The Effect of Spurious Cloud Edge Supersaturations in Lagrangian Cloud Models: An Analytical and Numerical Study

This study analyzes the production and the effect of spurious cloud edge supersaturations in Lagrangian cloud models (LCMs), which simulate droplets and aerosols explicitly as Lagrangian particles. By applying an idealized one-dimensional setup, it is shown that the production of spurious cloud edge supersaturations in LCMs and Eulerian cloud models is identical. In LCMs, however, the effect of spurious supersaturations on the number of activated/deactivated particles is decreased due to (i) a physically more appropriate representation of the activation process, and (ii) the LCM's ability to represent the distribution of liquid water on the subgrid scale. Additionally, an analytic solution for the production of spurious supersaturations in both Lagrangian and Eulerian cloud models is derived, enabling the identification of the upper limit of spurious supersaturations and the conditions under which they occur.