华北部分地区云凝结核的观测分析

利用美国DMT公司生产的连续气流单过饱和度云凝结核计数器对华北部分地区地面和空中云凝结核（CCN）进行了观测研究。地面观测结果表明，太原由于污染严重CCN数浓度高于石家庄。CCN数浓度日最大值、日平均值均随过饱和度的增加而增大。CCN数浓度具有明显的日变化特征，与气象因子、人类活动有关。降水对地面CCN具有明显的冲刷作用。利用关系式N=CSk拟合太原地面CCN活化谱，C〉2200cm-3，k〈l，C、k值很高，属于典型的大陆型核谱。飞机观测资料显示，CCN主要来源于地面，数浓度随高度增加明显减少。高空风向发生变化时，长距离气团输送提供CCN二次源。云对CCN有消耗作用，云内CCN比云外明显减少。

Observational analysis of cloud condensation nuclei in some regions of North China

Using a DMT（ Droplet Measurement Technologies） continuous flow streamwise thermal gra- dient cloud condensation nuclei （CCN） counter, the aircraft and ground measurements of CCN over some regions of North China are conducted. The field observations show that, due to the severe air pol- lution, CCN number concentration in Taiyuan city is higher than that in Shijiazhuang city. Daily mean and maximum CCN number concentrations increase with the supersaturation. With the influence of me- teorological factors and human activities, the variations of CCN number concentration display a distinc- tive diurnal cycle including two apparent peaks. Precipitation has an obvious scavenging effect on the ground CCN. The ground CCN spectra can be derived from the expression N = CSk. The fitting spectra parameters C（more than 2 200 cm-3） and k（ less than 1 ） represent the continental characteristic of CCN in Taiyuan city. The CCN is mainly transported from surface and CCN number concentration de- creases with the height. Long-distance transportation of particles provides secondary source for CCN when the upper wind direction changes. The cloud has a definite depletion effect on CCN particles so that CCN decreases obviously in clouds.