1995和1996年春季北京地区大气冰核浓度的观测与研究

STUDY OF ICE NUCLEI CONCENTRATION AT BEIJING IN SPRING OF 1995 AND 1996

中文关键词:  毕格型混合云室  冰核浓度  大气污染  沙暴  冰晶浓度

英文关键词:Bigg type mixing cloud chamber  Ice nuclei concentration  Air pollution  Sand storm  Ice crystal

中文摘要:

      利用毕格型混合云室于1995和1996年春季在北京西郊观测了4种温度条件下的大气冰核浓度。分析了冰核浓度逐日变化特点,与1963年的观测(方法相同)结果进行了对比分析。发现30a来,冰核浓度平均约增加了15倍。根据严重污染天气条件下能见度与冰核浓度的相关分析,推测人类活动作为冰核源的权重,冰核浓度增加。分析发现大气中高活性冰核在大气中的滞留时间明显小于低活性冰核。结合冰核活性与粒子尺度的相关,分析推测了大气冰核浓度随高度递减的特点,推测高活性冰核随高度递减更快。分析中参考了世界各地的观测结果,并对不同观测方法观测的结果进行了分析对比,对其中一些地区差异和特点进行了探讨。冰晶浓度与云中气溶胶粒子浓度的相关分析表明,两者有较好的正相关关系。高冰晶浓度常对应有较窄的粒子谱和较小的浓度峰值直径。利用飞机观测的云中雪粒子浓度与冰粒子浓度资料分析结果表明两者有正相关;初步分析表明,大气冰核浓度除对冰云微结构和云中降水过程有重要影响外;还可能对云的辐射特征产生影响,从而影响大气气候过程。

英文摘要:

      The ice nuclei concentrations were observed using a Bigg type mixing cloud chamber in the spring seasons of 1995 and 1996 at Beijing. The day to day changes of ice nuclei concentration were analysed. These observations have also been compared with the similar observations in 1963. The preliminary results show that the ice nuclei concentrations at Beijing have increased by fifteen times from 1963 to 1995 and are extremely high during heavy pollution conditions. The region with high concentration of IN was very large inferred by the relationship between visibility and IN concentration. It implied that the impact of human activities the as an important factor of ice nuclei source has been intensifing from 1963 to 1995. The analysis also showed that the existence period of higher activity IN(-15 to -20 ℃) was shorter than that of lower activity IN(-25 to -30℃).The vertical distribution of IN concentration with different activity was inferred by the relationship between IN activity and particle size, showing that the higher activity IN decreasing with height might be more rapid than that of lower activity IN.The relationship between ice crystal and aerosol particle concentrations was analysed using the results observed by aircraft with particle measuring system (PMS) in ice-clouds. The analyses show that a positive correlation can be established between them. Usually the ice crystal size distribution was narrower in the ice clouds with high ice crystal concentration than that with low ice crystal concentration,and the peak diameter of ice crystal was smaller. It implies that the ice nuclei concentration might play an important role to the microphysics structure of ice cloud. In this paper a comparison was made among the results observed at different places in the world and using different observing methods. Some differences of characterisitics among them were discussed preliminarily.