Enhanced aqueous formation and neutralization of fine atmospheric particles driven by extreme cold, Fairbanks, Alaska, 2022

Aqueous phase reactions in clouds, fogs, and fine particle water are important sources of secondary aerosol particles that affect the environment, human health, and climate. At moderate temperatures, the extent of these reactions is highly modulated by water concentration, making clouds key source regions. Under extreme cold (-20 to -35 degree Celsius (°C)), when aqueous particles exist in a metastable state, secondary aqueous chemistry becomes highly favored in supercooled fine particle water due to reduced volatility of gas-phase species. It also produces unusual behavior in particle pH, a key parameter affecting heterogeneous chemistry. This is demonstrated by Fairbanks wintertime hydroxymethanesulfonate (HMS), a compound only formed through aqueous phase reactions when pH is near neutral (4 to 5). This dataset contains outputs of ISORROPIA II ([H+], ALWC, [NH4+(aq)], [NH3(g)], pH) and ISORROPIA-Lite (ALWC).