10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Understanding Significant Variations of Particle Formation and Number Concentration from Surface to the Upper Troposphere over the Central Pacific Ocean
GAN LUO, Fangqun Yu, Charles Brock, Agnieszka Kupc, Christina Williamson, The State University of New York at Albany
Abstract Number: 1384 Working Group: Aerosol Modeling
Abstract Aerosol impacts significantly on cloud properties by serving as cloud condensation nuclei (CCN). The sources of CCN over remote oceans and key controlling parameters remain to be understood. Significant variations of particle formation and number concentration from 0.2 to 12 km altitude over the Central Pacific Ocean area were observed during the ATom first deployment (ATom-1, Aug 3rd-9th, 2016). To better understand the key factors controlling particle formation and number concentration from surface to the upper troposphere, a state-of-the-art global chemistry model with sectional advanced particle microphysics package (GEOS-Chem/APM) is employed in this study to simulate particle formation and size distribution evolution. The predicted condensation nuclei larger than 3 nm (CN3) and other variables along ATom-1 NASA DC-8 tracks are compared with those observed. Major characteristics of CN3 vertical distribution and variation sampled along NASA DC-8 tracks have been captured quite well by GEOS-Chem/APM. CN3 concentrations in the upper troposphere are generally ~10-100 times higher those near the surface and have the highest values over the tropical regions. Our study indicates that particle number concentration is dominated by new particle formation, and key parameters controlling nucleation rates include gas concentrations of sulfur acid and ammonia, temperature, ionization rate, and relative humidity. Precursor gases are transported from surface to the upper troposphere via convection, which result in high sulfur acid gas concentration, nucleation rate, and particle number concentration in the upper troposphere over tropical pacific oceans. The key parameters controlling the growth of new particles and their contribution to CCN at different altitudes over the remote oceans will be discussed.