Observed vs. simulated aerosol phase state during the ASIA-AQ campaign: its implication for climate forcing

Secondary inorganic aerosols undergo a phase transition between solid and liquid states as a function of relative humidity. Different aerosol phases affect their size, altering their optical properties, radiative effects, and heterogeneous chemical reactions. Despite its importance, however, state-of-the-art chemical transport models have not explicitly simulated aerosol phases because of their complex hysteresis with respect to relative humidity history. We use aerosol phase-state observations from the ASIA-AQ campaign to evaluate ISORROPIA thermodynamic calculations with different hysteresis pathways constrained with observed meteorological conditions from the campaign. Although we found a marginal difference in total aerosol concentrations with the different hysteresis pathways, simulated AODs differ significantly, depending on aerosol phase, suggesting their significance for aerosol radiative forcing.