2007年夏季我国西北地区云凝结核的观测研究

Observational Analyses on Cloud Condensation Nuclei in Northwestern China in Summer of 2007

利用连续气流纵向热梯度云凝结核仪对我国西北地区2007年夏季空中和地面的云凝结核(CCN)进行观测研究,并对观测结果进行了对比分析。飞机观测资料表明,西北地区的CCN主要来源于地面,近地层浓度较高,CCN浓度随高度增加而减少。污染城市上空的CCN比一般地区上空浓度高,浓度随高度变化趋势相同;地面观测结果显示,CCN具有明显的日变化,与人类活动、气象因子和下垫面相关;污染地区和清洁地区的CCN浓度在相同过饱和度下差异很大,在低过饱和度下浓度相差可达一个量级。根据关系式N=CSk拟合得到的地面CCN活化谱参数,银川地区的C值明显较大(>2200),k值较高(约0.7),表明银川地区具有大陆性特征;而祁连山地区C值较低(<2200)、k值较高(约0.77),属清洁型大陆性特征。

Cloud condensation nuclei-（CCN） was observed by DMT （Droplet Measurement Technologies） continuous flow stream wise thermal gradient CCN counter-on the ground atmosphere-in northwestern China in the summer of 2007 that is contrast analyzed.-It is-suggested-that the main source of CCN is from ground surface.-The CCN particles are the most concentrated in the lower-level troposphere,-and the CCN concentration is decreased with height.The comparison of vertical observation between polluted city-areas in Yinchuan and common-areas in Huinong shows that the former′s CCN concentration-is higher than-the latter′s one,and there is no-difference-in the concentration change.The CCN had a distinctive diurnal cycle-which is related with human activities,meteorological factors and surface conditions.The statistical results of CCN measurements show the obvious difference in concentration at the same supersaturation （ S ） in Shijiazhuang summertime.According to the expression N=CSk ,the CCN spectra can be derived.The fitted spectra parameters C （2200） and k （about 0.7） show the continental characteristic of CCN in Yinchuan,and the fitted spectra parameters C （2200） and k （about 0.77） show the clean continental characteristic of CCN in Qilianshan.