Computer Modeling of Hailstone Growth in Feeder Clouds

Abstract

The growth of hailstones is studied using a one-dimensional non-steady-state model of a growing feeder cloud. Conditions within the mature cloud are assumed to be adiabatic. Vertical velocity and liquid water content profiles change at a predetermined rate, beginning with small values and gradually increasing to values that can be expected in a mature thunderstorm. Hailstone growth equations used in the model are developed in terms of the well-known dry- and wet-growth regimes and include terms that account for growth in a mixture of supercooled cloud droplets and ice crystals. Hailstone embryos in the form of liquid cloud droplets are introduced into the model at various heights and times, and the subsequent trajectories are analyzed. Different versions of the model that incorporate changes in updraft magnitude and shape are tested. Results show that the model produces hailstones, radii ranging from near zero to 1.3 cm in 40 min or less, from 20 to 50 ? radius embryos introduced under a variety of updraft conditions, at many places in the life of the feeder cloud model.