冰雹化学成分:在深对流云中追踪冰雹轨迹的证据

Chemical composition of a hailstone:evidence for tracking hailstone trajectory in deep convection

冰雹这类强对流天气现象具有分布广、突发性强、发展演变迅速、破坏力强、时空尺度小等特点,对其中的冰雹粒子增长轨迹进行直接观测难度很大.本研究创新地提出冰雹分层化学分析工作可以为探测冰雹在强对流云中的运动轨迹提供良好信息载体的观点.基于2016年4月收集于广西大新县的一个大冰雹样本,本文分析了8种水溶性离子浓度(Na^+,K^+,Ca2^+,Cl^-,NO3^-,SO42^-,HCOO^-,CH3COO^-)和2种水的稳定同位素(δD和δ18O)的含量在该冰雹样本中的分层分布情况,发现它们从最内层至最外层均呈现"V"型分布,这表明强对流云内化学物质的垂直分布与冰雹粒子的生长过程有直接联系.水溶性离子浓度的分布表明了云内气溶胶可能参与云内水汽凝结物核化过程和碰并清除过程,水的稳定同位素含量分布则表明了冰雹运动轨迹与云内水汽分布特征的关联,两者共同佐证了该冰雹粒子在云内的倒"V"型轨迹.

Hail is produced by all types of deep convective storms and occurs commonly for short periods in most parts of the world[1].The growth path of hailstones in hailstorms remains largely uncertain[2-4].Due to the limitations hampering direct observations of severe hailstorms,it is difficult to identify definitively the in-cloud conditions and hailstone growth trajectories that lead to hailstone formation[2,3]-However,natural hailstones can provide insights into hydrometeors and aerosols in deep convective storms.Hailstones have been collected and examined,and various techniques have been applied to measure representative atmospheric chemical isotopes[2,5],which is of great help when investigating hailstones'origin and structure。