人工消雾试验中的雾微物理响应

2009年11—12月在天津市武清区实施了两次消雾外场试验。11月6—7日,利用燃烧烟条的方式播撒吸湿性焰剂对暖雾实施催化;11月30日—12月1日,利用播撒液氮的方式实施冷雾消雾试验。对两次消雾试验期间雾的微物理观测资料分析发现,雾对催化有明显响应,具体表现为:雾滴浓度先增后减且变化剧烈,液态水含量、雾滴大小等微物理特征量也发生了显著变化;催化期间雾滴谱均出现了谱宽加大的现象,催化结束后谱宽恢复至催化前状态;催化效应导致出现了处于不同发展阶段的雾滴,雾滴谱发生了单峰分布和双峰分布间的变换:催化前滴谱为单峰分布,催化期间出现双峰谱;多个短时双峰谱反复出现;首个双峰谱出现后,滴谱逐渐由单调递减向单峰、双峰转变;催化结束后,滴谱由双峰谱恢复为单峰谱。分析认为:催化后暖雾中发生成熟过程(Ripening Process),而冷雾催化后则启动了贝吉隆过程(Bergeron process)。

ANALYSES OF A MICROPHYSICAL RESPONSE TO THE SEEDING IN TWO ARTIFICIAL DISSIPATION CASES OF FOG

Two field experiments were performed in order to dissipate the fog at Wuqing District of Tianjin in November and December of 2009.Hygroscopic particles were seeded to dissipate fog droplets on 6-7 November,2009.Liquid nitrogen(LN) was seeded into the natural supercooled fog in the experiments of 30 November –1 December,2009.Significant response was found after seeding.Obvious changes were observed in the microstructure of fog in the field experiments.The number concentration of fog droplet changes dramatically;it increased first and then decreased after seeding.Remarkable variation also was found in the Liquid Water Content(LWC) and in the size of fog droplet.The Droplet size distribution(DSD) of fog broadened during the seeding experiments.The DSD became narrow after the seeding ended.Droplets at different stages of growth were found after seeding,resulting in a transform of DSD between unimodal distribution and bimodal distribution.The DSD was unimodal before seeding and then bimodal distributions emerged during the seeding experiment.Finally,the DSD became unimodally distributed once again.