冰核对云物理属性和降水影响的研究

系统回顾了冰核对云和降水影响的研究进展,详细分析了冰核对云的宏微观特征、对流系统结构和强度、辐射、雷电、降水量和降水强度的影响途径,并从云微物理过程的角度解释了其影响机制。得到如下结论:1通常情况下,冰核浓度增加,冰晶浓度增大,云滴浓度减小,云的生命史延长;2对于发展阶段的对流云,冰核在温度较高的过冷区活化使潜热在中低层提早释放,增加了对流系统中层不稳定能量,促进了对流系统的发展;3卷云中冰核浓度的增加,改变了冰相水物质与液相水物质的比例;削弱或抑制了卷云中同质核化,增大了卷云中冰晶粒子的平均半径;4冰核浓度的增加,能够使到达地气系统的净辐射增加;5冰核浓度的变化能够引起雷电活动发生频次和强度的变化;6冰核浓度增加,引起降水量的变化不确定,即降水量增加、减少或者变化不显著的情况都可能存在。这些结果为改进数值模式中冰核活化参数化方法提供指导,从而提高数值模式对云和降水的预报能力;同时为人工影响天气选择合适的人工催化剂和撒播时机提供参考。

A Study of the Effects of Ice Nuclei on Cloud Microphysical Properties and Precipitation

An overview of the progresses in the effects of Ice Nuclei (IN) on cloud microphysical properties and precipitation was made in this study. Detailed analysis of the effects of IN on cloud macro- and micro-physical characteristics, convective system, lighting, precipitation intensity and amount was accomplished, and explanations were proposed for those effects in view of the cloud microphysical processes of IN related. The results show that: ①in general, increasing IN leads to the increasing of ice crystal number concentration, reducing of cloud droplet number concentration, and extending of cloud lifetime; ②increase in IN concentration in developing convective cloud causes early release of latent heat at sub-cooling region at middle level cloud faction, which enhances instability energy in middle level clouds and thus promotes the development of convective system; ③the ratio of ice water content and liquid water content is altered and the homogeneous freezing process is reduced or suppressed due to increasing IN concentration in cirrus cloud, but has a significant contribution to the mean ice crystal size; ④as IN concentration increases, the earth-atmosphere system net radiative forcing increases; ⑤both lightning frequency and intensity can be modified by altering IN concentration in cloud; and ⑥the effect of increaing IN concentration on rainfall amount is indefinite, that is, increasing IN concentration can lead to increase, decrease, little change of the total amount of rainfall.