurements do not extend to nucleation size range but instead start at larger sizes (e.g. 7 nm) which limits the use of the particle data in NPF studies and poses a challenge in understanding NPF globally. In this study, we use previously derived analytical formula between “real” formation rate and the “apparent” formation rate of particles at larger sizes for which measurements are available. Our aim is to determine the formation rates of particles of 3 nm (J3) in diameter at Puijo, Finland site where the size distribution of particles below 7 nm is not measured. We have evaluated the formula over Hyytiälä, Finland site where the aerosol size distribution of particles larger than 3 nm is measured. We calculated formation rates of 7 nm particles (J7) and used the analytical formula to scale down to 3 nm. These estimated J3 were compared to observed J3 calculated directly from the size distribution. We have analyzed 55 NPF event days for which the formation and growth rates could be quantified. The daily arithmetic mean of J3 for each NPF day was calculated. The preliminary results show that 64 % of estimated J3 are within the factor of two of the observed J3; with the tendency of the analytical formula to overestimate the J3. NPF days where estimated J3 exceeded observed J3 by over the factor of two were characterized with more uncertainty in the analytical formula arising from the uncertainty in particle growth rate.