AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Springtime Secondary Particle Formation and Its Contribution to CCN in the Northeastern US
FANGQUN YU, Gan Luo, James Schwab, G. Garland Lala, Kenneth Demerjian, University at Albany, SUNY
Abstract Number: 504 Working Group: Aerosols, Clouds, and Climate
Abstract By acting as cloud condensation nuclei (CCN), atmospheric particles modify cloud properties and precipitation and thus affect the hydrological cycle and climate indirectly. New particle formation (NPF) is an important source of CCN in the troposphere. Here we study the springtime secondary particle formation and its contribution to CCN in the Northeastern US, through size-resolved aerosol simulations and comparisons with measurements obtained at the Pinnacle State Park in upstate New York, a rural site in the Northeastern US that is subject to the influence of anthropogenic emissions from the Ohio River Valley Region. The model employed for this study is WRF-Chem v3.7.1, with a size-resolved advanced particle microphysics (APM) module incorporated. We focus on two two-week periods (April 7-21, 2009 and May 7-21, 2012) when particle size distributions have been measured at the Pinnacle State Park. Strong NPF and growth events were observed in 19 out of the 28 days (68%). The model is able to capture most of event and non-event days. The non-event days are largely associated with cloudy or precipitation days when the solar radiation at the surface is low. Both the measurements and model simulations show that the strong NPF can increase CCN abundance by up to one order of magnitude. Based on WRF-Chem-APM simulations, secondary particles on average contribute ~90% to the CCN abundance at the PSP site while primary particles (mostly black carbon and primary organic carbon) contribute ~10%. On a regional scale, secondary particles contribute ~80-95% to CCN concentrations in most part of Northeastern US, highlighting the necessity for better representation of NPF in weather and climate models that take into account aerosol-cloud-precipitation interactions. The sensitivity of simulated CCN concentrations to the nucleation schemes and implications to simulated cloud properties and precipitation will be discussed.