Evaluating an Ice Crystal Trajectory Growth (ICTG) Model on a Quasi-Idealized Simulation of a Squall Line

A major challenge in numerical weather prediction models is the ability to accurately simulate the microphysical properties and growth of ice hydrometeors in clouds. Eulerian bulk microphysics schemes in these models tend to obscure the properties and evolution of individual ice crystals, often resulting in inaccurate simulations of storm structures. To address this issue, this study presents a novel ice crystal trajectory growth (ICTG) model that simultaneously grows and advects individual ice crystals while tracking their evolving properties along their trajectories. The model is evaluated on a 3D quasi-idealized leading-convective, trailing-stratiform squall line simulation. The ICTG model successfully produced a spatial distribution of ice crystal trajectories consistent with the simulated reflectivity structure of the storm above the melting level. Smaller initialized crystals (d <= 0.1 mm) were largely transported to the anvil and the trailing stratiform region. One primary trajectory involved sustained growth in the stratiform mesoscale updraft for similar to 1.5 hr, resulting in a density reduction down to 600 kg m(-3), a final particle size greater than 0.9 mm, and potential branching. In contrast, larger initialized crystals (d >= 0.5 mm) collected more rime and fell out primarily in the leading convective line. The ICTG model's realistic production of varied crystal growth properties owing to differences in transport and initial size suggests that it can be a valuable tool for learning about ice microphysical processes in a variety of cold cloud systems.

Automated summary

A major challenge in numerical weather prediction models is accurately simulating the microphysical properties and growth of ice hydrometeors in clouds. This study presents a novel ice crystal trajectory growth (ICTG) model that addresses this issue by simultaneously growing and advecting individual ice crystals while tracking their evolving properties. The model is evaluated on a simulated squall line and successfully produces a spatial distribution of ice crystal trajectories consistent with the storm's reflectivity structure. The realistic production of varied crystal growth properties suggests that the ICTG model can be a valuable tool for studying ice microphysical processes.