Annual Variability of Particle Size, Cloud Condensation Nuclei, and Particle Hygroscopicity in the Central Arctic

Xianda Gong, Jiaoshi Zhang, Betty Croft, Xin Yang, Markus Frey, Rachel Chang, Jessie Creamean, Chongai Kuang, Randall Martin, Arthur J. Sedlacek, Janek Uin, Sascha Willmes, Maria Zawadowicz, Jeffrey R. Pierce, Matthew Shupe, Julia Schmale, JIAN WANG, Washington University in St. Louis

     Abstract Number: 278
     Working Group: Remote and Regional Atmospheric Aerosol

Abstract
Temperatures in the Arctic are rising at more than twice the global average rate, and aerosol plays an important role in the Arctic climate. Currently, aerosol properties and sources remain poorly understood in the central Arctic, where observations are scarce. Here we present the seasonal variations of central Arctic aerosol properties observed during the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) campaign. Particle number size distribution exhibited high concentrations of accumulation mode (diameter > ~80 nm) during spring due to long-range transport pollution from lower latitudes and high concentrations of Aitken mode (diameter < ~80 nm) during summer as a result of more frequent new particle formation (NPF) events. CCN concentration (NCCN) during the springtime was often the highest (~110 cm-3 at a supersaturation of 0.30%). In comparison, NCCN during summer and fall was substantially lower (~ 20 cm-3) except when newly formed particles grew and reached a sufficiently large size (diameter > ~80 nm) to act as CCN. Particle hygroscopicity (expressed as a single parameter, κ) was low (~0.2 to 0.3) during summer and fall due to the strong contributions of organics to particle composition. During winter and spring, κ values ranged from ~0.5 to 1.2, indicating that sea salt particles generated from open leads/blowing snow contribute substantially to the aerosol population in the Arctic. Aerosol emissions, transport, and their effect on cloud properties need to be further studied to improve our understanding of Arctic climate change.