Automating the analysis of hailstone layers

Abstract

The layered structures inside hailstones provide a direct indication of their shape and properties at various stages during growth. Given the myriad of different trajectories that can exist, and the sensitivity of rime deposit type to environmental conditions, it must be expected that many different perturbations of hailstone properties occur within a single hailstorm; however, some commonalities are likely in the shared early stages of growth, for hailstones of similar size (especially those that grow along similar trajectories) and final growth near the melting level. It remains challenging to extract this information from a large sample of hailstones because of the time required to prepare cross sections and accurately measure individual layers. To reduce the labour and potential errors introduced by manual analysis of hailstones, an automated method for measuring layers from cross section photographs is introduced and applied to a set of hailstones collected in Melbourne, Australia. This work is motivated by new hail growth simulation tools that model the growth of layers within individual hailstones, for which accurate measurements of observed hailstone cross sections can be applied as validation. A first look at this new type of evaluation for hail growth simulations is demonstrated.