The impact of the hailstone embryos on simulated surface precipitation

Hailstorms cause significant damage to agriculture and property in many areas of the world. Therefore, it is useful to describe the size spectrum of hail and the mechanisms of formation in more detail. One important point in the formation of hail is the role of hailstone embryos, and an understanding of their mechanism would significantly improve our understanding of the evolution of hail, as well as the predicted amount of accumulated hail on the ground. We used a cloud-resolving mesoscale model to investigate the influence of the hailstone embryos on the measured ground precipitation. In this model, both types of the hailstone embryos (graupel and frozen raindrops) are incorporated. Therefore, the model predicts the mass and number concentration of the six microphysical elements - raindrops, ice crystals, snow, graupel, frozen raindrops and hail. The cloud droplet number concentration was prescribed. Thus, the primary goal of this sensitivity study was to examine the influence of hailstone embryos on the measured ground precipitation and the duration of precipitation. Thus, we performed a numerical comparison of the two microphysical schemes, one with hailstone embryos and the other without them. The sensitivity study indicated that the microphysical scenario with hailstone embryos leads to a greater increase in accumulated hail compared with the scheme without hailstone embryos. The time of hail occurrence on the ground occurs during the early stages of cloud life in the experiment without hailstone embryos. In the second case, the hail occurrence on the ground was delayed for the later stages of cloud life, which is much more realistic and in agreement with the measurements. The use of a model with hailstone embryos leads to a better description of the evolution of hail and a more accurate prediction of the accumulated hail on the ground.