典型层状云系催化试验的云物理响应研究

Study of Physical Response of Cloud for Typical Stratiform Cloud Seeding

利用2003年秋季延安地区一次典型层状云系加密探空和实时雷达观测资料,设计了催化和对比探测方案,计算得出催化影响区及下风方可能采集到响应值的区域。按照设计方案进行催化和探测。云物理响应观测结果表明:PNS粒子探测系统检测到催化后30min,小云滴减少;大冰晶的浓度增加;催化前冰晶以片状为主,催化后可看到有霰坯;催化前大雪晶浓度很小,雪晶之间没有攀附;催化后雪晶浓度增加,且大雪晶增加很多,可明显看到几个雪团攀附在一起形成的较大雪团;雷达观测到催化前拟播撒区内云的回波强度较弱、范围较小,催化后云体明显增大,强中心增加了5～10dBz;催化约1h后影响区雨量均有增加,说明催化引入的人工冰晶,使冰晶凝结比水滴凝结更有利于过冷云水转化为降水,冰晶效应和雪晶攀附过程是这次层状云系降水系统中的主要过程。过冷水冻结释放的潜热,导致云内升速加大,使催化区云和降水得到发展。

A seeding and contrast detection project was designed-based on the seeding area and leeward region which may collect response value by calculating the sounding and real-time radar data of a stratiform cloud system in Yan′an in spring of 2003.The PMS data of seeding and detection experimentation according to this project indicates that the concentration of big crystal increases in evidence while the number of cloud droplet decreases after 30 min seeding;the ice crystal are mostly hexagonal plates before seeding and the tapioca snow after that;the concentration of snow crystals （especially the big crystals） are increasing and the bigger snowballs are formed by several little snowballs after seeding.The radar echo shows that the cloud body is bigger evidently and the radar echo intensity increases 5~10 dBz after seeding;the precipitation of seeding area increases after 1 h seeding.It indicates that the seeded artificial ice crystals make ice crystal coagulation more helpful for super cold cloud transforming to rainfall than water droplet coagulation.Ice crystal effect and snow crystal aggregation are the main processes of this stratiform cloud rainfall system,in addition to the increased cloud rising speed from latent heat of super cold water solidification,these factors cause the development of cloud and rainfall in seeding area.