Numerical Simulations Of Ice Crystal Growth In Water Vapor Deposition Process For Typical Ice Habits

Ice particles are the main component in the mixed-phase cloud, and play a significant role during the precipitation process. Currently, precisely modeling the precipitation and the microphysical processes has been a key issue in the atmospheric physical study. Thus, modeling the evolution of ice particles in the clouds cannot only help us understand the microphysical processes, but also aid to improve the development for cloud models. Due to changes produced by the ambient temperature and water saturation, the ice crystal habit has been recognized as a critical parameter to impact cloud simulations. Ice particles have always been regarded as spherical shapes in the most cloud models. However, the shapes of ice crystals in the real atmosphere are much complicated. Ice crystal habits will change with the variation of ambient temperatures and water vapor saturations. Such habits have been proved as a critical parameter to impact cloud simulations. In this study, based on the theoretical model of the deposition growth of an ice crystal, we firstly simulated the growth of a single ice crystal by water vapor deposition under the temperatures from-1℃ to -30 ℃. The model can capture the evolution of axis length (a for prism face; c for basal face), mass and aspect ratio in comparison with the data observed in wind tunnels. We further simulated the water vapor deposition growth of non-spherical ice crystals with the two-dimensional positive definite advection transport algorithm (MPDATA). Furthermore, in order to test the feasibility to apply such a treatment into the Eulerian dynamical framework, the mass growth of ice crystals under different bin resolutions for the aspect ratio has been simulated. The results showed that the model used the MPDATA method can capture the evolution of ice crystals for both their mass and their aspect ratio. Even though, some Lagrangian models with bin microphysics involved microphysical processes for the non-spherical ice crystals. However, their schemes with the hybrid bin method cannot be applied into the cloud models under the Eulerian dynamical framework, which can simulate more complicated microphysical processes and dynamical processes involved in ice particles.