The Impact of Vertical Wind Shear on Hail Growth in Simulated Supercells

摘要

Severe hailstorms produce over $1 billion in insured losses annually in the United States, yet details of a given storm's hail threat (e.g., maximum hailstone size and total hailfall) remain challenging to forecast. Previous research suggests that, in addition to maximum updraft speed, the storm-relative airflow could be equally important for hail formation and growth. This study is a first step toward determining how changes in environmental wind shear and subsequent changes in simulated supercell storm structure affect hail growth. Using Cloud Model 1 (CM1) with 500-m horizontal and 250-m vertical grid spacing, 20 idealized simulations are performed in which the thermodynamic profile remains fixed but the environmental hodograph is systematically altered. Hail growth is quantified using the hail mass mixing ratio from composites of storms over the last hour of simulation time. Hailstone growth "pseudotrajectories'' are computed from these storm composites to determine favorable embryo source regions.