Combing the viscosity data from Fig. with annual average temperature and RH data in the troposphere following the approach used previously, yields predictions of BB-SOA viscosity as a function of latitude and altitude (Fig. ). This prediction shows that catechol + OH SOA is often in a liquid state (η < 10 2 Pa s) below ~2 km altitude, a semi-solid state (10 2 < η < 10 12 Pa s) between ~2 km and ~9 km, and a glassy state (η > 10 12 Pa s) above ~9 km. The viscosity also has important implications for the cloud formation ability of BB-SOA particles, in particular, their ability to act as ice nucleating particles (Fig. ). Highly viscous, glassy SOA particles are thought to promote ice nucleation in clouds, by providing a solid surface. Our results suggest that phenolic BB-SOA could provide a previously unrecognized source of ice nucleating particles above ~6-9 km in altitude. These altitudes are regularly reached by biomass burning plumes, which can be lifted into the upper troposphere and lower stratosphere by convection. The viscosity also impacts gas-particle partitioning and hence SOA formation and growth in biomass burning plumes. Knowledge of the mixing time of organic molecules in SOA is important for predicting SOA mass and size distributions and the long-range transport of pollutants in SOA. The mixing time of organics within BB-SOA particles as a function of RH and temperature, 𝜏 mix,org (RH, 𝑇), can be calculated as, 𝜏 mix,org (RH, 𝑇) =