Further laboratory investigations into the Relative Diffusional Growth Rate theory of thunderstorm electrification
Further laboratory investigations into the Relative Diffusional Growth Rate theory of thunderstorm electrification
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DOI：
10.1016/j.atmosres.2010.07.011
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发表时间：
2010-11
影响因子：
5.5
通讯作者：
C. Emersic;C. Saunders
中科院分区：
文献类型：
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作者：
C. Emersic;C. Saunders
从相对扩散增长率理论的预测，使我们能够进一步研究控制在实验室实验中涉及冰晶和雾凇碰撞的<$球电荷的迹象。这主要是通过使用双云实验来实现的，在双云实验中，过冷液滴云和冰晶云混合在一起。一系列的晶体云成核技术已经能够对冰晶表面生长速率的预处理进行实质性控制，例如在与起霜目标相互作用之前控制与液滴云混合时的瞬时快速晶体生长。我们定性地确定了晶体表面生长速率和尺寸对混合后瞬时快速生长速率的影响。在接近水饱和度的环境中具有较高表面生长速率的晶体减少了瞬态快速生长对混合的影响，从而导致正的充电。在接近冰饱和度的环境中具有较低表面生长速率的晶体增强混合时的瞬时快速生长-特别是对于较小的晶体尺寸-以促进负的霰充电。这与相对扩散增长率理论是一致的，该理论是从许多实验室研究中发展起来的，表明在冰粒之间的碰撞中，表面通过扩散正电荷增长得更快。使用最短和最长的成核技术，可以分别将负充电延长到大约−20°C和−14°C。能够控制云的微物理和确定其对电荷符号的影响导致的结论是，雷暴电荷发展的数值模型需要考虑到广泛的特定微物理条件及其对云粒子充电的影响，在许多地区和雷暴的寿命。我们还提供了证据，支持新的解释的结果，其他研究人员通过使用相对扩散增长率理论的预测，使实验技术的发展，以促进负的充电记录高温，从而允许负充电在任何零下的温度适用于雷暴。
Predictions from the Relative Diffusional Growth Rate theory have allowed us to further examine controls over the sign of graupel charge in laboratory experiments involving collisions between ice crystals and riming graupel. This has been achieved primarily through the use of two-cloud experiments in which a supercooled droplet cloud and an ice crystal cloud are mixed together. A range of crystal-cloud nucleation techniques has enabled substantial control over the preconditioning of ice crystal surface growth rates such as to control transient rapid crystal growth on mixing with a droplet cloud prior to interaction with a riming target. We have qualitatively identified the effects that crystal surface growth rate and size have on the rate of transient rapid growth after mixing. Crystals with higher surface growth rates in environments nearer to water saturation reduce the effect of transient rapid growth on mixing leading to positive graupel charging. Crystals with lower surface growth rates in environments nearer to ice saturation enhance transient rapid growth on mixing – particularly for smaller crystal sizes – to promote negative graupel charging. This is consistent with the Relative Diffusional Growth Rate theory which has been developed from many laboratory studies and shows that in collisions between ice particles, the surface growing faster by diffusion charges positively. Using both the shortest and longest nucleation techniques developed, it was possible to extend negative charging to approximately −20°C and −14°C respectively. Being able to control cloud microphysics and determine its effect on charge sign has led to the conclusion that numerical models of thunderstorm charge development need to take account of the wide range of specific microphysical conditions and their effects on cloud particle charging throughout many regions and the lifetime of a thunderstorm. We also provide evidence in support of new interpretations of the results of other researchers by using predictions of the Relative Diffusional Growth Rate theory to enable the development of experimental techniques to promote negative graupel charging to record high temperatures, and consequently allow negative charging at any sub-zero temperature applicable to thunderstorms.