AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Spring and Summer Contrast in New Particle Formation over Nine Forest Areas in North America
Fangqun Yu, Gan Luo, Viney Aneja, Kenneth Demerjian, Anna Gannet Hallar, Olga Hogrefe, W. Richard Leaitch, Shanhu Lee, John Ortega, Priya Pillai, Sara Pryor, JAMES SCHWAB, James N. Smith, John Walker, University at Albany
Abstract Number: 516 Working Group: Aerosol Chemistry
Abstract Recent laboratory chamber studies indicate a significant role for highly oxidized low volatile organics in new particle formation (NPF) - but the actual role of organics in NPF in the real atmosphere remains to be clarified. Here NPF events and non-events based on particle size distributions (PSDs) measured in nine forest areas in North America are analyzed and compared to model simulations with and without the involvement of extremely low volatile organics in nucleation. This study focuses on contrasting spring and summer months. On average NPF occurred on ~ 70% of days in a spring month for the four forest sites with spring time PSD measurements, while it occurred only on ~ 8% of days in a summer month for all nine forest sites. Two different nucleation schemes appear to capture the frequent NPF in the spring month. Yet the nucleation scheme considering the role of organics significantly over-predicts NPF and particle number concentrations in the summer month. The two schemes also predict quite different spatial patterns in nucleation rates in the spring over North America. Statistical analysis indicates that the scheme without organics agrees better overall with observations. The two nucleation schemes predict quite different concentrations of cloud condensation nuclei and aerosol first direct radiative forcing in North America, highlighting the necessity to reduce uncertainty in the NPF calculation in regional and global climate models.