Non-equilibrium evolution of HNO3/H2SO4/H2O stratospheric particles under multi-component diffusive condensation/evaporation regime

A box model is used to study the evolution of stratospheric HNO3/H2SO4/H2O solution particles along temperature variations, which force the droplet ensemble far from the thermodynamic equilibrium. In the case of rapid temperature fluctuations, i.e. orographically forced lee waves, the model shows that the micron-sized droplets meet the conditions to become precursors of solid particles, mainly constituted of nitric acid hydrates. This paper examines how the particle size distributions and compositions are influenced by the presence of rapid temperature fluctuations, comparing model calculations along prescribed thermal histories. There results a remarkable dependence of the particle physical status (solid and/or liquid) on the presence of wave-like perturbations in the former thermal history of the air mass.