Recently a team lead by investigators at Oxford University including scientists from the Department of Energy’s Pacific Northwest National Laboratory compared the vertical distribution of various aerosol types simulated by many aerosol models. They found considerable diversity in the simulated vertical distribution. Since each model uses different treatments of most of the processes that influence the vertical distribution, the team investigated the cause of the diversity by exploring the sensitivity of the vertical distribution simulated by one of the models using different treatments of many processes spanning the treatments used by the other models. The authors found that the simulated vertical distribution of aerosol depends on different sets of processes for different aerosol types. Researchers in this study found that the vertical distribution of emissions is important for the vertical distribution of biomass burning aerosols, vertical transport in cumulus clouds is important for all particles, removal of particles in droplets by precipitation is important for all particles except mineral dust, aerosol production by chemical reactions in cloud droplets is important for sulfate, and turbulent mixing and gravitational settling are important for coarse mineral dust and sea salt particles.