During cloud processes, aerosol particles undergo physical and chemical changes. In this work by Dr. Yu Yao, and Professor Nicole Riemer, a particle-resolved model was used to quantify the changes in aerosol mixing states. They linked the particle-resolved aerosol model PartMC-MOSAIC with the cloud chemistry module CAPRAM 2.4 and designed cloud simulations that simulated several cloud cycles to which particle populations may be exposed in polluted urban environments.
Ammonium nitrate and ammonium sulfate was added to the activated particles. Once the cloud evaporated, the activation potential of the resuspended aerosol particles increased for supersaturation thresholds that were lower than the maximum supersaturation that was attained in the cloud. Quantified by the mixing state index χ, the formation of sulfate and nitrate increased the internally mixed state of all the particle populations.
For a low aerosol number concentration case, where the activated fraction was up to 60%, χ increased up to ~50 percentage points after cloud processing, which reaches an almost completely internal mixture. Although, for a case with high aerosol emissions and activated fraction of less than 20%, the increase in χ < 20 percentage points, and χ remained below 80% after cloud processing. These findings highlight the complex influence of cloud processing on particle properties.
To read the full publication, please visit https://doi.org/10.1029/2021JD034992.
Yao, Y., M.L. Dawson, D. Dabdub, N. Riemer, 2021: Evaluating the Impacts of Cloud Processing on Resuspended Aerosol Particles After Cloud Evaporation Using a Particle Resolved Model, J. Geophys. Res., 126 (24), https://doi.org/10.1029/2021JD034992