ICTG Harvey radial output

A novel Lagrangian Ice Crystal Trajectory Growth (ICTG) model was used in conjunction with the Weather Research and Forecasting model to analyze the details of ice crystal evolution in a tropical cyclone eyewall. The initialization method was improved from previous studies to initialize at locations with positive freezing rates in WRF, and to span sizes within the ice water content distribution in the Thompson microphysics scheme at each WRF grid box. ICTG includes crystal growth equations informed by laboratory experiments capable of simulating complex crystal morphologies. It produced realistic crystal trajectories and was used to assess variations in crystal growth and advection based on initial altitude, radius, and size.

Results showed that the initial altitude of the crystal was most important for determining final mass, shape, location, and likelihood of sublimation. Crystals initialized above 8 km altitude or closer to the eye saw more sublimation, while crystals initialized just above the melting level were most likely to rime, grow rapidly, and fall out quickly. The largest final masses originated in the dendritic growth zone and had the smallest initial sizes in the grid box. Using a super-particle method to analyze the final locations and particle properties, most of the ice mass melted within or just beyond the eyewall. This region saw a large diversity of crystal morphologies. A much smaller amount of ice mass was ejected beyond 60 km radius. These findings will allow for further refinement of our understanding of hurricanes and improvement of model microphysics schemes.