Impact of the vertical velocity field on charging processes and charge separation in a simulated thunderstorm

Fei Wang,Yijun Zhang,Dong Zheng,Liangtao Xu

doi:10.1007/s13351-015-4023-0

Fei Wang, Yijun Zhang + Show 2 more

Open Access

https://doi.org/10.1007/s13351-015-4023-0

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Abstract

A three-dimensional (3D) charging-discharging cloud resolution model was used to investigate the impact of the vertical velocity field on the charging processes and the formation of charge structure in a strong thunderstorm. The distribution and evolution of ice particle content and charges on ice particles were analyzed in different vertical velocity fields. The results show that the ice particles in the vertical velocity range from 1 to 5 m s−1 obtained the most charge through charging processes during the lifetime of the thunderstorm. The magnitude of the charges could reach 1014 nC. Before the beginning of lightning activity, the charges produced in updraft region 2 (updraft speed ⩾ 13 m s−1) and updraft region 1 (updraft speed between 5 and 13 m s−1) were relatively significant. The magnitudes of charge reached 1013 nC, which clearly impacted upon the early lightning activity. The vertical velocity conditions in the quasi-steady region (updraft speed between −1 and 1 m s−1) were the most conducive for charge separation on ice particles on different scales. Accordingly, a net charge structure always appeared in the quasi-steady and adjacent regions. Based on the results, a conceptual model of ice particle charging, charge separation, and charge structure formation in the flow field was constructed. The model helps to explain observations of the “lightning hole” phenomenon.

Highlights

IntroductionEspecially strong updraft, in a thunderstorm is a key factor causing lightning activity
Updraft, especially strong updraft, in a thunderstorm is a key factor causing lightning activity
The results indicated that: (1) the negative charge on graupels due to charging processes in updraft region 2 was relatively significant before the start of lightning activity; (2) the increase in negative charge on graupel due to charging processes in updraft region 1 was significant during the first period of lightning activity; and (3) the negative charge on graupel due to charging processes in updraft region was significant during the last period of lightning activity

Summary

Introduction

Especially strong updraft, in a thunderstorm is a key factor causing lightning activity. Updraft is conducive to the development of graupel and ice crystals. It increases the collision probability, and strengthens the non-inductive charging processes between these two kinds of particles. Some researchers believed that the strong updraft existing in the mixed phase zone (–40 to 0°C) is important for the production of lightning (Workman and Reynolds, 1949; Williams and Lhermitte, 1983; Dye et al, 1989; Rutledge et al, 1992; Carey and Rutledge, 1996; Petersen et al, 1996, 1999; Wang et al, 2009; Heymsfield et al, 2010; Zheng et al, 2010; Palucki et al, 2011; Reinhart et al, 2014). Some researchers believed that the strong updraft existing in the mixed phase zone (–40 to 0°C) is important for the production of lightning (Workman and Reynolds, 1949; Williams and Lhermitte, 1983; Dye et al, 1989; Rutledge et al, 1992; Carey and Rutledge, 1996; Petersen et al, 1996, 1999; Wang et al, 2009; Heymsfield et al, 2010; Zheng et al, 2010; Palucki et al, 2011; Reinhart et al, 2014). Zipser (1994) hypothesized that weak updrafts in most oceanic storms produce insufficient concentrations of supercooled liquid water, large ice particles, and ice-ice collisions in the mixed phase

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