McSnow: A Monte‐Carlo Particle Model for Riming and Aggregation of Ice Particles in a Multidimensional Microphysical Phase Space

We present a novel Monte‐Carlo ice microphysics model, McSnow, to simulate the evolution of ice particles due to deposition, aggregation, riming, and sedimentation. The model is an application and extension of the super‐droplet method of Shima et al. (2009) to the more complex problem of rimed ice particles and aggregates. For each individual super‐particle, the ice mass, rime mass, rime volume, and the number of monomers are predicted establishing a four‐dimensional particle‐size distribution. The sensitivity of the model to various assumptions is discussed based on box model and one‐dimensional simulations. We show that the Monte‐Carlo method provides a feasible approach to tackle this high‐dimensional problem. The largest uncertainty seems to be related to the treatment of the riming processes. This calls for additional field and laboratory measurements of partially rimed snowflakes.