摘要:利用国内首台在线连续流量扩散云室，2017年冬季在华北地区高山站开展了大气冰核观测；结合常规气象要素、降水滴谱、气溶胶观测，分析了大气冰核数浓度特征，并对冰核活化参数化方法以及降雪对冰核的影响进行了研究。结果表明：（1）大气冰核在不同时间的浓度差异较大，?20°C时数浓度变化范围为2.50～76.8 L?1，平均值为18.347 L?1；（2）大气冰核浓度随活化温度降低呈指数增加趋势，随过饱和度增加呈指数增加，凝华核化所占比例约为18.64%；（3）大气冰核与粒径大于0.5 μm的气溶胶数浓度的关系可用参数化表示，相关性大于仅基于活化温度建立的参数化公式；（4）降雪过程大气冰核具有先增加后减少的特征。降雪开始后大气冰核数浓度增加，降雪后期系统过境伴随的大风，对气溶胶的清洗作用明显，大气冰核随之减少。本研究为在线连续流量扩散云室类型的冰核观测仪在国内首次使用，所建立的冰核参数化公式有助于华北地区冬季地形云及其降水的微物理特征研究，同时在云模式的发展和人工影响天气研究中也有重要的参考意义。
关键词:在线连续流量扩散云室/
大气冰核/
气溶胶/
冰核参数化/
华北地区
Abstract:In this paper, we measure ice-nucleating particle (INP) number concentrations at a mountain site on the northwestern margin of Beijing during the winter of 2017, which were obtained using a newly purchased continuous-flow diffusion chamber (BJ-CFDC). We analyzed the characteristics of the atmospheric INP number concentrations with respect to weather elements, the precipitation size distribution, and aerosol observations. We identified the relationships of the INP number concentration with activation temperature, super saturation with respect to water, and aerosol particles larger than 0.5 m. The results indicate that the atmospheric INP number concentration has a large variation with respect to different activation temperatures, ranging between 2.50–76.8 L?1 at ?20°C, with an average of 18.347 L?1. The atmospheric INP number concentration was found to increase exponentially both with decreasing temperature and increasing super saturation with respect to water. The results also revealed that the atmospheric INP number concentration has a good correlation with the concentration of aerosol particles larger than 0.5 m. With this relation, the relevance of the predicted and measured INP number concentrations is greater than the relationship based only on temperature. The atmospheric INP number concentration in snow days was found to first increase and later decrease. That is, the INP number concentration increases when the snow begins, but the strong wind in the later snow period scavenges the aerosols, which leads to a reduced INP number concentration. With the BJ-CFDC, the first instrument of its kind in China, the results of this study will advance the study of orographic cloud and precipitation in winter in North China, as well as facilitate the development of cloud modeling and weather modification studies.
Key words:Continuous-flow diffusion chamber/
Atmospheric ice-nucleating particle/
Aerosols/
Ice-nucleating particle (INP) parameterization/
North China
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