The impact of the hailstone embryos on simulated surface precipitation Nemanja Kovačević ⁎, Mladjen Ćurić Institute of Meteorology, University of Belgrade, 16 Dobračina, 11000 Belgrade, Serbia article info abstract Article history: Received 7 March 2013 Received in revised form 14 May 2013 Accepted 14 May 2013 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. © 2013 Elsevier B.V. All rights reserved. Keywords: Cloud-resolving model Convective clouds Hailstone embryos Hail precipitation 1. Introduction Hail causes serious damage to agriculture and property in many areas of the world. Hailstones are high-density elements that are greater than 0.5 cm in diameter. They are formed from strong riming of rimed-ice elements that could be called — hailstone embryos. Hailstone embryos can be distinguished by how they are formed. They are usually frozen raindrops and medium-density rimed-ice elements are called graupel. A complete description of the hail spectrum cannot be established without first presenting hailstone embryos. Thus, it is useful to describe the hail spectrum and the mechanisms of its formation in more detail. Over the past several decades, cloud-resolving mesoscale models have become widely used in simulating cloud microphysics and dynamics and ground-level precipitation characteristics. Cloud simulation can be completed by either explicit microphysics (Stevens et al., 1996; Rasmussen et al., 2002; Khain et al., 2011) or bulk microphysical schemes (Lin et al., 1983; Ćurić and Janc, 1993; Meyers et al., 1997; Xue et al., 2001; Carrió and Nicolini, 2002; Phillips et al., 2007). The bulk microphysical scheme assumes a size distribution function for cloud and precipitation elements. These micro- physical species are described by one or more moments of Atmospheric Research 132–133 (2013) 154–163 ⁎ Corresponding author. Tel.: +381 645558598. E-mail addresses: nemanja@ff.bg.ac.rs (N. Kovačević), curic@ff.bg.ac.rs (M. Ćurić). 0169-8095/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.atmosres.2013.05.013 Contents lists available at ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmos